Enhancement of the catalytic activity of Pt nanoparticles toward methanol electro-oxidation using doped-SnO2 supporting materials

NASA Astrophysics Data System (ADS)

Merati, Zohreh; Basiri Parsa, Jalal

2018-03-01

Catalyst supports play important role in governing overall catalyst activity and durability. In this study metal oxides (SnO2, Sb and Nb doped SnO2) were electrochemically deposited on titanium substrate (Ti) as a new support material for Pt catalyst in order to electro-oxidation of methanol. Afterward platinum nanoparticles were deposited on metal oxide film via electro reduction of platinum salt in an acidic solution. The surface morphology of modified electrodes were evaluated by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX) techniques. The electro-catalytic activities of prepared electrodes for methanol oxidation reaction (MOR) and oxidation of carbon monoxide (CO) absorbed on Pt was considered with cyclic voltammetry. The results showed high catalytic activity for Pt/Nb-SnO2/Ti electrode. The electrochemical surface area (ECSA) of a platinum electro-catalyst was determined by hydrogen adsorption. Pt/Nb-SnO2/Ti electrode has highest ECSA compared to other electrode resulting in high activity toward methanol electro-oxidation and CO stripping experiments. The doping of SnO2 with Sb and Nb improved ECSA and MOR activity, which act as electronic donors to increase electronic conductivity.

A novel enzymatic glucose sensor based on Pt nanoparticles-decorated hollow carbon spheres-modified glassy carbon electrode

NASA Astrophysics Data System (ADS)

Luhana, Charles; Bo, Xiang-Jie; Ju, Jian; Guo, Li-Ping

2012-10-01

A new glucose biosensor was developed based on hollow carbon spheres decorated with platinum nanoparticles (Pt/HCSs)-modified glassy carbon electrode immobilized with glucose oxidase (GOx) with the help of Nafion. The Pt nanoparticles were well dispersed on the HCSs with an average size of 2.29 nm. The detection of glucose was achieved via electrochemical detection of the enzymatically liberated H2O2 at +0.5 V versus Ag/AgCl at physiologic pH of 7.4. The Pt/HCSs-modified electrode exhibited excellent electrocatalytic activities toward both the oxidation and reduction of H2O2. The glucose biosensor showed good electrocatalytic performance in terms of high sensitivity (4.1 μA mM-1), low detection limit (1.8 μM), fast response time <3 s, and wide linear range (0.04-8.62 mM). The apparent Michaelis-Menten constant ( K m) and the maximum current density ( i max) values for the biosensor were 10.94 mM and 887 μA cm-2 respectively. Furthermore, this biosensor showed an acceptable reproducibility and high stability. The interfering signals from ascorbic acid and uric acid at concentration levels normally found in human blood were not much compared with the response to glucose. Blood serum samples were also tested with this biosensor and a good recovery was achieved for the two spiked serum samples.

Laser patterning of platinum electrodes for safe neurostimulation

NASA Astrophysics Data System (ADS)

Green, R. A.; Matteucci, P. B.; Dodds, C. W. D.; Palmer, J.; Dueck, W. F.; Hassarati, R. T.; Byrnes-Preston, P. J.; Lovell, N. H.; Suaning, G. J.

2014-10-01

Objective. Laser surface modification of platinum (Pt) electrodes was investigated for use in neuroprosthetics. Surface modification was applied to increase the surface area of the electrode and improve its ability to transfer charge within safe electrochemical stimulation limits. Approach. Electrode arrays were laser micromachined to produce Pt electrodes with smooth surfaces, which were then modified with four laser patterning techniques to produce surface structures which were nanosecond patterned, square profile, triangular profile and roughened on the micron scale through structured laser interference patterning (SLIP). Improvements in charge transfer were shown through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and biphasic stimulation at clinically relevant levels. A new method was investigated and validated which enabled the assessment of in vivo electrochemically safe charge injection limits. Main results. All of the modified surfaces provided electrical advantage over the smooth Pt. The SLIP surface provided the greatest benefit both in vitro and in vivo, and this surface was the only type which had injection limits above the threshold for neural stimulation, at a level shown to produce a response in the feline visual cortex when using an electrode array implanted in the suprachoroidal space of the eye. This surface was found to be stable when stimulated with more than 150 million clinically relevant pulses in physiological saline. Significance. Critical to the assessment of implant devices is accurate determination of safe usage limits in an in vivo environment. Laser patterning, in particular SLIP, is a superior technique for improving the performance of implant electrodes without altering the interfacial electrode chemistry through coating. Future work will require chronic in vivo assessment of these electrode patterns.

Fabrication of Metal Nanoparticle-Modified Screen Printed Carbon Electrodes for the Evaluation of Hydrogen Peroxide Content in Teeth Whitening Strips

ERIC Educational Resources Information Center

Popa, Adriana; Abenojar, Eric C.; Vianna, Adam; Buenviaje, Czarina Y. A.; Yang, Jiahua; Pascual, Cherrie B.; Samia, Anna Cristina S.

2015-01-01

A laboratory experiment in which students synthesize Ag, Au, and Pt nanoparticles (NPs) and use them to modify screen printed carbon electrodes for the electroanalysis of the hydrogen peroxide content in commercially available teeth whitening strips is described. This experiment is designed for two 3-h laboratory periods and can be adapted for…

The simultaneous electrochemical detection of ascorbic acid, dopamine, and uric acid using graphene/size-selected Pt nanocomposites.

PubMed

Sun, Chia-Liang; Lee, Hsin-Hsien; Yang, Jen-Ming; Wu, Ching-Chou

2011-04-15

In this study, a graphene/Pt-modified glassy carbon (GC) electrode was created to simultaneously characterize ascorbic acid (AA), dopamine (DA), and uric acid (UA) levels via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). During the preparation of the nanocomposite, size-selected Pt nanoparticles with a mean diameter of 1.7 nm were self-assembled onto the graphene surface. In the simultaneous detection of the three aforementioned analytes using CV, the electrochemical potential differences among the three detected peaks were 185 mV (AA to DA), 144 mV (DA to UA), and 329 mV (AA and UA), respectively. In comparison to the CV results of bare GC and graphene-modified GC electrodes, the large electrochemical potential difference that is achieved via the use of the graphene/Pt nanocomposites is essential to the distinguishing of these three analytes. An optimized adsorption of size-selected Pt colloidal nanoparticles onto the graphene surface results in a graphene/Pt nanocomposite that can provide a good platform for the routine analysis of AA, DA, and UA. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of caffeic acid in wine using PEDOT film modified electrode.

PubMed

Bianchini, C; Curulli, A; Pasquali, M; Zane, D

2014-08-01

A novel method using PEDOT (poly(3,4-ethylenedioxy) thiophene) modified electrode was developed for the determination of caffeic acid (CA) in wine. Cyclic voltammetry (CV) with the additions standard method was used to quantify the analyte at PEDOT modified electrodes. PEDOT films were electrodeposited on Platinum electrode (Pt) in aqueous medium by galvanostatic method using sodium poly(styrene-4-sulfonate) (PSS) as electrolyte and surfactant. CV allows detecting the analyte over a wide concentration range (10.0nmoll(-1)-6.5mmoll(-1)). The electrochemical method proposed showed good statistical and analytical parameters as linearity range, LOD, LOQ and sensitivity. Copyright © 2014 Elsevier Ltd. All rights reserved.

The influence of different modified graphene on property of DSSCs

NASA Astrophysics Data System (ADS)

Xu, Kai; Shen, Yue; Zhang, Zongkun; Cao, Meng; Gu, Feng; Wang, Linjun

2016-01-01

Two kinds of modified reduced graphene oxide (rGO) power with different hydrophilic property were synthesized in NH3/hydrazine hydrate (N-rGO) and KOH/hydrazine hydrate (K-rGO) reduction systems, respectively, and be used as counter electrode materials. The as-prepared rGO counter electrodes were confirmed as substitution for Pt counter electrode in dye-sensitized solar cells (DSSCs). The efficiency (η) of DSSCs based on N-rGO counter electrodes achieved 4.72% while that of K-rGO counter electrode was just 3.38%. The electrochemical impedance spectroscopy (EIS) measurements revealed that the hydrophilic K-rGO counter electrode has a low charge transfer resistance (Rct) and the hydrophobic N-rGO counter electrode has a low series resistance (Rs).

Modification of Glucose Oxidase biofuel cell by multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lotfi, Ladan; Farahbakhsh, Afshin; Aghili, Sina

2018-01-01

Biofuel cells are a subset of fuel cells that employ biocatalysts. Enzyme-based biofuel cells (EBFCs) generate electrical energy from biofuels such as glucose and ethanol, which are renewable and sustainable energy sources. Glucose biofuel cells (GBFCs) are particularly interesting nowadays due to continuous harvesting of oxygen and glucose from bioavailable substrates, activity inside the human body, and environmental benign, which generate electricity through oxidation of glucose on the anode and reduction of oxygen on the cathode. Promoting the electron transfer of redox enzymes at modified electrode utilizing Nano size materials, such as carbon nanotubes (CNT), to achieve the direct electrochemistry of enzymes has been reported. The polypyrrole-MWCNTs-glucose oxidase (PY-CNT-GOx) electrode has been investigated in the present work. Cyclic voltammetry tests were performed in a three-electrode electrochemical set-up with modified electrode (Pt/PPy/MWCNTs/GOx) was used as working electrode. Platinum flat and Ag/AgCl (saturated KCl) were used as counter electrode and the reference electrode, respectively. The biofuel cells probe was prepared by immobilizing MWCNTs at the tip of a platinum (Pt) electrode (0.5 cm2) with PPy as the support matrix We have demonstrated a well-dispersed nanomaterial PPy/MWNT, which is able to immobilize GOx firmly under the condition of the absence of any other cross-linking agent.

Nonenzymatic free-cholesterol detection via a modified highly sensitive macroporous gold electrode with platinum nanoparticles.

PubMed

Lee, Yi-Jae; Park, Jae-Yeong

2010-12-15

A sensitive macroporous Au electrode with a highly rough surface obtained through the use of with Pt nanoparticles (macroporous Au-/nPts) is reported. It has been designed for nonenzymatic free-cholesterol biosensor applications. A macroporous Au-/nPts electrode was fabricated by electroplating Pt nanoparticles onto a coral-like shaped macroporous Au electrode structure. The macroporous Au-/nPts electrode was physically characterized by field emission scanning electron microscopy (FESEM). It was confirmed that the Pt nanoparticles were well deposited on the surface of the macroporous Au electrode. The porosity and window pore size of the macroporous Au electrode were 50% and 100-300 nm, respectively. The electroplated Pt nanoparticle size was approximately 10-20 nm. Electrochemical experiments showed that the macroporous Au-/nPts exhibited a much larger surface activation area (roughness factor (RF)=2024.7) than the macroporous Au electrode (RF=46.07). The macroporous Au-/nPts also presented a much stronger electrocatalytic activity towards cholesterol oxidation than does the macroporous Au electrode. At 0.2 V, the electrode responded linearly up to a 5 mM cholesterol concentration in a neutral media, with a detection limit of 0.015 mM and detection sensitivity of 226.2 μA mM(-1) cm(-2). Meanwhile, interfering species such as ascorbic acid (AA), acetaminophen (AP), and uric acid (UA), were effectively avoided. This novel nonenzymatic detection electrode has strong applications as an electrochemically based cholesterol biosensor. Copyright © 2010 Elsevier B.V. All rights reserved.

A Nanostructured Bifunctional platform for Sensing of Glucose Biomarker in Artificial Saliva: Synergy in hybrid Pt/Au surfaces.

PubMed

Raymundo-Pereira, Paulo A; Shimizu, Flávio M; Coelho, Dyovani; Piazzeta, Maria H O; Gobbi, Angelo L; Machado, Sergio A S; Oliveira, Osvaldo N

2016-12-15

We report on a bimetallic, bifunctional electrode where a platinum (Pt) surface was patterned with nanostructured gold (Au) fingers with different film thicknesses, which was functionalized with glucose oxidase (GOx) to yield a highly sensitive glucose biosensor. This was achieved by using selective adsorption of a self-assembled monolayer (SAM) onto Au fingers, which allowed GOx immobilization only onto the Au-SAM surface. This modified electrode was termed bifunctional because it allowed to simultaneously immobilize the biomolecule (GOx) on gold to catalyze glucose, and detect hydrogen peroxide on Pt sites. Optimized electrocatalytic activity was reached for the architecture Pt/Au-SAM/GOx with 50nm thickness of Au, where synergy between Pt and Au allowed for detection of hydrogen peroxide (H2O2) at a low applied potential (0V vs. Ag/AgCl). Detection was performed for H2O2 in the range between 4.7 and 102.7 nmol L(-1), with detection limit of 3.4×10(-9) mol L(-1) (3.4 nmol L(-1)) and an apparent Michaelis-Menten rate constant of 3.2×10(-6)molL(-1), which is considerably smaller than similar devices with monometallic electrodes. The methodology was validated by measuring glucose in artificial saliva, including in the presence of interferents. The synergy between Pt and Au was confirmed in electrochemical impedance spectroscopy measurements with an increased electron transfer, compared to bare Pt and Au electrodes. The approach for fabricating the reproducible bimetallic Pt/Au electrodes is entirely generic and may be explored for other types of biosensors and biodevices where advantage can be taken of the combination of the two metals. Copyright © 2016 Elsevier B.V. All rights reserved.

Two dimensional visible-light-active Pt-BiOI photoelectrocatalyst for efficient ethanol oxidation reaction in alkaline media

NASA Astrophysics Data System (ADS)

Zhai, Chunyang; Hu, Jiayue; Sun, Mingjuan; Zhu, Mingshan

2018-02-01

Two dimensional (2D) BiOI nanoplates were synthesized and used as support for the deposition of Pt nanoparticles. Owing to broad visible light absorption (up to 660 nm), the as-obtained Pt-BiOI electrode was used as effective photoelectrocatalyst in the application of catalytic ethanol oxidation in alkaline media under visible light irradiation. Compared to dark condition, the Pt-BiOI modified electrode displayed 3 times improved catalytic activity towards ethanol oxidation under visible light irradiation. The synergistic effect of electrocatalytic and photocatalytic, and the unique of 2D structures contribute to the improvement of catalytic activity. The mechanism of enhanced photoelectrocatalytic process is proposed. The present results suggest that 2D visible-light-activated BiOI can be served as promising support for the decoration of Pt and applied in the fields of photoelectrochemical and photo-assisted fuel cell applications

Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface.

PubMed

Perales-Rondón, Juan Victor; Ferre-Vilaplana, Adolfo; Feliu, Juan M; Herrero, Enrique

2014-09-24

In order to improve catalytic processes, elucidation of reaction mechanisms is essential. Here, supported by a combination of experimental and computational results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by the incorporation of bismuth adatoms is revealed. In the proposed model, formic acid is first physisorbed on bismuth and then deprotonated and chemisorbed in formate form, also on bismuth, from which configuration the C-H bond is cleaved, on a neighbor Pt site, yielding CO2. It was found computationally that the activation energy for the C-H bond cleavage step is negligible, which was also verified experimentally.

Origin of Multiple Peaks in the Potentiodynamic Oxidation of CO Adlayers on Pt and Ru-Modified Pt Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongsen; Abruña, Héctor D.

2015-05-21

The study of the electrooxidation mechanism of COad on Pt based catalysts is very important for designing more effective CO-tolerant electrocatalysts for fuel cells. We have studied the origin of multiple peaks in the cyclic voltammograms of CO stripping from polycrystalline Pt and Ru modified polycrystalline Pt (Pt/Ru) surfaces in both acidic and alkaline media by differential electrochemical mass spectrometry (DEMS), DFT calculations, and kinetic Monte Carlo (KMC) simulations. A new COad electrooxidation kinetic model on heterogeneous Pt and Pt/Ru catalysts is proposed to account for the multiple peaks experimentally observed. In this model, OH species prefer to adsorb atmore » low-coordination sites or Ru sites and, thus, suppress CO repopulation from high-coordination sites onto these sites. Therefore, COad oxidation occurs on different facets or regions, leading to multiplicity of CO stripping peaks. This work provides a new insight into the CO electrooxidation mechanism and kinetics on heterogeneous catalysts.« less

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen.

PubMed

Johnson, Grant E; Colby, Robert; Engelhard, Mark; Moon, Daewon; Laskin, Julia

2015-08-07

Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was evaluated by employing the same experimental parameters to prepare nanoparticles on glassy carbon electrodes on three occasions separated by several days. Surfaces with almost identical electrochemical behavior were observed with CV, demonstrating the highly reproducible preparation of bare nanoparticles using physical synthesis in the gas-phase combined with soft landing of mass-selected ions.

Glucose oxidase immobilization on different modified surfaces of platinum nanowire for application in glucose detection

NASA Astrophysics Data System (ADS)

Thanh Tuyen Le, Thi; Duy Tran, Phu; Pham, Xuan Tung; Hien Tong, Duy; Chien Dang, Mau

2010-09-01

In this work, the surface of platinum (Pt) nanowires was modified by using several chemicals, including a compound of gelatin gel with SiO2, polyvinyl alcohol (PVA) with Prussian blue (PB) mediator and cysteamine self-assembled monolayers (SAM). Then, glucose oxidase (GOD) enzyme was immobilized on the modified surfaces of Pt nanowire electrodes by using techniques of electrochemical adsorption and chemical binding. The GOD immobilized Pt nanowires were used for application in glucose detection by performing a cyclic voltammetry measurement. The detection results showed that GOD was immobilized on all of the tested surfaces and the highest glucose detection sensitivity of 60 μM was obtained when the Pt nanowires were modified by PVA with PB mediator. Moreover, the sensors showed very high current response when the Pt nanowires were modified with the cysteamine SAM. The stability and catalyst activity of GOD are also reported here. For instance, the catalyst activity of GOD retained about 60% of its initial value after it was stored at 4 °C in a 100 mM PBS buffer solution with a pH of 7.2 for a period of 30 days.

Direct alcohol fuel cells: Increasing platinum performance by modification with sp-group metals

NASA Astrophysics Data System (ADS)

Figueiredo, Marta C.; Sorsa, Olli; Doan, Nguyet; Pohjalainen, Elina; Hildebrand, Helga; Schmuki, Patrik; Wilson, Benjamin P.; Kallio, Tanja

2015-02-01

By using sp group metals as modifiers, the catalytic properties of Pt can be improved toward alcohols oxidation. In this work we report the performance increase of direct alcohol fuel cells (DAFC) fuelled with ethanol or 2-propanol with platinum based anode electrodes modified with Bi and Sb adatoms. For example, by simply adding Sb to the Pt/C based anode ink during membrane electrode assembly fabrication of a direct ethanol fuel cell (DEFC) its performance is improved three-fold, with more than 100 mV increase in the open circuit potential. For the fuel cell fuelled with 2-propanol high power densities are obtained at very high potentials with these catalyst materials suggesting a great improvement for practical applications. Particularly in the case of Pt/C-Bi, the improvement is such that within 0.6 V (from 0.7 to 0.1 V) the power densities are between 7 and 9 mW/cm2. The results obtained with these catalysts are in the same range as those obtained with other bimetallic catalysts comprising of PtRu and PtSn, which are currently considered to be the best for these type of fuel cells and that are obtained by more complicated (and consequently more expensive) methods.

Highly-sensitive cholesterol biosensor based on platinum-gold hybrid functionalized ZnO nanorods.

PubMed

Wang, Chengyan; Tan, Xingrong; Chen, Shihong; Yuan, Ruo; Hu, Fangxin; Yuan, Dehua; Xiang, Yun

2012-05-30

A novel scheme for the fabrication of gold/platinum hybrid functionalized ZnO nanorods (Pt-Au@ZnONRs) and multiwalled carbon nanotubes (MWCNTs) modified electrode is presented and its application for cholesterol biosensor is investigated. Firstly, Pt-Au@ZnONRs was prepared by the method of chemical synthesis. Then, the Pt-Au@ZnONRs suspension was dropped on the MWCNTs modified glass carbon electrode, and followed with cholesterol oxidase (ChOx) immobilization by the adsorbing interaction between the nano-material and ChOx as well as the electrostatic interaction between ZnONRs and ChOx molecules. The combination of MWCNTs and Pt-Au@ZnONRs provided a favorable environment for ChOx and resulted in the enhanced analytical response of the biosensor. The resulted biosensor exhibited a linear response to cholesterol in the wide range of 0.1-759.3 μM with a low detection limit of 0.03 μM and a high sensitivity of 26.8 μA mM(-1). The calculated apparent Michaelis constant K(M)(app) was 1.84 mM, indicating a high affinity between ChOx and cholesterol. Copyright © 2012 Elsevier B.V. All rights reserved.

A novel fabrication method of carbon electrodes using 3D printing and chemical modification process.

PubMed

Tian, Pan; Chen, Chaoyang; Hu, Jie; Qi, Jin; Wang, Qianghua; Chen, Jimmy Ching-Ming; Cavanaugh, John; Peng, Yinghong; Cheng, Mark Ming-Cheng

2017-11-23

Three-dimensional (3D) printing is an emerging technique in the field of biomedical engineering and electronics. This paper presents a novel biofabrication method of implantable carbon electrodes with several advantages including fast prototyping, patient-specific and miniaturization without expensive cleanroom. The method combines stereolithography in additive manufacturing and chemical modification processes to fabricate electrically conductive carbon electrodes. The stereolithography allows the structures to be 3D printed with very fine resolution and desired shapes. The resin is then chemically modified to carbon using pyrolysis to enhance electrochemical performance. The electrochemical characteristics of 3D printing carbon electrodes are assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3D printing carbon electrodes is much higher than the same sized platinum (Pt) electrode. In-vivo electromyography (EMG) recording, 3D printing carbon electrodes exhibit much higher signal-to-noise ratio (40.63 ± 7.73) than Pt electrodes (14.26 ± 6.83). The proposed biofabrication method is envisioned to enable 3D printing in many emerging applications in biomedical engineering and electronics.

Quantitative determination of Escherichia coli based on the electrochemical measurement of bacterial catalase activity using H2O2-selective organic/inorganic-hybrid sol-gel film-modified Pt electrode.

PubMed

Hasebe, Yasushi; Fukuzawa, Michiru; Matsuhisa, Hironori

2009-01-01

Quantitative determination of Escherichia coli (E. coli) concentration was achieved by measuring the intrinsic catalase activity of E. coli using novel H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode. This hybrid sol-gel film is composed of three kinds of organosilanes and two biopolymers (i.e., chitosan and bovine serum albumin), and exhibited an excellent permselectivity toward H2O2 based on a size-exclusive mechanism. The steady-state anodic current for 100 [xmol/L H2O2 at +0.6 V (vs. Ag/AgCl) in 0.1 mol/L phosphate buffer (pH 6.5) solution was apparently diminished by the addition of E. coli samples, due to the decomposition of H2O2 by intrinsic catalase activity of E. coli. The time-dependent decrease in current (-AI/At) was significantly dependent on the E. coli concentration. The -AI/At was enhanced by the permeabilization pretreatment of E. coli samples with the mixed solution of polymyxin B and lysozyme. This H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode allowed quantitative determination of E. coli concentration ranging from 10(6) to 10(9) CFU/mL within 30 min. This method required no label and complicated procedure, and allowed rapid, simple and cost-effective quantitative electrochemical determination of catalase-positive bacteria.

Electrochemical behavior of platinum nanoparticles on a carbon xerogel support modified with a [(trifluoromethyl)-benzenesulfonyl]imide electrolyte.

PubMed

Liu, Bing; Mei, Hua; DesMarteau, Darryl; Creager, Stephen E

2014-12-11

A monoprotic [(trifluoromethyl)benzenesulfonyl]imide (SI) superacid electrolyte was used to covalently modify a mesoporous carbon xerogel (CX) support via reaction of the corresponding trifluoromethyl aryl sulfonimide diazonium zwitterion with the carbon surface. Electrolyte attachment was demonstrated by elemental analysis, acid-base titration, and thermogravimetric analysis. The ion-exchange capacity of the fluoroalkyl-aryl-sulfonimide-grafted carbon xerogel (SI-CX) was ∼0.18 mequiv g(-1), as indicated by acid-base titration. Platinum nanoparticles were deposited onto the SI-grafted carbon xerogel samples by the impregnation and reduction method, and these materials were employed to fabricate polyelectrolyte membrane fuel-cell (PEMFC) electrodes by the decal transfer method. The SI-grafted carbon-xerogel-supported platinum (Pt/SI-CX) was characterized by X-ray diffraction and transmission electron microscopy to determine platinum nanoparticle size and distribution, and the findings are compared with CX-supported platinum catalyst without the grafted SI electrolyte (Pt/CX). Platinum nanoparticle sizes are consistently larger on Pt/SI-CX than on Pt/CX. The electrochemically active surface area (ESA) of platinum catalyst on the Pt/SI-CX and Pt/CX samples was measured with ex situ cyclic voltammetry (CV) using both hydrogen adsorption/desorption and carbon monoxide stripping methods and by in situ CV within membrane electrode assemblies (MEAs). The ESA values for Pt/SI-CX are consistently lower than those for Pt/CX. Some possible reasons for the behavior of samples with and without grafted SI layers and implications for the possible use of SI-grafted carbon layers in PEMFC devices are discussed.

Soft Landing of Bare PtRu Nanoparticles for Electrochemical Reduction of Oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Grant E.; Colby, Robert J.; Engelhard, Mark H.

2015-08-07

Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu alloy nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 x 104 ions µm-2 and that their average height is centered at 4 nm. Scanning transmission electron microscopy images obtained in themore » high-angle annular dark field mode (STEM-HAADF) further confirm that the soft-landed PtRu alloy nanoparticles are uniform in size and have a Ru core decorated with small regions of Pt on the surface. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in relative atomic concentrations of ~9% and ~33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt4f and Ru3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the alloy nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He+ and O+ ions. The activity of electrodes containing 7 x 104 ions µm-2 of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the alloy nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was evaluated by employing the same experimental parameters to prepare nanoparticles on glassy carbon electrodes on three occasions separated by several days. Surfaces with almost identical electrochemical behavior were observed with CV, demonstrating the highly reproducible preparation of bare alloy nanoparticles using physical synthesis in the gas-phase combined with soft landing of mass-selected ions« less

Advanced cathode materials for polymer electrolyte fuel cells based on pt/ metal oxides: from model electrodes to catalyst systems.

PubMed

Fabbri, Emiliana; Pătru, Alexandra; Rabis, Annett; Kötz, Rüdiger; Schmidt, Thomas J

2014-01-01

The development of stable catalyst systems for application at the cathode side of polymer electrolyte fuel cells (PEFCs) requires the substitution of the state-of-the-art carbon supports with materials showing high corrosion resistance in a strongly oxidizing environment. Metal oxides in their highest oxidation state can represent viable support materials for the next generation PEFC cathodes. In the present work a multilevel approach has been adopted to investigate the kinetics and the activity of Pt nanoparticles supported on SnO2-based metal oxides. Particularly, model electrodes made of SnO2 thin films supporting Pt nanoparticles, and porous catalyst systems made of Pt nanoparticles supported on Sb-doped SnO2 high surface area powders have been investigated. The present results indicate that SnO2-based supports do not modify the oxygen reduction reaction mechanism on the Pt nanoparticle surface, but rather lead to catalysts with enhanced specific activity compared to Pt/carbon systems. Different reasons for the enhancement in the specific activity are considered and discussed.

A novel hierarchical Pt- and FTO-free counter electrode for dye-sensitized solar cell

PubMed Central

2014-01-01

A novel hierarchical Pt- and FTO-free counter electrode (CE) for the dye-sensitized solar cell (DSSC) was prepared by spin coating the mixture of TiO2 nanoparticles and poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) solution onto the glass substrate. Compared with traditional Pt/FTO CE, the cost of the new CE is dramatically reduced by the application of bilayer TiO2-PEDOT:PSS/PEDOT:PSS film and the glass substrate. The sheet resistance of this composite film is 35 Ω sq−1 and is low enough to be used as an electrode. The surface morphologies of TiO2-PEDOT:PSS layer and modified PEDOT:PSS layer were characterized by scanning electron microscope, which shows that the former had larger surface areas than the latter. Electrochemical impedance spectra and Tafel polarization curves prove that the catalytic activity of TiO2-PEDOT:PSS/PEDOT:PSS/glass CE is higher than that of PEDOT:PSS/FTO CE and is similar to Pt/FTO CE's. This new fabricated device with TiO2-PEDOT:PSS/PEDOT:PSS/glass CE achieves a high power conversion efficiency (PCE) of 4.67%, reaching 91.39% of DSSC with Pt/FTO CE (5.11%). PMID:24808802

The O2 reduction at the IFC modified O2 fuel cell electrode

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph; Baldwin, Richard S.; Johnson, Richard E.

1992-01-01

The International Fuel Corporation (IFC) state of the art (SOA) O2 electrode (Au-10 percent Pt electrocatalyst by weight) is currently being used in the alkaline H2-O2 fuel cell in the NASA Space Shuttle. Recently, IFC modified O2 electrode, as a possible replacement for the SOA electrode. In the present study, O2 reduction data were obtained for the modified electrode at temperatures between 23.3 and 91.7 C. BET measurements gave an electrode BET surface area of about 2070 sq. cm/sq. cm of geometric surface area. The Tafel data could be fitted to two straight line regions. The slope for the lower region, designated as the 0.04 V/decade region, was temperature dependent, and the transfer coefficient was about 1.5. The 'apparent' energy of activation for this region was about 19 kcal/mol. An O2 reduction mechanism for this 0.04 region is presented. In the upper region, designated as the 0.08 V/decade region, diffusion may be the controlling process. Tafel data are presented to illustrate the increase in performance with increasing temperature.

Analyzing the electrooxidation of ethylene glycol and glucose over platinum-modified gold electrocatalysts in alkaline electrolyte using in-situ infrared spectroscopy

NASA Astrophysics Data System (ADS)

Mahoney, Elizabeth G.; Sheng, Wenchao; Cheng, Mei; Lee, Kevin X.; Yan, Yushan; Chen, Jingguang G.

2016-02-01

Platinum modified gold (Pt/Au) catalysts are evaluated for the electrooxidation of ethylene glycol (EG) and glucose (Glc). The Pt/Au catalysts are synthesized on an Au disk and supported Au/C particles through the galvanic displacement of a copper monolayer with Pt. The Pt/Au catalysts are compared to monometallic Pt and Au catalysts for the oxidation of EG and Glc in alkaline electrolyte. The Pt/Au disk has an onset potential for these reactions that is similar to Pt and is lower than Au. The supported catalysts are less active toward the electrooxidation of EG and Glc than the corresponding disk electrodes, but the Pt/Au/C also has an onset potential similar to Pt/C. In-situ FTIR is used to analyze the C-C bond scission in both reactions on the surfaces of Pt, Au, and Pt/Au disks. While the Pt/Au disk is found to have a low onset potential for the oxidation of EG, it does not produce as much CO2 as bulk Pt. On the other hand, the FTIR results show that CO2 is produced for the oxidation of Glc on the Pt/Au disk. These results show promise for the possibility of decreasing the amount of Pt needed for the electrooxidation of polyol molecules.

High Pt utilization PEMFC electrode obtained by alternative ion-exchange/electrodeposition.

PubMed

Chen, Siguo; Wei, Zidong; Li, Hua; Li, Li

2010-12-14

High Pt utilization PEMFC electrodes were prepared by an alternative ion-exchange/electrodeposition (AIEE) technique. The results demonstrated that the MEA employing an AIEE electrode with a Pt loading of 0.014 mg Pt cm(-2) exhibits performance approximately 2.2 times larger than that employing a conventional Nafion-bonded Pt/C electrode with a same Pt loading.

Hydrogen peroxide sensing using ultrathin platinum-coated gold nanoparticles with core@shell structure.

PubMed

Li, Yongxin; Lu, Qiufang; Wu, Shengnan; Wang, Lun; Shi, Xianming

2013-03-15

Ultrathin platinum-coated gold (Pt@Au) nanoparticles with core@shell structure have been developed by under-potential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt(2+) produced a uniform Pt monolayer on the surface of gold nanoparticles, which are immobilized on glassy carbon electrode (GCE) surface based on electrostatic interaction. The ultrathin Pt@Au nanoparticles were confirmed by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Voltammetry and amperometric methodologies were used to evaluate the electrocatalytic activity of the Pt@Au nanoparticles modified electrode towards the reduction of hydrogen peroxide under the physiological condition. The present results show that ultrathin Pt coating greatly enhances the electrocatalytic activity towards the reduction of hydrogen peroxide, which can be utilized to fabricate the hydrogen peroxide sensor. Chronoamperometric experiments showed that at an applied potential of 0.08 V (vs. Ag/AgCl), the current reduction of hydrogen peroxide was linear to its concentration in the range of 1-450 μΜ, and the detection limit was found to be 0.18 μM (signal-to-noise ratio, S/N=3). Copyright © 2012 Elsevier B.V. All rights reserved.

Performance evaluation of platinum-molybdenum carbide nanocatalysts with ultralow platinum loading on anode and cathode catalyst layers of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Saha, Shibely; Cabrera Rodas, José Andrés; Tan, Shuai; Li, Dongmei

2018-02-01

An alternative catalyst platform, consisting of a phase-pure transition carbide (TMC) support and Pt nanoparticles (NPs) in the range of subnanometer to < 2.7 nm, is established that can be used in both anode and cathode catalyst layers. While some TMCs with low Pt loadings have demonstrated similar activity as commercial Pt catalyst in idealized disk electrode screening tests, few to none have been applied in a realistic fuel cell membrane electrode assembly (MEA). We recently reported that β-Mo2C hollow nanotubes modified with Pt NPs via atomic layer deposition (ALD) possess better activity and durability than 20% Pt/C. This paper presents systematic evaluation of the Pt/Mo2C catalysts in a MEA, investigating effects of different MEA preparation techniques, gas diffusion layers (GDL) and various Pt loadings in the ultralow range (<0.04 mg/cm2) on MEA performance. Most importantly, we demonstrate, for the first time, that Pt/Mo2C catalyst on both anode and cathode, with a loading of 0.02 mg (Pt) cm-2, generated peak power density of 414 mW cm-2 that corresponds to 10.35 kWgPt-1 using hydrogen (H2) and oxygen (O2). Accelerated degradation tests (ADT) on Pt/Mo2C catalysts show 111% higher power density than commercial 20% Pt/C after the vigorous ADT.

Fuel blends: Enhanced electro-oxidation of formic acid in its blend with methanol at platinum nanoparticles modified glassy carbon electrodes

NASA Astrophysics Data System (ADS)

El-Deab, Mohamed S.; El-Nagar, Gumaa A.; Mohammad, Ahmad M.; El-Anadouli, Bahgat E.

2015-07-01

The current study addresses, for the first time, the enhanced direct electro-oxidation of formic acid (FA) at platinum-nanoparticles modified glassy carbon (nano-Pt/GC) electrode in the presence of methanol (MeOH) as a blending fuel. This enhancement is probed by: (i) the increase of the direct oxidation current of FA to CO2 (Ipd, dehydrogenation pathway), (ii) suppressing the dehydration pathway (Ipind, producing the poisoning intermediate CO) and (iii) a favorable negative shift of the onset potential of Ipd with increasing the mole fraction of MeOH in the blend. Furthermore, the charge of the direct FA oxidation in 0.3 M FA + 0.3 M MeOH blend is by 14 and 21times higher than that observed for 0.3 M FA and 0.3 M MeOH, respectively. MeOH is believed to adsorb at the Pt surface sites and thus disfavor the "non-faradaic" dissociation of FA (which produces the poisoning CO intermediate), i.e., MeOH induces a high CO tolerance of the Pt catalyst. The enhanced oxidation activity indicates that FA/MeOH blend is a promising fuel system.

Polyamidoamine dendrimers-assisted electrodeposition of gold-platinum bimetallic nanoflowers.

PubMed

Qian, Lei; Yang, Xiurong

2006-08-24

Novel Au-Pt bimetallic flower nanostructures fabricated on a polyamidoamine dendrimers-modified surface by electrodeposition are reported. These polyamidoamine dendrimers were stable, and they assisted the formation of Au-Pt bimetallic nanoflowers during the electrodeposition process. These nanoflowers were characterized by field-emitted scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electrochemical methods. FE-SEM images showed that the bimetallic nanoflower included two parts: the "light" and the "pale" part. The two parts consisted of many small bimetallic nanoparticles, which was attributed to the progressive nucleation process. Moreover, the "light" part contained more bimetallic nanoparticles. The morphologies of bimetallic nanoflowers depended on the electrodeposition time and potential and the layer number of assembled dendrimers. The average size of nanoflowers increased with the increase in electrodeposition time. The layer number of assembled dendrimers obviously affected the size and morphologies of the "pale" parts of deposited nanoflowers. EDS and XPS indicated that the content of Au element was higher than that of Pt element in the nanoflowers. The bimetallic nanoflowers-modified electrode had electrochemical properties similar to those of bare gold and platinum electrodes. It also exhibited significant electrocatalytic activities toward oxygen reduction.

Surface Analysis of 4-Aminothiophenol Adsorption at Polycrystalline Platinum Electrodes

NASA Technical Reports Server (NTRS)

Rosario-Castro, Belinda I.; Fachini, Estevao R.; Contes, Enid J.; Perez-Davis, Marla E.; Cabrera, Carlos R.

2008-01-01

Formation of self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) on polycrystalline platinum electrodes has been studied by surface analysis and electrochemistry techniques. The 4-ATP monolayer was characterized by cyclic voltammetry (CV), Raman spectroscopy, reflection absorption infrared (RAIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) experiments give an idea about the packing quality of the monolayer. RAIR and Raman spectra for 4-ATP modified platinum electrodes showed the characteristic adsorption bands for neat 4-ATP indicating the adsorption of 4-ATP molecules on platinum surface. The adsorption on platinum was also evidenced by the presence of sulfur and nitrogen peaks by XPS survey spectra of the modified platinum electrodes. High resolution XPS studies and RAIR spectrum for platinum electrodes modified with 4-ATP indicate that molecules are sulfur-bonded to the platinum surface. The formation of S-Pt bond suggests that ATP adsorption gives up an amino terminated SAM. Thickness of the monolayer was evaluated via angle-resolved XPS (AR-XPS) analyses. Derivatization of 4-ATP SAM was performed using 16-Br hexadecanoic acid.

A genosensor for detection of consensus DNA sequence of Dengue virus using ZnO/Pt-Pd nanocomposites.

PubMed

Singhal, Chaitali; Pundir, C S; Narang, Jagriti

2017-11-15

An electrochemical genosensor based on Zinc oxide/platinum-palladium (ZnO/Pt-Pd) modified fluorine doped tin oxide (FTO) glass plate was fabricated for detection of consensus DNA sequence of Dengue virus (DENV) using methylene blue (MB) as an intercalating agent. To achieve it, probe DNA (PDNA) was immobilized on the surface of ZnO/Pt-Pd nanocomposites modified FTO electrode. The synthesized nano-composites were characterized by high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-Vis spectroscopy, X-ray diffraction (XRD) analysis and Fourier transform infra-red (FTIR) spectroscopy. This PDNA modified electrode (PDNA/ZnO/Pt-Pd/FTO) served as a signal amplification platform for the detection of the target hybridized DNA (TDNA). The hybridization between PDNA and TDNA was detected by reduction in current, generated by interaction of anionic mediator, i.e., methylene blue (MB) with free guanine (3'G) of ssDNA. The sensor showed a dynamic linear range of 1 × 10 -6 M to 100 × 10 -6 M with LOD as 4.3 × 10 -5 M and LOQ as 9.5 × 10 -5 M. Till date, majorly serotype specific biosensors for dengue detection have been developed. The genosensor reported here eliminates the possibility of false result as in case of serotype specific DNA sensor. This is the report where conserved sequences present in all the serotypes of Dengue virus has been employed for fabrication of a genosensor. Copyright © 2017 Elsevier B.V. All rights reserved.

Large thermoelectric efficiency of doped polythiophene junction: A density functional study

NASA Astrophysics Data System (ADS)

Golsanamlou, Zahra; Bagheri Tagani, Meysam; Rahimpour Soleimani, Hamid

2018-06-01

The thermoelectric properties of polythiophene (PT) coupled to the Au (111) electrodes are studied based on density functional theory with nonequilibrium Green function formalism. Specially, the effect of Li and Cl adsorbents on the thermoelectric efficiency of the PT junction is investigated in different concentrations of the dopants for two lengths of the PT. Results show that the presence of dopants can bring the structural changes in the oligomer and modify the arrangement of the molecular levels leading to the dramatic changes in the transmission spectra of the junction. Therefore, the large enhancement in thermopower and consequently figure of merit is obtained by dopants which makes the doped PT junction as a beneficial thermoelectric device.

Fabrication of Highly Sensitive Nonenzymatic Electrochemical H₂O₂ Sensor Based on Pt Nanoparticles Anchored Reduced Graphene Oxide.

PubMed

Dhara, Keerthy; Ramachandran, T; Nair, Bipin G; Babu, T G Satheesh

2018-06-01

A highly sensitive nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated using platinum nanoparticles decorated reduced graphene oxide (Pt/rGO) nanocomposite. The Pt/rGO nanocomposite was prepared by single-step chemical reduction method. Nanocomposite was characterized by various analytical techniques including Raman spectroscopy, X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscopy. Screen printed electrodes (SPEs) were fabricated and the nanocomposite was cast on the working area of the SPE. Cyclic voltammetry and amperometry demonstrated that the Pt/rGO/SPE displayed much higher electrocatalytic activity towards the reduction of H2O2 than the other modified electrodes. The sensor exhibited wide linear detection range (from 10 μM to 8 mM), very high sensitivity of 1848 μA mM-1 cm-2 and a lower limit of detection of 0.06 μM. The excellent performance of Pt/rGO/SPE sensor were attributed to the reduced graphene oxide being used as an effective matrix to load a number of Pt nanoparticles and the synergistic amplification effect of the two kinds of nanomaterials. Moreover, the sensor showed remarkable features such as good reproducibility, repeatability, long-term stability, and selectivity.

Fe local structure in Pt-free nitrogen-modified carbon based electrocatalysts: XAFS study

NASA Astrophysics Data System (ADS)

Witkowska, Agnieszka; Giuli, Gabriele; Renzi, Marco; Marzorati, Stefania; Yiming, Wubulikasimu; Nobili, Francesco; Longhi, Mariangela

2016-05-01

The paper presents a new results on the bonding environment (coordination number and geometry) and on oxidation states of Fe in nitrogen-modified Fe/C composites used as Pt-free catalysts for oxygen reduction in Direct Hydrogen Fuel Cells. Starting from glucose or fructose, two catalysts displaying different electrochemical performance were prepared and studied in the form of pristine powder and thin catalytic layer of electrode by Fe K-edge XAFS spectroscopy. The results show how the Fe local structure varies as a function of different synthesis conditions and how changes in the structural properties of the catalysts are related to fuel cell electrochemical performance increase during a cell activation period.

DNA-templated synthesis of PtAu bimetallic nanoparticle/graphene nanocomposites and their application in glucose biosensor

PubMed Central

2014-01-01

In this paper, single-stranded DNA (ss-DNA) is demonstrated to functionalize graphene (GR) and to further guide the growth of PtAu bimetallic nanoparticles (PtAuNPs) on GR with high densities and dispersion. The obtained nanocomposites (PtAuNPs/ss-DNA/GR) were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDS), and electrochemical techniques. Then, an enzyme nanoassembly was prepared by self-assembling glucose oxidase (GOD) on PtAuNP/ss-DNA/GR nanocomposites (GOD/PtAuNPs/ss-DNA/GR). The nanocomposites provided a suitable microenvironment for GOD to retain its biological activity. The direct and reversible electron transfer process between the active site of GOD and the modified electrode was realized without any extra electron mediator. Thus, the prepared GOD/PtAuNP/ss-DNA/GR electrode was proposed as a biosensor for the quantification of glucose. The effects of pH, applied potential, and temperature on the performance of the biosensor were discussed in detail and were optimized. Under optimal conditions, the biosensor showed a linearity with glucose concentration in the range of 1.0 to 1,800 μM with a detection limit of 0.3 μM (S/N = 3). The results demonstrate that the developed approach provides a promising strategy to improve the sensitivity and enzyme activity of electrochemical biosensors. PMID:24572068

Electrochemical Oxidation of EDTA in Nuclear Wastewater Using Platinum Supported on Activated Carbon Fibers

PubMed Central

Zhao, Bo; Zhu, Wenkun; Mu, Tao; Hu, Zuowen; Duan, Tao

2017-01-01

A novel Pt/ACF (Pt supported on activated carbon fibers) electrode was successfully prepared with impregnation and electrodeposition method. Characterization of the electrodes indicated that the Pt/ACF electrode had a larger effective area and more active sites. Electrochemical degradation of ethylenediaminetetra-acetic acid (EDTA) in aqueous solution with Pt/ACF electrodes was investigated. The results showed that the 3% Pt/ACF electrode had a better effect on EDTA removal. The operational parameters influencing the electrochemical degradation of EDTA with 3% Pt/ACF electrode were optimized and the optimal removal of EDTA and chemical oxygen demand (COD) were 94% and 60% after 100 min on condition of the electrolyte concentration, initial concentration of EDTA, current density and initial value of pH were 0.1 mol/L, 300 mg/L, 40 mA/cm2 and 5.0, respectively. The degradation intermediates of EDTA in electrochemical oxidation with 3% Pt/ACF electrode were identified by gas chromatography-mass spectrum (GC-MS). PMID:28754016

New electrocatalysts for unitized regenerative fuel cell: Pt-Ir alloy deposited on the proton exchange membrane surface by impregnation-reduction method.

PubMed

Wan, Chieh-Hao; Wu, Chun-Lin; Lin, Meng-Tsun; Shih, Chihhsiong

2010-07-01

In this paper, a modified technique to prepare Pt-Ir catalyst layer on the proton exchange membrane (PEM) surface using the impregnation-reduction (IR) method is proposed to improve the electrocatalytic activity as well as the life cycle of the bifunctional oxygen electrode (BOE). The resulted electrocatalysts were characterized by the Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe Micro-Analysis (EPMA), and Transmission Electron Microscope (TEM). The electrocatalytic properties of the Pt-Ir layer on PEM surface for the oxygen reduction and water oxidation reactions as well as the life cycle of MEA were investigated. Experimental results showed that the Ir particles were dispersed densely in the platinum layer through the modified IR technique. The atomic ratio of Pt over Ir elements was 9:1, and the resulted thickness of the obtained Pt-Ir catalyst layer was about 1.0 microm. The Pt-Ir catalyst layer was composed of Pt layer doped with Ir nano-particles comprising nano Pt-Ir alloy phase. The large surface area of Ir core with Pt shell particles and the presence of nano Pt-Ir alloy phase led to a higher electrocatalytic activity of BOE. Due to the good binding between the Nafion membrane and the Pt-Ir alloy catalyst, as well as the composite structure of the resulted Pt-Ir, the life cycle of Unitized Regenerative Fuel Cell (URFC) is improved through this novel BOE.

Simultaneous determination of 6-mercaptopruine, 6-thioguanine and dasatinib as three important anticancer drugs using nanostructure voltammetric sensor employing Pt/MWCNTs and 1-butyl-3-methylimidazolium hexafluoro phosphate.

PubMed

Karimi-Maleh, Hassan; Shojaei, Abdollah Fallah; Tabatabaeian, Khalil; Karimi, Fatemeh; Shakeri, Shahryar; Moradi, Reza

2016-12-15

6-Mercaptopurine, 6-thioguanine and dasatinib are three important anticancer drugs with high adverse effects in human body. In this study, a Pt/MWCNTs-1-butyl-3-methylimidazolium hexafluoro phosphate-modified carbon paste electrode was developed for the simultaneously determination of 6-mercaptopurine, 6-thioguanine and dasatinib for the first time. The Pt/MWCNTs synthesized by polyol method and have been characterized by transmission electron microscopy and X-ray diffraction methods. The obtained data revealed that the electro-oxidation of 6-mercaptopurine, 6-thioguanine and dasatinib is facilitated as a novel voltammetric sensor. After optimization of electrochemical parameters employing this sensor at pH 8.0, the oxidation peak currents for 6-mercaptopurine, 6-thioguanine and dasatinib were found to vary linearly with their concentrations in the range of 0.05-550μM; 0.1-500μM and 5.0-500μM with detection limits of 0.009μM, 0.05μM and 1.0μM respectively using square wave voltammetric method. The modified electrode has been applied for the selective and precise analysis of 6-mercaptopurine, 6-thioguanine and dasatinib in pharmaceutical formulations and urine samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Novel ferrocene-anchored ZnO nanoparticle/carbon nanotube assembly for glucose oxidase wiring: application to a glucose/air fuel cell.

PubMed

Haddad, Raoudha; Mattei, Jean-Gabriel; Thery, Jessica; Auger, Aurélien

2015-06-28

Glucose oxidase (GOx) is immobilized on ZnO nanoparticle-modified electrodes. The immobilized glucose oxidase shows efficient mediated electron transfer with ZnO nanoparticles to which the ferrocenyl moiety is π-stacked into a supramolecular architecture. The constructed ZnO-Fc/CNT modified electrode exhibits high ferrocene surface coverage, preventing any leakage of the π-stacked ferrocene from the newly described ZnO hybrid nanoparticles. The use of the new architecture of ZnO supported electron mediators to shuttle electrons from the redox centre of the enzyme to the surface of the working electrode can effectively bring about successful glucose oxidation. These modified electrodes evaluated as a highly efficient architecture provide a catalytic current for glucose oxidation and are integrated in a specially designed glucose/air fuel cell prototype using a conventional platinum-carbon (Pt/C) cathode at physiological pH (7.0). The obtained architecture leads to a peak power density of 53 μW cm(-2) at 300 mV for the Nafion® based biofuel cell under "air breathing" conditions at room temperature.

Ultrasensitive electroanalytical tool for detecting, sizing, and evaluating the catalytic activity of platinum nanoparticles.

PubMed

Dasari, Radhika; Robinson, Donald A; Stevenson, Keith J

2013-01-16

Here we describe a very simple, reliable, low-cost electrochemical approach to detect single nanoparticles (NPs) and evaluate NP size distributions and catalytic activity in a fast and reproducible manner. Single NPs are detected through an increase in current caused by electrocatalytic oxidation of N(2)H(4) at the surface of the NP when it contacts a Hg-modified Pt ultramicroelectrode (Hg/Pt UME). Once the NP contacts the Hg/Pt UME, Hg poisons the Pt NP, deactivating the N(2)H(4) oxidation reaction. Hence, the current response is a "spike" that decays to the background current level rather than a stepwise "staircase" response as previously described for a Au UME. The use of Hg as an electrode material has several quantitative advantages including suppression of the background current by 2 orders of magnitude over a Au UME, increased signal-to-noise ratio for detection of individual collisions, precise integration of current transients to determine charge passed and NP size, reduction of surface-induced NP aggregation and electrode fouling processes, and reproducible and renewable electrodes for routine detection of catalytic NPs. The NP collision frequency was found to scale linearly with the NP concentration (0.016 to 0.024 pM(-1)s(-1)). NP size distributions of 4-24 nm as determined from the current-time transients correlated well with theory and TEM-derived size distributions.

An ultrasensitive luminol cathodic electrochemiluminescence immunosensor based on glucose oxidase and nanocomposites: graphene-carbon nanotubes and gold-platinum alloy.

PubMed

Jiang, Xinya; Chai, Yaqin; Yuan, Ruo; Cao, Yaling; Chen, Yingfeng; Wang, Haijun; Gan, Xianxue

2013-06-14

In the present study, a novel and ultrasensitive electrochemiluminescence (ECL) immunosensor based on luminol cathodic ECL was fabricated by using Au nanoparticles and Pt nanoparticles (nano-AuPt) electrodeposited on graphene-carbon nanotubes nanocomposite as platform for the detection of carcinoembryonic antigen (CEA). For this introduced immunosensor, graphene (GR) and single wall carbon nanotubes (CNTs) dispersed in chitosan (Chi-GR-CNTs) were firstly decorated on the bare gold electrode (GE) surface. Then nano-AuPt were electrodeposited (DpAu-Pt) on the Chi-GR-CNTs modified electrode. Subsequently, glucose oxidase (GOD) was employed to block the non-specific sites of electrode surface. When glucose was present in the working buffer solution, GOD immediately catalyzed the oxidation of glucose to in situ generate hydrogen peroxide (H2O2), which could subsequently promote the oxidation of luminol with an amplified cathodic ECL signal. The proposed immunosensor was performed at low potential (-0.1 to 0.4V) and low concentration of luminol. The CEA was determined in the range of 0.1 pg mL(-1) to 40 ng mL(-1) with a limit of detection down to 0.03 pg mL(-1) (SN(-1)=3). Moreover, with excellent sensitivity, selectivity, stability and simplicity, the as-proposed luminol-based ECL immunosensor provided great potential in clinical applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Bifunctional alkaline oxygen electrodes

NASA Technical Reports Server (NTRS)

Swette, L.; Kackley, N.; Mccatty, S. A.

1991-01-01

The authors describe the identification and testing of electrocatalysts and supports for the positive electrode of moderate-temperature, single-unit, rechargeable alkaline fuel cells. Recent work on Na(x)Pt3O4, a potential bifunctional catalyst, is described, as well as the application of novel approaches to the development of more efficient bifunctional electrode structures. The three dual-character electrodes considered here showed similar superior performance; the Pt/RhO2 and Rh/RhO2 electrodes showed slightly better performance than the Pt/IrO2 electrode. It is concluded that Na(x)Pt3O4 continues to be a promising bifunctional oxygen electrode catalyst but requires further investigation and development.

SFG study of methanol dissociative adsorption at Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes surfaces

NASA Astrophysics Data System (ADS)

Vidal, F.; Busson, B.; Six, C.; Pluchery, O.; Tadjeddine, A.

2002-04-01

The Pt( hkl)/methanol in acidic solution interface which constitutes a model of the anodic part of a fuel cell is studied by infrared-visible sum frequency generation vibrational spectroscopy. Methanol dissociative adsorption leads to CO poisoning of the Pt electrode surfaces. The structure of the CO/Pt( hkl) interface depends strongly on the orientation of the surface electrode.

Ultra-fine Pt nanoparticles on graphene aerogel as a porous electrode with high stability for microfluidic methanol fuel cell

NASA Astrophysics Data System (ADS)

Kwok, Y. H.; Tsang, Alpha C. H.; Wang, Yifei; Leung, Dennis Y. C.

2017-05-01

Platinum-decorated graphene aerogel as a porous electrode for flow-through direct methanol microfluidic fuel cell is introduced. Ultra-fine platinum nanoparticles with size ranged from diameter 1.5 nm-3 nm are evenly anchored on the graphene nanosheets without agglomeration. The electrode is characterized by scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. Catalytic activity is confirmed by cyclic voltammetry. The electroactive surface area and catalytic activity of platinum on graphene oxide (Pt/GO) are much larger than commercial platinum on carbon black (Pt/C). A counterflow microfluidic fuel cell is designed for contrasting the cell performance between flow-over type and flow-through type electrodes using Pt/C on carbon paper and Pt/GO, respectively. The Pt/GO electrode shows 358% increment in specific power compared with Pt/C anode. Apart from catalytic activity, the effect of porous electrode conductivity to cell performance is also studied. The conductivity of the porous electrode should be further enhanced to achieve higher cell performance.

Improvement of High-Temperature Stability of Al₂O₃/Pt/ZnO/Al₂O₃ Film Electrode for SAW Devices by Using Al₂O₃ Barrier Layer.

PubMed

Liu, Xingpeng; Peng, Bin; Zhang, Wanli; Zhu, Jun; Liu, Xingzhao; Wei, Meng

2017-12-01

In order to develop film electrodes for the surface acoustic wave (SAW) devices operating in harsh high-temperature environments, novel Al₂O₃/Pt/ZnO/Al₂O₃ multilayered film electrodes were prepared by laser molecular beam epitaxy (LMBE) at 150 °C. The first Al₂O₃ layer was used as a barrier layer to prevent the diffusion of Ga, La, and Si atoms from the La₃Ga₅SiO 14 (LGS) substrate to the film electrode and thus improved the crystalline quality of ZnO and Pt films. It was found that the resistance of the Al₂O₃/Pt/ZnO/Al₂O₃ electrode did not vary up to a temperature of 1150 °C, suggesting a high reliability of electrode under harsh high-temperature environments. The mechanism of the stable resistance of the Al₂O₃/Pt/ZnO/Al₂O₃ film electrodes at high temperature was investigated by analyzing its microstructure. The proposed Al₂O₃/Pt/ZnO/Al₂O₃ film electrode has great potential for application in high-temperature SAW devices.

Improving the electrical contact at a Pt/TiO2 nanowire interface by selective application of focused femtosecond laser irradiation

NASA Astrophysics Data System (ADS)

Xing, Songling; Lin, Luchan; Zou, Guisheng; Liu, Lei; Peng, Peng; Wu, Aiping; Duley, Walter W.; Zhou, Y. Norman

2017-10-01

In this paper, we show that tightly focused femtosecond laser irradiation is effective in improving nanojoining of an oxide nanowire (NW) (TiO2) to a metal electrode (Pt), and how this process can be used to modify contact states. Enhanced chemical bondings are created due to localized plasmonically enhanced optical absorption at the Pt/TiO2 interface as confirmed by finite element simulations of the localized field distribution during irradiation. Nano Auger electron spectroscopy shows that the resulting heterojunction is depleted in oxygen, suggesting that a TiO2-x layer is formed between the Pt electrode and the TiO2 NW. The presence of this redox layer at the metal/oxide interface plays an important role in decreasing the Schottky barrier height and in facilitating chemical bonding. After laser irradiation at the cathode for 10 s at a fluence of 5.02 mJ cm-2, the Pt/TiO2 NW/Pt structure displays different electrical properties under forward and reverse bias voltage, respectively. The creation of this asymmetric electrical characteristic shows the way in which modification of the electronic interface by laser engineering can replace the electroforming process in resistive switching devices and how it can be used to control contact states in a metal/oxide interface.

Improving the electrical contact at a Pt/TiO2 nanowire interface by selective application of focused femtosecond laser irradiation.

PubMed

Xing, Songling; Lin, Luchan; Zou, Guisheng; Liu, Lei; Peng, Peng; Wu, Aiping; Duley, Walter W; Zhou, Y Norman

2017-10-06

In this paper, we show that tightly focused femtosecond laser irradiation is effective in improving nanojoining of an oxide nanowire (NW) (TiO 2 ) to a metal electrode (Pt), and how this process can be used to modify contact states. Enhanced chemical bondings are created due to localized plasmonically enhanced optical absorption at the Pt/TiO 2 interface as confirmed by finite element simulations of the localized field distribution during irradiation. Nano Auger electron spectroscopy shows that the resulting heterojunction is depleted in oxygen, suggesting that a TiO 2-x layer is formed between the Pt electrode and the TiO 2 NW. The presence of this redox layer at the metal/oxide interface plays an important role in decreasing the Schottky barrier height and in facilitating chemical bonding. After laser irradiation at the cathode for 10 s at a fluence of 5.02 mJ cm -2 , the Pt/TiO 2 NW/Pt structure displays different electrical properties under forward and reverse bias voltage, respectively. The creation of this asymmetric electrical characteristic shows the way in which modification of the electronic interface by laser engineering can replace the electroforming process in resistive switching devices and how it can be used to control contact states in a metal/oxide interface.

Diamond nanoparticles as a support for Pt and PtRu catalysts for direct methanol fuel cells.

PubMed

La-Torre-Riveros, Lyda; Guzman-Blas, Rolando; Méndez-Torres, Adrián E; Prelas, Mark; Tryk, Donald A; Cabrera, Carlos R

2012-02-01

Diamond in nanoparticle form is a promising material that can be used as a robust and chemically stable catalyst support in fuel cells. It has been studied and characterized physically and electrochemically, in its thin film and powder forms, as reported in the literature. In the present work, the electrochemical properties of undoped and boron-doped diamond nanoparticle electrodes, fabricated using the ink-paste method, were investigated. Methanol oxidation experiments were carried out in both half-cell and full fuel cell modes. Platinum and ruthenium nanoparticles were chemically deposited on undoped and boron doped diamond nanoparticles through the use of NaBH(4) as reducing agent and sodium dodecyl benzene sulfonate (SDBS) as a surfactant. Before and after the reduction process, samples were characterized by electron microscopy and spectroscopic techniques. The ink-paste method was also used to prepare the membrane electrode assembly with Pt and Pt-Ru modified undoped and boron-doped diamond nanoparticle catalytic systems, to perform the electrochemical experiments in a direct methanol fuel cell system. The results obtained demonstrate that diamond supported catalyst nanomaterials are promising for methanol fuel cells.

Reproducible fabrication of stable small nano Pt with high activity for sensor applications.

PubMed

Ye, Pingping; Guo, Xiaoyu; Liu, Guiting; Chen, Huifen; Pan, Yuxia; Wen, Ying; Yang, Haifeng

2013-07-26

Pt nanoparticles with an average size of 2-3 nm in diameter were reproducibly synthesized by reduction of H₂PtCl₆ solution containing inositol hexaphosphate (IP₆) as the stabilizing agent. Single crystals with Pt(111) faces of the resulting cubic nanoparticles were revealed by the electron diffraction pattern. The PtNPs-IP₆ nanoparticles were used to modify an electrode as a nonenzymatic sensor for H₂O₂ detection, exhibiting a fast response and high sensitivity. A low detection limit of 2.0 × 10⁻⁷ M (S/N = 3) with two linear ranges between 2.4 × 10⁻⁷ and 1.3 × 10⁻³ M (R² = 0.9987) and between 1.3 × 10⁻³ and 1.3 × 10⁻² M (R² = 0.9980) was achieved. The attractive electrochemical performance of PtNPs-IP₆ enables it to be employed as a promising material for the development of Pt-based analytical systems and other applications.

Stretchable Platinum Network-Based Transparent Electrodes for Highly Sensitive Wearable Electronics.

PubMed

Wang, Yuting; Cheng, Jing; Xing, Yan; Shahid, Muhammad; Nishijima, Hiroki; Pan, Wei

2017-07-01

A platinum network-based transparent electrode has been fabricated by electrospinning. The unique nanobelt structured electrode demonstrates low sheet resistance (about 16 Ω sq -1 ) and high transparency of 80% and excellent flexibility. One of the most interesting demonstrations of this Pt nanobelt electrode is its excellent reversibly resilient characteristic. The electric conductivity of the flexible Pt electrode can recover to its initial value after 160% extending and this performance is repeatable and stable. The good linear relationship between the resistance and strain of the unique structured Pt electrode makes it possible to assemble a wearable high sensitive strain sensor. Present reported Pt nanobelt electrode also reveals potential applications in electrode for flexible fuel cells and highly transparent ultraviolet (UV) sensors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption and desorption characteristics of gradient distributed Bragg reflector porous silicon layers.

PubMed

Um, Sungyong; Lee, Sung Gi; Woo, Hee-Gweon; Cho, Sungdong; Sohn, Honglae

2013-01-01

Adsorption and desorption characteristics of gradient distributed Bragg reflector (DBR) porous silicon (PSi) were investigated under the exposure of organic vapors. Gradient DBR PSi whose average pore size decreased as the lateral distance from the Pt electrode increased was generated by using an asymmetric etching configuration. The reflection resonances were measured as a function of lateral distance from a point closest to the plate Pt electrode to a position on the silicon surface. Two types of gradient DBR PSi (H- and HO-terminated gradient DBR PSi) were used in this study. The detection of volatile organic compounds (VOCs) using the gradient DBR PSi had been achieved. When the vapor of VOCs condensed in the nanopores, the gradient DBR PSi modified with hydrophobic and hydrophilic functionality exhibited different pore adsorption and desorption characteristics.

Preferential growth and enhanced dielectric properties of Ba0.7Sr0.3TiO3 thin films with preannealed Pt bottom electrode

NASA Astrophysics Data System (ADS)

Zhu, Xiaohong; Defaÿ, Emmanuel; Aïd, Marc; Ren, Yinjuan; Zhang, Caiyun; Zhu, Jiliang; Zhu, Jianguo; Xiao, Dingquan

2013-03-01

Ba0.7Sr0.3TiO3 (BST) thin films, about 100 nm in thickness, were prepared on unannealed and 700 °C-preannealed Pt bottom electrodes by the ion beam sputtering and post-deposition annealing method. It was found that the preannealed Pt layer has a more compact structure, making it not only a bottom electrode but also a good template for high-quality BST thin film growth. The BST films deposited on preannealed Pt bottom electrodes showed (0 0 l)-preferred orientation, dense and uniform microstructure with no intermediate phase formed at the film/electrode interface, and thus enhanced dielectric properties. As a result, the typical relative dielectric constant and tunability (under a dc electric field of 1 MV cm-1) reach 180 and 50.1%, respectively, for the BST thin films with preannealed Pt bottom electrodes, which are significantly higher than those (166 and 41.3%, respectively) for the BST thin films deposited on unannealed Pt bottom electrodes.

Nanopatterned conductive polymer films as a Pt, TCO-free counter electrode for low-cost dye-sensitized solar cells.

PubMed

Kwon, Jeong; Ganapathy, Veerappan; Kim, Young Hun; Song, Kyung-Deok; Park, Hong-Gyu; Jun, Yongseok; Yoo, Pil J; Park, Jong Hyeok

2013-09-07

A low-cost nanopatterned highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) thin film was fabricated on a flexible plastic substrate via a chemical polymerization method combined with a nanoimprinting technique and used as a platinum (Pt), TCO-free counter electrode for dye-sensitized solar cells (DSSCs). The catalytic properties of the nanopatterned PEDOT as the counter electrode in DSSCs were studied using cyclic voltammetry, J-V measurements, impedance spectroscopy, and finite-difference time-domain (FDTD) simulations. The nanopatterned PEDOT counter electrodes exhibit better functionality as a counter electrode for tri-iodide reduction when compared to non-patterned PEDOT-based counter electrodes. The Pt and TCO-free DSSCs with a nanopatterned PEDOT-based counter electrode exhibited a power conversion efficiency of 7.1% under one sunlight illumination (100 mW cm(-2)), which is comparable to that of conventional DSSCs with standard platinum Pt/FTO paired counter electrodes. The ability to modulate catalytic functionality with changes in nanoscale morphology represents a promising route for developing new counter electrodes of Pt and TCO-free DSSCs.

Enhanced dielectric constant and fatigue-resistance of PbZr0.4Ti0.6O3 capacitor with magnetic intermetallic FePt top electrode

NASA Astrophysics Data System (ADS)

Liu, B. T.; Zhao, J. W.; Li, X. H.; Zhou, Y.; Bian, F.; Wang, X. Y.; Zhao, Q. X.; Wang, Y. L.; Guo, Q. L.; Wang, L. X.; Zhang, X. Y.

2010-06-01

Both FePt/PbZr0.4Ti0.6O3(PZT)/Pt and Pt/PZT/Pt ferroelectric capacitors have been fabricated on Si substrates. It is found that up to 109 switching cycles, the FePt/PZT/Pt capacitor, measured at 50 kHz, with polarization decreased by 57%, is superior to the Pt/PZT/Pt capacitor by 82%, indicating that an intermetallic FePt top electrode can also improve the fatigue-resistance of a PZT capacitor. Maximum dielectric constants are 980 and 770 for PZT capacitors with FePt and Pt, respectively. This is attributed to the interface effect between PZT film and the top electrode since the interfacial capacitance of FePt/PZT is 3.5 times as large as that of Pt/PZT interface.

Supported noble metals on hydrogen-treated TiO2 nanotube arrays as highly ordered electrodes for fuel cells.

PubMed

Zhang, Changkun; Yu, Hongmei; Li, Yongkun; Gao, Yuan; Zhao, Yun; Song, Wei; Shao, Zhigang; Yi, Baolian

2013-04-01

Hydrogen-treated TiO2 nanotube (H-TNT) arrays serve as highly ordered nanostructured electrode supports, which are able to significantly improve the electrochemical performance and durability of fuel cells. The electrical conductivity of H-TNTs increases by approximately one order of magnitude in comparison to air-treated TNTs. The increase in the number of oxygen vacancies and hydroxyl groups on the H-TNTs help to anchor a greater number of Pt atoms during Pt electrodeposition. The H-TNTs are pretreated by using a successive ion adsorption and reaction (SIAR) method that enhances the loading and dispersion of Pt catalysts when electrodeposited. In the SIAR method a Pd activator can be used to provide uniform nucleation sites for Pt and leads to increased Pt loading on the H-TNTs. Furthermore, fabricated Pt nanoparticles with a diameter of 3.4 nm are located uniformly around the pretreated H-TNT support. The as-prepared and highly ordered electrodes exhibit excellent stability during accelerated durability tests, particularly for the H-TNT-loaded Pt catalysts that have been annealed in ultrahigh purity H2 for a second time. There is minimal decrease in the electrochemical surface area of the as-prepared electrode after 1000 cycles compared to a 68 % decrease for the commercial JM 20 % Pt/C electrode after 800 cycles. X-ray photoelectron spectroscopy shows that after the H-TNT-loaded Pt catalysts are annealed in H2 for the second time, the strong metal-support interaction between the H-TNTs and the Pt catalysts enhances the electrochemical stability of the electrodes. Fuel-cell testing shows that the power density reaches a maximum of 500 mWcm(-2) when this highly ordered electrode is used as the anode. When used as the cathode in a fuel cell with extra-low Pt loading, the new electrode generates a specific power density of 2.68 kWg(Pt) (-1) . It is indicated that H-TNT arrays, which have highly ordered nanostructures, could be used as ordered electrode supports. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral permselectivity in surface-modified nanoporous opal films.

PubMed

Cichelli, Julie; Zharov, Ilya

2006-06-28

Nanoporous 7 mum thin opal films comprising 35 layers of 200 nm diameter SiO2 spheres were assembled on Pt electrodes and modified with chiral selector moieties on the silica surface. Diffusion of chiral redox species through the opals was studied by cyclic voltammetry. The chiral opal films demonstrate high selectivity for transport of one enantiomer over the other. This chiral permselectivity is attributed to the surface-facilitated transport utilizing noncovalent interactions between the chiral permeant molecules and surface-bound chiral selectors.

Characterization of hierarchical α-MoO3 plates toward resistive heating synthesis: electrochemical activity of α-MoO3/Pt modified electrode toward methanol oxidation at neutral pH

NASA Astrophysics Data System (ADS)

Filippo, Emanuela; Baldassarre, Francesca; Tepore, Marco; Guascito, Maria Rachele; Chirizzi, Daniela; Tepore, Antonio

2017-05-01

The growth of MoO3 hierarchical plates was obtained by direct resistive heating of molybdenum foils at ambient pressure in the absence of any catalysts and templates. Plates synthesized after 60 min resistive heating typically grow in an single-crystalline orthorhombic structure that develop preferentially in the [001] direction, and are characterized by high resolution transmission electron microscopy, selected area diffraction pattern and Raman-scattering measurements. They are about 100-200 nm in thickness and a few tens of micrometers in length. As heating time proceeds to 80 min, plates of α-MoO3 form a branched structure. A more attentive look shows that primary plates formed at until 60 min could serve as substrates for the subsequent growth of secondary belts. Moreover, a full electrochemical characterization of α-MoO3 plates on platinum electrodes was done by cyclic voltammetric experiments, at pH 7 in phosphate buffer, to probe the activity of the proposed composite material as anode to methanol electro-oxidation. Reported results indicate that Pt MoO3 modified electrodes are appropriate to develop new an amperometric non-enzymatic sensor for methanol as well as to make anodes suitable to be used in direct methanol fuel cells working at neutral pH.

Growth mechanism of surface roughed platinum nanowires through electrodeposition current control and their electrochemical applications

NASA Astrophysics Data System (ADS)

Ruan, Dajiang

The aim of this work is to investigate the effect of current density on the grain size and surface morphology of electrodeposited platinum nanowires and their applications. Platinum (Pt) nanowires were fabricated by a galvanostatic electrodeposition method in a porous anodic alumina oxide (AAO) template with different current densities. Both direct current and pulse current electrodeposition were used to synthesize the Pt nanowires. The grain size and surface morphology of the Pt nanowires were studied by field emission scanning electron microscopy (FE-SEM), transmission electron microcopy (TEM) and X-ray diffraction (XRD). The experimental results showed that the current density was the key factor to control the surface roughness. The surface of the Pt nanowires became rougher and the grain sizes were increased by increasing the current densities. From the experimental results, a growth mechanism of Pt nanowires based on progressive nucleation and crystallization was proposed in order to find out the relationship between the surface morphology and current density. The electrochemical properties and catalytic activities of these surface roughed Pt nanowires were investigated in the detection of H20 2 and for the methanol oxidation. Cyclic voltammograms of Pt nanowire modified electrodes were obtained using a potentiostat, which showed that rougher Pt nanowires have higher response and better activity than that of smooth nanowires. For H202 detection, the effect of scan rate and H202 concentration were studied and it was found that the peak current for hydrogen peroxide reduction became larger with the increasing of either scan rate or H202 concentration. It can be inferred that the process of electrocatalytic hydrogen peroxide reduction may be controlled by diffusion of hydrogen peroxide and the Pt nanowire modified glassy carbon electrode (GCE) is well suited for the detection of H202. From the relationship between the peak current and square root of scan rates for methanol oxidation, it can be inferred that the process of electrocatalytic methanol oxidation was controlled by diffusion of methanol. To understand the effect of the morphological feature on the electrocatalytic activity of the Pt nanowire catalysts, the electrochemically active surface area (ECSA) as a function of deposited current density was investigated, which suggests that Pt nanowire catalysts deposited at highest current density had the most ECSA surface morphology of the Pt nanowires. The chronoamperometric curves and electrochemical impedance spectroscopy (EIS) results confirmed that the Pt nanowire catalyst synthesized at higher current density possessed longer durability and gave more efficient electrochemical performance.

Graphitized carbon nanofiber-Pt nanoparticle hybrids as sensitive tool for preparation of screen printing biosensors. Detection of lactate in wines and ciders.

PubMed

Loaiza, Oscar A; Lamas-Ardisana, Pedro J; Añorga, Larraitz; Jubete, Elena; Ruiz, Virginia; Borghei, Maryam; Cabañero, Germán; Grande, Hans J

2015-02-01

This work describes the fabrication of a new lactate biosensor. The strategy is based on the use of a novel hybrid nanomaterial for amperometric biosensors i.e. platinum nanoparticles (PtNps) supported on graphitized carbon nanofibers (PtNps/GCNF) prepared by chemical reduction of the Pt precursor at GCNF surfaces. The biosensors were constructed by covalent immobilization of lactate oxidase (LOx) onto screen printed carbon electrodes (SPCEs) modified with PtNps (PtNps/GCNF-SPCEs) using polyethyleneimine (PEI) and glutaraldehyde (GA). Experimental variables concerning both the biosensor design and the detection process were investigated for an optimal analytical performance. Lactate biosensors show good reproducibility (RSD 4.9%, n=10) and sensitivity (41,302±546) μA/Mcm(2), with a good limit of detection (6.9μM). Covalent immobilization of the enzyme allows the reuse of the biosensor for several measurements, converting them in a cheap alternative to the solid electrodes. The long-term stability of the biosensors was also evaluated. 90% of the signal was kept after 3months of storage at room temperature (RT), while 95% was retained after 18months at -20°C. These results demonstrate that the method provides sensitive electrochemical lactate biosensors where the stability of the enzymatic activity can be preserved for a long period of time in adequate storage conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

Disposable sensor based on enzyme-free Ni nanowire array electrode to detect glutamate.

PubMed

Jamal, Mamun; Hasan, Maksudul; Mathewson, Alan; Razeeb, Kafil M

2013-02-15

Enzyme free electrochemical sensor platform based on a vertically aligned nickel nanowire array (NiNAE) and Pt coated nickel nanowire array (Pt/NiNAE) have been developed to detect glutamate. Morphological characterisation of Ni electrodes was carried out using scanning and transmission electron microscopy combined with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and amperometry were used to evaluate the catalytic activity of the NiNAE and the Pt/NiNAE for glutamate. It has been found that both NiNAE and Pt/NiNAE electrodes showed remarkably enhanced electrocatalytic activity towards glutamate compared to planar Ni electrodes, and showed higher catalytic activity when compared to other metallic nanostructure electrodes such as gold nanowire array electrodes (AuNAE) and Pt coated gold nanowire array electrode (Pt/AuNAE). The sensitivity of NiNAE and Pt/NiNAE has been found to be 65 and 96 μA mM(-1) cm(-2), respectively, which is approximately 6 to 9 times higher than the state of the art glutamate sensor. Under optimal detection conditions, the as prepared sensors exhibited linear behaviour for glutamate detection in the concentration up to 8mM for both NiNAE and Pt/NiNAE with a limit of detection of 68 and 83 μM, respectively. Experimental results show that the vertically aligned ordered nickel nanowire array electrode (NiNAE) has significant promise for fabricating cost effective, enzyme-less, sensitive, stable and selective sensor platform. Copyright © 2012 Elsevier B.V. All rights reserved.

Porous WO3/graphene/polyester textile electrode materials with enhanced electrochemical performance for flexible solid-state supercapacitors.

PubMed

Jin, Li-Na; Liu, Ping; Jin, Chun; Zhang, Jia-Nan; Bian, Shao-Wei

2018-01-15

In this work, a flexible and porous WO 3 /grapheme/polyester (WO 3 /G/PT) textile electrode was successfully prepared by in situ growing WO 3 on the fiber surface inside G/PT composite fabrics. The unique electrode structure facilitates to enhance the energy storage performance because the 3D conductive network constructed by the G/PT increase the electron transportation rate, nanotructured WO 3 exposed enhanced electrochemically active surface area and the hierarchically porous structure improved the electrolyte ion diffusion rate. The optimized WO 3 /G/PT textile electrode exhibited good electrochemical performance with a high areal capacitance of 308.2mFcm -2 at a scan rate of 2mVs -1 and excellent cycling stability. A flexible asymmetric supercapacitor (ASC) device was further fabricated by using the WO 3 /G/PT electrode and G/PT electrode, which exhibited a good specific capacitance of 167.6mFcm -3 and high energy density of 60μWhcm -3 at the power density of 2320 μWcm -3 . Copyright © 2017 Elsevier Inc. All rights reserved.

First-principles calculations of perpendicular magnetic anisotropy for spintronic applications

NASA Astrophysics Data System (ADS)

Ansarino, Masoud; Ravan, Bahram Abedi

2017-01-01

A combination of density functional theory and non-equilibrium Green’s function methods are used to simulate spin-dependent electronic transport in monatomic Au-nanowires sandwiched between ferromagnetic electrodes. Electrodes of the junction are in turn composed of tetragonal FeCo, FePd and FePt alloys. Magnetic anisotropy energies of the electrodes are calculated for different values of the c/a ratios of the electrode lattice constants and it is shown that at c/a = 1.05, the FePt electrodes gain a relatively large amount of magnetic anisotropy energy (MAE). Hence, it is concluded that the ferromagnetic FePt alloy can be used as a suitable type of electrode for applications in perpendicular magnetic tunnel junctions (MTJs). We observe that increasing the c/a ratio leads to notable improvements in the spin filtering of the FeCo and FePd MTJs while it only has a slight effect on the filtering of the FePt MTJ. Later, we show that by removing the interfacial Pt atoms of the FePt MTJ, we are able to enhance its filtering property.

Electrocatalytic performance of Pt nanoparticles sputter-deposited on indium tin oxide toward methanol oxidation reaction: The particle size effect

NASA Astrophysics Data System (ADS)

Ting, Chao-Cheng; Chao, Chih-Hsuan; Tsai, Cheng Yu; Cheng, I.-Kai; Pan, Fu-Ming

2017-09-01

We sputter-deposited Pt nanoparticles with an average size ranging from 2.0 nm to 8.5 nm on the indium-tin oxide (ITO) glass substrate, and studied the effect of the size of Pt nanoparticles on electrocatalytic activity of the Pt/ITO electrode toward methanol oxidation reaction (MOR) in acidic solution. X-ray photoelectron spectroscopy (XPS) reveals an interfacial oxidized Pt layer present between Pt nanoparticles and the ITO substrate, which may modify the surface electronic structure of Pt nanoparticles and thus influences the electrocatalytic properties of the Pt catalyst toward MOR. According to electrochemical analyses, smaller Pt nanoparticles exhibit slower kinetics for CO electrooxidation and MOR. However, a smaller particle size enables better CO tolerance because the bifunctional mechanism is more effective on smaller Pt nanoparticles. The electrocatalytic activity decays rapidly for Pt nanoparticles with a size smaller than 3 nm and larger than 8 nm. The rapid activity decay is attributed to Pt dissolution for smaller nanoparticles and to CO poisoning for larger ones. Pt nanoparticles of 5-6 nm in size loaded on ITO demonstrate a greatly improved electrocatalytic activity and stability compared with those deposited on different substrates in our previous studies.

Impact of ultra-low Pt loadings on the performance of anode/cathode in a proton-exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Billy, E.; Maillard, F.; Morin, A.; Guetaz, L.; Emieux, F.; Thurier, C.; Doppelt, P.; Donet, S.; Mailley, S.

This study focuses on the elaboration of PEMFC electrodes containing ultra-low platinum (Pt) loadings by direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD). DLI-MOCVD offers a large number of advantages for the elaboration of model PEMFC electrodes. First, by using different metal precursors or elaboration temperature, the size of the Pt nanoparticles and thus the intrinsic catalytic activity can easily be tailored in the nanometer range. In this work, Pt nanoparticles (1-5 nm) with remarkable low degree of agglomeration and uniform distribution were deposited onto the microporous side of a commercial gas-diffusion layer (GDL). Second, reduction of the Pt loading is made possible by varying the Pt deposition time and its influence of the cell performance can be extracted without variation of the thickness of the catalytic layer (in previous studies, a decrease of the catalyst utilization was observed when increasing the Pt loading, i.e. the thickness of the catalytic layer (CL)). The electrocatalytic activity of home-made Pt nanoparticles elaborated by DLI-MOCVD was measured in liquid electrolyte or in complete fuel cell operating on H 2/O 2 or H 2/air and compared vs. that of a commercially available electrode containing 500 μg Pt cm -2 (Pt Ref500). At the cathode, the performance of the electrodes containing 104-226 μg of Pt per cm 2 of electrode compares favorably with that of the Pt Ref500 in H 2/O 2 conditions. In H 2/air conditions, additional mass-transport losses are detected in the low-current density region but the high effectiveness of our electrodes improves the performance in the high-current density region. At the anode, the Pt loading can be reduced to 35 μg Pt cm -2 without any voltage loss in agreement with previous observations.

Influence of different nanoparticles on electrochemical behavior of glucose biosensor

NASA Astrophysics Data System (ADS)

Nenkova, R. D.; Ivanov, Y. L.; Godjevargova, T. I.

2017-02-01

The influence of nanosized particles on the glucose oxidase loading and the performance of amperometric glucose bionsensors were studied. Four enzyme electrodes (Pt/PAN/GOD, Pt/PAN/NZ/GOD, Pt/PAN/NZ/MNP/GOD, Pt/PAN/NZ/MWNT/GOD) were prepared by cross-linking of glucose oxidase (GOD) on nanocomposite material. Nanocomposites were prepared by entrapping nanozeolite (NZ), multiwalled carbon nanotubes (MWNT) and magnetic nanoparticles (MNP) in polyacrylonitrile (PAN) film. Cyclic voltammetric kinetic studies have been carried out with the four biosensors and the surface concentration of the adsorbed electroactive species on the electrodes was estimated. The highest enzyme concentration on the electrode surface corresponded to the electrodes prepared by nanozeolite separate (Pt/PAN/NZ/GOD) and combined with multi-walled carbon nanotubes (Pt/PAN/NZ/MWNT/GOD). The sensitivity of these two biosensors was the highest and that is in accordance with the greater amount of the adsorbed electroactive species on the electrodes (0.373 mol.cm-2). This was indication that a good synergistic effect happened when MWNTs and NZ were combined and these greatly improve the electron transfer ability of the sensor interface. Amperometric measurement of the two glucose oxidase electrodes (Pt/PAN/NZ/GOD and Pt/PAN/NZ/MWNT/GOD) with best results was carried out. The linear concentration interval of the Pt/PAN/NZ/MWNT/GOD biosensor was up to 3 mM, the detection limit - 0.02 mM glucose and the storage stability - 81% of its initial current response after 30 days.

Fabrication of SrTiO3 Layer on Pt Electrode for Label-Free Capacitive Biosensors

PubMed Central

Carapella, Giovanni; Pilloton, Roberto; Di Matteo, Marisa

2018-01-01

Due to their interesting ferroelectric, conductive and dielectric properties, in recent years, perovskite-structured materials have begun to attract increasing interest in the biosensing field. In this study, a strontium titanate perovskite layer (SrTiO3) has been synthesized on a platinum electrode and exploited for the development of an impedimetric label-free immunosensor for Escherichia coli O157:H7 detection. The electrochemical characterization of the perovskite-modified electrode during the construction of the immunosensor, as well as after the interaction with different E. coli O157:H7 concentrations, showed a reproducible decrease of the total capacitance of the system that was used for the analytical characterization of the immunosensor. Under optimized conditions, the capacitive immunosensor showed a linear relationship from to 1 to 7 log cfu/mL with a low detection limit of 1 log cfu/mL. Moreover, the atomic force microscopy (AFM) technique underlined the increase in roughness of the SrTiO3-modified electrode surface after antibody immobilization, as well as the effective presence of cells with the typical size of E. coli. PMID:29547521

Nanotubular MnO2/graphene oxide composites for the application of open air-breathing cathode microbial fuel cells.

PubMed

Gnana Kumar, G; Awan, Zahoor; Suk Nahm, Kee; Xavier, J Stanley

2014-03-15

Nanotubular shaped α-MnO2/graphene oxide nanocomposites were synthesized via a simple, cost and time efficient hydrothermal method. The growth of hollow structured MnO2 nanotubes preferentially occurred along the [001] direction as evidenced from the morphological and structural characterizations. The tunnels of α-MnO2 nanotubes easily accommodated the molecular oxygen and exhibited excellent catalytic activity towards the oxygen reduction reaction over the rod structure and was further enhanced with the effective carbon support graphene oxide. The MnO2 nanotubes/graphene oxide nanocomposite modified electrode exhibited a maximum power density of 3359 mW m(-2) which is 7.8 fold higher than that of unmodified electrode and comparable with the Pt/C modified electrode. The microbial fuel cell equipped with MnO2 nanotubes/graphene oxide nanocomposite modified cathode exhibited quick start up and excellent durability over the studied electrodes and is attributed to the high surface area and number of active sites. These findings not only provide the fundamental studies on carbon supported low-dimensional transition-metal oxides but also open up the new possibilities of their applications in green energy devices. © 2013 Elsevier B.V. All rights reserved.

Electrical properties of Bi2Mg2/3Nb4/3O7 (BMN) pyrochlore thin films deposited on Pt and Cu metal at low temperatures for embedded capacitor applications

NASA Astrophysics Data System (ADS)

Xian, Cheng-Ji; Park, Jong-Hyun; Ahn, Kyung-Chan; Yoon, Soon-Gil; Lee, Jeong-Won; Kim, Woon-Chun; Lim, Sung-Taek; Sohn, Seung-Hyun; Moon, Jin-Seok; Jung, Hyung-Mi; Lee, Seung-Eun; Lee, In-Hyung; Chung, Yul-Kyo; Jeon, Min-Ku; Woo, Seong-Ihl

2007-01-01

200-nm-thick BMN films were deposited on Pt /TiO2/SiO2/Si and Cu /Ti/SiO2/Si substrates at various temperatures by pulsed laser deposition. The dielectric constant and capacitance density of the films deposited on Pt and Cu electrodes show similar tendency with increasing deposition temperature. On the other hand, dielectric loss of the films deposited on Cu electrode varies from 0.7% to 1.3%, while dielectric loss of films on Pt constantly shows 0.2% even though the deposition temperature increases. The low value of breakdown strength in BMN films on Pt compared to films deposited on Cu electrode was attributed to the increase of surface roughness by the formation of secondary phases at interface between BMN films and Pt electrodes.

Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

NASA Astrophysics Data System (ADS)

Liu, Wenlong; Liu, Yen-Yu; Do, Jing-Shan; Li, Jing

2016-12-01

Room temperature NH3 gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH3 gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06 μA ppm-1 cm-2 .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

Design and development of amperometric biosensor for the detection of lead and mercury ions in water matrix-a permeability approach.

PubMed

Gumpu, Manju Bhargavi; Krishnan, Uma Maheswari; Rayappan, John Bosco Balaguru

2017-07-01

Intake of water contaminated with lead (Pb 2+ ) and mercury (Hg 2+ ) ions leads to various toxic effects and health issues. In this context, an amperometric urease inhibition-based biosensor was developed to detect Pb 2+ and Hg 2+ ions in water matrix. The modified Pt/CeO 2 /urease electrode was fabricated by immobilizing CeO 2 nanoparticles and urease using a semi-permeable adsorption layer of nafion. With urea as a substrate, urease catalytic activity was examined through cyclic voltammetry. Further, maximum amperometric inhibitive response of the modified Pt/CeO 2 /urease electrode was observed in the presence of Pb 2+ and Hg 2+ ions due to the urease inhibition at specific potentials of -0.03 and 0 V, respectively. The developed sensor exhibited a detection limit of 0.019 ± 0.001 μM with a sensitivity of 89.2 × 10 -3  μA μM -1 for Pb 2+ ions. A detection limit of 0.018 ± 0.003 with a sensitivity of 94.1 × 10 -3  μA μM -1 was achieved in detecting Hg 2+ ions. The developed biosensor showed a fast response time (<1 s) with a linear range of 0.5-2.2 and 0.02-0.8 μM for Pb 2+ and Hg 2+ ions, respectively. The modified electrode offered a good stability for 20 days with a good repeatability and reproducibility. The developed sensor was used to detect Pb 2+ and Hg 2+ ions contaminating Cauvery river water and the observed results were in good co-ordination with atomic absorption spectroscopic data.

Fabrication of three-dimensional buckypaper catalyst layer with Pt nanoparticles supported on polyelectrolyte functionalized carbon nanotubes for proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Zhu, Shiyao; Zheng, Junsheng; Huang, Jun; Dai, Ningning; Li, Ping; Zheng, Jim P.

2018-07-01

Polyelectrolyte poly(diallyldimethylammonium chloride) (PDDA) functionalized carbon nanotubes (CNTs) supported Pt electrocatalyst was synthesized as a substitute for commonly used Pt/C and Pt/CNTs (modified by harsh acid-oxidation treatment) catalysts. In addition, this catalyst was fabricated as the cathode catalyst layer (CL) with a unique double-layered structure for proton exchange membrane fuel cells (PEMFCs). Thermogravimetric analysis shows an enhanced thermal stability of Pt/PDDA-CNTs. The Pt/PDDA-CNTs catalyst with an average Pt particle size of ∼3.1 nm exhibits the best electrocatalytic activity and a significantly enhanced electrochemical stability. Scanning electron microscope, energy dispersive spectrometer and mercury intrusion porosimetry results demonstrate the gradient distribution of Pt content and pore size along the thickness of buckypaper catalyst layer (BPCL). The accelerated degradation test results of BPCLs indicate that this gradient structure can ensure a high Pt utilization in the BPCLs (up to 90%) and further improve the catalyst durability. In addition, the membrane electrode assembly (MEA) fabricated with cathode BPCL-PDDA shows the best single cell performance and long-term stability, and a reduction of Pt loading can be achieved. The feasibility of BPCL for improving the Pt utilization is also demonstrated by the cathode cyclic voltammetry in MEA.

Development of a DNA Sensor Based on Nanoporous Pt-Rich Electrodes

NASA Astrophysics Data System (ADS)

Van Hao, Pham; Thanh, Pham Duc; Xuan, Chu Thi; Hai, Nguyen Hoang; Tuan, Mai Anh

2017-06-01

Nanoporous Pt-rich electrodes with 72 at.% Pt composition were fabricated by sputtering a Pt-Ag alloy, followed by an electrochemical dealloying process to selectively etch away Ag atoms. The surface properties of nanoporous membranes were investigated by energy-dispersive x-ray spectroscopy (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM), a documentation system, and a gel image system (Gel Doc Imager). A single strand of probe deoxyribonucleic acid (DNA) was immobilized onto the electrode surface by physical adsorption. The DNA probe and target hybridization were measured using a lock-in amplifier and an electrochemical impedance spectroscope (EIS). The nanoporous Pt-rich electrode-based DNA sensor offers a fast response time of 3.7 s, with a limit of detection (LOD) of 4.35 × 10-10 M of DNA target.

The electrochemistry of "solid/water" interfaces involved in PEM-H2O reactors: part I. The "Pt/water" interfaces.

PubMed

Wang, Qiang; Cha, Chuan-Sin; Lu, Juntao; Zhuang, Lin

2009-01-28

The nature and properties of Pt surfaces in contact with pure water in PEM-H2O reactors were mimetically studied by employing CV measurements with microelectrode techniques. These "Pt/water" interfaces were found to be electrochemically polarizable, and the local interfacial potential relative to reversible hydrogen electrode (RHE) potential in pure water is numerically the same as the potential value measured against a RHE in contact with PEM as the reference electrode. However, the structural parameters of the electric double layer at the "Pt/water" interfaces can be quite different from those at the "Pt/PEM" interfaces, and the kinetics of electrode processes could be seriously affected by the structure of electric double layer in pure water media. Besides, there is active diffusional flow of intermediates of electrode reactions between the "Pt/water" and the "Pt/PEM" interfaces, thus facilitating the active involvement of the "Pt/water" interfaces in the current-generation mechanism of PEM fuel cells and other types of PEM-H2O reactors.

Characterization of PZT Capacitor Structures with Various Electrode Materials Processed In-Situ Using AN Automated, Rotating Elemental Target, Ion Beam Deposition System

NASA Astrophysics Data System (ADS)

Gifford, Kenneth Douglas

Ferroelectric thin film capacitor structures containing lead zirconate titanate (PZT) as the dielectric, with the chemical formula Pb(rm Zr_{x }Ti_{1-x})O_3, were synthesized in-situ with an automated ion beam sputter deposition system. Platinum (Pt), conductive ruthenium oxide (RuO_2), and two types of Pt-RuO_2 hybrid electrodes were used as the electrode materials. The capacitor structures are characterized in terms of microstructure and electrical characteristics. Reduction or elimination of non-ferroelectric phases, that nucleate during PZT processing on Pt/TiO _2/MgO and RuO_2/MgO substrates, is achieved by reducing the thickness of the individually deposited layers and by interposing a buffer layer (~100-200A) of PbTiO _3 (PT) between the bottom electrode and the PZT film. Capacitor structures containing a Pt electrode exhibit poor fatigue resistance, irregardless of the PZT microstructure or the use of a PT buffer layer. From these results, and results from similar capacitors synthesized with sol-gel and laser ablation, PZT-based capacitor structures containing Pt electrodes are considered to be unsuitable for use in memory devices. Using a PT buffer layer, in capacitor structures containing RuO_2 top and bottom electrodes and polycrystalline, highly (101) oriented PZT, reduces or eliminates the nucleation of zirconium-titanium oxide, non-ferroelectric species at the bottom electrode interface during processing. This results in good fatigue resistance up to ~2times10^ {10} switching cycles. DC leakage current density vs. time measurements follow the Curie-von Schweidler law, J(t) ~ t^ {rm -n}. Identification of the high electric field current conduction mechanism is inconclusive. The good fatigue resistance, low dc leakage current, and excellent retention, qualifies the use of these capacitor structures in non-volatile random access (NVRAM) and dynamic random access (DRAM) memory devices. Excellent fatigue resistance (10% loss in remanent polarization up to ~2times10^ {10} switching cycles), low dc leakage current, and excellent retention are observed in capacitor structures containing polycrystalline PZT (exhibiting dominant (001) and (100) XRD reflections), a Pt-RuO_2 hybrid bottom electrode (Type IA), and an RuO _2 top electrode. These results, and electrical characterization results on capacitors containing co-deposited Pt-RuO_2 hybrid electrodes (Type II), show potential for application of these capacitor structures in NVRAM and DRAM memory devices.

Electrochemical quartz crystal microbalance analysis of the oxygen reduction reaction on Pt-based electrodes. Part 2: adsorption of oxygen species and ClO4(-) anions on Pt and Pt-Co alloy in HClO4 solutions.

PubMed

Omura, J; Yano, H; Tryk, D A; Watanabe, M; Uchida, H

2014-01-14

To gain deeper insight into the role of adsorbed oxygenated species in the O2 reduction reaction (ORR) kinetics on platinum and platinum-cobalt alloys for fuel cells, we carried out a series of measurements with the electrochemical quartz crystal microbalance (EQCM) and the rotating disk electrode (RDE) in acid solution. The effects of anion adsorption on the activities for the ORR were first assessed in HClO4 and HF electrolyte solutions at various concentrations. In our previous work (Part 1), we reported that the perchlorate anion adsorbs specifically on bulk-Pt, with a Frumkin-Temkin isotherm, that is, a linear relationship between Δm and log[HClO4]. Here, we find that the specific adsorption on the Pt-skin/Pt3Co alloy was significantly stronger than that on bulk-Pt, in line with its modified electronic properties. The kinetically controlled current density j(k) for the O2 reduction at the Pt-skin/Pt3Co-RDE was about 9 times larger than that of the bulk-Pt-RDE in 0.01 M HClO4 saturated with air, but the j(k) values on Pt-skin/Pt3Co decreased with increasing [HClO4] more steeply than in the case of Pt, due to the blocking of the active sites by the specifically adsorbed ClO4(-). We have detected reversible mass changes for one or more adsorbed oxygen-containing species (Ox = O2, O, OH, H2O) on the Pt-skin/Pt3Co-EQCM and Pt-EQCM in O2-saturated and He-purged 0.01 M HClO4 solutions, in which the specific adsorption of ClO4(-) anions was negligible. The coverages of oxygen species θ(Ox) on the Pt-skin/Pt3Co in the potential range from 0.86 to 0.96 V in the O2-saturated solution were found to be larger than those on pure Pt, providing strong evidence that the higher O2 reduction activity on the Pt3Co is correlated with higher θ(Ox), contrary to the conventional view.

Bar piezoelectric ceramic transformers.

PubMed

Erhart, Jiří; Pulpan, Půlpán; Rusin, Luboš

2013-07-01

Bar-shaped piezoelectric ceramic transformers (PTs) working in the longitudinal vibration mode (k31 mode) were studied. Two types of the transformer were designed--one with the electrode divided into two segments of different length, and one with the electrodes divided into three symmetrical segments. Parameters of studied transformers such as efficiency, transformation ratio, and input and output impedances were measured. An analytical model was developed for PT parameter calculation for both two- and three-segment PTs. Neither type of bar PT exhibited very high efficiency (maximum 72% for three-segment PT design) at a relatively high transformation ratio (it is 4 for two-segment PT and 2 for three-segment PT at the fundamental resonance mode). The optimum resistive loads were 20 and 10 kΩ for two- and three-segment PT designs for the fundamental resonance, respectively, and about one order of magnitude smaller for the higher overtone (i.e., 2 kΩ and 500 Ω, respectively). The no-load transformation ratio was less than 27 (maximum for two-segment electrode PT design). The optimum input electrode aspect ratios (0.48 for three-segment PT and 0.63 for two-segment PT) were calculated numerically under no-load conditions.

Making ultrafine and highly-dispersive multimetallic nanoparticles in three-dimensional graphene with supercritical fluid as excellent electrocatalyst for oxygen reduction reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yazhou; Yen, Clive H.; Hu, Yun Hang

2016-01-01

Three-dimensional (3D) graphene showed an advanced support for designing porous electrode materials due to its high specific surface area, large pore volume, and excellent electronic property. However, the electrochemical properties of reported porous electrode materials still need to be improved further. The current challenge is how to deposit desirable nanoparticles (NPs) with controllable structure, loading and composition in 3D graphene while maintaining the high dispersion. Herein, we demonstrate a modified supercritical fluid (SCF) technique to address this issue by controlling the SCF system. Using this superior method, a series of Pt-based/3D graphene materials with the ultrafine-sized, highly dispersive and controllablemore » composition multimetallic NPs were successfully synthesized. Specifically, the resultant Pt40Fe60/3D graphene showed a significant enhancement in electrocatalytic performance for the oxygen reduction reaction (ORR), including a factor of 14.2 enhancement in mass activity (1.70 A mgPt 1), a factor of 11.9 enhancement in specific activity (1.55 mA cm 2), and higher durability compared with that of Pt/C catalyst. After careful comparison, the Pt40Fe60/3D graphene catalyst shows the higher ORR activity than most of the reported similar 3D graphene-based catalysts. The successful synthesis of such attractive materials by this method also paves the way to develop 3D graphene in widespread applications.« less

Electrodeposition of gold-platinum alloy nanoparticles on ionic liquid-chitosan composite film and its application in fabricating an amperometric cholesterol biosensor.

PubMed

Safavi, Afsaneh; Farjami, Fatemeh

2011-01-15

An electrodeposition method was applied to form gold-platinum (AuPt) alloy nanoparticles on the glassy carbon electrode (GCE) modified with a mixture of an ionic liquid (IL) and chitosan (Ch) (AuPt-Ch-IL/GCE). AuPt nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. AuPt-Ch-IL/GCE electrocatalyzed the reduction of H(2)O(2) and thus was suitable for the preparation of biosensors. Cholesterol oxidase (ChOx) was then, immobilized on the surface of the electrode by cross-linking ChOx and chitosan through addition of glutaraldehyde (ChOx/AuPt-Ch-IL/GCE). The fabricated biosensor exhibited two wide linear ranges of responses to cholesterol in the concentration ranges of 0.05-6.2 mM and 6.2-11.2 mM. The sensitivity of the biosensor was 90.7 μA mM(-1) cm(-2) and the limit of detection was 10 μM of cholesterol. The response time was less than 7 s. The Michaelis-Menten constant (K(m)) was found as 0.24 mM. The effect of the addition of 1 mM ascorbic acid and glucose was tested on the amperometric response of 0.5 mM cholesterol and no change in response current of cholesterol was observed. Copyright © 2010 Elsevier B.V. All rights reserved.

Bimetallic Pt-Au nanocatalysts electrochemically deposited on boron-doped diamond electrodes for nonenzymatic glucose detection.

PubMed

Nantaphol, Siriwan; Watanabe, Takeshi; Nomura, Naohiro; Siangproh, Weena; Chailapakul, Orawon; Einaga, Yasuaki

2017-12-15

The enormous demand for medical diagnostics has encouraged the fabrication of high- performance sensing platforms for the detection of glucose. Nonenzymatic glucose sensors are coming ever closer to being used in practical applications. Bimetallic catalysts have been shown to be superior to single metal catalysts in that they have greater activity and selectivity. Here, we demonstrate the preparation, characterization, and electrocatalytic characteristics of a new bimetallic Pt/Au nanocatalyst. This nanocatalyst can easily be synthesized by electrodeposition by sequentially depositing Au and Pt on the surface of a boron-doped diamond (BDD) electrode. We characterized the nanocatalyst by scanning electron microscopy (SEM), X-ray diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the electrodeposition process and the molar ratio between the Pt and Au precursors. The electrocatalytic characteristics of a Pt/Au/BDD electrode for the nonenzymatic oxidation of glucose were systematically investigated by cyclic voltammetry. The electrode exhibits higher catalytic activity for glucose oxidation than Pt/BDD and Au/BDD electrodes. The best catalytic activity and stability was obtained with a Pt:Au molar ratio of 50:50. Moreover, the presence of Au can significantly enhance the long-term stability and poisoning tolerance during the electro-oxidation of glucose. Measurements of glucose using the Pt/Au/BDD electrode were linear in the range from 0.01 to 7.5mM, with a detection limit of 0.0077mM glucose. The proposed electrode performs selective electrochemical analysis of glucose in the presence of common interfering species (e.g., acetaminophen, uric and ascorbic acids), avoiding the generation of overlapping signals from such species. Copyright © 2017 Elsevier B.V. All rights reserved.

Note: A quartz cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope measurements.

PubMed

Xia, Zhigang; Wang, Jihao; Hou, Yubin; Lu, Qingyou

2014-09-01

In this paper, we provide and demonstrate a design of a unique cell with Pt single crystal bead electrode for electrochemical scanning tunneling microscope (ECSTM) measurements. The active metal Pt electrode can be protected from air contamination during the preparation process. The transparency of the cell allows the tip and bead to be aligned by direct observation. Based on this, a new and effective alignment method is introduced. The high-quality bead preparations through this new cell have been confirmed by the ECSTM images of Pt (111).

Effects of electrodes on the properties of sol-gel PZT based capacitors in FeRAM

NASA Astrophysics Data System (ADS)

Zhang, Ming-Ming; Jia, Ze; Ren, Tian-Ling

2009-05-01

The effects of electrodes on the properties of capacitors applied in ferroelectric random access memories (FeRAM) are investigated in this work. Pt and Ir are used as bottom and top electrodes (BE and TE), respectively, in sol-gel Pb(Zr xTi 1-x)O 3 (PZT) based capacitors. Bottom electrodes are found to play a dominant role in the properties of PZT films and capacitors. Capacitors using Pt as bottom electrode have larger remnant polarization (2Pr) than those using Ir which may result from the different orientations of PZT films. The higher Schottky barrier, more dense film and smaller roughness are believed to be the reasons for the better leakage performance of capacitors using Pt as bottom electrodes. Different vacancies types and interface conditions are believed to be the main reasons for the better fatigue (less than 10% initial 2Pr loss after 10 11 fatigue cycles) and better imprint properties of TE/PZT/Ir capacitors. Top electrodes are found to have smaller impact on the properties of capacitors compared with bottom electrodes. A decrease in 2Pr is found when Ir is used as top electrode instead of Pt for PZT/Pt, which is believed to be caused by the stress resulting from lattice mismatch. The different thermal processes that top and bottom electrodes suffered are believed to be the reason for the different impacts they have on capacitors.

A study of Na(x)Pt3O4 as an O2 electrode bifunctional electrocatalyst

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph

1991-01-01

The present study suggests that polytetrafluoroethylene (PTFE) bonded Na(X)Pt3O4 gas porous diffusion electrodes may be a viable candidate for bifunctional O2 reduction and evolution activity. The electrodes exhibited Tafel slopes of about 0.06 V/decade for both O2 reduction an evolution. For O2 reduction, the 0.06 slope doubled to 0.12 V/decade at larger current densities. Preliminary stability testing at 24 C suggest that the Na(x)Pt3O4 electrodes were relatively stable at reducing and oxidizing potentials typically encountered at the O2 electrodes in a regenerative fuel cell.

Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

PubMed

Pullamsetty, Ashok; Sundara, Ramaprabhu

2016-10-01

Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. Copyright © 2016 Elsevier Inc. All rights reserved.

Activity of platinum/carbon and palladium/carbon catalysts promoted by Ni2 P in direct ethanol fuel cells.

PubMed

Li, Guoqiang; Feng, Ligang; Chang, Jinfa; Wickman, Björn; Grönbeck, Henrik; Liu, Changpeng; Xing, Wei

2014-12-01

Ethanol is an alternative fuel for direct alcohol fuel cells, in which the electrode materials are commonly based on Pt or Pd. Owing to the excellent promotion effect of Ni2 P that was found in methanol oxidation, we extended the catalyst system of Pt or Pd modified by Ni2 P in direct ethanol fuel cells. The Ni2 P-promoted catalysts were compared to commercial catalysts as well as to reference catalysts promoted with only Ni or only P. Among the studied catalysts, Pt/C and Pd/C modified by Ni2 P (30 wt %) showed both the highest activity and stability. Upon integration into the anode of a homemade direct ethanol fuel cell, the Pt-Ni2 P/C-30 % catalyst showed a maximum power density of 21 mW cm(-2) , which is approximately two times higher than that of a commercial Pt/C catalyst. The Pd-Ni2 P/C-30 % catalyst exhibited a maximum power density of 90 mW cm(-2) . This is approximately 1.5 times higher than that of a commercial Pd/C catalyst. The discharge stability on both two catalysts was also greatly improved over a 12 h discharge operation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low platinum loading cathode modified with Cs3H2PMo10V2O40 for polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Renzi, M.; D'Angelo, G.; Marassi, R.; Nobili, F.

2016-09-01

The catalytic activity of commercial Pt nanoparticles mixed with mesoporous polyoxometalate Cs3H2PMo10V2O40 towards oxygen reduction reaction is evaluated. The polyoxometalate co-catalyst is prepared by titration of an aqueous solution of phosphovanadomolibdic acid. SEM micrography shows reduction particle size to less than 300 nm, while XRD confirms that the resulting salt maintains the Kegging structure. The composite catalyst is prepared by mixing the POM salt with Pt/C by sonication. RRDE studies show better kinetics for ORR with low Pt loading at the electrode surface. A MEA is assembled by using a Pt/POM-based cathode, in order to assess performance in a working fuel cell. Current vs. potential curves reveals comparable or better performances at 100%, 62% and 17% relative humidity for the POM-modified MEA with respect to a commercial MEA with higher Pt loading at the cathode. Electrochemical impedance spectroscopy (EIS) confirms better kinetics at low relative humidity. Finally, an accelerated stress test (AST) with square wave (SW) between 0.4 V and 0.8 V is performed to evaluate MEA stability for at least 100 h and make predictions about lifetime, showing that after initial losses the catalytic system can retain stable performance and good morphological stability.

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

DOE PAGES

Mauger, Scott A.; Neyerlin, K. C.; Alia, Shaun M.; ...

2018-03-13

Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalystmore » materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation.« less

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauger, Scott A.; Neyerlin, K. C.; Alia, Shaun M.

Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalystmore » materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation.« less

Fast synthesis of platinum nanopetals and nanospheres for highly-sensitive non-enzymatic detection of glucose and selective sensing of ions

NASA Astrophysics Data System (ADS)

Taurino, Irene; Sanzó, Gabriella; Mazzei, Franco; Favero, Gabriele; de Micheli, Giovanni; Carrara, Sandro

2015-10-01

Novel methods to obtain Pt nanostructured electrodes have raised particular interest due to their high performance in electrochemistry. Several nanostructuration methods proposed in the literature use costly and bulky equipment or are time-consuming due to the numerous steps they involve. Here, Pt nanostructures were produced for the first time by one-step template-free electrodeposition on Pt bare electrodes. The change in size and shape of the nanostructures is proven to be dependent on the deposition parameters and on the ratio between sulphuric acid and chloride-complexes (i.e., hexachloroplatinate or tetrachloroplatinate). To further improve the electrochemical properties of electrodes, depositions of Pt nanostructures on previously synthesised Pt nanostructures are also performed. The electroactive surface areas exhibit a two order of magnitude improvement when Pt nanostructures with the smallest size are used. All the biosensors based on Pt nanostructures and immobilised glucose oxidase display higher sensitivity as compared to bare Pt electrodes. Pt nanostructures retained an excellent electrocatalytic activity towards the direct oxidation of glucose. Finally, the nanodeposits were proven to be an excellent solid contact for ion measurements, significantly improving the time-stability of the potential. The use of these new nanostructured coatings in electrochemical sensors opens new perspectives for multipanel monitoring of human metabolism.

Electrochemical sensor based on molecularly imprinted membranes at platinum nanoparticles-modified electrode for determination of 17β-estradiol.

PubMed

Yuan, Lihua; Zhang, Jun; Zhou, Ping; Chen, Jiaxing; Wang, Ruoyu; Wen, Tingting; Li, Yun; Zhou, Xuemin; Jiang, Huijun

2011-11-15

In this paper, an electrochemical sensor for 17β-estradiol (E2) based on the molecular imprinting polymer (MIP) membranes had been constructed. 6-mercaptonicotinic acid (MNA) and E2 were first assembled on the surface of platinum nanoparticles-modified glassy carbon electrode (PtNPs/GCE) by the formation of Pt-S bonds and hydrogen-bonding interactions, and subsequently the polymer membranes were formed by electropolymerization. Finally, a novel molecularly imprinted sensor (MIS) was obtained after removal of E2. Experimental parameters such as deposition time, scan cycles, pH value and accumulation condition were optimized. Under optimal conditions, the MIS exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of 3.0×10(-8)-5.0×10(-5)molL(-1) (r=0.996) with an estimated detection limit of 1.6×10(-8)molL(-1). MIS had been successfully used to analyze E2 in water samples without complex pretreatment. Meanwhile, the average recoveries were higher than 93.9% with RSD<3.7%. All results above reveal that MIS is an effective electrochemical technique to determine E2 real-time in complicated matrix. Copyright © 2011 Elsevier B.V. All rights reserved.

Cyclic voltammetric analysis of C 1-C 4 alcohol electrooxidations with Pt/C and Pt-Ru/C microporous electrodes

NASA Astrophysics Data System (ADS)

Lee, Choong-Gon; Umeda, Minoru; Uchida, Isamu

The effect of temperature on methanol, ethanol, 2-propanol, and 2-butanol electrooxidation is investigated with Pt/C and Pt-Ru/C microporous electrodes. Cyclic voltammetry is employed in temperatures ranging from 25 to 80 °C to provide quantitative and qualitative information on the kinetics of alcohol oxidation. Methanol displays the greatest activity atom alcohols. The addition of ruthenium reduces the poisoning effect, although it is ineffective with secondary alcohols. Secondary alcohols undergo a different oxidation mechanism at higher temperatures. Microporous electrodes provide detailed information on alcohol oxidation.

V-doped TiO2 supported Pt as a promising oxygen reduction reaction catalyst: Synthesis, characterization and in-situ evaluation in proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Bharti, Abha; Cheruvally, Gouri

2017-09-01

This study deals with the synthesis and characterization of V-doped, TiO2 supported Pt catalyst (Pt/V-TiO2) for oxygen reduction reaction (ORR) and its in-situ performance investigation in proton exchange membrane (PEM) fuel cell. Pt/V-TiO2 nanocomposite catalyst is prepared via a facile sol-gel and microwave assisted, modified chemical reduction route and its performance is compared with the undoped TiO2 supported catalyst, Pt/TiO2 prepared in an identical way. The prepared Pt/V-TiO2 and Pt/TiO2 catalysts are employed as cathode catalyst in PEM fuel cell and compared with standard Pt/C catalyst. Their comparative studies are conducted with physical and electrochemical techniques. In-situ electrochemical characterization studies show improved ORR catalytic activity of Pt/V-TiO2 compared to Pt/TiO2. Furthermore, both Pt/TiO2 and Pt/V-TiO2 are more stable than Pt/C when subjected to 6000 voltammetric cycles in the range of 0.2-1.2 V vs. standard hydrogen electrode in operating fuel cell conditions, losing only <20% of its electrochemical surface area as compared to 50% loss exhibited by Pt/C. This study thus demonstrates Pt/V-TiO2 nanocomposite material as a potential cathode catalyst for PEM fuel cell with immense scope for further investigation.

Electrochemical sensor based on gold nanoparticles fabricated molecularly imprinted polymer film at chitosan-platinum nanoparticles/graphene-gold nanoparticles double nanocomposites modified electrode for detection of erythromycin.

PubMed

Lian, Wenjing; Liu, Su; Yu, Jinghua; Xing, Xianrong; Li, Jie; Cui, Min; Huang, Jiadong

2012-01-01

A molecularly imprinted electrochemical sensor was fabricated based on gold electrode decorated by chitosan-platinum nanoparticles (CS-PtNPs) and graphene-gold nanoparticles (GR-AuNPs) nanocomposites for convenient and sensitive determination of erythromycin. The synergistic effects of CS-PtNPs and GR-AuNPs nanocomposites improved the electrochemical response and the sensitivity of the sensor. The molecularly imprinted polymers (MIPs) were prepared by HAuCl(4), 2-mercaptonicotinic acid (MNA) and erythromycin. Erythromycin and MNA were used as template molecule and functional monomer, respectively. They were first assembled on the surface of GR-AuNPs/CS-PtNPs/gold electrode by the formation of Au-S bonds and hydrogen-bonding interactions. Then the MIPs were formed by electropolymerization of HAuCl(4), MNA and erythromycin. The sensor was characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), UV-visible (UV-vis) absorption speactra and amperometry. The linear range of the sensor was from 7.0 × 10(-8)mol/L-9.0 × 10(-5)mol/L, with the limit of detection (LOD) of 2.3 × 10(-8)mol/L (S/N=3). The sensor showed high selectivity, excellent stability and good reproducibility for the determination of erythromycin, and it was successfully applied to the detection of erythromycin in real spiked samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Commercial materials as cathode for hydrogen production in microbial electrolysis cell.

PubMed

Farhangi, Sara; Ebrahimi, Sirous; Niasar, Mojtaba Shariati

2014-10-01

The use of commercial electrodes as cathodes in a single-chamber microbial electrolysis cell has been investigated. The cell was operated in sequencing batch mode and the performance of the electrodes was compared with carbon cloth containing 0.5 mg Pt cm(-2). Overall H2 recovery [Formula: see text] was 66.7 ± 1.4, 58.7 ± 1.1 and 55.5 ± 1.5 % for Pt/CC, Ni and Ti mesh electrodes, respectively. Columbic efficiencies of the three cathodes were in the same range (74.8 ± 1.5, 77.6 ± 1.7 and 75.7 ± 1.2 % for Pt/CC, Ni and Ti mesh electrodes, respectively). A similar performance for the three cathodes under near-neutral pH and ambient temperature was obtained. The commercial electrodes are much cheaper than carbon cloth containing Pt. Low cost and good performance of these electrodes suggest they are suitable cathode materials for large scale application.

Oxygen reduction reaction on stepped platinum surfaces in alkaline media.

PubMed

Rizo, Ruben; Herrero, Enrique; Feliu, Juan M

2013-10-07

The oxygen reduction reaction (ORR) in 0.1 M NaOH on platinum single crystal electrodes has been studied using hanging meniscus rotating disk electrode configuration. Basal planes and stepped surfaces with (111) and (100) terraces have been employed. The results indicate that the Pt(111) electrode has the highest electrocatalytic activity among all the studied surfaces. The addition of steps on this electrode surface significantly diminishes the reactivity of the surface towards the ORR. In fact, the reactivity of the steps on the surfaces with wide terraces can be considered negligible with respect to that measured for the terrace. On the other hand, Pt(100) and Pt(110) electrodes have much lower activity than the Pt(111) electrode. These results have been compared with those obtained in acid media to understand the effect of the pH and the adsorbed OH on the mechanism. It is proposed that the surface covered by adsorbed OH is active for the reduction of the oxygen molecules.

Single-wall carbon nanotube-based proton exchange membrane assembly for hydrogen fuel cells.

PubMed

Girishkumar, G; Rettker, Matthew; Underhile, Robert; Binz, David; Vinodgopal, K; McGinn, Paul; Kamat, Prashant

2005-08-30

A membrane electrode assembly (MEA) for hydrogen fuel cells has been fabricated using single-walled carbon nanotubes (SWCNTs) support and platinum catalyst. Films of SWCNTs and commercial platinum (Pt) black were sequentially cast on a carbon fiber electrode (CFE) using a simple electrophoretic deposition procedure. Scanning electron microscopy and Raman spectroscopy showed that the nanotubes and the platinum retained their nanostructure morphology on the carbon fiber surface. Electrochemical impedance spectroscopy (EIS) revealed that the carbon nanotube-based electrodes exhibited an order of magnitude lower charge-transfer reaction resistance (R(ct)) for the hydrogen evolution reaction (HER) than did the commercial carbon black (CB)-based electrodes. The proton exchange membrane (PEM) assembly fabricated using the CFE/SWCNT/Pt electrodes was evaluated using a fuel cell testing unit operating with H(2) and O(2) as input fuels at 25 and 60 degrees C. The maximum power density obtained using CFE/SWCNT/Pt electrodes as both the anode and the cathode was approximately 20% better than that using the CFE/CB/Pt electrodes.

CO2 electroreduction characteristics of Pt-Ru/C powder and Pt-Ru sputtered electrodes under acidic condition

NASA Astrophysics Data System (ADS)

Furukawa, Hiroto; Matsuda, Shofu; Tanaka, Shoji; Shironita, Sayoko; Umeda, Minoru

2018-03-01

The objective of this study was to overcome the issue about the underpotential adsorption of the CO2 electroreductant on the surface of the Pt electrocatalyst under acidic conditions by the alloying of Pt and Ru. As evaluation parameters, the CO2 reduction onset potential and CO2-reductant reoxidation onset potential were employed. We prepared a porous microelectrode filled with Pt-Ru/C powder and a Pt-Ru sputtered electrode. For the Pt-Ru/C powder electrocatalyst, the CO2 reduction onset potential as well as the CO2-reductant reoxidation onset potential shifted in the direction of the CO2/CO2-reductant standard redox potential dependent on the Ru content, which is indicative of a decrease in the underpotential-adsorption energy of the CO2 reductant. For the Pt-Ru sputtered electrode, only the CO2 reduction onset potential shifted in the direction of the redox potential. Consequently, we demonstrated that the Pt-Ru/C powder electrode improved the reactivity of the CO2/CO2-reductant when discussing the relationship between the CO2 reduction onset potential and the CO2-reductant reoxidation onset potential. Based on our findings, the Pt-Ru/C (1:9) powder is the most effective electrocatalyst for the CO2 reduction, which could minimize the underpotential adsorption.

Electrocatalytic cermet sensor

DOEpatents

Shoemaker, E.L.; Vogt, M.C.

1998-06-30

A sensor is described for O{sub 2} and CO{sub 2} gases. The gas sensor includes a plurality of layers driven by a cyclic voltage to generate a unique plot characteristic of the gas in contact with the sensor. The plurality of layers includes an alumina substrate, a reference electrode source of anions, a lower electrical reference electrode of Pt coupled to the reference source of anions, a solid electrolyte containing tungsten and coupled to the lower reference electrode, a buffer layer for preventing flow of Pt ions into the solid electrolyte and an upper catalytically active Pt electrode coupled to the buffer layer. 16 figs.

Electrocatalytic cermet sensor

DOEpatents

Shoemaker, Erika L.; Vogt, Michael C.

1998-01-01

A sensor for O.sub.2 and CO.sub.2 gases. The gas sensor includes a plurality of layers driven by a cyclic voltage to generate a unique plot characteristic of the gas in contact with the sensor. The plurality of layers includes an alumina substrate, a reference electrode source of anions, a lower electrical reference electrode of Pt coupled to the reference source of anions, a solid electrolyte containing tungsten and coupled to the lower reference electrode, a buffer layer for preventing flow of Pt ions into the solid electrolyte and an upper catalytically active Pt electrode coupled to the buffer layer.

Preparation of Pt/polypyrrole-para toluene sulfonate hydrogen peroxide sensitive electrode for the utilizing as a biosensor.

PubMed

Çete, Servet; Bal, Özgür

2013-12-01

A film electrode with electropolymerization of pyrrole (Py) and para-toluene sulfonate (pTS) as a anionic dopant is prepared and its sensitivity to hydrogen peroxide is investigated. The polypyrrole is deposited on a 0.5 cm(2) Pt plate an electrochemically prepared pTS ion-doped polypyrrole film by scanning the electrode potential between - 0.8 and + 0.8 V at a scan rate of 20 mV/s. The electrode's sensitivity to hydrogen peroxide is investigated at room temperature using 0.1 M phosphate buffer at pH 7.5. The working potential is found as a 0.3 V. The concentrations of pyrrole and pTS are 50mM M and 25 mM. Polypyrrole was coated on the electrode surface within 10 cycles. İmmobilization of glucose oxidase carried out on Pt/polypyrrole-para toluene sulfonate (Pt/PPy-pTS) film by cross-linking with glutaraldehyde. The morphology of electrodes was characterized by SEM and AFM. Moreover, contact angle measurements were made with 1 μL water of polymer film and enzyme electrode. It has shown that enzyme electrode is very sensitive against to glucose.

Conducting polymer electrodes for visual prostheses.

PubMed

Green, R A; Devillaine, F; Dodds, C; Matteucci, P; Chen, S; Byrnes-Preston, P; Poole-Warren, L A; Lovell, N H; Suaning, G J

2010-01-01

Conducting polymers (CPs) have the potential to provide superior neural interfaces to conventional metal electrodes by introducing more efficient charge transfer across the same geometric area. In this study the conducting polymer poly(ethylene dioxythiophene) (PEDOT) was coated on platinum (Pt) microelectrode arrays. The in vitro electrical characteristics were assessed during biphasic stimulation regimes applied between electrode pairs. It was demonstrated that PEDOT could reduce the potential excursion at a Pt electrode interface by an order of magnitude. The charge injection limit of PEDOT was found to be 15 x larger than Pt. Additionally, PEDOT coated electrodes were acutely implanted in the suprachoroidal space of a cat retina. It was demonstrated that PEDOT coated electrodes also had lower potential excursions in vivo and electrically evoked potentials (EEPs) could be detected within the vision cortex.

Electroanalytical method for determination of lead(II) in orange and apple using kaolin modified platinum electrode.

PubMed

El Mhammedi, M A; Achak, M; Bakasse, M; Chtaini, A

2009-08-01

This paper reports on the use of platinum electrode modified with kaolin (K/Pt) and square wave voltammetry for analytical detection of trace lead(II) in pure water, orange and apple samples. The electroanalytical procedure for determination of the Pb(II) comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using square wave voltammetry. The analytical performances of the extraction method has been explored by studying the incubating time, and effect of interferences due to other ions. During the preconcentration step, Pb(II) was accumulated on the surface of the kaolin. The observed detection and quantification limits in pure water were 3.6x10(-9)molL(-1) and 1.2x10(-8)molL(-1), respectively. The precision of the method was also determined; the results was 2.35% (n=5).

To alloy or not to alloy? Cr modified Pt/C cathode catalysts for PEM fuel cells.

PubMed

Wells, Peter P; Qian, Yangdong; King, Colin R; Wiltshire, Richard J K; Crabb, Eleanor M; Smart, Lesley E; Thompsett, David; Russell, Andrea E

2008-01-01

The cathode electrocatalysts for proton exchange membrane (PEM) fuel cells are commonly platinum and platinum based alloy nanoparticles dispersed on a carbon support. Control over the particle size and composition has, historically, been attained empirically, making systematic studies of the effects of various structural parameters difficult. The controlled surface modification methodology used in this work has enabled the controlled modification of carbon supported Pt nanoparticles by Cr so as to yield nanoalloy particles with defined compositions. Subsequent heat treatment in 5% H2 in N2 resulted in the formation of a distinct Pt3Cr alloy phase which was either restricted to the surface of the particles or present throughout the bulk of the particle structure. Measurement of the oxygen reduction activity of the catalysts was accomplished using the rotating thin film electrode method and the activities obtained were related to the structure of the nanoalloy catalyst particles, largely determined using Cr K edge and Pt L3 edge XAS.

Crystallographic orientation and electrode nature are key factors for electric current generation by Geobacter sulfurreducens.

PubMed

Maestro, Beatriz; Ortiz, Juan M; Schrott, Germán; Busalmen, Juan P; Climent, Víctor; Feliu, Juan M

2014-08-01

We have investigated the influence of electrode material and crystallographic structure on electron transfer and biofilm formation of Geobacter sulfurreducens. Single-crystal gold-Au(110), Au(111), Au(210)-and platinum-Pt(100), Pt(110), Pt(111), Pt(210)-electrodes were tested and compared to graphite rods. G. sulfurreducens electrochemically interacts with all these materials with different attachment kinetics and final current production, although redox species involved in the electron transfer to the anode are virtually the same in all cases. Initial bacterial colonization was fastest on graphite up to the monolayer level, whereas gold electrodes led to higher final current densities. Crystal geometry was shown to have an important influence, with Au(210) sustaining a current density of up to 1442±101μAcm(-2) at the steady state, over Au(111) with 961±94μAcm(-2) and Au(110) with 944±89μAcm(-2). On the other hand, the platinum electrodes displayed the lowest performances, including Pt(210). Our results indicate that both crystal geometry and electrode material are key parameters for the efficient interaction of bacteria with the substrate and should be considered for the design of novel materials and microbial devices to optimize energy production. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and electrical properties of Pb(ZrxTi1-x)O3 deposited on textured Pt thin films

NASA Astrophysics Data System (ADS)

Hong, Jongin; Song, Han Wook; Lee, Hee Chul; Lee, Won Jong; No, Kwangsoo

2001-08-01

The texturing of the bottom electrode plays a key role in the structure and electrical properties of Pb(Zr, Ti)O3 (PZT) thin films. We fabricated Pt bottom electrodes having a different thickness on MgO single crystals at 600 °C by rf magnetron sputtering. As the thickness of platinum (Pt) thin film increased, the preferred orientation of Pt thin film changed from (200) to (111). PZT thin films were fabricated at 450 °C by electron cyclotron resonance-plasma enhanced metal organic chemical vapor deposition on the textured Pt thin films. The texturing of the bottom electrode caused drastic changes in the C-V characteristics, P-E characteristics, and fatigue characteristics of metal/ferroelectric material/metal (MFM) capacitors. The difference of the electrical properties between the PZT thin films having different texturing was discussed in terms-of the x-y alignment and the interface between electrode and PZT in MFM capacitors.

Electrodeposition of platinum nanoparticles in a room-temperature ionic liquid.

PubMed

Zhang, Da; Chang, Wan Cheng; Okajima, Takeyoshi; Ohsaka, Takeo

2011-12-06

The electrochemistry of the [PtCl(6)](2-)-[PtCl(4)](2-)-Pt redox system on a glassy carbon (GC) electrode in a room-temperature ionic liquid (RTIL) [i.e., N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate (DEMEBF(4))] has been examined. The two-step four-electron reduction of [PtCl(6)](2-) to Pt, i.e., reduction of [PtCl(6)](2-) to [PtCl(4)](2-) and further reduction of [PtCl(4)](2-) to Pt, occurs separately in this RTIL in contrast to the one-step four-electron reduction of [PtCl(6)](2-) to Pt in aqueous media. The cathodic and anodic peaks corresponding to the [PtCl(6)](2-)/[PtCl(4)](2-) redox couple were observed at ca. -1.1 and 0.6 V vs a Pt wire quasi-reference electrode, respectively, while those observed at -2.8 and -0.5 V were found to correspond to the [PtCl(4)](2-)/Pt redox couple. The disproportionation reaction of the two-electron reduction product of [PtCl(6)](2-) (i.e., [PtCl(4)](2-)) to [PtCl(6)](2-) and Pt metal was also found to occur significantly. The electrodeposition of Pt nanoparticles could be carried out on a GC electrode in DEMEBF(4) containing [PtCl(6)](2-) by holding the potential at -3.5 or -2.0 V. At -3.5 V, the four-electron reduction of [PtCl(6)](2-) to Pt can take place, while at -2.0 V the two-electron reduction of [PtCl(6)](2-) to [PtCl(4)](2-) occurs. The results obtained demonstrate that the electrodeposition of Pt at -3.5 V may occur via a series of reductions of [PtCl(6)](2-) to [PtCl(4)](2-) and further [PtCl(4)](2-) to Pt and at -2.0 V via a disproportionation reaction of [PtCl(4)](2-) to [PtCl(6)](2-) and Pt. Furthermore, the deposition potential of Pt nanoparticles was found to largely influence their size and morphology as well as the relative ratio of Pt(110) and Pt(100) crystalline orientation domains. The sizes of the Pt nanoparticles prepared by holding the electrode potential at -2.0 and -3.5 V are almost the same, in the range of ca. 1-2 nm. These small nanoparticles are "grown" to form bigger particles with different morphologies: In the case of the deposition at -2.0 V, the GC electrode surface is totally, relatively compactly covered with Pt particles of relatively uniform size of ca. 10-50 nm. On the other hand, in the case of the electrodeposition at -3.5 V, small particles of ca. 50-100 nm and the grown-up particles of ca. 100-200 nm cover the GC surface irregularly and coarsely. Interestingly, the Pt nanoparticles prepared by holding the potential at -2.0 and -3.5 V are relatively enriched in Pt(100) and Pt(110) facets, respectively. © 2011 American Chemical Society

High loading of uniformly dispersed Pt nanoparticles on polydopamine coated carbon nanotubes and its application in simultaneous determination of dopamine and uric acid

NASA Astrophysics Data System (ADS)

Lin, Mouhong; Huang, Haoliang; Liu, Yingju; Liang, Canjian; Fei, Shidong; Chen, Xiaofen; Ni, Chunlin

2013-02-01

Multiwalled carbon nanotubes (MWCNT) were homogeneously covered with a bio-functional polydopamine (PDOP) by a simple dip-coating approach in mild basic solution. Then, uniformly dispersed and highly loaded platinum nanoparticles (PtNPs) were deposited on MWCNT@PDOP by a mild reductant, and were characterized by transmission electron microscopy and x-ray photoelectron spectroscopy. Afterwards, this nanocomposite was modified on the glass carbon electrode and applied to simultaneously determine dopamine (DA) and uric acid (UA) by differential pulse voltammetry (DPV). Results showed that a linear electro-oxidation response was found for DA and UA in the range of 0.25-20 μM and 0.3-13 μM with the detection limit (S/N = 3) of 0.08 μM and 0.12 μM, respectively. In addition, the detection sensitivities for DA and UA by DPV were 1.03 μA μM-1 and 2.09 μA μM-1, respectively, which were much higher than those from a cyclic voltammogram. Finally, the reproducibility and stability of the nanocomposite were also evaluated, demonstrating that such MWCNT@PDOP@PtNPs can be a promising candidate for advanced electrode material in electrochemical sensing and other electrocatalytic applications.

In vitro biocompatibility and electrical stability of thick-film platinum/gold alloy electrodes printed on alumina

NASA Astrophysics Data System (ADS)

Carnicer-Lombarte, Alejandro; Lancashire, Henry T.; Vanhoestenberghe, Anne

2017-06-01

Objective. High-density electrode arrays are a powerful tool in both clinical neuroscience and basic research. However, current manufacturing techniques require the use of specialised techniques and equipment, which are available to few labs. We have developed a high-density electrode array with customisable design, manufactured using simple printing techniques and with commercially available materials. Approach. Electrode arrays were manufactured by thick-film printing a platinum-gold alloy (Pt/Au) and an insulating dielectric on 96% alumina ceramic plates. Arrays were conditioned in serum and serum-free conditions, with and without 1 kHz, 200 µA, charge balanced stimulation for up to 21 d. Array biocompatibility was assessed using an extract assay and a PC-12 cell contact assay. Electrode impedance, charge storage capacity and charge injection capacity were before and after array conditioning. Main results. The manufactured Pt/Au electrodes have a highly porous surface and exhibit electrical properties comparable to arrays manufactured using alternative techniques. Materials used in array manufacture were found to be non-toxic to L929 fibroblasts by extract assay, and neuronal-like PC-12 cells adhered and extended neurites on the array surfaces. Arrays remained functional after long-term delivery of electrical pulses while exposed to protein-rich environments. Charge storage capacities and charge injection capacities increased following stimulation accounted for by an increase in surface index (real surface area) observed by vertical scanning interferometry. Further, we observed accumulation of proteins at the electrode sites following conditioning in the presence of serum. Significance. This study demonstrates the in vitro biocompatibility of commercially available thick-film printing materials. The printing technique is both simple and versatile, with layouts readily modified to produce customized electrode arrays. Thick-film electrode arrays are an attractive tool that may be implemented for general tissue engineering and neuroscience research.

Single-crystalline nanogap electrodes: enhancing the nanowire-breakdown process with a gaseous environment.

PubMed

Suga, Hiroshi; Sumiya, Touru; Furuta, Shigeo; Ueki, Ryuichi; Miyazawa, Yosuke; Nishijima, Takuya; Fujita, Jun-ichi; Tsukagoshi, Kazuhito; Shimizu, Tetsuo; Naitoh, Yasuhisa

2012-10-24

A method for fabricating single-crystalline nanogaps on Si substrates was developed. Polycrystalline Pt nanowires on Si substrates were broken down by current flow under various gaseous environments. The crystal structure of the nanogap electrode was evaluated using scanning electron microscopy and transmission electron microscopy. Nanogap electrodes sandwiched between Pt-large-crystal-grains were obtained by the breakdown of the wire in an O(2) or H(2) atmosphere. These nanogap electrodes show intense spots in the electron diffraction pattern. The diffraction pattern corresponds to Pt (111), indicating that single-crystal grains are grown by the electrical wire breakdown process in an O(2) or H(2) atmosphere. The Pt wires that have (111)-texture and coherent boundaries can be considered ideal as interconnectors for single molecular electronics. The simple method for fabrication of a single-crystalline nanogap is one of the first steps toward standard nanogap electrodes for single molecular instruments and opens the door to future research on physical phenomena in nanospaces.

Use of Pd-Pt loaded graphene aerogel on nickel foam in direct ethanol fuel cell

NASA Astrophysics Data System (ADS)

Tsang, Chi Him A.; Leung, D. Y. C.

2018-01-01

A size customized binder-free bimetallic Pd-Pt loaded graphene aerogel deposited on nickel foam plate (Pd-Pt/GA/NFP) was prepared and used as an electrode for an alkaline direct ethanol fuel cell (DEFC) under room temperature. The effect of fuel concentration and metal composition on the output power density of the DEFC was systematically investigated. Under the optimum fuel concentration, the cell could achieve a value of 3.6 mW cm-2 at room temperature for the graphene electrode with Pd/Pt ratio approaching 1:1. Such results demonstrated the possibility of producing a size customized metal loaded GA/NFP electrode for fuel cell with high performance.

Colorimetric assay of heparin in plasma based on the inhibition of oxidase-like activity of citrate-capped platinum nanoparticles.

PubMed

You, Jyun-Guo; Liu, Yao-Wen; Lu, Chi-Yu; Tseng, Wei-Lung; Yu, Cheng-Ju

2017-06-15

We report citrate-capped platinum nanoparticles (Pt NPs) as oxidase mimetics for effectively catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid), dopamine, and methylene blue in the presence of O 2 . To confirm oxidase-like activity of citrate-capped Pt NPs, their activity toward oxygen reduction reaction was studied using cyclic voltammetry and rotating ring-disk electrode method. The results obtained showed that Pt NP NPs can catalyze the oxidation of organic substrates to the colored product and the reduction of oxygen to water through a four-electron exchange process. Because the aggregation of Pt NPs can inhibit their oxidase-like activity and protamine can recognize heparin, we prepared the protamine-modified Pt NPs through direct adsorption on the surface of citrate-capped Pt NPs. The electrostatic attraction between heparin and protamine-stabilized Pt NPs induced nanoparticle aggregation, inhibiting their catalytic activity. Therefore, the lowest detectable heparin concentrations through UV-vis absorption and by the naked eye were estimated to be 0.3 and 60nM, respectively. Moreover, the proposed system enabled the determination of the therapeutic heparin concentration in a single drop of blood. Copyright © 2016 Elsevier B.V. All rights reserved.

PEM regenerative fuel cells

NASA Technical Reports Server (NTRS)

Swette, Larry L.; Laconti, Anthony B.; Mccatty, Stephen A.

1993-01-01

This paper will update the progress in developing electrocatalyst systems and electrode structures primarily for the positive electrode of single-unit solid polymer proton exchange membrane (PEM) regenerative fuel cells. The work was done with DuPont Nafion 117 in complete fuel cells (40 sq cm electrodes). The cells were operated alternately in fuel cell mode and electrolysis mode at 80 C. In fuel cell mode, humidified hydrogen and oxygen were supplied at 207 kPa (30 psi); in electrolysis mode, water was pumped over the positive electrode and the gases were evolved at ambient pressure. Cycling data will be presented for Pt-Ir catalysts and limited bifunctional data will be presented for Pt, Ir, Ru, Rh, and Na(x)Pt3O4 catalysts as well as for electrode structure variations.

Electrochemical and in situ spectroscopic studies of materials of relevance to energy storage and electrocatalysis

NASA Astrophysics Data System (ADS)

Mo, Yibo

In situ X-ray absorption (XAS), surface enhanced Raman spectroscopy (SERS) and rotating ring disk electrode techniques have been employed for the characterization of materials of relevance to electrochemical energy storage and electrocatalysis. In particular, analysis of in situ Ir LIII-edge extended X-ray absorption fine structure (EXAFS) of IrO2 films electrodeposited on Au substrates yielded Ir-O bond lengths decreasing in the sequence 2.02, 1.97 and 1.93 A, for Ir3+, Ir4+ and Ir5+ sites, respectively. Although features consistent with the presence of crystalline IrO2 in the highly hydrated films were found from in situ SERS, the lack of intense shells in the FT of the EXAFS function beyond the nearest oxygen neighbors indicates that the films by and large do not display long range order. In similar studies, the Fourier transform of the k3-weighted Ru K-edge EXAFS of electrodeposited RuO2 films recorded in situ were characterized by two shells attributed to Ru-O and Ru-Ru interactions at 1.94(1) and 3.12(2) A, in agreement with results obtained ex situ for Ru4+ in hydrous RuO2, whereas films in the reduced state yielded a single Ru-O interaction shell at 2.02(1) A. Extensions of these in situ XAS to the study of electrocatalysts for the nitrite reduction made it possible to identify and characterize the electronic and structural properties of a nitrosyl iron porphyrin adduct adsorbed on an electrode surface via the analysis of Fe K-edge XAS data. The effects of Se and S ad-atoms on the electrocatalytic activity of Pt electrodes have been examined using RRDE techniques. In acid, within a rather narrow range of coverages, both S- and Se-modified Pt surfaces promote the 2-electron reduction of dioxygen to hydrogen peroxide at ca. 100% faradaic efficiency over a wide potential region. Also developed were methods for immobilizing unsupported dispersed high area Pt particles a glassy carbon (GC) disk of a rotating Pt(ring)/GC(disk) electrode assembly allowing electrochemical measurements to be performed under forced convection with only minimal losses of Pt from the surface.

Electrochemical Generation of a Hydrogen Bubble at a Recessed Platinum Nanopore Electrode.

PubMed

Chen, Qianjin; Luo, Long; White, Henry S

2015-04-21

We report the electrochemical generation of a single hydrogen bubble within the cavity of a recessed Pt nanopore electrode. The recessed Pt electrode is a conical pore in glass that contains a micrometer-scale Pt disk (1-10 μm radius) at the nanopore base and a nanometer-scale orifice (10-100 nm radius) that restricts diffusion of electroactive molecules and dissolved gas between the nanopore cavity and bulk solution. The formation of a H2 bubble at the Pt disk electrode in voltammetric experiments results from the reduction of H(+) in a 0.25 M H2SO4 solution; the liquid-to-gas phase transformation is indicated in the voltammetric response by a precipitous decrease in the cathodic current due to rapid bubble nucleation and growth within the nanopore cavity. Finite element simulations of the concentration distribution of dissolved H2 within the nanopore cavity, as a function of the H(+) reduction current, indicate that H2 bubble nucleation at the recessed Pt electrode surface occurs at a critical supersaturation concentration of ∼0.22 M, in agreement with the value previously obtained at (nonrecessed) Pt disk electrodes (∼0.25 M). Because the nanopore orifice limits the diffusion of H2 out of the nanopore cavity, an anodic peak corresponding to the oxidation of gaseous and dissolved H2 trapped in the recessed cavity is readily observed on the reverse voltammetric scan. Integration of the charge associated with the H2 oxidation peak is found to approach that of the H(+) reduction peak at high scan rates, confirming the assignment of the anodic peak to H2 oxidation. Preliminary results for the electrochemical generation of O2 bubbles from water oxidation at a recessed nanopore electrode are consistent with the electrogeneration of H2 bubbles.

Construction and operation of microbial fuel cell with Chlorella vulgaris biocathode for electricity generation.

PubMed

Wu, Xia-yuan; Song, Tian-shun; Zhu, Xu-jun; Wei, Ping; Zhou, Charles C

2013-12-01

In this study, a modified microbial fuel cell (MFC) with a tubular photobioreactor (PHB) configuration as a cathode compartment was constructed by introducing Chlorella vulgaris to the cathode chamber used to generate oxygen in situ. Two types of cathode materials and light/dark cycles were used to test the effect on MFC with algae biocathode. Results showed that the use of algae is an effective approach because these organisms can act as efficient in situ oxygenators, thereby facilitating the cathodic reaction. Dissolved oxygen and voltage output displayed a clear light positive response and were drastically enhanced compared with the abiotic cathode. In particular, carbon paper-coated Pt used as a cathode electrode increased voltage output at a higher extent than carbon felt used as an electrode. The maximum power density of 24.4 mW/m2 was obtained from the MFC with algae biocathode which utilized the carbon paper-coated Pt as the cathode electrode under intermittent illumination. This density was 2.8 times higher than that of the abiotic cathode. Continuous illumination shortened the algal lifetime. These results demonstrated that intermittent illumination and cathode material-coated catalyst are beneficial to a more efficient and prolonged operation of MFC with C. vulgaris biocathode.

Construction and operation of microbial fuel cell with Chlorella vulgaris biocathode for electricity generation.

PubMed

Wu, Xia-yuan; Song, Tian-shun; Zhu, Xu-jun; Wei, Ping; Zhou, Charles C

2013-12-01

In this study, a modified microbial fuel cell (MFC) with a tubular photobioreactor (PHB) configuration as a cathode compartment was constructed by introducing Chlorella vulgaris to the cathode chamber used to generate oxygen in situ. Two types of cathode materials and light/dark cycles were used to test the effect on MFC with algae biocathode. Results showed that the use of algae is an effective approach because these organisms can act as efficient in situ oxygenators, thereby facilitating the cathodic reaction. Dissolved oxygen and voltage output displayed a clear light positive response and were drastically enhanced compared with the abiotic cathode. In particular, carbon paper-coated Pt used as a cathode electrode increased voltage output at a higher extent than carbon felt used as an electrode. The maximum power density of 24.4 mW/m(2) was obtained from the MFC with algae biocathode which utilized the carbon paper-coated Pt as the cathode electrode under intermittent illumination. This density was 2.8 times higher than that of the abiotic cathode. Continuous illumination shortened the algal lifetime. These results demonstrated that intermittent illumination and cathode material-coated catalyst are beneficial to a more efficient and prolonged operation of MFC with C. vulgaris biocathode.

High-surface-area architectures for improved charge transfer kinetics at the dark electrode in dye-sensitized solar cells.

PubMed

Hoffeditz, William L; Katz, Michael J; Deria, Pravas; Martinson, Alex B F; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

2014-06-11

Dye-sensitized solar cell (DSC) redox shuttles other than triiodide/iodide have exhibited significantly higher charge transfer resistances at the dark electrode. This often results in poor fill factor, a severe detriment to device performance. Rather than moving to dark electrodes of untested materials that may have higher catalytic activity for specific shuttles, the surface area of platinum dark electrodes could be increased, improving the catalytic activity by simply presenting more catalyst to the shuttle solution. A new copper-based redox shuttle that experiences extremely high charge-transfer resistance at conventional Pt dark electrodes yields cells having fill-factors of less than 0.3. By replacing the standard Pt dark electrode with an inverse opal Pt electrode fabricated via atomic layer deposition, the dark electrode surface area is boosted by ca. 50-fold. The resulting increase in interfacial electron transfer rate (decrease in charge-transfer resistance) nearly doubles the fill factor and therefore the overall energy conversion efficiency, illustrating the utility of this high-area electrode for DSCs.

Facile synthesis of nitrogen-doped reduced graphene oxide as an efficient counter electrode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Liguo; Wang, Ping; Yang, Yulin; Luo, Ruidong; Li, Jinqi; Gu, Xiaohu; Zhan, Zhaoshun; Dong, Yongli; Song, Weina; Fan, Ruiqing

2018-04-01

A nitrogen-doped reduced graphene oxide (N-RGO) nanosheet was synthesized by a simple hydrothermal method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electrode microscopy. After being deposited as counter electrode film for dye-sensitized solar cells (DSSCs), it is found that the synthesized N-RGO nanosheet has smaller charge-transfer resistance and better electrocatalytic activity towards reduction of triiodide than the reduced graphene oxide (RGO) nanosheet. Consequently, the DSSCs based on the N-RGO counter electrode achieve an energy conversion efficiency of 4.26%, which is higher than that of the RGO counter electrode (2.85%) prepared under the same conditions, and comparable to the value (5.21%) obtained with the Pt counter electrode as a reference. This N-RGO counter electrode offers the advantages of not only saving the cost of Pt itself but also simplifying the process of counter electrode preparation. Therefore, an inexpensive N-RGO nanosheet is a promising counter electrode material to replace noble metal Pt. [Figure not available: see fulltext.

Peripheral Ferroelectric Domain Switching and Polarization Fatigue in Nonvolatile Memory Elements of Continuous Pt/SrBi2Ta2O9/Pt Thin-Film Capacitors

NASA Astrophysics Data System (ADS)

Chen, Min-Chuan; Jiang, An-Quan

2011-07-01

We verify the domain sideway motion around the peripheral regions of the crossed capacitors of top and bottom electrode bars without electrode coverage. To avoid the crosstalk problem between adjacent memory cells, the safe distance between adjacent elements of Pt/SrBi2Ta2O9/Pt thin-film capacitors is estimated to be 0.156 μm. Moreover, the fatigue of Pt/SrBi2Ta2O9/Pt thin-film capacitors is independent of the individual memory size due to the absence of etching damage.

High Electrocatalytic Activity of Vertically Aligned Single-Walled Carbon Nanotubes towards Sulfide Redox Shuttles.

PubMed

Hao, Feng; Dong, Pei; Zhang, Jing; Zhang, Yongchang; Loya, Phillip E; Hauge, Robert H; Li, Jianbao; Lou, Jun; Lin, Hong

2012-01-01

Vertically aligned single-walled carbon nanotubes (VASWCNTs) have been successfully transferred onto transparent conducting oxide glass and implemented as efficient low-cost, platinum-free counter electrode in sulfide -mediated dye-sensitized solar cells (DSCs), featuring notably improved electrocatalytic activity toward thiolate/disulfide redox shuttle over conventional Pt counter electrodes. Impressively, device with VASWCNTs counter electrode demonstrates a high fill factor of 0.68 and power conversion efficiency up to 5.25%, which is significantly higher than 0.56 and 3.49% for that with a conventional Pt electrode. Moreover, VASWCNTs counter electrode produces a charge transfer resistance of only 21.22 Ω towards aqueous polysulfide electrolyte commonly applied in quantum dots-sensitized solar cells (QDSCs), which is several orders of magnitude lower than that of a typical Pt electrode. Therefore, VASWCNTs counter electrodes are believed to be a versatile candidate for further improvement of the power conversion efficiency of other iodine-free redox couple based DSCs and polysulfide electrolyte based QDSCs.

Comparative Study of Hydrogen- and Deuterium-Induced Degradation of Ferroelectric (Pb,La)(Zr,Ti)O3 Capacitors Using Time-of-Flight Secondary Ion Measurement.

PubMed

Takada, Yoko; Okamoto, Naoki; Saito, Takeyasu; Yoshimura, Takeshi; Fujimura, Norifumi; Higuchi, Koji; Kitajima, Akira; Shishido, Rie

2016-10-01

Ferroelectric (Pb,La)(Zr,Ti)O 3 (PLZT) capacitors were fabricated with Pt, Al:ZnO (AZO), or Sn:In 2 O 3 (ITO) top electrodes. Hydrogen- or deuterium-induced degradation was investigated for the three capacitors by annealing in a 3% H 2 /balance N 2 or 3% D 2 /balance N 2 ambient environment at 200 °C and 1 torr. The remnant polarization of all capacitors decreased after annealing in both H 2 and D 2 ambient after 45 min, and the remnant polarization of the Pt/PLZT/Pt capacitor significantly decreased after 45-min annealing compared with that of the AZO/PLZT/Pt and ITO/PLZT/Pt capacitors, even though the initial remnant polarization for the Pt/PLZT/Pt capacitor was larger. Time-of-flight secondary ion mass spectrometry showed slight differences in hydrogen content for the three different capacitors after H 2 annealing. In contrast, the deuterium content of the Pt/PLZT/Pt and AZO/PLZT/Pt or ITO/PLZT/PT capacitors was significantly different after deuterium annealing. Deuterium depth profiles for the Pt/PLZT/Pt capacitor after annealing showed that deuterium conformally exists in the PLZT layer of the Pt/PLZT/Pt capacitor, and deuterium accumulation under the Pt bottom electrode was also observed. This result suggests that diffusion of deuterium in Pt was much higher than that in PLZT. AZO and ITO top electrodes could act as a hydrogen barrier layer for ferroelectric films.

Methanol and ethanol electroxidation using Pt electrodes prepared by the polymeric precursor method

NASA Astrophysics Data System (ADS)

Freitas, R. G.; Santos, M. C.; Oliveira, R. T. S.; Bulhões, L. O. S.; Pereira, E. C.

The results of methanol and ethanol oxidation in acidic medium on Pt electrodes deposited on Ti substrate using the Pechini method are presented. In this route the metallic salts were dissolved in a mixture of ethylene glycol (EG) and citric acid (CA) forming a polyester network, which is painted onto a Ti substrate and then heat treated at 600 °C in order to obtain the metallic Pt thin films. The X-ray diffraction analysis showed the presence of Pt pattern peaks. The presence of the (4 2 0) plane in a higher amount compared to bulk Pt was observed and the peak position of the planes (2 0 0) and (4 2 0) were displaced by approximately -0.3°. The roughness data presented almost the same values for Ti and Ti/Pt. The electrochemical characterization of the electrodes in 0.1 M HClO 4 showed a typical Pt voltammetric profile. Although the voltammetric profiles of Ti/Pt and bulk Pt were the same, the electrocatalytical behavior for methanol oxidation showed an enhancement of the oxidation current density peak, which increased by 170% compared to bulk platinum. Although, the current density peak for ethanol oxidation on Ti/Pt is smaller than for Pt, it began at 0.11 V less positive than the same process on bulk Pt. The chronoamperometric experiments for methanol and ethanol oxidation on Ti/Pt increased by almost 934% and 440%, respectively, compared with Pt bulk.

Amperometric determination of acetylcholine-A neurotransmitter, by chitosan/gold-coated ferric oxide nanoparticles modified gold electrode.

PubMed

Chauhan, Nidhi; Pundir, C S

2014-11-15

An amperometric acetylcholine biosensor was constructed by co-immobilizing covalently, a mixture of acetylcholinesterase (AChE) and choline oxidase (ChO) onto nanocomposite of chitosan (CHIT)/gold-coated ferric oxide nanoparticles (Fe@AuNPs) electrodeposited onto surface of a Au electrode and using it as a working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through potentiostat. The biosensor is based on electrochemical measurement of H2O2 generated from oxidation of choline by immobilized ChO, which in turn is produced from hydrolysis of acetylcholine by immobilized AChE. The biosensor exhibited optimum response within 3s at +0.2V, pH 7.0 and 30°C. The enzyme electrode had a linear working range of 0.005-400 µM, with a detection limit of 0.005 µM for acetylcholine. The biosensor measured plasma acetylcholine in apparently healthy and persons suffering from Alzheimer's disease. The enzyme electrode was unaffected by a number of serum substances but lost 50% of its initial activity after its 100 uses over a period of 3 months, when stored at 4°C. Copyright © 2014 Elsevier B.V. All rights reserved.

\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}${\\mbi{\\mu }}$\\end{document}-Foil Polymer Electrode Array for Intracortical Neural Recordings

PubMed Central

Köhler, Per; Granmo, Marcus; Schouenborg, Jens; Bengtsson, Martin; Wallman, Lars

2014-01-01

We have developed a multichannel electrode array—termed \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}\\(\\mu \\) \\end{document}-foil—that comprises ultrathin and flexible electrodes protruding from a thin foil at fixed distances. In addition to allowing some of the active sites to reach less compromised tissue, the barb-like protrusions that also serves the purpose of anchoring the electrode array into the tissue. This paper is an early evaluation of technical aspects and performance of this electrode array in acute in vitro/in vivo experiments. The interface impedance was reduced by up to two decades by electroplating the active sites with platinum black. The platinum black also allowed for a reduced phase lag for higher frequency components. The distance between the protrusions of the electrode array was tailored to match the architecture of the rat cerebral cortex. In vivo acute measurements confirmed a high signal-to-noise ratio for the neural recordings, and no significant crosstalk between recording channels. PMID:27170864

In vivo monitor oxidative burst induced by Cd2+ stress for the oilseed rape (Brassica napus L.) based on electrochemical microbiosensor.

PubMed

Xu, Qiao; Wei, Fang; Wang, Zhan; Yang, Qin; Zhao, Yuan-Di; Chen, Hong

2010-01-01

Since the mechanism of Cd(2+) stress for plants is not clear, an in vivo method to monitor Cd(2+) stress for plants is necessary. However, oxidative burst (OB) is a signal messenger in the process of Cd(2+) stress for plants. To establish an electrochemical method with poly-o-phenylenediamine and Pt microparticle modified Pt electrode (POPD-Pt-MP-Pt) as a microbiosensor for the in vivo detection of oxidative burst induced by Cd(2+) stress in oilseed rape (Brassica napus L.). The optimal fabrication of POPD-Pt-MP-Pt biosensor was achieved. Electrochemical signal was collected by amperometry. After oilseed rape was exposed to 84.9 mM CdCl(2) stress, three oxidative bursts were observed in oilseed rape by amperometry at 3.3 h, 8.4 h and 13.2 h, respectively. However, there was no obvious signal observed in the controlled assay. This contribution presents the in vivo monitoring of the OB process induced by Cd(2+) stress in oilseed rape by POPD-Pt-MP-Pt microbiosensor in real-time. The novel electrochemical microbiosensor not only facilitates the real-time study in plant self-defence response to the adverse environment such as Cd(2+) stress, but also provides an effective tool for probing the self-defence mechanism in plants.

Microbial Communities and Electrochemical Performance of Titanium-Based Anodic Electrodes in a Microbial Fuel Cell▿

PubMed Central

Michaelidou, Urania; ter Heijne, Annemiek; Euverink, Gerrit Jan W.; Hamelers, Hubertus V. M.; Stams, Alfons J. M.; Geelhoed, Jeanine S.

2011-01-01

Four types of titanium (Ti)-based electrodes were tested in the same microbial fuel cell (MFC) anodic compartment. Their electrochemical performances and the dominant microbial communities of the electrode biofilms were compared. The electrodes were identical in shape, macroscopic surface area, and core material but differed in either surface coating (Pt- or Ta-coated metal composites) or surface texture (smooth or rough). The MFC was inoculated with electrochemically active, neutrophilic microorganisms that had been enriched in the anodic compartments of acetate-fed MFCs over a period of 4 years. The original inoculum consisted of bioreactor sludge samples amended with Geobacter sulfurreducens strain PCA. Overall, the Pt- and Ta-coated Ti bioanodes (electrode-biofilm association) showed higher current production than the uncoated Ti bioanodes. Analyses of extracted DNA of the anodic liquid and the Pt- and Ta-coated Ti electrode biofilms indicated differences in the dominant bacterial communities. Biofilm formation on the uncoated electrodes was poor and insufficient for further analyses. Bioanode samples from the Pt- and Ta-coated Ti electrodes incubated with Fe(III) and acetate showed several Fe(III)-reducing bacteria, of which selected species were dominant, on the surface of the electrodes. In contrast, nitrate-enriched samples showed less diversity, and the enriched strains were not dominant on the electrode surface. Isolated Fe(III)-reducing strains were phylogenetically related, but not all identical, to Geobacter sulfurreducens strain PCA. Other bacterial species were also detected in the system, such as a Propionicimonas-related species that was dominant in the anodic liquid and Pseudomonas-, Clostridium-, Desulfovibrio-, Azospira-, and Aeromonas-related species. PMID:21131513

Pt metallization of laser transformed medical grade silicone rubber: Last step toward a miniaturized nerve electrode fabrication process

NASA Astrophysics Data System (ADS)

Dupas-Bruzek, C.; Dréan, P.; Derozier, D.

2009-10-01

Chronic nerve recording and stimulation became possible through the use of implanted electrodes cuffs. In particular, self-sizing spiral electrode cuffs limit mechanical damage to the tissue: these have been shown to be suitable for long term implantation in animal and in man. However, up to now, such electrode cuffs were handmade and were hardly reproducible. They possessed a small number of electrodes (dot contacts), each being linked to its own wire. In order to improve the selectivity of nerve recording and/or stimulation (functional electrical stimulation), the numbers of electrodes and tracks have to be increased within the same electrode cuff surface. To fulfill this requirement, we have developed a fabrication process that uses an UV laser to induce surface modification, which activates the silicone rubber and is used with a mask to give high definition tracks and electrodes. After this primary step, silicone rubber is immersed in a Pt autocatalytic bath leading to a selective Pt metallization of the laser activated tracks and electrodes. We report our process as well as the results on the Pt metallization, including its morphology, how the DC resistance of Pt tracks depends on the laser used and the irradiation conditions, and also the electrical resistance of Pt tracks submitted to Scotch tape tests or to imposed strains. We show that (i) the type of laser and the irradiation conditions have a strong influence on the nucleation and growth rate of platinum and thus on the DC resistance of the tracks, (ii) the tracks of width 400 μm and thickness 10 μm have a sheet resistivity of 0.2 Ω/sq, (iii) DC resistance does not change much during a 6 month soak in saline, (iv) strains above 2% breaks the track continuity, and (v) when strains below 53% are relaxed, the DC resistance returns to a low value. This recovery from large tensile strains means that nerve cuffs with such metallization could be handled by the surgeon without great care before and during implantation.

Hemispherical platinum : silver core : shell nanoparticles for miRNA detection.

PubMed

Spain, Elaine; Adamson, Kellie; Elshahawy, Mohammad; Bray, Isabella; Keyes, Tia E; Stallings, Raymond L; Forster, Robert J

2017-02-27

Defects within a self-assembled monolayer (SAM) of dodecanethiol on gold have been used as nucleation sites for the electrodeposition of mushroom shaped platinum nanoparticles (PtNPs). The top surfaces of these PtNPs were then decorated with a layer of silver creating a hemispherical - platinum : silver core : shell nanoparticle (Pt-AgNP). Thiolated probe strand miRNA was then immobilised onto the upper silver surface. These regioselectively modified particles were desorbed by applying a current jump to yield nanoparticles capable of hybridising to a complementary miRNA target with electrocatalysis occurring on the non-functionalized lower surface. A second electrode was functionalized with single stranded capture miRNA that has a sequence that is complementary to an miRNA, miR-132, associated with the childhood cancer, Neuroblastoma but leaves a section of the target available to bind the nucleic acid sequence on the core : shell Pt-AgNPs. Following hybridization of the target and capture strands the surface was exposed to the miRNA labelled electrocatalytic Pt-AgNPs. The concentration of the target was then determined by monitoring the current associated with the reduction of hydrogen peroxide in a solution of H 2 SO 4 . Calibration plots of the log[miRNA] vs. faradaic current were linear from 1 aM to 1 μM and aM concentrations could be detected without the need for chemical amplification of the target, e.g., using PCR or NASBA. The regioselectively modified particles were also immobilised within the interior of gold microcavity arrays via miRNA hybridisation and their Raman properties investigated.

Electrodeposition of copper on a Pt(111) electrode in sulfuric acid containing poly(ethylene glycol) and chloride ions as probed by in situ STM.

PubMed

Fu, YunLin; Pao, Te; Chen, Sih-Zih; Yau, ShuehLin; Dow, Wei-Ping; Lee, Yuh-Lang

2012-07-03

This study employed real-time in situ STM imaging to examine the adsorption of PEG molecules on Pt(111) modified by a monolayer of copper adatoms and the subsequent bulk Cu deposition in 1 M H(2)SO(4) + 1 mM CuSO(4)+ 1 mM KCl + 88 μM PEG. At the end of Cu underpotential deposition (~0.35 V vs Ag/AgCl), a highly ordered Pt(111)-(√3 × √7)-Cu + HSO(4)(-) structure was observed in 1 M H(2)SO(4) + 1 mM CuSO(4). This adlattice restructured upon the introduction of poly(ethylene glycol) (PEG, molecular weight 200) and chloride anions. At the onset potential for bulk Cu deposition (~0 V), a Pt(111)-(√3 × √3)R30°-Cu + Cl(-) structure was imaged with a tunneling current of 0.5 nA and a bias voltage of 100 mV. Lowering the tunneling current to 0.2 nA yielded a (4 × 4) structure, presumably because of adsorbed PEG200 molecules. The subsequent nucleation and deposition processes of Cu in solution containing PEG and Cl(-) were examined, revealing the nucleation of 2- to 3-nm-wide CuCl clusters on an atomically smooth Pt(111) surface at overpotentials of less than 50 mV. With larger overpotential (η > 150 mV), Cu deposition seemed to bypass the production of CuCl species, leading to layered Cu deposition, starting preferentially at step defects, followed by lateral growth to cover the entire Pt electrode surface. These processes were observed with both PEG200 and 4000, although the former tended to produce more CuCl nanoclusters. Raising [H(2)SO(4)] to 1 M substantiates the suppressing effect of PEG on Cu deposition. This STM study provided atomic- or molecular-level insight into the effect of PEG additives on the deposition of Cu.

Nickel incorporated carbon nanotube/nanofiber composites as counter electrodes for dye-sensitized solar cells.

PubMed

Joshi, Prakash; Zhou, Zhengping; Poudel, Prashant; Thapa, Amit; Wu, Xiang-Fa; Qiao, Qiquan

2012-09-21

A nickel incorporated carbon nanotube/nanofiber composite (Ni-CNT-CNF) was used as a low cost alternative to Pt as counter electrode (CE) for dye-sensitized solar cells (DSCs). Measurements based on energy dispersive X-rays spectroscopy (EDX) showed that the majority of the composite CE was carbon at 88.49 wt%, while the amount of Ni nanoparticles was about 11.51 wt%. Measurements based on electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (R(ct)) of the Ni-CNT-CNF composite electrode was 0.71 Ω cm(2), much lower than that of the Pt electrode (1.81 Ω cm(2)). Such a low value of R(ct) indicated that the Ni-CNT-CNF composite carried a higher catalytic activity than the traditional Pt CE. By mixing with CNTs and Ni nanoparticles, series resistance (R(s)) of the Ni-CNT-CNF electrode was measured as 5.96 Ω cm(2), which was close to the R(s) of 5.77 Ω cm(2) of the Pt electrode, despite the significant difference in their thicknesses: ∼22 μm for Ni-CNT-CNF composite, while ∼40 nm for Pt film. This indicated that use of a thick layer (tens of microns) of Ni-CNT-CNF counter electrode does not add a significant amount of resistance to the total series resistance (R(s-tot)) in DSCs. The DSCs based on the Ni-CNT-CNF composite CEs yielded an efficiency of 7.96% with a short circuit current density (J(sc)) of 15.83 mA cm(-2), open circuit voltage (V(oc)) of 0.80 V, and fill factor (FF) of 0.63, which was comparable to the device based on Pt, that exhibited an efficiency of 8.32% with J(sc) of 15.01 mA cm(-2), V(oc) of 0.83, and FF of 0.67.

Development of a spectro-electrochemical cell for soft X-ray photon-in photon-out spectroscopy

NASA Astrophysics Data System (ADS)

Ishihara, Tomoko; Tokushima, Takashi; Horikawa, Yuka; Kato, Masaru; Yagi, Ichizo

2017-10-01

We developed a spectro-electrochemical cell for X-ray absorption and X-ray emission spectroscopy, which are element-specific methods to study local electronic structures in the soft X-ray region. In the usual electrochemical measurement setup, the electrode is placed in solution, and the surface/interface region of the electrode is not normally accessible by soft X-rays that have low penetration depth in liquids. To realize soft X-ray observation of electrochemical reactions, a 15-nm-thick Pt layer was deposited on a 150-nm-thick film window with an adhesive 3-nm-thick Ti layer for use as both the working electrode and the separator window between vacuum and a sample liquid under atmospheric pressure. The designed three-electrode electrochemical cell consists of a Pt film on a SiC window, a platinized Pt wire, and a commercial Ag|AgCl electrode as the working, counter, and reference electrodes, respectively. The functionality of the cell was tested by cyclic voltammetry and X-ray absorption and emission spectroscopy. As a demonstration, the electroplating of Pb on the Pt/SiC membrane window was measured by X-ray absorption and real-time monitoring of fluorescence intensity at the O 1s excitation.

Manganese porphyrin decorated on DNA networks as quencher and mimicking enzyme for construction of ultrasensitive photoelectrochemistry aptasensor.

PubMed

Huang, Liaojing; Zhang, Li; Yang, Liu; Yuan, Ruo; Yuan, Yali

2018-05-01

In this work, the manganese porphyrin (MnPP) decorated on DNA networks could serve as quencher and mimicking enzyme to efficiently reduce the photocurrent of photoactive material 3,4,9,10-perylene tetracarboxylic acid (PTCA), which was elaborately used to construct a novel label-free aptasensor for ultrasensitive detection of thrombin (TB) in a signal-off manner. The Au-doped PTCA (PTCA-PEI-Au) with outstanding membrane-forming and photoelectric property was modified on electrode to acquire a strong initial photoelectrochemistry (PEC) signal. Afterward, target binding aptamer Ι (TBAΙ) was modified on electrode to specially recognize target TB, which could further combine with TBAII and single-stranded DNA P1-modified platinum nanoparticles (TBAII-PtNPs-P1) for immobilizing DNA networks with abundant MnPP. Ingeniously, the MnPP could not only directly quench the photocurrent of PTCA, but also acted as hydrogen peroxide (HRP) mimicking enzyme to remarkably stimulate the deposition of benzo-4-chlorhexidine (4-CD) on electrode for further decreasing the photocurrent of PTCA, thereby obtaining a definitely low photocurrent for detection of TB. As a result, the proposed PEC aptasensor illustrated excellent sensitivity with a low detection limit down to 3 fM, exploiting a new avenue about intergrating two functions in one substance for ultrasensitive biological monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

Analysis of forecasting and inventory control of raw material supplies in PT INDAC INT’L

NASA Astrophysics Data System (ADS)

Lesmana, E.; Subartini, B.; Riaman; Jabar, D. A.

2018-03-01

This study discusses the data forecasting sales of carbon electrodes at PT. INDAC INT L uses winters and double moving average methods, while for predicting the amount of inventory and cost required in ordering raw material of carbon electrode next period using Economic Order Quantity (EOQ) model. The result of error analysis shows that winters method for next period gives result of MAE, MSE, and MAPE, the winters method is a better forecasting method for forecasting sales of carbon electrode products. So that PT. INDAC INT L is advised to provide products that will be sold following the sales amount by the winters method.

Catalytic, conductive, and transparent platinum nanofiber webs for FTO-free dye-sensitized solar cells.

PubMed

Kim, Jongwook; Kang, Jonghyun; Jeong, Uiyoung; Kim, Heesuk; Lee, Hyunjung

2013-04-24

We report a multifunctional platinium nanofiber (PtNF) web that can act as a catalyst layer in dye-sensitized solar cell (DSSC) to simultaneously function as a transparent counter electrode (CE), i.e., without the presence of an indium-doped tin oxide (ITO) or fluorine-doped tin oxide (FTO) glass. This PtNF web can be easily produced by electrospinning, which is highly cost-effective and suitable for large-area industrial-scale production. Electrospun PtNFs are straight and have a length of a few micrometers, with a common diameter of 40-70 nm. Each nanofiber is composed of compact, crystalline Pt grains and they are well-fused and highly interconnected, which should be helpful to provide an efficient conductive network for free electron transport and a large surface area for electrocatalytic behavior. A PtNF web is served as a counter electrode in DSSC and the photovoltaic performance increases up to a power efficiency of 6.0%. It reaches up to 83% of that in a conventional DSSC using a Pt-coated FTO glass as a counter electrode. Newly designed DSSCs containing PtNF webs display highly stable photoelectric conversion efficiencies, and excellent catalytic, conductive, and transparent properties, as well as long-term stability. Also, while the DSSC function is retained, the fabrication cost is reduced by eliminating the transparent conducting layer on the counter electrode. The presented method of fabricating DSSCs based on a PtNF web can be extended to other electrocatalytic optoelectronic devices that combine superior catalytic activity with high conductivity and transparency.

Synthesis of Pt-Ni-Fe/CNT/CP nanocomposite as an electrocatalytic electrode for PEM fuel cell cathode

NASA Astrophysics Data System (ADS)

Litkohi, Hajar Rajaei; Bahari, Ali; Ojani, Reza

2017-08-01

In order to use carbon nanotube (CNT)-supported catalyst as fuel cell electrodes, Pt-Ni-Fe/CNT/carbon paper (CP) electrode was prepared using an ethylene glycol reduction method. CNTs were directly synthesized on Ni-impregnated carbon paper, plain carbon cloth, and Teflonized carbon cloth using chemical vapor deposition. FESEM and TEM images and thermogravimetric analysis indicated that in situ CNT on carbon paper (ICNT/CP) possesses more appropriate structural quality and stronger adhesion to the substrate than other substrates. The contact angle analysis demonstrated that the degree of ICNT/CP surface hydrophobicity encountered a 24% increase in comparison to CP and promoted to superhydrophobicity from hydrophobicity. The polarization curves and electrochemical impedance spectroscopy results of the loaded Pt-Ni-Fe on in situ and ex situ CNT/CP illustrated that the power density increased and charge transfer resistance reduced compared to commercial Pt/C loaded on CP. The results can be attributed to the outstanding properties of CNTs and high catalytic activity of triple catalysts causing alloying of Pt with Ni and Fe, which makes them a proper candidate to be used as cathode electrodes in proton exchange membrane fuel cells.

Ultrasonic-electrodeposition of PtPd alloy nanoparticles on ionic liquid-functionalized graphene paper: towards a flexible and versatile nanohybrid electrode

NASA Astrophysics Data System (ADS)

Sun, Yimin; Zheng, Huaming; Wang, Chenxu; Yang, Mengmeng; Zhou, Aijun; Duan, Hongwei

2016-01-01

Here we fabricate a new type of flexible and versatile nanohybrid paper electrode by ultrasonic-electrodeposition of PtPd alloy nanoparticles on freestanding ionic liquid (IL)-functionalized graphene paper, and explore its multifunctional applications in electrochemical catalysis and sensing systems. The graphene-based paper materials demonstrate intrinsic flexibility, exceptional mechanical strength and high electrical conductivity, and therefore can serve as an ideal freestanding flexible electrode for electrochemical devices. Furthermore, the functionalization of graphene with IL (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate) not only increases the electroactive surface area of a graphene-based nanohybrid paper electrode, but also improves the adhesion and dispersion of metal nanoparticles on the paper surface. These unique attributes, combined with the merits of an ultrasonic-electrodeposition method, lead to the formation of PtPd alloy nanoparticles on IL-graphene paper with high loading, uniform distribution, controlled morphology and favourable size. Consequently, the resultant nanohybrid paper electrode exhibits remarkable catalytic activity as well as excellent cycle stability and improved anti-poisoning ability towards electrooxidation of fuel molecules such as methanol and ethanol. Furthermore, for nonenzymatic electrochemical sensing of some specific biomarkers such as glucose and reactive oxygen species, the nanohybrid paper electrode shows high selectivity, sensitivity and biocompatibility in these bio-catalytic processes, and can be used for real-time tracking hydrogen peroxide secretion by living human cells. All these features demonstrate its promising application as a versatile nanohybrid electrode material in flexible and lightweight electrochemical energy conversion and biosensing systems such as bendable on-chip power sources, wearable/implantable detectors and in vivo micro-biosensors.Here we fabricate a new type of flexible and versatile nanohybrid paper electrode by ultrasonic-electrodeposition of PtPd alloy nanoparticles on freestanding ionic liquid (IL)-functionalized graphene paper, and explore its multifunctional applications in electrochemical catalysis and sensing systems. The graphene-based paper materials demonstrate intrinsic flexibility, exceptional mechanical strength and high electrical conductivity, and therefore can serve as an ideal freestanding flexible electrode for electrochemical devices. Furthermore, the functionalization of graphene with IL (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate) not only increases the electroactive surface area of a graphene-based nanohybrid paper electrode, but also improves the adhesion and dispersion of metal nanoparticles on the paper surface. These unique attributes, combined with the merits of an ultrasonic-electrodeposition method, lead to the formation of PtPd alloy nanoparticles on IL-graphene paper with high loading, uniform distribution, controlled morphology and favourable size. Consequently, the resultant nanohybrid paper electrode exhibits remarkable catalytic activity as well as excellent cycle stability and improved anti-poisoning ability towards electrooxidation of fuel molecules such as methanol and ethanol. Furthermore, for nonenzymatic electrochemical sensing of some specific biomarkers such as glucose and reactive oxygen species, the nanohybrid paper electrode shows high selectivity, sensitivity and biocompatibility in these bio-catalytic processes, and can be used for real-time tracking hydrogen peroxide secretion by living human cells. All these features demonstrate its promising application as a versatile nanohybrid electrode material in flexible and lightweight electrochemical energy conversion and biosensing systems such as bendable on-chip power sources, wearable/implantable detectors and in vivo micro-biosensors. Electronic supplementary information (ESI) available: The stress-strain curve of the IL-rGOP, EDX spectrum of PtPd/IL-rGOP, the particle size and size distribution of Pt, PtPd and Pd nanoparticles electrodeposited on IL-rGOP derived from SEM, and the structural parameters of Pt, PtPd and Pd nanoparticles electrodeposited on IL-rGOP derived from XRD, influence of the potential interfering species towards glucose detection. See DOI: 10.1039/c5nr06912b

Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

PubMed Central

Vomero, Maria; Castagnola, Elisa; Ciarpella, Francesca; Maggiolini, Emma; Goshi, Noah; Zucchini, Elena; Carli, Stefano; Fadiga, Luciano; Kassegne, Sam; Ricci, Davide

2017-01-01

We report on the superior electrochemical properties, in-vivo performance and long term stability under electrical stimulation of a new electrode material fabricated from lithographically patterned glassy carbon. For a direct comparison with conventional metal electrodes, similar ultra-flexible, micro-electrocorticography (μ-ECoG) arrays with platinum (Pt) or glassy carbon (GC) electrodes were manufactured. The GC microelectrodes have more than 70% wider electrochemical window and 70% higher CTC (charge transfer capacity) than Pt microelectrodes of similar geometry. Moreover, we demonstrate that the GC microelectrodes can withstand at least 5 million pulses at 0.45 mC/cm2 charge density with less than 7.5% impedance change, while the Pt microelectrodes delaminated after 1 million pulses. Additionally, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was selectively electrodeposited on both sets of devices to specifically reduce their impedances for smaller diameters (<60 μm). We observed that PEDOT-PSS adhered significantly better to GC than Pt, and allowed drastic reduction of electrode size while maintaining same amount of delivered current. The electrode arrays biocompatibility was demonstrated through in-vitro cell viability experiments, while acute in vivo characterization was performed in rats and showed that GC microelectrode arrays recorded somatosensory evoked potentials (SEP) with an almost twice SNR (signal-to-noise ratio) when compared to the Pt ones. PMID:28084398

Electrocatalytic effect of polyvinyl pyrrolidone capped platinum nanoparticles electrodeposited on platinum electrode for ammonia oxidation

NASA Astrophysics Data System (ADS)

Mayedwa, Noluthando; Matinise, Nolubabalo; Mongwaketsi, Nametso; Maaza, Malik

2018-05-01

The aim of this work was to study structural and kinetic parameters as well as the mechanism of platinum nanoparticles (PtNP) reduced with sodium borohydride (NaBH4) and capped with polyvinyl pyrrolidone (PVP). The nanoparticles were supported on Pt electrode for ammonia oxidation in fuel cell application. X-ray diffraction (XRD) was used to study structural composition and high resolution transmission electron microscopy (HRTEM) was used for morphological study of the nanoalloy. The electrocatalysts were studied in alkaline solution of potassium hydroxide (KOH) by cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). CV showed that the ammonia oxidation over potential for PtNP was -431 mV and with exchange current density of 1.726 × 10-4 A. EIS showed that the charge transfer resistance (Rct) of PtNP was the lowest (Rct = 1.943 × 106 Ω) compared to that of bare Pt working electrode (2.0604 × 106 Ω), indicating that the Pt nanoparticles have good conductivity and played an important role in accelerating the transfer of electrons.

Preparation of Platinum (Pt) Counter Electrode Coated by Electrochemical Technique at High Temperature for Dye-sensitized Solar Cell (DSSC) Application

NASA Astrophysics Data System (ADS)

Ponken, Tanachai; Tagsin, Kamonlapron; Suwannakhun, Chuleerat; Luecha, Jakkrit; Choawunklang, Wijit

2017-09-01

Pt counter electrode was coated by electrochemical method. Electrolyte solution was synthesized by platinum (IV) choloride (PtCl4) powder dissolved in hydrochloric acid solution. Pt films were deposited on the FTO substrate. Deposition time of 10, 30 and 60 minutes, the coating current of 5, 10, 15 and 20 mA and electrolyte solution temperatures for Pt layer synthesis of 25, 30 and 40°C were varied. Surface morphology and optical properties was analyzed by digital microscopic and UV-vis spectrophotometer. Pt films exhibit uniform surface area highly for all the conditions of coating current in the deposition time of 30 and 40 minutes at 40°C. Transmittance values of Pt films deposited on FTO substrate has approximately of 5 to 50 % show that occur high reflection corresponding to dye molecule absorption increases. DSSC device was fabricated from the TiO2 standard and immersed in dye N719 for 24 hours. Efficiency was measured by solar simulator. Efficiency value obtains as high as 5.91 % for the coating current, deposition time and solution temperature of 15 mA, 30 minutes and 40°C. Summary, influence of temperature effects efficiency increasing. Pt counter electrode can be prepared easily and the suitable usefully for DSSC.

A three-layer PMMA electrophoresis microchip with Pt microelectrodes insulated by a thin film for contactless conductivity detection.

PubMed

Liu, Junshan; Wang, Junyao; Chen, Zuanguang; Yu, Yong; Yang, Xiujuan; Zhang, Xianbin; Xu, Zheng; Liu, Chong

2011-03-07

A three-layer poly (methyl methacrylate) (PMMA) electrophoresis microchip integrated with Pt microelectrodes for contactless conductivity detection is presented. A 50 μm-thick PMMA film is used as the insulating layer and placed between the channel plate (containing the microchannel) and the electrode plate (containing the microelectrode). The three-layer structure facilitates the achievement of a thin insulating layer, obviates the difficulty of integrating microelectrodes on a thin film, and does not compromise the integration of microchips. To overcome the thermal and chemical incompatibilities of polymers and photolithographic techniques, a modified lift-off process was developed to integrate Pt microelectrodes onto the PMMA substrate. A novel two-step bonding method was created to assemble the complete PMMA microchip. A low limit of detection of 1.25 μg ml(-1) for Na(+) and high separation efficiency of 77,000 and 48,000 plates/m for Na(+) and K(+) were obtained when operating the detector at a low excitation frequency of 60 kHz.

Advanced Catalysts for Fuel Cells

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram R.; Whitacre, Jay; Valdez, T. I.

2006-01-01

This viewgraph presentation reviews the development of catalyst for Fuel Cells. The objectives of the project are to reduce the cost of stack components and reduce the amount of precious metal used in fuel cell construction. A rapid combinatorial screening technique based on multi-electrode thin film array has been developed and validated for identifying catalysts for oxygen reduction; focus shifted from methanol oxidation in FY05 to oxygen reduction in FY06. Multi-electrode arrays of thin film catalysts of Pt-Ni and Pt-Ni-Zr have been deposited. Pt-Ni and have been characterized electrochemically and structurally. Pt-Ni-Zr and Pt-Ni films show higher current density and onset potential compared to Pt. Electrocatalytic activity and onset potential are found to be strong function of the lattice constant. Thin film Pt(59)Ni(39)Zr(2) can provide 10 times the current density of thin film Pt. Thin film Pt(59)Ni(39)Zr(2) also shows 65mV higher onset potential than Pt.

Highly exposed Pt nanoparticles supported on porous graphene for electrochemical detection of hydrogen peroxide in living cells.

PubMed

Liu, Jian; Bo, Xiangjie; Zhao, Zheng; Guo, Liping

2015-12-15

In this study, we developed a novel biosensor based on highly exposed Pt nanoparticles (Pt NPs) decorated porous graphene (PG) for the reliable detection of extracellular hydrogen peroxide (H2O2) released from living cells. The commercially available low-cost hydrophilic CaCO3 spheres were used as template for preparing PG. The porous structure provided larger surface area and more active sites. Due to the porous structure of PG, the Pt NPs supported on PG were not secluded by aggregated graphene layers and were highly exposed to target molecules. Ultrafine Pt NPs were well dispersed and loaded on PG by a method of microwave assistance. Electrochemical performances of the Pt/PG nanocomposites modified glassy carbon electrode (GCE) were investigated. The electrocatalytic reduction of H2O2 showed a wide linear range from 1 to 1477 μM, with a high sensitivity of 341.14 μA mM(-1) cm(-2) and a limit of detection (LOD) as low as 0.50 μM. Moreover, the Pt/PG/GCE exhibited excellent anti-interference property, reproducibility and long-term storage stability. Because of these remarkable analytical advantages, the constructed sensor was used to determine H2O2 released from living cells with satisfactory results. The superior catalytic activity makes Pt/PG nanocomposites a promising candidate for electrochemical sensors and biosensors design. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of platinum-nanodendrite modification on the glucose-sensing properties of a zinc-oxide-nanorod electrode

NASA Astrophysics Data System (ADS)

Abdul Razak, Khairunisak; Neoh, Soo Huan; Ridhuan, N. S.; Mohamad Nor, Noorhashimah

2016-09-01

The properties of ZnO nanorods (ZnONRs) decorated with platinum nanodendrites (PtNDs) were studied. Various sizes of PtNDs were synthesized and spin coated onto ZnONRs, which were grown on indium-titanium-oxide (ITO) substrates through a low-temperature hydrothermal method. Scanning electron microscopy and X-ray diffraction analyses were conducted to analyze the morphology and structural properties of the electrodes. The effects of PtND size, glucose concentration, and Nafion amount on glucose-sensing properties were investigated. The glucose-sensing properties of electrodes with immobilized glucose oxidase (GOx) were measured using cyclic voltammetry. The bio-electrochemical properties of Nafion/GOx/42 nm PtNDs/ZnONRs/ITO glucose sensor was observed with linear range within 1-18 mM, with a sensitivity value of 5.85 μA/mM and a limit of detection of 1.56 mM. The results of this study indicate that PtNDs/ZnONRs/ITO has potential in glucose sensor applications.

Carbon nanotubes based methanol sensor for fuel cells application.

PubMed

Kim, D W; Lee, J S; Lee, G S; Overzet, L; Kozlov, M; Aliev, A E; Park, Y W; Yang, D J

2006-11-01

An electrochemical sensor is built using vertically grown multi-walled carbon nanotubes (MWNTs) micro-array to detect methanol concentration in water. This study is done for the potential use of the array as methanol sensor for portable units of direct methanol fuel cells (DMFCs). Platinum (Pt) nanoparticles electro-deposited CNTs (Pt/CNTs) electrode shows high sensitivity in the measurement of methanol concentration in water with cyclic voltammetry (CV) measurement at room temperature. Further investigation has also been undertaken to measure the concentration by changing the amount of the mixture of methanol and formic acid in water. We compared the performance of our micro array sensor built with Pt/CNTs electrodes versus that of Pt wire electrode using CV measurement. We found that our Pt/CNTs array sensor shows high sensitivity and detects methanol concentrations in the range of 0.04 M to 0.10 M. In addition, we found that co-use of formic acid as electrolyte enables us to measure up to 1.0 M methanol concentration.

Characterizing Electrolyte and Platinum Interface in PEM Fuel Cells Using CO Displacement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrick, Taylor R.; Moylan, Thomas E.; Yarlagadda, Venkata

Relatively large O 2 transport resistance at the ionomer and Pt interface has been thought to be responsible for the large performance loss at high power for a low Pt loading proton-exchange-membrane fuel cell. A facile method to characterize the interface in the fuel cell electrode is needed. In this study, the CO displacement method was explored on polycrystalline Pt and carbon-supported Pt nanoparticles. The displacement charge coverages were used to quantify the adsorption of perchlorate, sulfate, and perfluorosulfonic acid ionomer. The application of this method in a fuel cell electrode was demonstrated.

Characterizing Electrolyte and Platinum Interface in PEM Fuel Cells Using CO Displacement

DOE PAGES

Garrick, Taylor R.; Moylan, Thomas E.; Yarlagadda, Venkata; ...

2016-12-13

Relatively large O 2 transport resistance at the ionomer and Pt interface has been thought to be responsible for the large performance loss at high power for a low Pt loading proton-exchange-membrane fuel cell. A facile method to characterize the interface in the fuel cell electrode is needed. In this study, the CO displacement method was explored on polycrystalline Pt and carbon-supported Pt nanoparticles. The displacement charge coverages were used to quantify the adsorption of perchlorate, sulfate, and perfluorosulfonic acid ionomer. The application of this method in a fuel cell electrode was demonstrated.

Performance of conducting polymer electrodes for stimulating neuroprosthetics

NASA Astrophysics Data System (ADS)

Green, R. A.; Matteucci, P. B.; Hassarati, R. T.; Giraud, B.; Dodds, C. W. D.; Chen, S.; Byrnes-Preston, P. J.; Suaning, G. J.; Poole-Warren, L. A.; Lovell, N. H.

2013-02-01

Objective. Recent interest in the use of conducting polymers (CPs) for neural stimulation electrodes has been growing; however, concerns remain regarding the stability of coatings under stimulation conditions. These studies examine the factors of the CP and implant environment that affect coating stability. The CP poly(ethylene dioxythiophene) (PEDOT) is examined in comparison to platinum (Pt), to demonstrate the potential performance of these coatings in neuroprosthetic applications. Approach. PEDOT is coated on Pt microelectrode arrays and assessed in vitro for charge injection limit and long-term stability under stimulation in biologically relevant electrolytes. Physical and electrical stability of coatings following ethylene oxide (ETO) sterilization is established and efficacy of PEDOT as a visual prosthesis bioelectrode is assessed in the feline model. Main results. It was demonstrated that PEDOT reduced the potential excursion at a Pt electrode interface by 72% in biologically relevant solutions. The charge injection limit of PEDOT for material stability was found to be on average 30× larger than Pt when tested in physiological saline and 20× larger than Pt when tested in protein supplemented media. Additionally stability of the coating was confirmed electrically and morphologically following ETO processing. It was demonstrated that PEDOT-coated electrodes had lower potential excursions in vivo and electrically evoked potentials (EEPs) could be detected within the visual cortex. Significance. These studies demonstrate that PEDOT can be produced as a stable electrode coating which can be sterilized and perform effectively and safely in neuroprosthetic applications. Furthermore these findings address the necessity for characterizing in vitro properties of electrodes in biologically relevant milieu which mimic the in vivo environment more closely.

Enhancing motor performance improvement by personalizing non-invasive cortical stimulation with concurrent functional near-infrared spectroscopy and multi-modal motor measurements

NASA Astrophysics Data System (ADS)

Khan, Bilal; Hodics, Timea; Hervey, Nathan; Kondraske, George; Stowe, Ann; Alexandrakis, George

2015-03-01

Transcranial direct current stimulation (tDCS) is a non-invasive cortical stimulation technique that can facilitate task specific plasticity that can improve motor performance. Current tDCS interventions uniformly apply a chosen electrode montage to a subject population without personalizing electrode placement for optimal motor gains. We propose a novel perturbation tDCS (ptDCS) paradigm for determining a personalized electrode montage in which tDCS intervention yields maximal motor performance improvements during stimulation. PtDCS was applied to ten healthy adults and five stroke patients with upper hemiparesis as they performed an isometric wrist flexion task with their non-dominant arm. Simultaneous recordings of torque applied to a stationary handle, muscle activity by electromyography (EMG), and cortical activity by functional near-infrared spectroscopy (fNIRS) during ptDCS helped interpret how cortical activity perturbations by any given electrode montage related to changes in muscle activity and task performance quantified by a Reaction Time (RT) X Error product. PtDCS enabled quantifying the effect on task performance of 20 different electrode pair montages placed over the sensorimotor cortex. Interestingly, the electrode montage maximizing performance in all healthy adults did not match any of the ones being explored in current literature as a means of improving the motor performance of stroke patients. Furthermore, the optimal montage was found to be different in each stroke patient and the resulting motor gains were very significant during stimulation. This study supports the notion that task-specific ptDCS optimization can lend itself to personalizing the rehabilitation of patients with brain injury.

Durability of Pt-Co Alloy Polymer Electrolyte Fuel Cell Cathode Catalysts under Accelerated Stress Tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papadias, D. D.; Ahluwalia, R. K.; Kariuki, N.

The durability of Pt-Co alloy cathode catalysts supported on high surface area carbon is investigated by subjecting them to accelerated stress tests (ASTs). The catalysts had different initial Co contents and nanoparticle morphologies: a “spongy” porous morphology for the high-Co (H) content catalyst, and a fully alloyed crystalline morphology for the medium-Co (M) and low-Co (L) content catalysts. The specific activity of the catalysts depends on their initial Co content, morphology and nanoparticle size, and remained higher than 1000 μA/cm 2-Pt after 27–50% Co loss. The H-catalyst electrode showed the smallest kinetic overpotentials (η c s) due to higher initialmore » Pt loading than the other two electrodes, but it had the fastest increase in ηcs with AST cycling due to lower Co retention; the L-catalyst electrode showed higher η c s due to a lower initial Pt loading, but had a smaller increase in η c s with aging due to higher Co retention; the M-catalyst electrode showed a similar increase in η c s with aging, but this increase was due to the combined effects of Co dissolution and electrochemically active surface area (ECSA) loss. In conclusion, the modeled increase in mass transfer overpotentials with aging correlates with the initial Pt loading, ECSA loss and the initial catalyst morphology« less

Durability of Pt-Co Alloy Polymer Electrolyte Fuel Cell Cathode Catalysts under Accelerated Stress Tests

DOE PAGES

Papadias, D. D.; Ahluwalia, R. K.; Kariuki, N.; ...

2018-03-17

The durability of Pt-Co alloy cathode catalysts supported on high surface area carbon is investigated by subjecting them to accelerated stress tests (ASTs). The catalysts had different initial Co contents and nanoparticle morphologies: a “spongy” porous morphology for the high-Co (H) content catalyst, and a fully alloyed crystalline morphology for the medium-Co (M) and low-Co (L) content catalysts. The specific activity of the catalysts depends on their initial Co content, morphology and nanoparticle size, and remained higher than 1000 μA/cm 2-Pt after 27–50% Co loss. The H-catalyst electrode showed the smallest kinetic overpotentials (η c s) due to higher initialmore » Pt loading than the other two electrodes, but it had the fastest increase in ηcs with AST cycling due to lower Co retention; the L-catalyst electrode showed higher η c s due to a lower initial Pt loading, but had a smaller increase in η c s with aging due to higher Co retention; the M-catalyst electrode showed a similar increase in η c s with aging, but this increase was due to the combined effects of Co dissolution and electrochemically active surface area (ECSA) loss. In conclusion, the modeled increase in mass transfer overpotentials with aging correlates with the initial Pt loading, ECSA loss and the initial catalyst morphology« less

The use of carbon black-TiO2 composite prepared using solid state method as counter electrode and E. conferta as sensitizer for dye-sensitized solar cell (DSSC) applications

NASA Astrophysics Data System (ADS)

Jaafar, Hidayani; Ahmad, Zainal Arifin; Ain, Mohd Fadzil

2018-05-01

In this paper, counter electrodes based on carbon black (CB)-TiO2 composite are proposed as a cost-effective alternative to conventional Pt counter electrodes used in dye-sensitized solar cell (DSSC) applications. CB-TiO2 composite counter electrodes with different weight percentages of CB were prepared using the solid state method and coated onto fluorine-doped tin oxide (FTO) glass using doctor blade method while Eleiodoxa conferta (E. conferta) and Nb-doped TiO2 were used as sensitizer and photoanode, respectively, with electrolyte containing I-/I-3 redox couple. The experimental results revealed that the CB-TiO2 composite influenced the photovoltaic performance by enhancing the electrocatalytic activity. As the amount of CB increased, the catalytic activity improved due to the increase in surface area which then led to low charge-transfer resistance (RCT) at the electrolyte/CB electrode interface. Due to the use of the modified photoanode together with natural dye sensitizers, the counter electrode based on 15 wt% CB-TiO2 composite was able to produce the highest energy conversion efficiency (2.5%) making it a viable alternative counter electrode.

A mini-electrochemical system integrated micropipet tip and pencil graphite electrode for detection of anticancer drug sensitivity in vitro.

PubMed

Guo, Xiaoling; Wang, Qian; Li, Jinlian; Cui, Jiwen; Zhou, Shi; Hao, Sue; Wu, Dongmei

2015-02-15

Developing a reliable and cost-effective miniaturized electroanalysis tool is of vital importance for cell electrochemical analysis. In this work, a novel mini-electrochemical system has been constructed for trace detection of cell samples. The mini-electrochemical system was constructed by integrating a pencil graphite modified by threonine (PT/PGE) as working electrode, an Ag/AgCl (Sat'd) as reference electrode, platinum wire as counter electrode and a micropipet tip as electrochemical cell. The mini-electrochemical system not only saved dramatically usage of samples from 500 μL in traditional electrochemical system to 10 μL, but also possessed an adjustable active surface area by changing the length of PT/PGE immersed into the cell suspension from 3mm to 15 mm, and the linear equation was ipa = 2.25 l-2.64 (R(2) = 0.990). The system was successfully used in detection of MCF-7 cells, and a nonlinear exponent relationship between peak current and the cell number range from 3.0 × l0(3) to 7.0 × l0(6) cells mL(-1) was established firstly with the index equation ipa = 59.557 e (-C/1.709)-71.486 (R(2) = 0.954). Finally, the system was used for evaluating the sensitivity of cyclophosphamide on MCF-7 cell, and the result was corresponded well with that of MTT assay. The proposed system is sufficiently simple, cheap and easy operated, and could be applied in electrochemical detection of other biological samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermally Deposited Palladium-Tungsten Carbide and Platinum-Tungsten Carbide Counter Electrodes for a High Performance Dye-Sensitized Solar Cell Based on Organic T-/T₂ Electrolyte.

PubMed

Towannang, Madsakorn; Thiangkaew, Anongnad; Maiaugree, Wasan; Ratchaphonsaenwong, Kunthaya; Jarernboon, Wirat; Pimanpang, Samuk; Amornkitbamrung, Vittaya

2018-02-01

Tungsten carbide (WC) particles (~1 μm) were dispersed in DI water and dropped onto conductive glass. The resulting WC films were used as dye-sensitized solar cell (DSSC) counter electrodes. The performance of the WC DSSC based on the organic thiolate/disulfide (T-/T2) electrolyte was ~0.78%. The cell efficiency was greatly improved after decorating palladium (Pd) or platinum (Pt) nanoparticles on WC particles with a promising efficiency of ~2.15% for Pd-WC DSSC and ~4.62% for Pt-WC DSSC. The efficiency improvement of the composited (Pd-WC and Pt-WC) cells is attributed to co-functioning catalysts, the large electrode interfacial area and a low charge-transfer resistance at the electrolyte/counter electrode interface.

Membrane electrode assembly fabricated with the combination of Pt/C and hollow shell structured-Pt-SiO2@ZrO2 sphere for self-humidifying proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Ko, Y. D.; Yang, H. N.; Züttel, Andreas; Kim, S. D.; Kim, W. J.

2017-11-01

The Pt-supported hollow structured Pt-HZrO2 with the shell thickness of 27 nm is successfully synthesized. The water retention ability of Pt-HZrO2 is significantly enhanced compared with that of SiO2@ZrO2 due to the hydrophilic hollow structured HZrO2with high BET surface area. Pt-C and Pt-HZrO2 are combined with different weight fractions to prepare the double catalyst electrode (DCE). The membrane electrode assembly with the DCE is fabricated and applied to both anode and cathode or anode side only. The water flooding and thus rapid voltage drop is affected by the presence/or absence of the DCE at the cathode side. The cell test and visual experiment suggests that the Pt-HZrO2 layer adsorb the water molecules generated by the oxygen reduction reaction (ORR), preventing the water flooding. The power generation under RH 0% strongly suggests the back-diffusion of water molecules generated by the ORR. The flow rate to the cathode significantly affects the water flooding and cell performance. Higher flow rate to the cathode is advantageous to expel the water generated by the ORR, thus preventing water flooding and enhancing the cell performance. Therefore, the weight fraction of Pt-C to Pt-HZrO2 and the flow rate to the cathode should be well balanced.

High-Frequency Oscillations Recorded on the Scalp of Patients With Epilepsy Using Tripolar Concentric Ring Electrodes

PubMed Central

Martínez-Juárez, Iris E.; Makeyev, Oleksandr; Gaitanis, John N.; Blum, Andrew S.; Fisher, Robert S.; Medvedev, Andrei V.

2014-01-01

Epilepsy is the second most prevalent neurological disorder (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}\\(\\sim 1\\) \\end{document}% prevalence) affecting \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}\\(\\sim 67\\) \\end{document} million people worldwide with up to 75% from developing countries. The conventional electroencephalogram is plagued with artifacts from movements, muscles, and other sources. Tripolar concentric ring electrodes automatically attenuate muscle artifacts and provide improved signal quality. We performed basic experiments in healthy humans to show that tripolar concentric ring electrodes can indeed record the physiological alpha waves while eyes are closed. We then conducted concurrent recordings with conventional disc electrodes and tripolar concentric ring electrodes from patients with epilepsy. We found that we could detect high frequency oscillations, a marker for early seizure development and epileptogenic zone, on the scalp surface that appeared to become more narrow-band just prior to seizures. High frequency oscillations preceding seizures were present in an average of 35.5% of tripolar concentric ring electrode data channels for all the patients with epilepsy whose seizures were recorded and absent in the corresponding conventional disc electrode data. An average of 78.2% of channels that contained high frequency oscillations were within the seizure onset or irritative zones determined independently by three epileptologists based on conventional disc electrode data and videos. PMID:27170874

Effect of Particle Size and Operating Conditions on Pt 3Co PEMFC Cathode Catalyst Durability

DOE PAGES

Gummalla, Mallika; Ball, Sarah; Condit, David; ...

2015-05-29

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt 3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes withmore » the smallest Pt 3Co particle size was the highest and that of the largest Pt 3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt 3Co over the 4.9 nm Pt 3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt 3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.« less

Anisotropic multi-spot DBR porous silicon chip for the detection of human immunoglobin G.

PubMed

Cho, Bomin; Um, Sungyong; Sohn, Honglae

2014-07-01

Asymmetric porous silicon multilayer (APSM)-based optical biosensor was developed to specify human Immunoglobin G (Ig G). APSM chip was generated by an electrochemical etching of silicon wafer using an asymmetric electrode configuration in aqueous ethanolic HF solution and constituted with nine arrayed porous silicon multilayer. APSM prepared from anisotropic etching conditions displayed a sharp reflection resonance in the reflectivity spectrum. Each spot displayed single reflection resonance at different wavelengths as a function of the lateral distance from the Pt counter electrode. The sensor system was consisted of the 3 x 3 spot array of APSM modified with protein A. The system was probed with an aqueous human Ig G. Molecular binding and specificity was monitored as a shift in wavelength of reflection resonance.

Dynamic wet-ETEM observation of Pt/C electrode catalysts in a moisturized cathode atmosphere.

PubMed

Yoshida, Kenta; Bright, Alexander N; Ward, Michael R; Lari, Leonardo; Zhang, Xudong; Hiroyama, Tomoki; Boyes, Edward D; Gai, Pratibha L

2014-10-24

The gas injection line of the latest spherical aberration-corrected environmental transmission electron microscope has been modified for achieving real-time/atomic-scale observations in moisturised gas atmospheres for the first time. The newly developed Wet-TEM system is applied to platinum carbon electrode catalysts to investigate the effect of water molecules on the platinum/carbon interface during deactivation processes such as sintering and corrosion. Dynamic in situ movies obtained in dry and 24% moisturised nitrogen environments visualize the rapid rotation, migration and agglomeration of platinum nanoparticles due to the physical adsorption of water and the hydroxylation of the carbon surface. The origin of the long-interconnected aggregation of platinum nanoparticles was discovered to be a major deactivation process in addition to conventional carbon corrosion.

Polarization fatigue of BiFeO3 films with ferromagnetic metallic electrodes

NASA Astrophysics Data System (ADS)

Chen, Chen; Wang, Ji; Li, Chen; Wen, Zheng; Xu, Qingyu; Du, Jun

2017-05-01

BiFeO3 (BFO) thin films were epitaxially grown on (001) SrTiO3 substrates using LaNiO3 as bottom electrode by pulsed laser deposition. The ferroelectric properties of BFO layer with ferromagnetic Ni21Fe79 (NiFe) or non-magnetic Pt electrode are investigated. Well saturated polarization-electric field (P-E) hysteresis loops are observed. Significant fatigue and associated drastic decrease in switchable polarization have been observed with cycling number exceeds 106, which can be explained by the domain wall pinning due to the oxygen vacancies trapping. With increasing cycle number to above 107, the polarization is rejuvenated. The polarization for BFO layer with NiFe electrode recovers to the initial value, while only about 75% of initial polarization is recovered for BFO layer with Pt electrode. Furthermore, the imprint is alleviated and the P-E hysteresis loops become more symmetric after the polarization recovery. The difference can be understood by the different interface state of NiFe/BFO and Pt/BFO.

Electrochemical Co-Reduction Synthesis of AuPt Bimetallic Nanoparticles-Graphene Nanocomposites for Selective Detection of Dopamine in the Presence of Ascorbic Acid and Uric Acid

PubMed Central

Zhao, Zongya; Zhang, Mingming; Chen, Xiang; Li, Youjun; Wang, Jue

2015-01-01

In this paper, AuPt bimetallic nanoparticles-graphene nanocomposites were obtained by electrochemical co-reduction of graphene oxide (GO), HAuCl4 and H2PtCl6. The as-prepared AuPt bimetallic nanoparticles-graphene nanocomposites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and other electrochemical methods. The morphology and composition of the nanocomposite could be easily controlled by adjusting the HAuCl4/H2PtCl6 concentration ratio. The electrochemical experiments showed that when the concentration ratio of HAuCl4/H2PtCl6 was 1:1, the obtained AuPt bimetallic nanoparticles-graphene nanocomposite (denoted as Au1Pt1NPs-GR) possessed the highest electrocatalytic activity toward dopamine (DA). As such, Au1Pt1NPs-GR nanocomposites were used to detect DA in the presence of ascorbic acid (AA) and uric acid (UA) using the differential pulse voltammetry (DPV) technique and on the modified electrode, there were three separate DPV oxidation peaks with the peak potential separations of 177 mV, 130 mV and 307 mV for DA and AA, DA and UA, AA and UA, respectively. The linear range of the constructed DA sensor was from 1.6 μM to 39.7 μM with a detection limit of 0.1 μM (S/N = 3). The obtained DA sensor with good stability, high reproducibility and excellent selectivity made it possible to detect DA in human urine samples. PMID:26184200

Electrochemical Co-Reduction Synthesis of AuPt Bimetallic Nanoparticles-Graphene Nanocomposites for Selective Detection of Dopamine in the Presence of Ascorbic Acid and Uric Acid.

PubMed

Zhao, Zongya; Zhang, Mingming; Chen, Xiang; Li, Youjun; Wang, Jue

2015-07-09

In this paper, AuPt bimetallic nanoparticles-graphene nanocomposites were obtained by electrochemical co-reduction of graphene oxide (GO), HAuCl4 and H2PtCl6. The as-prepared AuPt bimetallic nanoparticles-graphene nanocomposites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and other electrochemical methods. The morphology and composition of the nanocomposite could be easily controlled by adjusting the HAuCl4/H2PtCl6 concentration ratio. The electrochemical experiments showed that when the concentration ratio of HAuCl4/H2PtCl6 was 1:1, the obtained AuPt bimetallic nanoparticles-graphene nanocomposite (denoted as Au1Pt1NPs-GR) possessed the highest electrocatalytic activity toward dopamine (DA). As such, Au1Pt1NPs-GR nanocomposites were used to detect DA in the presence of ascorbic acid (AA) and uric acid (UA) using the differential pulse voltammetry (DPV) technique and on the modified electrode, there were three separate DPV oxidation peaks with the peak potential separations of 177 mV, 130 mV and 307 mV for DA and AA, DA and UA, AA and UA, respectively. The linear range of the constructed DA sensor was from 1.6 μM to 39.7 μM with a detection limit of 0.1 μM (S/N = 3). The obtained DA sensor with good stability, high reproducibility and excellent selectivity made it possible to detect DA in human urine samples.

Effect of nitrogen-accommodation ability of electrodes in SiNx-based resistive switching devices

NASA Astrophysics Data System (ADS)

Yang, Mei; Wang, Hong; Ma, Xiaohua; Gao, Haixia; Wang, Bin

2017-12-01

Nitrides could create opportunities of tuning resistive-switching (RS) characteristics due to their different electrical properties and ionic chemistry with oxides. Here, we reported on the effect of nitrogen-accommodation ability of electrodes in SiNx-based RS devices. The Ti/SiNx/Pt devices show a self-compliance bipolar RS with excellent reliability. The W/SiNx/Pt devices provide an unstable RS and fall to an intermediate resistance state (IRS) after a set process. The low resistance states of the Ti/SiNx/Pt devices obey Ohmic conduction and Frenkel-Poole emission from a conductive channel. The IRS of the W/SiNx/Pt devices conforms to Schottky emission and Fowler-Nordheim tunneling from a conductive channel/insulator/electrode structure. A nitrogen-ion-based model is proposed to explain the experimental results. According to the model, the nitrogen-accommodation ability of the electrodes dominates the nitrogen-reservoir size and the nitrogen-ion migration at the metal/SiNx interface, modulating the RS characteristics of the SiNx memory devices.

Silicon Photoelectrode Thermodynamics and Hydrogen Evolution Kinetics Measured by Intensity-Modulated High-Frequency Resistivity Impedance Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Nicholas C.; Carroll, Gerard M.; Pekarek, Ryan T.

Here, we present an impedance technique based on light intensity-modulated high-frequency resistivity (IMHFR) that provides a new way to elucidate both the thermodynamics and kinetics in complex semiconductor photoelectrodes. We apply IMHFR to probe electrode interfacial energetics on oxide-modified semiconductor surfaces frequently used to improve the stability and efficiency of photoelectrochemical water splitting systems. Combined with current density-voltage measurements, the technique quantifies the overpotential for proton reduction relative to its thermodynamic potential in Si photocathodes coated with three oxides (SiO x, TiO 2, and Al 2O 3) and a Pt catalyst. In pH 7 electrolyte, the flatband potentials of TiOmore » 2- and Al 2O 3-coated Si electrodes are negative relative to samples with native SiO x, indicating that SiO x is a better protective layer against oxidative electrochemical corrosion than ALD-deposited crystalline TiO 2 or Al 2O 3. Adding a Pt catalyst to SiO x/Si minimizes proton reduction overpotential losses but at the expense of a reduction in available energy characterized by a more negative flatband potential relative to catalyst-free SiO x/Si.« less

Silicon Photoelectrode Thermodynamics and Hydrogen Evolution Kinetics Measured by Intensity-Modulated High-Frequency Resistivity Impedance Spectroscopy

DOE PAGES

Anderson, Nicholas C.; Carroll, Gerard M.; Pekarek, Ryan T.; ...

2017-10-05

Here, we present an impedance technique based on light intensity-modulated high-frequency resistivity (IMHFR) that provides a new way to elucidate both the thermodynamics and kinetics in complex semiconductor photoelectrodes. We apply IMHFR to probe electrode interfacial energetics on oxide-modified semiconductor surfaces frequently used to improve the stability and efficiency of photoelectrochemical water splitting systems. Combined with current density-voltage measurements, the technique quantifies the overpotential for proton reduction relative to its thermodynamic potential in Si photocathodes coated with three oxides (SiO x, TiO 2, and Al 2O 3) and a Pt catalyst. In pH 7 electrolyte, the flatband potentials of TiOmore » 2- and Al 2O 3-coated Si electrodes are negative relative to samples with native SiO x, indicating that SiO x is a better protective layer against oxidative electrochemical corrosion than ALD-deposited crystalline TiO 2 or Al 2O 3. Adding a Pt catalyst to SiO x/Si minimizes proton reduction overpotential losses but at the expense of a reduction in available energy characterized by a more negative flatband potential relative to catalyst-free SiO x/Si.« less

Size-dependent electronic structure controls activity for ethanol electro-oxidation at Ptn/indium tin oxide (n = 1 to 14).

PubMed

von Weber, Alexander; Baxter, Eric T; Proch, Sebastian; Kane, Matthew D; Rosenfelder, Michael; White, Henry S; Anderson, Scott L

2015-07-21

Understanding the factors that control electrochemical catalysis is essential to improving performance. We report a study of electrocatalytic ethanol oxidation - a process important for direct ethanol fuel cells - over size-selected Pt centers ranging from single atoms to Pt14. Model electrodes were prepared by soft-landing of mass-selected Ptn(+) on indium tin oxide (ITO) supports in ultrahigh vacuum, and transferred to an in situ electrochemical cell without exposure to air. Each electrode had identical Pt coverage, and differed only in the size of Pt clusters deposited. The small Ptn have activities that vary strongly, and non-monotonically with deposited size. Activity per gram Pt ranges up to ten times higher than that of 5 to 10 nm Pt particles dispersed on ITO. Activity is anti-correlated with the Pt 4d core orbital binding energy, indicating that electron rich clusters are essential for high activity.

Fabrication of reduced graphene oxide/macrocyclic cobalt complex nanocomposites as counter electrodes for Pt-free dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tsai, Chih-Hung; Shih, Chun-Jyun; Wang, Wun-Shiuan; Chi, Wen-Feng; Huang, Wei-Chih; Hu, Yu-Chung; Yu, Yuan-Hsiang

2018-03-01

In this study, macrocyclic Co complexes were successfully grafted onto graphene oxide (GO) to produce GO/Co nanocomposites with a large surface area, high electrical conductivity, and excellent catalytic properties. The novel GO/Co nanocomposites were applied as counter electrodes for Pt-free dye-sensitized solar cells (DSSCs). Various ratios of macrocyclic Co complexes were used as the reductant to react with the GO, with which the surface functional groups of the GO were reduced and the macrocyclic ligand of the Co complexes underwent oxidative dehydrogenation, after which the conjugated macrocyclic Co systems were grafted onto the surface of the reduced GO to form GO/Co nanocomposites. The surface morphology, material structure, and composition of the GO/Co composites and their influences on the power-conversion efficiency of DSSC devices were comprehensively investigated. The results showed that the GO/Co (1:10) counter electrode (CE) exhibited an optimal power conversion efficiency of 7.48%, which was higher than that of the Pt CE. The GO/Co (1:10) CE exhibited superior electric conductivity, catalytic capacity, and redox capacity. Because GO/Co (1:10) CEs are more efficient and cheaper than Pt CEs, they could potentially be used as a replacement for Pt electrodes.

Tungsten trioxide nanoplate array supported platinum as a highly efficient counter electrode for dye-sensitized solar cells.

PubMed

Song, Dandan; Cui, Peng; Zhao, Xing; Li, Meicheng; Chu, Lihua; Wang, Tianyue; Jiang, Bing

2015-03-19

A tungsten trioxide (WO₃) nanoplate array is fabricated directly on the FTO/glass substrate and used as a platinum (Pt) nanoscale supporter for a highly efficient and low Pt-consumption counter electrode (CE) in dye-sensitized solar cells (DSCs). A Pt/WO₃ composite structure, with Pt nanoparticles having a diameter of 2-3 nm, increases the electrochemical catalytic activity in catalyzing the reduction of triiodide. Accordingly, the power conversion efficiency is increased from less than 1% for WO₃ CE and 8.1% for Pt CE, respectively, to 8.9% for Pt/WO₃ CE. Moreover, the use of Pt/WO₃ CE can dramatically reduce the consumption of scarce Pt material, with a relatively low Pt-loading of ∼2 μg cm(-2), while maintaining a much better performance. The excellent performance of Pt/WO₃ CE is attributed to the efficient electron injection and transport via WO₃ supporters, as well as the nanostructure array morphology of WO₃ for deposition of fine Pt nanoparticles. This work provides an approach for developing highly catalytic and low-cost Pt based CEs, which also has implications for the development of Pt/WO₃ nanoplate arrays for other applications.

Interpenetrating polyaniline-gold electrodes for SERS and electrochemical measurements

NASA Astrophysics Data System (ADS)

West, R. M.; Semancik, S.

2016-11-01

Facile fabrication of nanostructured electrode arrays is critical for development of bimodal SERS and electrochemical biosensors. In this paper, the variation of applied potential at a polyaniline-coated Pt electrode is used to selectivity deposit Au on the polyaniline amine sites or on the underlying Pt electrode. By alternating the applied potential, the Au is grown simultaneously from the top and the bottom of the polyaniline film, leading to an interpenetrated, nanostructured polymer-metal composite extending from the Pt electrode to the electrolyte solution. The resulting films have unique pH-dependent electrochemical properties, e.g. they retain electrochemical activity in both acidic and neutral solutions, and they also include SERS-active nanostructures. By varying the concentration of chloroaurate used during deposition, Au nanoparticles, nanodendrites, or nanosheets can be selectively grown. For the films deposited under optimal conditions, using 5 mmol/L chloroaurate, the SERS enhancement factor for Rhodamine 6G was found to be as high as 1.1 × 106 with spot-to-spot and electrode-to-electrode relative standard deviations as low as 8% and 12%, respectively. The advantages of the reported PANI-Au composite electrodes lie in their facile fabrication, enabling the targeted deposition of tunable nanostructures on sensing arrays, and their ability to produce orthogonal optical and electrochemical analytical results.

Photocatalytic events of CdSe quantum dots in confined media. Electrodic behavior of coupled platinum nanoparticles.

PubMed

Harris, Clifton; Kamat, Prashant V

2010-12-28

The electrodic behavior of platinum nanoparticles (2.8 nm diameter) and their role in influencing the photocatalytic behavior of CdSe quantum dots (3.4 nm diameter) has been evaluated by confining both nanoparticles together in heptane/dioctyl sulphosuccinate/water reverse micelles. The particles spontaneously couple together within the micelles via micellar exchange processes and thus facilitate experimental observation of electron transfer reactions inside the water pools. Electron transfer from CdSe to Pt is found to occur with a rate constant of 1.22 × 10(9) s(-1). With the use of methyl viologen (MV(2+)) as a probe molecule, the role of Pt in the photocatalytic process is established. Ultrafast oxidation of the photogenerated MV(+•) radicals indicates that Pt acts as an electron sink, scavenging electrons from MV(+•) with a rate constant of 3.1 × 10(9) s(-1). The electron transfer between MV(+•) and Pt, and a drastically lower yield of MV(+•) under steady state irradiation, confirms the ability of Pt nanoparticles to discharge electrons quickly. The kinetic details of photoinduced processes in CdSe-Pt assemblies and the electrodic behavior of Pt nanoparticles provide important information for the development of light energy conversion devices.

Tuning of platinum nano-particles by Au usage in their binary alloy for direct ethanol fuel cell: Controlled synthesis, electrode kinetics and mechanistic interpretation

NASA Astrophysics Data System (ADS)

Dutta, Abhijit; Mondal, Achintya; Datta, Jayati

2015-06-01

Understanding of the electrode-kinetics and mechanism of ethanol oxidation reaction (EOR) is of considerable interest for optimizing electro-catalysis in direct ethanol fuel cell (DEFC). This work attempts to design Pt based electro-catalyst on carbon support, tuned with gold nano-particles (NPs), for their use in DEFC operating in alkaline medium. The platinum-gold alloyed NPs are synthesized at desired compositions and size (2-10 nm) by controlled borohydride reduction method and successfully characterized by XRD, TEM, EDS and XPS techniques. The kinetic parameters along with the activation energies for the EOR are evaluated over the temperature range 20-80 °C and the oxidation reaction products estimated through ion chromatographic analysis. Compared to single Pt/C catalyst, the over potential of EOR is reduced by ca. 500 mV, at the onset during the reaction, for PtAu/C alloy with only 23% Pt content demonstrating the ability of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pt. Furthermore, a considerable increase in the peak power density (>191%) is observed in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC using the best performing Au covered Pt electrode (23% Pt) compared to the monometallic Pt catalyst.

Methanol electro-oxidation on platinum modified tungsten carbides in direct methanol fuel cells: a DFT study.

PubMed

Sheng, Tian; Lin, Xiao; Chen, Zhao-Yang; Hu, P; Sun, Shi-Gang; Chu, You-Qun; Ma, Chun-An; Lin, Wen-Feng

2015-10-14

In exploration of low-cost electrocatalysts for direct methanol fuel cells (DMFCs), Pt modified tungsten carbide (WC) materials are found to be great potential candidates for decreasing Pt usage whilst exhibiting satisfactory reactivity. In this work, the mechanisms, onset potentials and activity for electrooxidation of methanol were studied on a series of Pt-modified WC catalysts where the bare W-terminated WC(0001) substrate was employed. In the surface energy calculations of a series of Pt-modified WC models, we found that the feasible structures are mono- and bi-layer Pt-modified WCs. The tri-layer Pt-modified WC model is not thermodynamically stable where the top layer Pt atoms tend to accumulate and form particles or clusters rather than being dispersed as a layer. We further calculated the mechanisms of methanol oxidation on the feasible models via methanol dehydrogenation to CO involving C-H and O-H bonds dissociating subsequently, and further CO oxidation with the C-O bond association. The onset potentials for the oxidation reactions over the Pt-modified WC catalysts were determined thermodynamically by water dissociation to surface OH* species. The activities of these Pt-modified WC catalysts were estimated from the calculated kinetic data. It has been found that the bi-layer Pt-modified WC catalysts may provide a good reactivity and an onset oxidation potential comparable to pure Pt and serve as promising electrocatalysts for DMFCs with a significant decrease in Pt usage.

Unusual attempt to direct the growth of bimetallic Ag@Pt nanorods on electrochemically reduced graphene oxide nanosheets by electroless exchange of Cu by Pt for an efficient alcohol oxidation

NASA Astrophysics Data System (ADS)

Jeena, S. E.; Gnanaprakasam, P.; Selvaraju, T.

2017-01-01

A simple and an efficient tool for the direct growth of bimetallic Ag@Pt nanorods (NRDs) on electrochemically reduced graphene oxide (ERGO) nanosheets was developed at glassy carbon electrode (GCE). Initially, Cu shell was grown on Ag core as Ag@Cu NRD by the seed-mediated growth method. Accordingly, Cu shell has been successfully replaced by Pt using the electroless galvanic replacement method with ease by effective functionalization of L-tryptophan on ERGO surface (L-ERGO), which eventually plays an important role in the direct growth of one-dimensional bimetallic NRDs. As a result, the synthesized Ag@Pt NRD-supported L-ERGO nanosheets (Ag@Pt NRDs/L-ERGO/GCE) were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX) and Raman spectroscopy. Anodic stripping voltammetry was used to explore its electrochemical properties. Finally, the developed bimetallic Ag@Pt NRDs/L-ERGO/GCEs were studied as a better electrocatalyst compared to the commercial catalysts such as Pt40/C or Pt20/C-loaded electrode for the oxidation of ethanol or methanol with a high tolerance level and an enhanced current density. In addition, the long-term stability was studied using chronoamperometry for 1000 s at the bimetallic NRD electrode for alcohol oxidation which impedes the fouling properties. The unfavourable and favourable electrooxidation of ethanol at Ag@Cu NRDs/L-ERGO/GCE (a) and Ag@Pt NRDs/L-ERGO/GCE (b) is discussed. The synergistic effect of Ag core and catalytic properties of Pt shell at Ag@Pt NRDs/L-ERGO/GCE tend to strongly minimize the CO poisoning effect and enhanced ethanol electrooxidation.

Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

NASA Astrophysics Data System (ADS)

Devrim, Yilser; Albostan, Ayhan

2016-08-01

The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

Nonfaradaic nanoporous electrochemistry for conductometry at high electrolyte concentration.

PubMed

Bae, Je Hyun; Kang, Chung Mu; Choi, Hyoungseon; Kim, Beom Jin; Jang, Woohyuk; Lim, Sung Yul; Kim, Hee Chan; Chung, Taek Dong

2015-02-17

Nanoporous electrified surfaces create a unique nonfaradaic electrochemical behavior that is sensitively influenced by pore size, morphology, ionic strength, and electric field modulation. Here, we report the contributions of ion concentration and applied ac frequency to the electrode impedance through an electrical double layer overlap and ion transport along the nanopores. Nanoporous Pt with uniform pore size and geometry (L2-ePt) responded more sensitively to conductivity changes in aqueous solutions than Pt black with poor uniformity despite similar real surface areas and enabled the previously difficult quantitative conductometry measurements at high electrolyte concentrations. The nanopores of L2-ePt were more effective in reducing the electrode impedance and exhibited superior linear responses to not only flat Pt but also Pt black, leading to successful conductometric detection in ion chromatography without ion suppressors and at high ionic strengths.

Concentration Effects of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Activity for Three Platinum Catalysts

DOE PAGES

Christ, J. M.; Neyerlin, K. C.; Richards, R.; ...

2014-10-04

A rotating disk electrode (RDE) along with cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were used to investigate the impact of two model compounds representing degradation products of Nafion and 3M perfluorinated sulfonic acid membranes on the electrochemical surface area (ECA) and oxygen reduction reaction (ORR) activity of polycrystalline Pt, nano-structured thin film (NSTF) Pt (3M), and Pt/Vulcan carbon (Pt/Vu) (TKK) electrodes. ORR kinetic currents (measured at 0.9 V and transport corrected) were found to decrease linearly with the log of concentration for both model compounds on all Pt surfaces studied. Ultimately, model compound adsorption effects on ECA weremore » more abstruse due to competitive organic anion adsorption on Pt surfaces superimposing with the hydrogen underpotential deposition (HUPD) region.« less

Characterization of electro-oxidation catalysts using scanning electrochemical and mass spectral methods

NASA Astrophysics Data System (ADS)

Jambunathan, Krishnakumar

Low temperature fuel cells have many potential benefits, including high efficiency, high energy density and environmental friendliness. However, logistically appealing fuels for this system, such as reformed hydrocarbons or alcohols, exhibit poor performance because of catalyst poisoning that occurs during oxidation at the anode. This research focuses on the analysis of several model fuels and catalyst materials to understand the impact of catalyst poisoning on reactivity. Two novel experimental tools were developed based upon the local measurement of catalyst performance using scanning, reactivity mapping probes. The Scanning Electrochemical Microscope (SECM) was used to directly measure the rate constant for hydrogen oxidation in the presence and absence of dissolved CO. The Scanning Differential Electrochemical Mass Spectrometer (SDEMS) was exploited to measure the partial and complete oxidation products of methanol and ethanol oxidation. The reactivity of Pt and Pt/Ru catalysts towards the hydrogen oxidation reaction in the absence and presence of adsorbed CO was elucidated using the SECM. Steady state rate constant measurements in the absence of CO showed that the rate of hydrogen oxidation reaction exceeded 1 cms-1 . Steady state rate constant measurements in the presence of CO indicated that the platinum surface is completely inactive due to adsorbed CO. Addition of as little as 6% Ru to the Pt electrode was found to significantly improve the activity of the electrode towards CO removal. SDEMS was used to study the electro-oxidation of methanol on Pt xRuy electrodes at different electrode potentials and temperatures. Screening measurements performed with the SDEMS showed that PtxRu y electrodes containing 6--40% Ru had the highest activity for methanol oxidation. Current efficiencies for CO2 were also calculated under different conditions. SDEMS was also used to study the electro-oxidation of ethanol on Pt xRuy electrodes. The reaction was found to occur more slowly than the methanol oxidation reaction. Addition of 22%--40% Ru to the Pt electrode was found to increase the current densities and lower the onset potentials. The reaction was found to occur though a parallel path mechanism, which was confirmed by the detection of ethanol and acetic acid apart from CO2.

Effects on Ferroelectric Thin-Film Stacks and Devices for Piezoelectric MEMS Applications at Varied Total Ionizing Dose (TID)

DTIC Science & Technology

2017-03-01

Overall, the devices with IrO2 top electrode were less impacted by the irradiation compared to the Pt top electrode devices. Keywords: lead...displacement and ionization events. However, prior research has primarily concentrated only on the effects of irradiation as polarization degradation...thin films deposited on platinized silicon wafers, with IrO2 or Pt top electrodes. All samples were irradiated with 0.2, 0.5, 1, 2, 5, and 10

Graphene-doped electrospun nanofiber membrane electrodes and proton exchange membrane fuel cell performance

NASA Astrophysics Data System (ADS)

Wei, Meng; Jiang, Min; Liu, Xiaobo; Wang, Min; Mu, Shichun

2016-09-01

A rational electrode structure can allow proton exchange membrane (PEM) fuel cells own high performance with a low noble metal loading and an optimal transport pathway for reaction species. In this study, we develop a graphene doped polyacrylonitile (PAN)/polyvinylident fluoride (PVDF) (GPP) electrospun nanofiber electrode with improved electrical conductivity and high porosity, which could enhance the triple reaction boundary and promote gas and water transport throughout the porous electrode. Thus the increased electrochemical active surface area (ECSA) of Pt catalysts and fuel cell performance can be expected. As results, the ECSA of hot-pressed electrospun electrodes with 2 wt% graphene oxide (GO) is up to 84.3 m2/g, which is greatly larger than that of the conventional electrode (59.5 m2/g). Significantly, the GPP nanofiber electrospun electrode with Pt loading of 0.2 mg/cm2 exhibits higher fuel cell voltage output and stability than the conventional electrode.

Electrochemical oxidation of hydrazine and its derivatives on the surface of metal electrodes in alkaline media

NASA Astrophysics Data System (ADS)

Asazawa, Koichiro; Yamada, Koji; Tanaka, Hirohisa; Taniguchi, Masatoshi; Oguro, Keisuke

Electrochemical oxidation of hydrazine and its derivatives on the surface of various metal electrodes in alkaline media was investigated. A comparison of various polycrystalline metal electrodes (Ni, Co, Fe, Cu, Ag, Au, and Pt) showed that Co and Ni electrodes have a lower onset potential for hydrazine oxidation than the Pt electrode. The onset oxidation potential of APA (aminopolyacrylamide), a hydrazine derivative (-0.127 V vs. reversible hydrogen electrode, RHE), was similar to that of hydrazine hydrate (-0.178 V vs. RHE) in the case of the Co electrode. APA oxidation was possible because of hydrazine desorption that was caused by APA hydrolysis. The hydrolysis reaction was brought about by a heat treatment. This result suggests that the hydrazine hydrolysis reaction of hydrazine derivatives makes it possible to store hydrazine hydrate safely.

Low-Temperature Preparation of (111)-oriented Pb(Zr,Ti)O3 Films Using Lattice-Matched (111)SrRuO3/Pt Bottom Electrode by Metal-Organic Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Kuwabara, Hiroki; Sumi, Akihiro; Okamoto, Shoji; Hoko, Hiromasa; Cross, Jeffrey S.; Funakubo, Hiroshi

2009-04-01

Pb(Zr0.35Ti0.65)O3 (PZT) films 170 nm thick were prepared at 415 °C by pulsed metal-organic chemical vapor deposition. The (111)-oriented PZT films with local epitaxial growth were obtained on (111)SrRuO3/(111)Pt/TiO2/SiO2/Si substrates and their ferroelectricities were ascertained. Ferroelectricity was improved by postannealing under O2 gas flow up to 550 °C. Larger remanent polarization and better fatigue endurance were obtained using a SrRuO3 top electrode compared to a Pt top electrode for PZT films after annealing at 500 °C.

Effect of bottom electrode on dielectric property of sputtered-(Ba,Sr)TiO{sub 3} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Shinichi; Yamada, Tomoaki; Takahashi, Kenji

2009-03-15

(Ba{sub 0.5}Sr{sub 0.5})TiO{sub 3} (BST) films were deposited on (111)Pt/TiO{sub 2}/SiO{sub 2}/Al{sub 2}O{sub 3} substrates by rf sputtering. By inserting a thin layer of SrRuO{sub 3} in between BST film and (111)Pt electrode, the BST films grew fully (111)-oriented without any other orientations. In addition, it enables us to reduce the growth temperature of BST films while keeping the dielectric constant and tunability as high as those of BST films directly deposited on Pt at higher temperatures. The dielectric loss of the films on SrRuO{sub 3}-top substrates was comparable to that on Pt-top substrates for the same level of dielectricmore » constant. The results suggest that the SrRuO{sub 3} thin layer on (111)Pt electrode is an effective approach to growing highly crystalline BST films with (111) orientation at lower deposition temperatures.« less

Three-Dimensional Macroporous Polypyrrole-Derived Graphene Electrode Prepared by the Hydrogen Bubble Dynamic Template for Supercapacitors and Metal-Free Catalysts.

PubMed

Yang, Xiaoqing; Liu, Anran; Zhao, Yuewu; Lu, Huijia; Zhang, Yuanjian; Wei, Wei; Li, Ying; Liu, Songqin

2015-10-28

We report a general method for the fabrication of three-dimensional (3D) macroporous graphene/conducting polymer modified electrode and nitrogen-doped graphene modified electrode. This method involves three consecutive steps. First, the 3D macroporous graphene (3D MG) electrode was fabricated electrochemically by reducing graphene oxide dispersion on different conducting substrates and used hydrogen bubbles as the dynamic template. The morphology and pore size of 3D MG could be governed by the use of surfactants and the dynamics of bubble generation and departure. Second, 3D macroporous graphene/polypyrrole (MGPPy) composites were constructed via directly electropolymerizing pyrrole monomer onto the networks of 3D MG. Due to the benefit of the good conductivity of 3D MG and pseudocapacitance of PPy, the composites manifest outstanding area specific capacitance of 196 mF cm(-2) at a current density of 1 mA cm(-2). The symmetric supercapacitor device assembled by the composite materials had a good capacity property. Finally, the nitrogen-doped MGPPy (N-MGPPy or MGPPy-X) with 3D macroporous nanostructure and well-regulated nitrogen doping was prepared via thermal treatment of the composites. The resultant N-MGPPy electrode was explored as a good electrocatalyst for the oxygen reduction reaction (ORR) with the current density value of 5.56 mA cm(-2) (-0.132 V vs Ag/AgCl). Moreover, the fuel tolerance and durability under the electrochemical environment of the N-MGPPy catalyst were found to be superior to the Pt/C catalyst.

Development of a sensor prepared by entrapment of MIP particles in electrosynthesised polymer films for electrochemical detection of ephedrine.

PubMed

Mazzotta, E; Picca, R A; Malitesta, C; Piletsky, S A; Piletska, E V

2008-02-28

A voltammetric sensor for (-)-ephedrine has been prepared by a novel approach based on immobilisation of an imprinted polymer for ephedrine (MIPE) in an electrosynthesised polypyrrole (PPY) film. Composite films were grown potentiostatically at 1.0 V vs. Pt (QRE) on a glassy carbon electrode using an unconventional "upside-down" (UD) geometry for the three-electrode cell. As a consequence, a high MIP loading was obtained, as revealed by SEM. The sensor response was evaluated, after overoxidation of PPY matrix, by cyclic voltammetry after pre-concentration in a buffered solution of analyte in 0.5-3 mM concentration range. An ephedrine peak at approximately 0.9 V increasing with concentration and saturating at high concentrations was evident. PPY-modified electrode showed a response, which was distinctly lower than the MIP response for the same concentration of the template. The effect of potential interferences including compounds usually found in human fluids (ascorbic acid, uric acid, urea, glucose, sorbitol, glycine, dopamine) was examined.

Sputtered Modified Barium Titanate for Thin-Film Capacitor Applications.

PubMed

Reynolds, Glyn J; Kratzer, Martin; Dubs, Martin; Felzer, Heinz; Mamazza, Robert

2012-04-10

New apparatus and a new process for the sputter deposition of modified barium titanate thin-films were developed. Films were deposited at temperatures up to 900 °C from a Ba₀ .96 Ca 0. 04 Ti 0. 82 Zr 0. 18 O₃ (BCZTO) target directly onto Si, Ni and Pt surfaces and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Film texture and crystallinity were found to depend on both deposition temperature and substrate: above 600 °C, the as-deposited films consisted of well-facetted crystallites with the cubic perovskite structure. A strongly textured Pt (111) underlayer enhanced the (001) orientation of BCZTO films deposited at 900 °C, 10 mtorr pressure and 10% oxygen in argon. Similar films deposited onto a Pt (111) textured film at 700 °C and directly onto (100) Si wafers showed relatively larger (011) and diminished intensity (00ℓ) diffraction peaks. Sputter ambients containing oxygen caused the Ni underlayers to oxidize even at 700 °C: Raising the process temperature produced more diffraction peaks of NiO with increased intensities. Thin-film capacitors were fabricated using ~500 nm thick BCZTO dielectrics and both Pt and Ni top and bottom electrodes. Small signal capacitance measurements were carried out to determine capacitance and parallel resistance at low frequencies and from these data, the relative permittivity (e r ) and resistivity (r) of the dielectric films were calculated; values ranged from ~50 to >2,000, and from ~10⁴ to ~10 10 Ω∙cm, respectively.

Synthesis and application of polypyrrole/carrageenan nano-bio composite as a cathode catalyst in microbial fuel cells.

PubMed

Esmaeili, Chakavak; Ghasemi, Mostafa; Heng, Lee Yook; Hassan, Sedky H A; Abdi, Mahnaz M; Daud, Wan Ramli Wan; Ilbeygi, Hamid; Ismail, Ahmad Fauzi

2014-12-19

A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m(2) while it was 46.8 mW/m(2) and 28.8 mW/m(2) for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m(2)) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Atomic structure of (111) SrTiO3/Pt interfaces

NASA Astrophysics Data System (ADS)

Schmidt, Steffen; Klenov, Dmitri O.; Keane, Sean P.; Lu, Jiwei; Mates, Thomas E.; Stemmer, Susanne

2006-03-01

Atomic resolution high-angle annular dark field (HAADF) imaging in scanning transmission electron microscopy was used to investigate the interface atomic structure of epitaxial, (111) oriented SrTiO3 films on epitaxial Pt electrodes grown on (0001) sapphire. The cube-on-cube orientation relationship of SrTiO3 on Pt was promoted by the use of a Ti adhesion layer underneath the Pt electrode. While a Ti-rich Pt surface was observed before SrTiO3 growth, HAADF images showed an atomically abrupt SrTiO3/Pt interface with no interfacial layers. The SrTiO3 films contained two twin variants that were related by a 180° rotation about the ⟨111⟩ surface normal. HAADF images showed two different interface atomic arrangements for the two twins. The role of Ti in promoting (111) epitaxy and the implications for the dielectric properties are discussed.

Abiotic-biotic characterization of Pt/Ir microelectrode arrays in chronic implants

PubMed Central

Prasad, Abhishek; Xue, Qing-Shan; Dieme, Robert; Sankar, Viswanath; Mayrand, Roxanne C.; Nishida, Toshikazu; Streit, Wolfgang J.; Sanchez, Justin C.

2014-01-01

Pt/Ir electrodes have been extensively used in neurophysiology research in recent years as they provide a more inert recording surface as compared to tungsten or stainless steel. While floating microelectrode arrays (FMA) consisting of Pt/Ir electrodes are an option for neuroprosthetic applications, long-term in vivo functional performance characterization of these FMAs is lacking. In this study, we have performed comprehensive abiotic-biotic characterization of Pt/Ir arrays in 12 rats with implant periods ranging from 1 week up to 6 months. Each of the FMAs consisted of 16-channel, 1.5 mm long, and 75 μm diameter microwires with tapered tips that were implanted into the somatosensory cortex. Abiotic characterization included (1) pre-implant and post-explant scanning electron microscopy (SEM) to study recording site changes, insulation delamination and cracking, and (2) chronic in vivo electrode impedance spectroscopy. Biotic characterization included study of microglial responses using a panel of antibodies, such as Iba1, ED1, and anti-ferritin, the latter being indicative of blood-brain barrier (BBB) disruption. Significant structural variation was observed pre-implantation among the arrays in the form of irregular insulation, cracks in insulation/recording surface, and insulation delamination. We observed delamination and cracking of insulation in almost all electrodes post-implantation. These changes altered the electrochemical surface area of the electrodes and resulted in declining impedance over the long-term due to formation of electrical leakage pathways. In general, the decline in impedance corresponded with poor electrode functional performance, which was quantified via electrode yield. Our abiotic results suggest that manufacturing variability and insulation material as an important factor contributing to electrode failure. Biotic results show that electrode performance was not correlated with microglial activation (neuroinflammation) as we were able to observe poor performance in the absence of neuroinflammation, as well as good performance in the presence of neuroinflammation. One biotic change that correlated well with poor electrode performance was intraparenchymal bleeding, which was evident macroscopically in some rats and presented microscopically by intense ferritin immunoreactivity in microglia/macrophages. Thus, we currently consider intraparenchymal bleeding, suboptimal electrode fabrication, and insulation delamination as the major factors contributing toward electrode failure. PMID:24550823

Pt-coated cylindrical micropatterned honeycomb Petri dishes as an efficient TCO-free counter electrode in liquid junction photovoltaic devices

NASA Astrophysics Data System (ADS)

Dao, Van-Duong; Bui, Van-Tien; Choi, Ho-Suk

2018-02-01

The Pt layer deposited on a cylindrical micro cavity patterned Petri dish, which is produced using a one-step solvent-immersion phase separation, is fabricated for the first time as an FTO-free counter electrode (CE) for dye-sensitized solar cells (DSCs). Due to the high specific active surface area of the Pt-deposited honeycomb substrate CE, the efficiency of the DSC using the developed CE substrate is enhanced by 14.5% compared with the device using a Pt-sputtered flat substrate. This design strategy has potential in fabricating highly efficient and low-cost CE materials with FTO-free substrates for DSCs.

Polythiophene coated aromatic polyimide enabled ultrafast and sustainable lithium ion batteries

DOE PAGES

Lyu, Hailong; Liu, Jiurong; Mahurin, Shannon; ...

2017-10-31

Organic composite electrode materials based on aromatic polyimide (PI) and electron conductive polythiophene (PT) have been prepared by a facilein situchemical oxidation polymerization method. The optimized composite electrode PI30PT delivers a remarkable high-rate cyclability, achieving a high capacity of 89.6 mA h g -1at 20 C with capacity retention of 94% after 1000 cycles.

Economically synthesized NiCo2S4/reduced graphene oxide composite as efficient counter electrode in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Nan, Hui; Han, Jianhua; Luo, Qiang; Yin, Xuewen; Zhou, Yu; Yao, Zhibo; Zhao, Xiaochong; Li, Xin; Lin, Hong

2018-04-01

Exploiting efficient Pt-free counter-electrode materials with low cost and highly catalytic property is a hot topic in the field of Dye-sensitized solar cells (DSCs). Here, NiCo2S4/reduced graphene oxide (RGO) was prepared via an economical synthesis route, and the as-prepared composite exhibited comparable electrocatalytic property with the conventional Pt electrode as the counter-electrode. Notably, the introduction of RGO into the NiCo2S4 counter-electrode induces a significantly promoted electrocatalytic rate towards the triiodide reduction than that of pristine NiCo2S4 by increasing surface area in the composite electrode, as revealed by electrochemical impedance spectroscopic measurement and Tafel polarization measurement. The easy synthesis, low cost and excellent electrochemical performance of the NiCo2S4/RGO composites enable themselves to serve as promising counter-electrode candidates for efficient DSCs.

Preparation and properties of low-cost graphene counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wu, Qishuang; Shen, Yue; Wang, Qiandi; Gu, Feng; Cao, Meng; Wang, Linjun

2013-12-01

With the advantages of excellent electrical properties, high catalytic activity and low-cost preparation, Graphene is one of the most expected carbon materials to replace the expensive Pt as counter electrodes for dye-sensitized solar cells (DSSCs). In this paper, graphene counter electrodes were obtained by simple doctor-blade coating method on fluorine tin oxides (FTOs). The samples were investigated by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscope (SEM). Then the low-cost graphene electrodes were applied in typical sandwich-type DSSCs with TiO2 or ZnO as photoanodes, and their photoelectric conversion efficiency (η) were about 4.34% and 2.28%, respectively, which were a little lower than those of Pt electrodes but much higher than those of graphite electrodes. This law was consistent with the test results of electrochemical impedance spectroscopy (EIS). Low-cost graphene electrodes can be applied in DSSCs by process optimization.

Study of different nanostructured carbon supports for fuel cell catalysts

NASA Astrophysics Data System (ADS)

Mirabile Gattia, Daniele; Antisari, Marco Vittori; Giorgi, Leonardo; Marazzi, Renzo; Piscopiello, Emanuela; Montone, Amelia; Bellitto, Serafina; Licoccia, Silvia; Traversa, Enrico

Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction.

Hydrogen Oxidation-Selective Electrocatalysis by Fine Tuning of Pt Ensemble Sites to Enhance the Durability of Automotive Fuel Cells.

PubMed

Yun, Su-Won; Park, Shin-Ae; Kim, Tae-June; Kim, Jun-Hyuk; Pak, Gi-Woong; Kim, Yong-Tae

2017-02-08

A simple, inexpensive approach is proposed for enhancing the durability of automotive proton exchange membrane fuel cells by selective promotion of the hydrogen oxidation reaction (HOR) and suppression of the oxygen reduction reaction (ORR) at the anode in startup/shutdown events. Dodecanethiol forms a self-assembled monolayer (SAM) on the surface of Pt particles, thus decreasing the number of Pt ensemble sites. Interestingly, by controlling the dodecanethiol concentration during SAM formation, the number of ensemble sites can be precisely optimized such that it is sufficient for the HOR but insufficient for the ORR. Thus, a Pt surface with an SAM of dodecanethiol clearly effects HOR-selective electrocatalysis. Clear HOR selectivity is demonstrated in unit cell tests with the actual membrane electrode assembly, as well as in an electrochemical three-electrode setup with a thin-film rotating disk electrode configuration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of graphene-platinum nanocomposite for the direct electrochemistry and electrocatalysis of myoglobin.

PubMed

Sun, Wei; Li, Linfang; Lei, Bingxin; Li, Tongtong; Ju, Xiaomei; Wang, Xiuzheng; Li, Guangjiu; Sun, Zhenfan

2013-05-01

In this paper a platinum (Pt) nanoparticle decorated graphene (GR) nanosheet was synthesized and used for the investigation on direct electrochemistry of myoglobin (Mb). By integrating GR-Pt nanocomposite with Mb on the surface of carbon ionic liquid electrode (CILE), a new electrochemical biosensor was fabricated. UV-Vis absorption and FT-IR spectra indicated that Mb remained its native structure in the nanocomposite film. Electrochemical behaviors of Nafion/Mb-GR-Pt/CILE were investigated with a pair of well-defined redox peak appeared, which indicated that direct electron transfer of Mb was realized on the underlying electrode with the usage of the GR-Pt nanocomposite. The fabricated electrode showed good electrocatalytic activity to the reduction of trichloroacetic acid in the linear range from 0.9 to 9.0 mmol/L with the detection limit as 0.32 mmol/L (3σ), which showed potential application for fabricating novel electrochemical biosensors and bioelectronic devices. Copyright © 2012 Elsevier B.V. All rights reserved.

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method.

PubMed

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-03-16

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced.

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method

PubMed Central

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-01-01

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced. PMID:29608166

Real-time electrochemical detection of hydrogen peroxide secretion in live cells by Pt nanoparticles decorated graphene-carbon nanotube hybrid paper electrode.

PubMed

Sun, Yimin; He, Kui; Zhang, Zefen; Zhou, Aijun; Duan, Hongwei

2015-06-15

In this work, we develop a new type of flexible and lightweight electrode based on highly dense Pt nanoparticles decorated free-standing graphene-carbon nanotube (CNT) hybrid paper (Pt/graphene-CNT paper), and explore its practical application as flexible electrochemical biosensor for the real-time tracking hydrogen peroxide (H2O2) secretion by live cells. For the fabrication of flexible nanohybrid electrode, the incorporation of CNT in graphene paper not only improves the electrical conductivity and the mechanical strength of graphene paper, but also increases its surface roughness and provides more nucleation sites for metal nanoparticles. Ultrafine Pt nanoparticles are further decorated on graphene-CNT paper by well controlled sputter deposition method, which offers several advantages such as defined particle size and dispersion, high loading density and strong adhesion between the nanoparticles and the substrate. Consequently, the resultant flexible Pt/graphene-CNT paper electrode demonstrates a variety of desirable electrochemical properties including large electrochemical active surface area, excellent electrocatalytic activity, high stability and exceptional flexibility. When used for nonenzymatic detection of H2O2, Pt/graphene-CNT paper exhibits outstanding sensing performance such as high sensitivity, selectivity, stability and reproducibility. The sensitivity is 1.41 µA µM(-1) cm(-2) with a linear range up to 25 µM and a low detection limit of 10 nM (S/N=3), which enables the resultant biosensor for the real-time tracking H2O2 secretion by live cells macrophages. Copyright © 2015. Published by Elsevier B.V.

Ultrasensitive electrochemical immunosensors for multiplexed determination using mesoporous platinum nanoparticles as nonenzymatic labels.

PubMed

Cui, Zhentao; Wu, Dan; Zhang, Yong; Ma, Hongmin; Li, He; Du, Bin; Wei, Qin; Ju, Huangxian

2014-01-07

An ultrasensitive multiplexed immunoassay method was developed at a disposable immunosensor array using mesoporous platinum nanoparticles (M-Pt NPs) as nonenzymatic labels. M-Pt NPs were prepared by ultrasonic method and employed to label the secondary antibody (Ab2) for signal amplification. The immunosensor array was constructed by covalently immobilizing capture antibody (Ab1) on graphene modified screen printed carbon electrodes (SPECs). After the sandwich-type immunoreactions, the M-Pt-Ab2 was bound to immunosensor surface to catalyze the electro-reduction of H2O2 reaction, which produced detectable signals for readout of analytes. Using breast cancer related panel of tumor markers (CA125, CA153 and CEA) as model analytes, this method showed wide linear ranges of over 4 orders of magnitude with the detection limits of 0.002 U mL(-1), 0.001 U mL(-1) and 7.0 pg mL(-1) for CA125, CA153 and CEA, respectively. The disposable immunosensor array possessed excellent clinical value in cancer screening as well as convenient point of care diagnostics. Copyright © 2013 Elsevier B.V. All rights reserved.

Evaluation of MOSFET-type glucose sensor using platinum electrode with glucose oxidase

NASA Astrophysics Data System (ADS)

Ooe, Katsutoshi; Hamamoto, Yasutaro; Hirano, Yoshiaki

2005-02-01

As the population ages, health management will be one of the important issues. The development of a safe medical machine based on MEMS technologies for the human body will be the primary research project in the future. We have developed the glucose sensor, as one of the medical based devices, for use in the Health Monitoring System (HMS). HMS is the device that continuously monitors human health conditions. For example, blood is the monitoring target of HMS. The glucose sensor specifically detects the glucose levels of the blood and monitors the glucose concentration as the blood sugar level. This glucose sensor has a "separated Au electrode", which immobilizes GOx. In our previous work, GOx was immobilized onto Au electrode by the SAMs (Self-Assembled Monolayer) method, and the sensor, using this working electrode, detected the glucose concentration of an aqueous glucose solution. In this report, we used a Pt electrode, which immobilized GOx, as a working electrode. Au electrode, which was used previously, was dissolved by the application of current in the presence of chloride ions. Based on the above-mentioned fact, a new working electrode, which immobilized GOx, was produced using Pt, which did not possess such characteristics. These Pt working electrodes were produced using the covalent binding method and the cross-link method, and both the electrodes displayed a good sensing property. In addition, the electrode using glutaraldehyde (GA) and bovine serum albumin (BSA) as crosslinking agents was produced, and it displayed better characteristics as compared with those displayed by the electrode that used only GA. Based on the above-mentioned techniques, the improvement in performance of the sensor was confirmed.

Continuous minimally-invasive alcohol monitoring using microneedle sensor arrays.

PubMed

Mohan, A M Vinu; Windmiller, Joshua Ray; Mishra, Rupesh K; Wang, Joseph

2017-05-15

The present work describes an attractive skin-worn microneedle sensing device for the minimally invasive electrochemical monitoring of subcutaneous alcohol. The device consists of an assembly of pyramidal microneedle structures integrated with Pt and Ag wires, each with a microcavity opening. The microneedle aperture was modified by electropolymerizing o-phenylene diamine onto the Pt wire microtransducer, followed by the immobilization of alcohol oxidase (AOx) in an intermediate chitosan layer, along with an outer Nafion layer. The resulting microneedle-based enzyme electrode displays an interference-free ethanol detection in artificial interstitial fluid without compromising its sensitivity, stability and response time. The skin penetration ability and the efficaciousness of the biosensor performance towards subcutaneous alcohol monitoring was substantiated by the ex vivo mice skin model analysis. Our results reveal that the new microneedle sensor holds considerable promise for continuous non-invasive alcohol monitoring in real-life situations. Copyright © 2017 Elsevier B.V. All rights reserved.

Continuous minimally-invasive alcohol monitoring using microneedle sensor arrays

PubMed Central

Vinu Mohan, A. M.; Windmiller, Joshua Ray; Mishra, Rupesh K.; Wang, Joseph

2017-01-01

The present work describes an attractive skin-worn microneedle sensing device for the minimally invasive electrochemical monitoring of subcutaneous alcohol. The device consists of an assembly of pyramidal microneedle structures integrated with Pt and Ag wires, each with a microcavity opening. The microneedle aperture was modified by electropolymerizing o-phenylene diamine onto the Pt wire microtransducer, followed by the immobilization of alcohol oxidase (AOx) in an intermediate chitosan layer, along with an outer Nafion layer. The resulting microneedle-based enzyme electrode displays an interference-free ethanol detection in artificial interstitial fluid without compromising its sensitivity, stability and response time. The skin penetration ability and the efficaciousness of the biosensor performance towards subcutaneous alcohol monitoring was substantiated by the ex vivo mice skin model analysis. Our results reveal that the new microneedle sensor holds considerable promise for continuous non-invasive alcohol monitoring in real-life situations. PMID:28088750

SFG study of platinum electrodes in perchloric acid solutions

NASA Astrophysics Data System (ADS)

Zheng, W. Q.; Pluchery, O.; Tadjeddine, A.

2002-04-01

Infrared-visible sum-frequency generation (SFG) spectroscopy has been used to study the structure of water molecules (and/or its derivatives OH -, H 3O + etc.) at aqueous electrolyte/electrode interfaces. For Pt(1 1 0) and Pt(1 0 0) electrodes in 0.1 M perchloric acid solution, we did not observe any significant O-H stretching resonance. In striking contrast to the resonant SFG signal, the nonresonant SFG (NRSFG) signal varies sensitively with the applied electrochemical potential, indicating that the interaction of water molecules with platinum electrodes is relatively weak as compared to that of H + and ClO 4- ions. From changes in the NRSFG signal and on the basis of an ionic adsorption model, we can also deduce that the potential of zero charge of Pt(1 1 0) in 0.1 M HClO 4 should be located at about 0.22 V (vs. NHE). This value is in good agreement with that measured recently by electrochemical method.

Glucose oxidase-initiated cascade catalysis for sensitive impedimetric aptasensor based on metal-organic frameworks functionalized with Pt nanoparticles and hemin/G-quadruplex as mimicking peroxidases.

PubMed

Zhou, Xingxing; Guo, Shijing; Gao, Jiaxi; Zhao, Jianmin; Xue, Shuyan; Xu, Wenju

2017-12-15

Based on cascade catalysis amplification driven by glucose oxidase (GOx), a sensitive electrochemical impedimetric aptasensor for protein (carcinoembryonic antigen, CEA as tested model) was proposed by using Cu-based metal-organic frameworks functionalized with Pt nanoparticles, aptamer, hemin and GOx (Pt@CuMOFs-hGq-GOx). CEA aptamer loaded onto Pt@CuMOFs was bound with hemin to form hemin@G-quadruplex (hGq) with mimicking peroxidase activity. Through sandwich-type reaction of target CEA and CEA aptamers (Apt1 and Apt2), the obtained Pt@CuMOFs-hGq-GOx as signal transduction probes (STPs) was captured to the modified electrode interface. When 3,3-diaminobenzidine (DAB) and glucose were introduced, the cascade reaction was initiated by GOx to catalyze the oxidation of glucose, in situ generating H 2 O 2 . Simultaneously, the decomposition of the generated H 2 O 2 was greatly promoted by Pt@CuMOFs and hGq as synergistic peroxide catalysts, accompanying with the significant oxidation process of DAB and the formation of nonconductive insoluble precipitates (IPs). As a result, the electron transfer in the resultant sensing interface was effectively hindered and the electrochemical impedimetric signal (EIS) was efficiently amplified. Thus, the high sensitivity of the proposed CEA aptasensor was successfully improved with 0.023pgmL -1 , which may be promising and potential in assaying certain clinical disease related to CEA. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly sensitive glucose sensors based on enzyme-modified whole-graphene solution-gated transistors

NASA Astrophysics Data System (ADS)

Zhang, Meng; Liao, Caizhi; Mak, Chun Hin; You, Peng; Mak, Chee Leung; Yan, Feng

2015-02-01

Noninvasive glucose detections are convenient techniques for the diagnosis of diabetes mellitus, which require high performance glucose sensors. However, conventional electrochemical glucose sensors are not sensitive enough for these applications. Here, highly sensitive glucose sensors are successfully realized based on whole-graphene solution-gated transistors with the graphene gate electrodes modified with an enzyme glucose oxidase. The sensitivity of the devices is dramatically improved by co-modifying the graphene gates with Pt nanoparticles due to the enhanced electrocatalytic activity of the electrodes. The sensing mechanism is attributed to the reaction of H2O2 generated by the oxidation of glucose near the gate. The optimized glucose sensors show the detection limits down to 0.5 μM and good selectivity, which are sensitive enough for non-invasive glucose detections in body fluids. The devices show the transconductances two orders of magnitude higher than that of a conventional silicon field effect transistor, which is the main reason for their high sensitivity. Moreover, the devices can be conveniently fabricated with low cost. Therefore, the whole-graphene solution-gated transistors are a high-performance sensing platform for not only glucose detections but also many other types of biosensors that may find practical applications in the near future.

Highly sensitive glucose sensors based on enzyme-modified whole-graphene solution-gated transistors

PubMed Central

Zhang, Meng; Liao, Caizhi; Mak, Chun Hin; You, Peng; Mak, Chee Leung; Yan, Feng

2015-01-01

Noninvasive glucose detections are convenient techniques for the diagnosis of diabetes mellitus, which require high performance glucose sensors. However, conventional electrochemical glucose sensors are not sensitive enough for these applications. Here, highly sensitive glucose sensors are successfully realized based on whole-graphene solution-gated transistors with the graphene gate electrodes modified with an enzyme glucose oxidase. The sensitivity of the devices is dramatically improved by co-modifying the graphene gates with Pt nanoparticles due to the enhanced electrocatalytic activity of the electrodes. The sensing mechanism is attributed to the reaction of H2O2 generated by the oxidation of glucose near the gate. The optimized glucose sensors show the detection limits down to 0.5 μM and good selectivity, which are sensitive enough for non-invasive glucose detections in body fluids. The devices show the transconductances two orders of magnitude higher than that of a conventional silicon field effect transistor, which is the main reason for their high sensitivity. Moreover, the devices can be conveniently fabricated with low cost. Therefore, the whole-graphene solution-gated transistors are a high-performance sensing platform for not only glucose detections but also many other types of biosensors that may find practical applications in the near future. PMID:25655666

Tungsten trioxide nanoplate array supported platinum as a highly efficient counter electrode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Song, Dandan; Cui, Peng; Zhao, Xing; Li, Meicheng; Chu, Lihua; Wang, Tianyue; Jiang, Bing

2015-03-01

A tungsten trioxide (WO3) nanoplate array is fabricated directly on the FTO/glass substrate and used as a platinum (Pt) nanoscale supporter for a highly efficient and low Pt-consumption counter electrode (CE) in dye-sensitized solar cells (DSCs). A Pt/WO3 composite structure, with Pt nanoparticles having a diameter of 2-3 nm, increases the electrochemical catalytic activity in catalyzing the reduction of triiodide. Accordingly, the power conversion efficiency is increased from less than 1% for WO3 CE and 8.1% for Pt CE, respectively, to 8.9% for Pt/WO3 CE. Moreover, the use of Pt/WO3 CE can dramatically reduce the consumption of scarce Pt material, with a relatively low Pt-loading of ~2 μg cm-2, while maintaining a much better performance. The excellent performance of Pt/WO3 CE is attributed to the efficient electron injection and transport via WO3 supporters, as well as the nanostructure array morphology of WO3 for deposition of fine Pt nanoparticles. This work provides an approach for developing highly catalytic and low-cost Pt based CEs, which also has implications for the development of Pt/WO3 nanoplate arrays for other applications.A tungsten trioxide (WO3) nanoplate array is fabricated directly on the FTO/glass substrate and used as a platinum (Pt) nanoscale supporter for a highly efficient and low Pt-consumption counter electrode (CE) in dye-sensitized solar cells (DSCs). A Pt/WO3 composite structure, with Pt nanoparticles having a diameter of 2-3 nm, increases the electrochemical catalytic activity in catalyzing the reduction of triiodide. Accordingly, the power conversion efficiency is increased from less than 1% for WO3 CE and 8.1% for Pt CE, respectively, to 8.9% for Pt/WO3 CE. Moreover, the use of Pt/WO3 CE can dramatically reduce the consumption of scarce Pt material, with a relatively low Pt-loading of ~2 μg cm-2, while maintaining a much better performance. The excellent performance of Pt/WO3 CE is attributed to the efficient electron injection and transport via WO3 supporters, as well as the nanostructure array morphology of WO3 for deposition of fine Pt nanoparticles. This work provides an approach for developing highly catalytic and low-cost Pt based CEs, which also has implications for the development of Pt/WO3 nanoplate arrays for other applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06787h

Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix.

PubMed

Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

2015-11-05

The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion(®) ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg(-1)Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion(®) ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture.

Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix

NASA Astrophysics Data System (ADS)

Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

2015-11-01

The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg-1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture.

Platinum-free, carbon-based materials as efficient counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Widiyandari, Hendri; Prasetio, Adi; Purwanto, Agus; Subagio, Agus; Hidayat, Rachmat

2018-06-01

The electrocatalytic potential of carbon materials makes them the most viable candidate to replace Pt as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). In this research, we report our study using graphite, CNT/graphite composite, CNT, and Pt-based CEs in DSSCs. The electrochemical impedance spectroscopy (EIS) measurement showed that the CNT-based CE (CNT-CE) has the lowest charge transport resistance (R ct) compared with graphite and the CNT/graphite composite. The photovoltaic performance measurement showed that the CNT-CE resulted in a short-circuit photocurrent density (J sc) of 3.59 mA·cm‑2 whereas the Pt-based CE (Pt-CE) resulted in a J sc of 2.76 mA·cm‑2.

Microwave decoration of Pt nanoparticles on entangled 3D carbon nanotube architectures as PEM fuel cell cathode.

PubMed

Sherrell, Peter C; Zhang, Weimin; Zhao, Jie; Wallace, Gordon G; Chen, Jun; Minett, Andrew I

2012-07-01

Proton-exchange membrane fuel cells (PEMFCs) are expected to provide a complementary power supply to fossil fuels in the near future. The current reliance of fuel cells on platinum catalysts is undesirable. However, even the best-performing non-noble metal catalysts are not as efficient. To drive commercial viability of fuel cells forward in the short term, increased utilization of Pt catalysts is paramount. We have demonstrated improved power and energy densities in a single PEMFC using a designed cathode with a Pt loading of 0.1 mg cm(-2) on a mesoporous conductive entangled carbon nanotube (CNT)-based architecture. This electrode allows for rapid transfer of both fuel and waste to and from the electrode, respectively. Pt particles are bound tightly, directly to CNT sidewalls by a microwave-reduction technique, which provided increased charge transport at this interface. The Pt entangled CNT cathode, in combination with an E-TEK 0.2 mg cm(-2) anode, has a maximum power and energy density of 940 mW cm(-2) and 2700 mA cm(-2), respectively, and a power and energy density of 4.01 W mg(Pt)(-1) and 6.35 A mg(Pt)(-1) at 0.65 V. These power densities correspond to a specific mass activity of 0.81 g Pt per kW for the combined mass of both anode and cathode electrodes, approaching the current US Department of Energy efficiency target. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct and continuous strain control of catalysts with tunable battery electrode materials

DOE PAGES

Wang, Haotian; Xu, Shicheng; Tsai, Charlie; ...

2016-11-24

We report a method for using battery electrode materials to directly and continuously control the lattice strain of platinum (Pt) catalyst and thus tune its catalytic activity for the oxygen reduction reaction (ORR). Whereas the common approach of using metal overlayers introduces ligand effects in addition to strain, by electrochemically switching between the charging and discharging status of battery electrodes the change in volume can be precisely controlled to induce either compressive or tensile strain on supported catalysts. Lattice compression and tension induced by the lithium cobalt oxide substrate of ~5% were directly observed in individual Pt nanoparticles with aberration-correctedmore » transmission electron microscopy. As a result, we observed 90% enhancement or 40% suppression in Pt ORR activity under compression or tension, respectively, which is consistent with theoretical predictions.« less

Performance assessments of vertically aligned carbon nanotubes multi-electrode arrays using Cath.a-differentiated (CAD) cells

NASA Astrophysics Data System (ADS)

Jeong, Du Won; Jung, Jongjin; Kim, Gook Hwa; Yang, Cheol-Soo; Kim, Ju Jin; Jung, Sang Don; Lee, Jeong-O.

2015-08-01

In this work, Cath.a-differentiated (CAD) cells were used in place of primary neuronal cells to assess the performance of vertically aligned carbon nanotubes (VACNTs) multi-electrode arrays (MEA). To fabricate high-performance MEA, VACNTs were directly grown on graphene/Pt electrodes via plasma enhanced chemical deposition technique. Here, graphene served as an intermediate layer lowering contact resistance between VACNTs and Pt electrode. In order to lower the electrode impedance and to enhance the cell adhesion, VACNTs-MEAs were treated with UV-ozone for 20 min. Impedance of VACNTs electrode at 1 kHz frequency exhibits a reasonable value (110 kΩ) for extracellular signal recording, and the signal to noise ratio the is good enough to measure low signal amplitude (15.7). Spontaneous firing events from CAD cells were successfully measured with VACNTs MEAs that were also found to be surprisingly robust toward the biological interactions.

Performance assessments of vertically aligned carbon nanotubes multi-electrode arrays using Cath.a-differentiated (CAD) cells.

PubMed

Jeong, Du Won; Jung, Jongjin; Kim, Gook Hwa; Yang, Cheol-Soo; Kim, Ju Jin; Jung, Sang Don; Lee, Jeong-O

2015-08-21

In this work, Cath.a-differentiated (CAD) cells were used in place of primary neuronal cells to assess the performance of vertically aligned carbon nanotubes (VACNTs) multi-electrode arrays (MEA). To fabricate high-performance MEA, VACNTs were directly grown on graphene/Pt electrodes via plasma enhanced chemical deposition technique. Here, graphene served as an intermediate layer lowering contact resistance between VACNTs and Pt electrode. In order to lower the electrode impedance and to enhance the cell adhesion, VACNTs-MEAs were treated with UV-ozone for 20 min. Impedance of VACNTs electrode at 1 kHz frequency exhibits a reasonable value (110 kΩ) for extracellular signal recording, and the signal to noise ratio the is good enough to measure low signal amplitude (15.7). Spontaneous firing events from CAD cells were successfully measured with VACNTs MEAs that were also found to be surprisingly robust toward the biological interactions.

Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films.

PubMed

Kim, Seong Keun; Han, Sora; Jeon, Woojin; Yoon, Jung Ho; Han, Jeong Hwan; Lee, Woongkyu; Hwang, Cheol Seong

2012-09-26

Rutile structured Al-doped TiO(2) (ATO) and TiO(2) films were grown on bimetal electrodes (thin Ru/thick TiN, Pt, and Ir) for high-performance capacitors. The work function of the top Ru layer decreased on TiN and increased on Pt and Ir when it was thinner than ~2 nm, suggesting that the lower metal within the electrodes influences the work function of the very thin Ru layer. The use of the lower electrode with a high work function for bottom electrode eventually improves the leakage current properties of the capacitor at a very thin Ru top layer (≤2 nm) because of the increased Schottky barrier height at the interface between the dielectric and the bottom electrode. The thin Ru layer was necessary to achieve the rutile structured ATO and TiO(2) dielectric films.

Platinum supported on titanium–ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles

PubMed Central

Parrondo, Javier; Han, Taehee; Niangar, Ellazar; Wang, Chunmei; Dale, Nilesh; Adjemian, Kev; Ramani, Vijay

2014-01-01

We report a unique and highly stable electrocatalyst—platinum (Pt) supported on titanium–ruthenium oxide (TRO)—for hydrogen fuel cell vehicles. The Pt/TRO electrocatalyst was exposed to stringent accelerated test protocols designed to induce degradation and failure mechanisms identical to those seen during extended normal operation of a fuel cell automobile—namely, support corrosion during vehicle startup and shutdown, and platinum dissolution during vehicle acceleration and deceleration. These experiments were performed both ex situ (on supports and catalysts deposited onto a glassy carbon rotating disk electrode) and in situ (in a membrane electrode assembly). The Pt/TRO was compared against a state-of-the-art benchmark catalyst—Pt supported on high surface-area carbon (Pt/HSAC). In ex situ tests, Pt/TRO lost only 18% of its initial oxygen reduction reaction mass activity and 3% of its oxygen reduction reaction-specific activity, whereas the corresponding losses for Pt/HSAC were 52% and 22%. In in situ-accelerated degradation tests performed on membrane electrode assemblies, the loss in cell voltage at 1 A · cm−2 at 100% RH was a negligible 15 mV for Pt/TRO, whereas the loss was too high to permit operation at 1 A · cm−2 for Pt/HSAC. We clearly show that electrocatalyst support corrosion induced during fuel cell startup and shutdown is a far more potent failure mode than platinum dissolution during fuel cell operation. Hence, we posit that the need for a highly stable support (such as TRO) is paramount. Finally, we demonstrate that the corrosion of carbon present in the gas diffusion layer of the fuel cell is only of minor concern. PMID:24367118

Platinum supported on titanium-ruthenium oxide is a remarkably stable electrocatayst for hydrogen fuel cell vehicles.

PubMed

Parrondo, Javier; Han, Taehee; Niangar, Ellazar; Wang, Chunmei; Dale, Nilesh; Adjemian, Kev; Ramani, Vijay

2014-01-07

We report a unique and highly stable electrocatalyst-platinum (Pt) supported on titanium-ruthenium oxide (TRO)-for hydrogen fuel cell vehicles. The Pt/TRO electrocatalyst was exposed to stringent accelerated test protocols designed to induce degradation and failure mechanisms identical to those seen during extended normal operation of a fuel cell automobile-namely, support corrosion during vehicle startup and shutdown, and platinum dissolution during vehicle acceleration and deceleration. These experiments were performed both ex situ (on supports and catalysts deposited onto a glassy carbon rotating disk electrode) and in situ (in a membrane electrode assembly). The Pt/TRO was compared against a state-of-the-art benchmark catalyst-Pt supported on high surface-area carbon (Pt/HSAC). In ex situ tests, Pt/TRO lost only 18% of its initial oxygen reduction reaction mass activity and 3% of its oxygen reduction reaction-specific activity, whereas the corresponding losses for Pt/HSAC were 52% and 22%. In in situ-accelerated degradation tests performed on membrane electrode assemblies, the loss in cell voltage at 1 A · cm(-2) at 100% RH was a negligible 15 mV for Pt/TRO, whereas the loss was too high to permit operation at 1 A · cm(-2) for Pt/HSAC. We clearly show that electrocatalyst support corrosion induced during fuel cell startup and shutdown is a far more potent failure mode than platinum dissolution during fuel cell operation. Hence, we posit that the need for a highly stable support (such as TRO) is paramount. Finally, we demonstrate that the corrosion of carbon present in the gas diffusion layer of the fuel cell is only of minor concern.

Impact of metal cations on the electrocatalytic properties of Pt/C nanoparticles at multiple phase interfaces.

PubMed

Durst, Julien; Chatenet, Marian; Maillard, Frédéric

2012-10-05

Proton-exchange membrane fuel cells (PEMFCs) use carbon-supported nanoparticles based on platinum and its alloys to accelerate the rate of the sluggish oxygen-reduction reaction (ORR). The most common metals alloyed to Pt include Co, Ni and Cu, and are thermodynamically unstable in the PEMFC environment. Their dissolution yields the formation and redistribution of metal cations (M(y+)) within the membrane electrode assembly (MEA). Metal cations can also contaminate the MEA when metallic bipolar plates are used as current collectors. In each case, the electrical performance of the PEMFC severely decreases, an effect that is commonly attributed to the poisoning of the sulfonic acid groups of the perfluorosulfonated membrane (PEM) and the resulting decrease of the proton transport properties. However, the impact of metal cations on the kinetics of electrochemical reactions involving adsorption/desorption and bond-breaking processes remains poorly understood. In this paper, we use model electrodes to highlight the effect of metal cations on Pt/C nanoparticles coated or not with a perfluorosulfonated ionomer for the CO electrooxidation reaction and the oxygen reduction reaction. We show that metal cations negatively impact the ORR kinetics and the mass-transport resistance of molecular oxygen. However, the specific adsorption of sulfonate groups of the Nafion® ionomer locally modifies the double layer structure and increases the tolerance to metal cations, even in the presence of sulphate ions in the electrolyte. The survey is extended by using an ultramicroelectrode with cavity and a solid state cell (SSC) specifically developed for this study.

Electrochemical treatment of anti-cancer drug carboplatin on mixed-metal oxides and boron doped diamond electrodes: Density functional theory modelling and toxicity evaluation.

PubMed

Barışçı, Sibel; Turkay, Ozge; Ulusoy, Ebru; Soydemir, Gülfem; Seker, Mine Gul; Dimoglo, Anatoli

2018-02-15

This study represents the electrooxidation of anti-cancer drug carboplatin (CrbPt) with different mixed metal oxide (MMO) and boron doped diamond (BDD) electrodes. The most effective anode was found as Ti/RuO 2 with the complete degradation of CrbPt in just 5min. The effect of applied current density, pH and electrolyte concentration on CrbPt degradation has been studied. The degradation of CrbPt significantly increased at the initial stages of the process with increasing current density. However, further increase in current density did not affect the degradation rate. While complete degradation of CrbPt was provided at pH 7, the degradation rates were 49% and 75% at pH 9 and 4, respectively. Besides, increasing supporting electrolyte (Na 2 SO 4 ) concentration provided higher degradation rate but further increase in Na 2 SO 4 concentration did not provide higher degradation rate due to excess amount of SO 4 -2 . According to the DFT calculations, the formation of [Pt(NH 3 ) 2 (H 2 O) 2 ] 2+ and [Pt(NH 3 ) 2 (OH) 2 ] takes place with molecular weights of 265 and 263gmol -1 , respectively. Toxicity of treated samples at BDD and Ti/RuO 2 electrodes has been also evaluated in this study. The results showed that Ti/RuO 2 anode provided zero toxicity at the end of the process. Copyright © 2017 Elsevier B.V. All rights reserved.

Advantages of electrodes with dendrimer-protected platinum nanoparticles and carbon nanotubes for electrochemical methanol oxidation.

PubMed

Siriviriyanun, Ampornphan; Imae, Toyoko

2013-04-14

Electrochemical sensors consisting of electrodes loaded with carbon nanotubes and Pt nanoparticles (PtNPs) protected by dendrimers have been developed using a facile method to fabricate them on two types of disposable electrochemical printed chips with a screen-printed circular gold or a screen-printed circular glassy carbon working electrode. The electrochemical performance of these sensors in the oxidation of methanol was investigated by cyclic voltammetry. It was revealed that such sensors possess stable durability and high electrocatalytic activity: the potential and the current density of an anodic peak in the oxidation of methanol increased with increasing content of PtNPs on the electrodes, indicating the promotion of electrocatalytic activity in relation to the amount of catalyst. The low anodic potential suggests the easy electrochemical reaction, and the high catalyst tolerance supports the almost complete oxidation of methanol to carbon dioxide. The significant performance of these sensors in the detection of methanol oxidation comes from the high electrocatalytic ability of PtNPs, excellent energy transfer of carbon nanotubes and the remarkable ability of dendrimers to act as binders. Thus these systems are effective for a wide range of applications as chemical, biomedical, energy and environmental sensors and as units of direct methanol fuel cells.

Effect of conductive LaNiO3 electrode on the structural and ferroelectric properties of Bi3.25La0.75Ti3O12 films

NASA Astrophysics Data System (ADS)

Jain, M.; Kang, B. S.; Jia, Q. X.

2006-12-01

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) films were grown on Pt /Ti/SiO2/Si (Pt/Si), LaNiO3/Pt /Si, and LaNiO3/Si substrates using chemical solution deposition technique. X-ray diffraction analysis shows that films grown on conductive LaNiO3 electrodes had higher degree of (117) orientation as compared to that grown directly on Pt /Si substrate. High remanent polarization value (2Pr)˜43.14μC/cm2 (Ec of 111kV/cm) under an applied field of 396kV/cm was obtained for BLT film on LaNiO3/Pt /Si as compared to a value of 26μC/cm2 obtained for BLT film on Pt/Si directly. There was no degradation in the switchable polarization (Psw-Pns) after 1010 switching cycles.

Durability test with fuel starvation using a Pt/CNF catalyst in PEMFC.

PubMed

Jung, Juhae; Park, Byungil; Kim, Junbom

2012-01-05

In this study, a catalyst was synthesized on carbon nanofibers [CNFs] with a herringbone-type morphology. The Pt/CNF catalyst exhibited low hydrophilicity, low surface area, high dispersion, and high graphitic behavior on physical analysis. Electrodes (5 cm2) were prepared by a spray method, and the durability of the Pt/CNF was evaluated by fuel starvation. The performance was compared with a commercial catalyst before and after accelerated tests. The fuel starvation caused carbon corrosion with a reverse voltage drop. The polarization curve, EIS, and cyclic voltammetry were analyzed in order to characterize the electrochemical properties of the Pt/CNF. The performance of a membrane electrode assembly fabricated from the Pt/CNF was maintained, and the electrochemical surface area and cell resistance showed the same trend. Therefore, CNFs are expected to be a good support in polymer electrolyte membrane fuel cells.

Durability test with fuel starvation using a Pt/CNF catalyst in PEMFC

PubMed Central

2012-01-01

In this study, a catalyst was synthesized on carbon nanofibers [CNFs] with a herringbone-type morphology. The Pt/CNF catalyst exhibited low hydrophilicity, low surface area, high dispersion, and high graphitic behavior on physical analysis. Electrodes (5 cm2) were prepared by a spray method, and the durability of the Pt/CNF was evaluated by fuel starvation. The performance was compared with a commercial catalyst before and after accelerated tests. The fuel starvation caused carbon corrosion with a reverse voltage drop. The polarization curve, EIS, and cyclic voltammetry were analyzed in order to characterize the electrochemical properties of the Pt/CNF. The performance of a membrane electrode assembly fabricated from the Pt/CNF was maintained, and the electrochemical surface area and cell resistance showed the same trend. Therefore, CNFs are expected to be a good support in polymer electrolyte membrane fuel cells. PMID:22221426

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices.

PubMed

Batra, Nitin M; Patole, Shashikant P; Abdelkader, Ahmed; Anjum, Dalaver H; Deepak, Francis L; Costa, Pedro M F J

2015-11-06

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode-interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode-nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Photoelectrocatalytic reduction of CO2 into chemicals using Pt-modified reduced graphene oxide combined with Pt-modified TiO2 nanotubes.

PubMed

Cheng, Jun; Zhang, Meng; Wu, Gai; Wang, Xin; Zhou, Junhu; Cen, Kefa

2014-06-17

The photoelectrocatalytic (PEC) reduction of CO2 into high-value chemicals is beneficial in alleviating global warming and advancing a low-carbon economy. In this work, Pt-modified reduced graphene oxide (Pt-RGO) and Pt-modified TiO2 nanotubes (Pt-TNT) were combined as cathode and photoanode catalysts, respectively, to form a PEC reactor for converting CO2 into valuable chemicals. XRD, XPS, TEM, AFM, and SEM were employed to characterize the microstructures of the Pt-RGO and Pt-TNT catalysts. Reduction products, such as C2H5OH and CH3COOH, were obtained from CO2 under band gap illumination and biased voltage. A combined liquid product generation rate (CH3OH, C2H5OH, HCOOH, and CH3COOH) of approximately 600 nmol/(h·cm(2)) was observed. Carbon atom conversion rate reached 1,130 nmol/(h·cm(2)), which were much higher than those achieved using Pt-modified carbon nanotubes and platinum carbon as cathode catalysts.

Atmospheric-pressure plasma jet processed Pt/ZnO composites and its application as counter-electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lee, Chia-Chun; Wan, Ting-Hao; Hsu, Cheng-Che; Cheng, I.-Chun; Chen, Jian-Zhang

2018-04-01

Nitrogen dc-pulse atmospheric pressure plasma jet (APPJ) is used to fabricate Pt/ZnO composites as the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). Due to the synergetic effect of the reactive plasma species and heat in nitrogen APPJ, the spin-coated precursors including chloroplatinic acid and zinc acetate can be reduced on fluorine-doped tin oxide (FTO) glass substrates in a few seconds. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses indicate that the precursors are reduced to Pt/ZnO under APPJ calcination. Electrochemical impedance spectroscopy (EIS) and Tafel measurement show the promising catalytic activities of Pt/ZnO CEs with low charge transfer resistance and high exchange current density. The efficiency of a DSSC with a 30-s APPJ-calcined Pt/ZnO CE is similar to that with a conventional furnace-annealed Pt CE for 15 min. The results indicate that nitrogen dc-pulse APPJ treatment is an efficient tool for rapidly fabricating Pt/ZnO composite CEs of DSSCs.

Negligible degradation upon in situ voltage cycling of a PEMFC using an electrospun niobium-doped tin oxide supported Pt cathode.

PubMed

Savych, Iuliia; Subianto, Surya; Nabil, Yannick; Cavaliere, Sara; Jones, Deborah; Rozière, Jacques

2015-07-14

Novel platinum-catalysed, corrosion-resistant, loose-tube-structured electrocatalysts for proton exchange membrane fuel cells have been obtained using single-needle electrospinning associated with a microwave-assisted polyol method. Monodisperse platinum particles supported on Nb-SnO2 demonstrated higher electrochemical stability than conventional Pt/C electrodes during ex situ potential cycling and comparable activity in the oxygen reduction reaction. In situ fuel cell operation under accelerated stress test conditions of a membrane electrode assembly elaborated using a Pt/C anode and Pt/Nb-SnO2 cathode confirmed that the voltage loss is significantly lower for the novel cathode than for an MEA prepared using conventional Pt/C supported electrocatalysts. Furthermore, the Nb-SnO2 stabilised the supported platinum nanoparticles against dissolution, migration and reprecipitation in the membrane. Pt/Nb-SnO2 loose-tubes constitute a mitigation strategy for two known degradation mechanisms in PEMFC: corrosion of the carbon support at the cathode, and dissolution of Pt at high cell voltages.

Platinum Electrodeposition at Unsupported Electrochemically Reduced Nanographene Oxide for Enhanced Ammonia Oxidation

PubMed Central

2015-01-01

The electrochemical reduction of highly oxidized unsupported graphene oxide nanosheets and its platinum electrodeposition was done by the rotating disk slurry electrode technique. Avoiding the use of a solid electrode, graphene oxide was electrochemically reduced in a slurry solution with a scalable process without the use of a reducing agent. Graphene oxide nanosheets were synthesized from carbon platelet nanofibers to obtain highly hydrophilic layers of less than 250 nm in width. The graphene oxide and electrochemically reduced graphene oxide/Pt (erGOx/Pt) hybrid materials were characterized through different spectroscopy and microscopy techniques. Pt nanoparticles with 100 facets, clusters, and atoms at erGOx were identified by high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry was used to characterize the electrocatalytic activity of the highly dispersed erGOx/Pt hybrid material toward the oxidation of ammonia, which showed a 5-fold current density increase when compared with commercially available Vulcan/Pt 20%. This is in agreement with having Pt (100) facets present in the HRTEM images of the erGOx/Pt material. PMID:24417177

Ethanol oxidation on Pt single-crystal electrodes: surface-structure effects in alkaline medium.

PubMed

Busó-Rogero, Carlos; Herrero, Enrique; Feliu, Juan M

2014-07-21

Ethanol oxidation in 0.1 M NaOH on single-crystal electrodes has been studied using electrochemical and FTIR techniques. The results show that the activity order is the opposite of that found in acidic solutions. The Pt(111) electrode displays the highest currents and also the highest onset potential of all the electrodes. The onset potential for the oxidation of ethanol is linked to the adsorption of OH on the electrode surface. However, small (or even negligible) amounts of CO(ads) and carbonate are detected by FTIR, which implies that cleavage of the C-C bond is not favored in this medium. The activity of the electrodes diminishes quickly upon cycling. The diminution of the activity is proportional to the measured currents and is linked to the formation and polymerization of acetaldehyde, which adsorbs onto the electrode surface and prevents further oxidation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biointerfacial Property of Plasma-Treated Single-Walled Carbon Nanotube Film Electrodes for Electrochemical Biosensors

NASA Astrophysics Data System (ADS)

Kim, Joon Hyub; Lee, Jun-Yong; Jin, Joon-Hyung; Park, Eun Jin; Min, Nam Ki

2013-01-01

The single-walled carbon nanotube (SWCNT)-based thin film was spray-coated on the Pt support and functionalized using O2 plasma. The effects of plasma treatment on the biointerfacial properties of the SWCNT films were analyzed by cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The plasma-functionalized (pf) SWCNT electrodes modified with Legionella pneumophila-specific probe DNA strands showed a much higher peak current and a smaller peak separation in differential pulse voltammetry and a lower charge transfer resistance, compared to the untreated samples. These results suggest that the pf-SWCNT films have a better electrocatalytic character and an electron transfer capability faster than the untreated SWCNTs, due to the fact that the oxygen-containing functional groups promote direct electron transfer in the biointerfacial region of the electrocatalytic activity of redox-active biomolecules.

Enlarging photovoltaic effect: combination of classic photoelectric and ferroelectric photovoltaic effects.

PubMed

Zhang, Jingjiao; Su, Xiaodong; Shen, Mingrong; Dai, Zhihua; Zhang, Lingjun; He, Xiyun; Cheng, Wenxiu; Cao, Mengyu; Zou, Guifu

2013-01-01

Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm²) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials.

Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability.

PubMed

Jackson, Ariel; Strickler, Alaina; Higgins, Drew; Jaramillo, Thomas Francisco

2018-01-12

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications. The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1 ), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.

Facile fabrication of network film electrodes with ultrathin Au nanowires for nonenzymatic glucose sensing and glucose/O2 fuel cell.

PubMed

Yang, Lu; Zhang, Yijia; Chu, Mi; Deng, Wenfang; Tan, Yueming; Ma, Ming; Su, Xiaoli; Xie, Qingji; Yao, Shuozhuo

2014-02-15

We report here on the facile fabrication of network film electrodes with ultrathin Au nanowires (AuNWs) and their electrochemical applications for high-performance nonenzymatic glucose sensing and glucose/O2 fuel cell under physiological conditions (pH 7.4, containing 0.15M Cl(-)). AuNWs with an average diameter of ~7 or 2 nm were prepared and can self-assemble into robust network films on common electrodes. The network film electrode fabricated with 2-nm AuNWs exhibits high sensitivity (56.0 μA cm(-2)mM(-1)), low detection limit (20 μM), short response time (within 10s), excellent selectivity, and good storage stability for nonenzymatic glucose sensing. Glucose/O2 fuel cells were constructed using network film electrodes as the anode and commercial Pt/C catalyst modified glassy carbon electrode as cathode. The glucose/O2 fuel cell using 2-nm AuNWs as anode catalyst output a maximum power density of is 126 μW cm(-2), an open-circuit cell voltage of 0.425 V, and a short-circuit current density of 1.34 mA cm(-2), respectively. Due to the higher specific electroactive surface area of 2-nm AuNWs, the network film electrode fabricated with 2-nm AuNWs exhibited higher electrocatalytic activity toward glucose oxidation than the network film electrode fabricated with 7-nm AuNWs. The network film electrode exhibits high electrocatalytic activity toward glucose oxidation under physiological conditions, which is helpful for constructing implantable electronic devices. © 2013 Elsevier B.V. All rights reserved.

An amperometric enzyme electrode and its biofuel cell based on a glucose oxidase-poly(3-anilineboronic acid)-Pd nanoparticles bionanocomposite for glucose biosensing.

PubMed

Sun, Lingen; Ma, Yixuan; Zhang, Pei; Chao, Long; Huang, Ting; Xie, Qingji; Chen, Chao; Yao, Shouzhuo

2015-06-01

A new amperometric enzyme electrode and its biofuel cell were fabricated based on a glucose oxidase (GOx)-poly(3-anilineboronic acid) (PABA)-Pd nanoparticles (PdNPs) bionanocomposite for biosensing of glucose. Briefly, Pd was electroplated on a multiwalled carbon nanotubes (MWCNTs)-modified Au electrode, and the GOx-PABA-PdNPs bionanocomposite was prepared on the Pd(plate)/MWCNTs/Au electrode through the chemical oxidation of a GOx-3-anilineboronic acid adduct by Na2PdCl4, followed by electrode-modification with an outer-layer chitosan (CS) film. The thus-prepared CS/GOx-PABA-PdNPs/Pd(plate)/MWCNTs/Au electrode exhibited a linear amperometric response to glucose concentration from 2.0 μM to 4.5 mM with a sensitivity of 160 μA/mM/cm(2), sub-μM detection limit, and excellent operation/storage stability in the first-generation biosensing mode, as well as excellent analytical performance in the second-generation biosensing mode. The good recoveries of glucose obtained from spiked urine samples revealed the application potential of our amperometric enzyme electrode. In addition, a glucose/O2 biofuel cell was constructed using this enzyme electrode as the anode and a Pt/MWCNTs/Au electrode as the cathode, and this biofuel cell as a self-powered biosensing device showed a linear voltage response to glucose concentration from 100 μM to 13.5 mM with a sensitivity of 43.5 mV/mM/cm(2) and excellent operation/storage stability. Copyright © 2015 Elsevier B.V. All rights reserved.

In situ study of an oxidation reaction on a Pt/C electrode by ambient pressure hard X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takagi, Yasumasa, E-mail: ytakagi@ims.ac.jp; Uemura, Yohei; Yokoyama, Toshihiko

2014-09-29

We have constructed an ambient pressure X-ray photoelectron spectroscopy instrument that uses hard X-ray radiation at the high-performance undulator beamline BL36XU of SPring-8. The dependence of the Au 4f peak intensity from Au foil on the ambient N{sub 2} pressure was measured. At a photon energy of 7.94 keV, the Au 4f peak intensity maintained 40% at 3000 Pa compared with that at high vacuum. We designed a polymer electrolyte fuel cell that allows us to perform X-ray photoelectron spectroscopy measurements of an electrode under working conditions. The oxidized Pt peaks were observed in the Pt 3d{sub 5/2} level of Pt nanoparticlesmore » in the cathode, and the peaks clearly depended on the applied voltage between the anode and cathode. Our apparatus can be applied as a valuable in situ tool for the investigation of the electronic states and adsorbed species of polymer electrolyte fuel cell electrode catalysts under the reaction conditions.« less

Platinum-Free Counter Electrode Comprised of Metal-Organic-Framework (MOF)-Derived Cobalt Sulfide Nanoparticles for Efficient Dye-Sensitized Solar Cells (DSSCs)

PubMed Central

Hsu, Shao-Hui; Li, Chun-Ting; Chien, Heng-Ta; Salunkhe, Rahul R.; Suzuki, Norihiro; Yamauchi, Yusuke; Ho, Kuo-Chuan; Wu, Kevin C.-W.

2014-01-01

We fabricated a highly efficient (with a solar-to-electricity conversion efficiency (η) of 8.1%) Pt-free dye-sensitized solar cell (DSSC). The counter electrode was made of cobalt sulfide (CoS) nanoparticles synthesized via surfactant-assisted preparation of a metal organic framework, ZIF-67, with controllable particle sizes (50 to 320 nm) and subsequent oxidation and sulfide conversion. In contrast to conventional Pt counter electrodes, the synthesized CoS nanoparticles exhibited higher external surface areas and roughness factors, as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) element mapping, and electrochemical analysis. Incident photon-to-current conversion efficiency (IPCE) results showed an increase in the open circuit voltage (VOC) and a decrease in the short-circuit photocurrent density (Jsc) for CoS-based DSSCs compared to Pt-based DSSCs, resulting in a similar power conversion efficiency. The CoS-based DSSC fabricated in the study show great potential for economically friendly production of Pt-free DSSCs. PMID:25382139

Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

DOE PAGES

Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; ...

2016-03-08

The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities comparedmore » to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.« less

Three-Dimensional Array of TiN@Pt3Cu Nanowires as an Efficient Porous Electrode for the Lithium-Oxygen Battery.

PubMed

Luo, Wen-Bin; Pham, Thien Viet; Guo, Hai-Peng; Liu, Hua-Kun; Dou, Shi-Xue

2017-02-28

The nonaqueous lithium-oxygen battery is a promising candidate as a next-generation energy storage system because of its potentially high energy density (up to 2-3 kW kg -1 ), exceeding that of any other existing energy storage system for storing sustainable and clean energy to reduce greenhouse gas emissions and the consumption of nonrenewable fossil fuels. To achieve high round-trip efficiency and satisfactory cycling stability, the air electrode structure and the electrocatalysts play important roles. Here, a 3D array composed of one-dimensional TiN@Pt 3 Cu nanowires was synthesized and employed as a whole porous air electrode in a lithium-oxygen battery. The TiN nanowire was primarily used as an air electrode frame and catalyst support to provide a high electronic conductivity network because of the high-orientation one-dimensional crystalline structure. Meanwhile, deposited icosahedral Pt 3 Cu nanocrystals exhibit highly efficient catalytic activity owing to the abundant {111} active lattice facets and multiple twin boundaries. This porous air electrode comprises a one-dimensional TiN@Pt 3 Cu nanowire array that demonstrates excellent energy conversion efficiency and rate performance in full discharge and charge modes. The discharge capacity is up to 4600 mAh g -1 along with an 84% conversion efficiency at a current density of 0.2 mA cm -2 , and when the current density increased to 0.8 mA cm -2 , the discharge capacity is still greater than 3500 mAh g -1 together with a nearly 70% efficiency. This designed array is a promising bifunctional porous air electrode for lithium-oxygen batteries, forming a continuous conductive and high catalytic activity network to facilitate rapid gas and electrolyte diffusion and catalytic reaction throughout the whole energy conversion process.

Composite electronic materials based on poly(3,4-propylenedioxythiophene) and highly charged poly(aryleneethynylene)-wrapped carbon nanotubes for supercapacitors.

PubMed

Rosario-Canales, Mariem R; Deria, Pravas; Therien, Michael J; Santiago-Avilés, Jorge J

2012-01-01

Supercapacitor charge storage media were fabricated using the semiconducting polymer poly(3,4-propylenedioxythiophene) (PProDOT) and single-walled carbon nanotubes (SWNTs) that were helically wrapped with ionic, conjugated poly[2,6-{1,5-bis(3-propoxysulfonicacidsodiumsalt)}naphthylene]ethynylene (PNES). These PNES-wrapped SWNTs (PNES-SWNTs) enable efficient dispersion of individualized nanotubes in a wide range of organic solvents. PNES-SWNT film-modified Pt electrodes were prepared by drop casting PNES-SWNT suspensions in MeOH; high stability, first-generation PProDOT/PNES/SWNT composites were realized via electropolymerization of the ProDOT parent monomer (3,4-propylenedioxythiophene) in a 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/propylene carbonate solution at the PNES-SWNT-modified electrode. The electrochemical properties of PProDOT and PProDOT/PNES/SWNT single electrodes and devices were examined using cyclic voltammetric methods. The hybrid composites were found to enhance key supercapacitor figures of merit (charge capacity and capacitance) by approximately a factor of 2 relative to those determined for benchmark Type I devices that exploited a classic PProDOT-based electrode material. The charge/discharge stability of the supercapacitors was probed by repeated rounds of cyclic voltammetric evaluation at a minimum depth of discharge of 73%; these experiments demonstrated that the hybrid PProDOT/PNES/SWNT composites retained ~90% of their initial charge capacity after 21,000 charge/discharge cycles, contrasting analogous data obtained for PProDOT-based devices, which showed only 84% retention of their initial charge capacity. © 2011 American Chemical Society

Development of an amperometric sulfite biosensor based on SO(x)/PBNPs/PPY modified ITO electrode.

PubMed

Rawal, Rachna; Pundir, C S

2012-11-01

A sulfite oxidase (SO(x)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SO(x)/PBNPs/PPY/ITO electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SO(x). The biosensor showed optimum response within 2s, when operated at 20 mV s⁻¹ in 0.1M Tris-HCl buffer, pH 8.5 and at 35 °C. Linear range and minimum detection limit were 0.5-1000 μM and 0.12 μM (S/N=3) respectively. There was good correlation (r=0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4 °C. Copyright © 2012 Elsevier B.V. All rights reserved.

Mechanical and thermal behavior of ionic polymer metal composites: effects of electroded metals

NASA Astrophysics Data System (ADS)

Park, Il-Seok; Kim, Sang-Mun; Kim, Kwang J.

2007-08-01

In this study, we investigated the mechanical properties of various types of ionic polymer-metal composites (IPMCs) and Pt, Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5-7 µm-doped layer and nanosized Au particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in dried conditions. With regards to thermal behavior, Au IPMC had the highest Tg (153 °C) and Tm (263 °C) in both the DMA and DSC results. The fracture behavior of various types of IPMCs followed the behavior of the base material, Nafion™, which is represented as the semicrystalline polymer characteristic.

Passivation of Cu-Zn alloy on low carbon steel electrodeposited from a pyrophosphate medium

NASA Astrophysics Data System (ADS)

Yavuz, Abdulcabbar; Yakup Hacıibrahimoğlu, M.; Bedir, Metin

2018-01-01

The motivation of this study is to understand whether zinc-based alloy also has a passivation behaviour similar to zinc itself. Cu-Zn alloys were electrodeposited potentiostatically from a pyrophosphate medium on a carbon steel electrode and their corrosion behaviours were studied. Pt and carbon steel electrodes were used in order to examine the corrosion/passivation behaviour of bare Cu, bare Zn and Cu-Zn alloy coatings. The passivation behaviour of all brass-modified electrodes having Zn content between 10% and 100% was investigated. The growth potential affects the morphology and structure of crystals. The brass coatings are more porous than their pure components. The crystalline structure of Cu-Zn alloys can be obtained by changing the deposition potential. The zinc content in brass increases when the deposition voltage applied decreases. However, the growth potential and the ratio of zinc in brass do not affect the passivation behaviour of the resulting alloys. The coatings obtained by applying different growth potentials were immersed in tap water for 24 h to compare their corrosion behaviours with carbon steel having pitting formation.

A comparative study of CO adsorption on tetrahexahedral Pt nanocrystals and interrelated Pt single crystal electrodes by using cyclic voltammetry and in situ FTIR spectroscopy.

PubMed

Liu, Hai-Xia; Tian, Na; Ye, Jin-Yu; Lu, Bang-An; Ren, Jie; Huangfu, Zhi-Chao; Zhou, Zhi-You; Sun, Shi-Gang

2014-01-01

This study focuses on CO adsorption at tetrahexahedral Pt nanocrystals (THH Pt NCs) by using cyclic voltammetry and in situ FTIR spectroscopy. Since the electrochemically prepared THH Pt NCs in this study are enclosed by {730} facets which could be considered by a subfacet configuration of 2{210} + {310}, we have also studied CO adsorption on the interrelated Pt(310) and Pt(210) single crystal electrodes as a comparison. Cyclic voltammetry results demonstrated that CO adsorbs dominantly on the (100) sites of THH Pt NCs at low CO coverage (θ(CO)≤ 0.135), while on both (100) and (110) sites at higher CO coverage. On ordered Pt(310) and Pt(210), i.e. they were flame annealed and then cooled in H(2) + Ar, CO adsorption also illustrates relative priority on (100) sites at low CO coverage; while at high CO coverage or on oxygen-disordered Pt(310) and Pt(210) when they were cooled in air after flame annealing, the adsorption of CO presents a weak preference on (100) sites of Pt(310) and even no preference at all on (100) sites of Pt(210). In situ FTIR spectroscopic studies illustrated that CO adsorption on THH Pt NCs yields anomalous infrared effects (AIREs), which are depicted by the Fano-like IR feature on a dense distribution (60 μm(-2)) and the enhancement of abnormal IR absorption on a sparse distribution (22 μm(-2)) of THH Pt NCs on glassy carbon substrate. Systematic investigation of CO coverage dependence of IR features revealed that, on THH Pt NCs, the IR band center (ν(COL)) of linearly bonded CO (COL) is rapidly shifted to higher wavenumbers along with the increase of CO coverage to 0.184, yielding a fast linear increase rate with a high slope (dν(COL)/dθ(IR)(CO) = 219 cm(-1)); when θ > 0.184, the increase of ν(COL) with θCO slows down and deviates drastically from linearity. In contrast, the ν(COL) on the ordered Pt(310) electrode maintains a linear increase with θ(IR)(CO) for the whole range of θ(IR)(CO) variation, and gives a much smaller increase rate of slope 74.3 cm(-1). The significant differences in CO adsorption behavior on THH Pt NCs and on interrelated Pt single crystal planes demonstrated clearly the unique properties of nanoparticles enclosed by high-index facets.

Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix

PubMed Central

Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan

2015-01-01

The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg−1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture. PMID:26537781

Electrodeposition of uranium and thorium onto small platinum electrodes

NASA Astrophysics Data System (ADS)

Reichenberger, Michael A.; Ito, Takashi; Ugorowski, Philip B.; Montag, Benjamin W.; Stevenson, Sarah R.; Nichols, Daniel M.; McGregor, Douglas S.

2016-03-01

Preparation of thin U- and Th-coated 0.3 mm diameter Pt working electrodes by the cyclic potential sweep method is described. Uranyl- and thorium hydroxide layers were electrodeposited from ethanol solutions containing 0.02 M natural uranyl and 0.02 M natural thorium nitrate, each with 3.6 M ammonium nitrate. The cell for electrodeposition was specially developed in order to accommodate the small working electrodes for this research by including a working electrode probe, 3-D translation stage, and microscope. The source material deposition was analyzed using digital microscopy and scanning electron microscopy, and confirmed using x-ray fluorescence measurements. The appropriate potential range for electrodeposition was determined to be -0.62 V to -0.64 V for a 0.3 mm diameter Pt working electrode placed 1 cm from the counter electrode. Smooth, uniform deposition was observed near the central region of the working electrode, while surface cracking and crystalline formations were found near the edge of the working electrode. The final procedure for sample substrate preparation, electrolytic solution preparation and electrodeposition are described.

Low Fatigue in Epitaxial Pb(Zr0.2Ti0.8)O3 on Si Substrates with LaNiO3 Electrodes by RF Sputtering

NASA Astrophysics Data System (ADS)

Wang, Chun; Kryder, Mark H.

2009-09-01

Epitaxial PZT (001) thin films with a LaNiO3 bottom electrode were deposited by radio-frequency (RF) sputtering onto Si(001) single-crystal substrates with SrTiO3/TiN buffer layers. Pb(Zr0.2Ti0.8)O3 (PZT) samples were shown to consist of a single perovskite phase and to have an (001) orientation. The orientation relationship was determined to be PZT(001)[110]∥LaNiO3(001)[110]∥SrTiO3 (001)[110]∥TiN(001)[110]∥Si(001)[110]. Atomic force microscope (AFM) measurements showed the PZT films to have smooth surfaces with a roughness of 1.15 nm. The microstructure of the multilayer was studied using transmission electron microscopy (TEM). Electrical measurements were conducted using both Pt and LaNiO3 as top electrodes. The measured remanent polarization P r and coercive field E c of the PZT thin film with Pt top electrodes were 23 μC/cm2 and 75 kV/cm, and were 25 μC/cm2 and 60 kV/cm for the PZT film with LaNiO3 top electrodes. No obvious fatigue after 1010 switching cycles indicated good electrical endurance of the PZT films using LaNiO3 electrodes, compared with the PZT film with Pt top electrodes showing a significant polarization loss after 108 cycles. These PZT films with LaNiO3 electrodes could be potential recording media for probe-based high-density data storage.

Plain to point network reduced graphene oxide - activated carbon composites decorated with platinum nanoparticles for urine glucose detection

NASA Astrophysics Data System (ADS)

Hossain, Mohammad Faruk; Park, Jae Y.

2016-02-01

In this study, a hydrothermal technique was applied to synthesize glucose-treated reduced graphene oxide-activated carbon (GRGO/AC) composites. Platinum nanoparticles (PtNP) were electrochemically deposited on the modified GRGO/AC surface, and chitosan-glucose oxidase (Chit-GOx) composites and nafion were integrated onto the modified surface of the working electrode to prepare a highly sensitive glucose sensor. The fabricated biosensor exhibited a good amperometric response to glucose in the detection range from 0.002 mM to 10 mM, with a sensitivity of 61.06 μA/mMcm2, a short response time (4 s) and a low detection limit of 2 μM (signal to noise ratio is 3). The glucose sensor exhibited a negligible response to interference and good stability. In addition, the glucose levels in human urine were tested in order to conduct a practical assessment of the proposed sensor, and the results indicate that the sensor had superior urine glucose recognition. These results thus demonstrate that the noble nano-structured electrode with a high surface area and electrocatalytic activity offers great promise for use in urine glucose sensing applications.

A bimetallic nanocomposite modified genosensor for recognition and determination of thalassemia gene.

PubMed

Hamidi-Asl, Ezat; Raoof, Jahan Bakhsh; Naghizadeh, Nahid; Akhavan-Niaki, Haleh; Ojani, Reza; Banihashemi, Ali

2016-10-01

The main roles of DNA in the cells are to maintain and properly express genetic information. It is important to have analytical methods capable of fast and sensitive detection of DNA damage. DNA hybridization sensors are well suited for diagnostics and other purposes, including determination of bacteria and viruses. Beta thalassemias (βth) are due to mutations in the β-globin gene. In this study, an electrochemical biosensor which detects the sequences related to the β-globin gene issued from real samples amplified by polymerase chain reaction (PCR) is described for the first time. The biosensor relies on the immobilization of 20-mer single stranded oligonucleotide (probe) related to βth sequence on the carbon paste electrode (CPE) modified by 15% silver (Ag) and platinum (Pt) nanoparticles to prepare the bimetallic nanocomposite electrode and hybridization of this oligonucleotide with its complementary sequence (target). The extent of hybridization between the probe and target sequences was shown by using linear sweep voltammetry (LSV) with methylene blue (MB) as hybridization indicator. The selectivity of sensor was investigated using PCR samples containing non-complementary oligonucleotides. The detection limit of biosensor was calculated about 470.0pg/μL. Copyright © 2016 Elsevier B.V. All rights reserved.

Plain to point network reduced graphene oxide - activated carbon composites decorated with platinum nanoparticles for urine glucose detection

PubMed Central

Hossain, Mohammad Faruk; Park, Jae Y.

2016-01-01

In this study, a hydrothermal technique was applied to synthesize glucose-treated reduced graphene oxide-activated carbon (GRGO/AC) composites. Platinum nanoparticles (PtNP) were electrochemically deposited on the modified GRGO/AC surface, and chitosan-glucose oxidase (Chit-GOx) composites and nafion were integrated onto the modified surface of the working electrode to prepare a highly sensitive glucose sensor. The fabricated biosensor exhibited a good amperometric response to glucose in the detection range from 0.002 mM to 10 mM, with a sensitivity of 61.06 μA/mMcm2, a short response time (4 s) and a low detection limit of 2 μM (signal to noise ratio is 3). The glucose sensor exhibited a negligible response to interference and good stability. In addition, the glucose levels in human urine were tested in order to conduct a practical assessment of the proposed sensor, and the results indicate that the sensor had superior urine glucose recognition. These results thus demonstrate that the noble nano-structured electrode with a high surface area and electrocatalytic activity offers great promise for use in urine glucose sensing applications. PMID:26876368

Improving Impedance of Implantable Microwire Multi-Electrode Arrays by Ultrasonic Electroplating of Durable Platinum Black

PubMed Central

Desai, Sharanya Arcot; Rolston, John D.; Guo, Liang; Potter, Steve M.

2010-01-01

Implantable microelectrode arrays (MEAs) have been a boon for neural stimulation and recording experiments. Commercially available MEAs have high impedances, due to their low surface area and small tip diameters, which are suitable for recording single unit activity. Lowering the electrode impedance, but preserving the small diameter, would provide a number of advantages, including reduced stimulation voltages, reduced stimulation artifacts and improved signal-to-noise ratio. Impedance reductions can be achieved by electroplating the MEAs with platinum (Pt) black, which increases the surface area but has little effect on the physical extent of the electrodes. However, because of the low durability of Pt black plating, this method has not been popular for chronic use. Sonicoplating (i.e. electroplating under ultrasonic agitation) has been shown to improve the durability of Pt black on the base metals of macro-electrodes used for cyclic voltammetry. This method has not previously been characterized for MEAs used in chronic neural implants. We show here that sonicoplating can lower the impedances of microwire multi-electrode arrays (MMEA) by an order of magnitude or more (depending on the time and voltage of electroplating), with better durability compared to pulsed plating or traditional DC methods. We also show the improved stimulation and recording performance that can be achieved in an in vivo implantation study with the sonicoplated low-impedance MMEAs, compared to high-impedance unplated electrodes. PMID:20485478

Platinum porous nanoparticles hybrid with metal ions as probes for simultaneous detection of multiplex cancer biomarkers.

PubMed

Wang, Zifeng; Liu, Na; Ma, Zhanfang

2014-03-15

In this work, platinum porous nanoparticles (PtPNPs) absorbed metal ions as electrochemical signals were fabricated. Clean-surface PtPNPs were prepared by a surfactant-free method and decorated with amino groups via 2-aminoethanethiol. Amino capped PtPNPs complexation with Cd(2+) and Cu(2+) to form PtPNPs-Cd(2+) and PtPNPs-Cu(2+) hybrids, respectively. Anti-CEA and Anti-AFP separately labeled with PtPNPs-Cd(2+) and PtPNPs-Cu(2+) were used as distinguishable signal tags for capturing antigens. The metal ions were detected in a single run through differential pulse voltammetry (DPV) without acid dissolution, electric potentials and peak heights of which reflected the identity and concentrations of the corresponding antigen. Ionic liquid reduced graphene oxide (IL-rGO) modified glassy carbon electrode (GCE) was used as a substrate, which was rich in amino groups to immobilize antibodies by glutaraldehyde through cross-link between aldehyde groups and amino groups. Using the proposed probes and platform, a novel sandwich-type electrochemical immunosensor for simultaneous detecting carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was successfully developed. This immunoassay possessed good linearity from 0.05 ng mL(-1) to 200 ng mL(-1) for both CEA and AFP. The detection limit of CEA was 0.002 ng mL(-1) and that of AFP was 0.05 ng mL(-1) (S/N=3). Furthermore, analysis of clinical serum samples using this immunosensor was well consistent with the data determined by the enzyme-linked immunosorbent assay (ELISA). It suggested that the proposed electrochemical immunoassay provided a potential application of clinical screening for early-stage cancers. © 2013 Published by Elsevier B.V.

Enhanced peroxidase-like properties of Au@Pt DNs/NG/Cu2+ and application of sandwich-type electrochemical immunosensor for highly sensitive detection of CEA.

PubMed

Lv, Hui; Li, Yueyun; Zhang, Xiaobo; Gao, Zengqiang; Zhang, Chunyan; Zhang, Shuan; Dong, Yunhui

2018-07-30

Effective treatment of cancer depends upon the early detection of the tumor marker. Here, we report on the development of a new immunosensor for early detection of carcinoembryonic antigen (CEA). Cubic Au@Pt dendritic nanomaterials functionalized nitrogen-doped graphene loaded with copper ion (Au@Pt DNs/NG/Cu 2+ ) with enhanced peroxidase-like properties was synthesized as labels to effectively capture and immobilize secondary anti-CEA. The Au@Pt DNs with more active surface area could efficiently enhance electrocatalysis for reduction of hydrogen peroxide (H 2 O 2 ). Meanwhile, with good conductivity and large specific surface area, NG can immobilize a large amount of Au@Pt DNs. Furthermore, after adsorbed Cu 2+ can further promote the redox of H 2 O 2 and amplify the signal of the immunosensor. For the immobilization of primary antibodies, Au nanoparticles functionalized polydopamine (Au@PDA) were used as transducing materials to modify glassy carbon electrodes and enhance the electron transfer efficiently. Under optimal conditions, the immunosensor exhibited a satisfactory response to CEA with a limit detection of 0.167 pg/mL and linear detection range from 0.5 pg/mL to 50 ng/mL. Based on the high sensitivity and specificity of the immunosensor, we propose this multiple amplified biosensor for early detection of CEA. Copyright © 2018 Elsevier B.V. All rights reserved.

Substrate dependent stability of conducting polymer coatings on medical electrodes.

PubMed

Green, Rylie A; Hassarati, Rachelle T; Bouchinet, Lucie; Lee, Chaekyung S; Cheong, Gin L M; Yu, Jin F; Dodds, Christopher W; Suaning, Gregg J; Poole-Warren, Laura A; Lovell, Nigel H

2012-09-01

Conducting polymer (CP) coatings on medical electrodes have the potential to provide superior performance when compared to conventional metallic electrodes, but their stability is strongly dependant on the substrate properties. The aim of this study was to examine the effect of laser roughening of underlying platinum (Pt) electrode surfaces on the mechanical, electrical and biological performance of CP coatings. In addition, the impact of dopant type on electrical performance and stability was assessed. The CP poly(ethylene dioxythiophene) (PEDOT) was coated on Pt microelectrode arrays, with three conventional dopant ions. The in vitro electrical characteristics were assessed by cyclic voltammetry and biphasic stimulation. Results showed that laser roughening of the underlying substrate did not affect the charge injection limit of the coated material, but significantly improved the passive stability and chronic stimulation lifetime without failure of the coating. Accelerated material ageing and long-term biphasic stimulus studies determined that some PEDOT variants experienced delamination within as little as 10 days when the underlying Pt was smooth, but laser roughening to produce a surface index of 2.5 improved stability, such that more than 1.3 billion stimulation cycles could be applied without evidence of failure. PEDOT doped with paratoluene sulfonate (PEDOT/pTS) was found to be the most stable CP on roughened Pt, and presented a surface topography which encouraged neural cell attachment. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Interdigitated array of Pt electrodes for electrical stimulation and engineering of aligned muscle tissue.

PubMed

Ahadian, Samad; Ramón-Azcón, Javier; Ostrovidov, Serge; Camci-Unal, Gulden; Hosseini, Vahid; Kaji, Hirokazu; Ino, Kosuke; Shiku, Hitoshi; Khademhosseini, Ali; Matsue, Tomokazu

2012-09-21

Engineered skeletal muscle tissues could be useful for applications in tissue engineering, drug screening, and bio-robotics. It is well-known that skeletal muscle cells are able to differentiate under electrical stimulation (ES), with an increase in myosin production, along with the formation of myofibers and contractile proteins. In this study, we describe the use of an interdigitated array of electrodes as a novel platform to electrically stimulate engineered muscle tissues. The resulting muscle myofibers were analyzed and quantified in terms of their myotube characteristics and gene expression. The engineered muscle tissues stimulated through the interdigitated array of electrodes demonstrated superior performance and maturation compared to the corresponding tissues stimulated through a conventional setup (i.e., through Pt wires in close proximity to the muscle tissue). In particular, the ES of muscle tissue (voltage 6 V, frequency 1 Hz and duration 10 ms for 1 day) through the interdigitated array of electrodes resulted in a higher degree of C2C12 myotube alignment (∼80%) as compared to ES using Pt wires (∼65%). In addition, higher amounts of C2C12 myotube coverage area, myotube length, muscle transcription factors and protein biomarkers were found for myotubes stimulated through the interdigitated array of electrodes compared to those stimulated using the Pt wires. Due to the wide array of potential applications of ES for two- and three-dimensional (2D and 3D) engineered tissues, the suggested platform could be employed for a variety of cell and tissue structures to more efficiently investigate their response to electrical fields.

Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Ariel; Strickler, Alaina; Higgins, Drew

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications.more » The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.« less

Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

DOE PAGES

Jackson, Ariel; Strickler, Alaina; Higgins, Drew; ...

2018-01-12

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications.more » The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.« less

Potentiometric sensors with carbon black supporting platinum nanoparticles.

PubMed

Paczosa-Bator, Beata; Cabaj, Leszek; Piech, Robert; Skupień, Krzysztof

2013-11-05

For the first time, a single-piece, all-solid-state ion-selective electrode was fabricated with carbon black supporting platinum nanoparticles (PtNPs-CB) and a polymeric membrane. The PtNPs-CB, as an intermediate layer, was drop-casted directly on the solid substrate, and then an ionophore-doped solvent polymeric membrane was added in order to form a sensor. The performance of the newly developed electrodes was evaluated on the basis of potassium and nitrate ions. The stability of the electrical potential for the electrodes was examined by performing current-reversal chronopotentiometry, and the influence of the interfacial water film was assessed by the potentiometric aqueous-layer test. Fabricated potassium- and nitrate-selective electrodes displayed a Nernstian slope and several outstanding properties such as high long-term potential stability, potential repeatability, and reproducibility.

Fabrication of a nanosize-Pt-embedded membrane electrode assembly to enhance the utilization of Pt in proton exchange membrane fuel cells.

PubMed

Choe, Junseok; Kim, Doyoung; Shim, Jinyong; Lee, Inhae; Tak, Yongsug

2011-08-01

A procedure to locate the Pt nanostructure inside the hydrophilic channel of a Nafion membrane was developed in order to enhance Pt utilization in PEMFCs. Nanosize Pt-embedded MEA was constructed by Cu electroless plating and subsequent Pt electrodeposition inside the hydrophilic channels of the Nafion membrane. The metallic Pt nanostructure fabricated inside the membrane was employed as an oxygen reduction catalyst for a PEMFC and facilitated effective use of the hydrophilic channels inside the membrane. Compared to the conventional MEA, a Pt-embedded MEA with only 68% Pt loading showed better PEMFC performance.

Vertically aligned single-walled carbon nanotubes as low-cost and high electrocatalytic counter electrode for dye-sensitized solar cells.

PubMed

Dong, Pei; Pint, Cary L; Hainey, Mel; Mirri, Francesca; Zhan, Yongjie; Zhang, Jing; Pasquali, Matteo; Hauge, Robert H; Verduzco, Rafael; Jiang, Mian; Lin, Hong; Lou, Jun

2011-08-01

A novel dye-sensitized solar cell (DSSC) structure using vertically aligned single-walled carbon nanotubes (VASWCNTs) as the counter electrode has been developed. In this design, the VASWCNTs serve as a stable high surface area and highly active electrocatalytic counter-electrode that could be a promising alternative to the conventional Pt analogue. Utilizing a scalable dry transfer approach to form a VASWCNTs conductive electrode, the DSSCs with various lengths of VASWCNTs were studied. VASWCNTs-DSSC with 34 μm original length was found to be the optimal choice in the present study. The highest conversion efficiencies of VASWCNTs-DSSC achieved 5.5%, which rivals that of the reference Pt DSSC. From the electrochemical impedance spectroscopy analysis, it shows that the new DSSC offers lower interface resistance between the electrolyte and the counter electrode. This reproducible work emphasizes the promise of VASWCNTs as efficient and stable counter electrode materials in DSSC device design, especially taking into account the low-cost merit of this promising material.

A nanocomposite-based electrochemical sensor for non-enzymatic detection of hydrogen peroxide

PubMed Central

Du, Xin; Chen, Yuan; Dong, Wenhao; Han, Bingkai; Liu, Min; Chen, Qiang; Zhou, Jun

2017-01-01

Hydrogen peroxide (H2O2) plays important signaling roles in normal physiology and disease. However, analyzing the actions of H2O2 is often impeded by the difficulty in detecting this molecule. Herein, we report a novel nanocomposite-based electrochemical sensor for non-enzymatic detection of H2O2. Graphene oxide (GO) was selected as the dopant for the synthesis of polyaniline (PANI), leading to the successful fabrication of a water-soluble and stable GO-PANI composite. GO-PANI was subsequently subject to cyclic voltammetry to generate reduced GO-PANI (rGO-PANI), enhancing the conductivity of the material. Platinum nanoparticles (PtNPs) were then electrodeposited on the surface of the rGO-PANI-modified glassy carbon electrode (GCE) to form an electrochemical H2O2 sensor. Compared to previously reported sensors, the rGO-PANI-PtNP/GCE exhibited an expanded linear range, higher sensitivity, and lower detection limit in the quantification of H2O2. In addition, the sensor displayed outstanding reproducibility and selectivity in real-sample examination. Our study suggests that the rGO-PANI-PtNP/GCE may have broad utility in H2O2 detection under physiological and pathological conditions. PMID:28035076

Hybrid approach combining multiple characterization techniques and simulations for microstructural analysis of proton exchange membrane fuel cell electrodes

NASA Astrophysics Data System (ADS)

Cetinbas, Firat C.; Ahluwalia, Rajesh K.; Kariuki, Nancy; De Andrade, Vincent; Fongalland, Dash; Smith, Linda; Sharman, Jonathan; Ferreira, Paulo; Rasouli, Somaye; Myers, Deborah J.

2017-03-01

The cost and performance of proton exchange membrane fuel cells strongly depend on the cathode electrode due to usage of expensive platinum (Pt) group metal catalyst and sluggish reaction kinetics. Development of low Pt content high performance cathodes requires comprehensive understanding of the electrode microstructure. In this study, a new approach is presented to characterize the detailed cathode electrode microstructure from nm to μm length scales by combining information from different experimental techniques. In this context, nano-scale X-ray computed tomography (nano-CT) is performed to extract the secondary pore space of the electrode. Transmission electron microscopy (TEM) is employed to determine primary C particle and Pt particle size distributions. X-ray scattering, with its ability to provide size distributions of orders of magnitude more particles than TEM, is used to confirm the TEM-determined size distributions. The number of primary pores that cannot be resolved by nano-CT is approximated using mercury intrusion porosimetry. An algorithm is developed to incorporate all these experimental data in one geometric representation. Upon validation of pore size distribution against gas adsorption and mercury intrusion porosimetry data, reconstructed ionomer size distribution is reported. In addition, transport related characteristics and effective properties are computed by performing simulations on the hybrid microstructure.

Effect of valence state and particle size on NO oxidation in fresh and aged Pt-based diesel oxidation catalysts

NASA Astrophysics Data System (ADS)

Liang, Yanli; Ding, Xinmei; Zhao, Ming; Wang, Jianli; Chen, Yaoqiang

2018-06-01

To stabilize Pt, Magnesium-modified SiO2-Al2O3 materials was used to impregnate with Pt, which could strengthen the bonding effect between Pt and Mg. Before and after aging, both showed a higher dispersion. High valence state of Pt in fresh modified catalyst was unfavorable of NO oxidation, indicating that the valence state of Pt was the leader factor in fresh catalytic performance. While for the aged Mg-modified sample, its reaction temperature of 30% NO conversion lowered by around 30 °C. The Pt stabilization via interacting with Mg derives a relation that the variation of Pt valence state and its exposed sites played a significant role in fresh and aged catalytic NO activity, respectively.

A dual electrochemical microsensor for simultaneous imaging of oxygen and pH over the rat kidney surface.

PubMed

Ha, Yejin; Myung, Dongshin; Shim, Jun Ho; Kim, Myung Hwa; Lee, Youngmi

2013-09-21

In this study, a dual microsensing electrochemical probe for measuring oxygen (O2) and pH levels was developed based on a dual recessed Pt disk electrode (each disk diameter, 10 μm) with the use of two Ag/AgCl reference electrodes (one for each disk of the dual electrode). One of the recessed Pt disks of the dual electrode was electrodeposited with a porous Pt layer and then coated with a hydrophobic photocured polymer (partially fluorinated epoxy diacrylate, abbreviated as FED). The Pt-FED covered disk was used as an amperometric O2 sensor and exhibited a linear current increase that was proportional to the PO2 level (partial O2 pressure) with high sensitivity (168.4 ± 33.8 pA mmHg(-1)) and fast response time (t90% = 0.17 ± 0.05 s). The other recessed Pt disk was electrodeposited with an IrO2 layer. The potential between the IrO2 deposited electrode and the Ag/AgCl reference electrode produced a reliable Nernstian response to pH changes (58.3 ± 1.5 mV pH(-1)) with a t90% of 0.43 ± 0.09 s. The sensor displayed high stability in the in vitro organ tissue measurements for at least 2.5 h. By using the developed dual O2/pH microsensor as a probe tip for scanning electrochemical microscopy, the two-dimensional images of the location-dependent PO2 and pH levels were simultaneously acquired and could be used to assess the surface of a rat kidney tissue slice. When compared to the corresponding medullary levels, both PO2 and pH were observed to be higher in the cortex area, while the modest level gradient was observed near the cortex-medulla border. This finding suggests that there is a direct relationship between the tissue O2 supply/consumption and pH, which is mainly determined by metabolite, such as CO2, production.

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf2N ionic liquid.

PubMed

Sandoval, Andrea P; Suárez-Herrera, Marco F; Feliu, Juan M

2015-01-01

Thin films of PEDOT synthesized on platinum single electrodes in contact with the ionic liquid 1-ethyl-2,3-dimethylimidazolium triflimide ([EMMIM]Tf2N) were studied by cyclic voltammetry, chronoamperometry, infrared spectroscopy and atomic force microscopy. It was found that the polymer grows faster on Pt(111) than on Pt(110) or Pt(100) and that the redox reactions associated with the PEDOT p-doping process are much more reversible in [EMMIM]Tf2N than in acetonitrile. Finally, the ion exchange and charge carriers' formation during the p-doping reaction of PEDOT were studied using in situ FTIR spectroscopy.

Ti Porous Film-Supported NiCo₂S₄ Nanotubes Counter Electrode for Quantum-Dot-Sensitized Solar Cells.

PubMed

Deng, Jianping; Wang, Minqiang; Song, Xiaohui; Yang, Zhi; Yuan, Zhaolin

2018-04-17

In this paper, a novel Ti porous film-supported NiCo₂S₄ nanotube was fabricated by the acid etching and two-step hydrothermal method and then used as a counter electrode in a CdS/CdSe quantum-dot-sensitized solar cell. Measurements of the cyclic voltammetry, Tafel polarization curves, and electrochemical impedance spectroscopy of the symmetric cells revealed that compared with the conventional FTO (fluorine doped tin oxide)/Pt counter electrode, Ti porous film-supported NiCo₂S₄ nanotubes counter electrode exhibited greater electrocatalytic activity toward polysulfide electrolyte and lower charge-transfer resistance at the interface between electrolyte and counter electrode, which remarkably improved the fill factor, short-circuit current density, and power conversion efficiency of the quantum-dot-sensitized solar cell. Under illumination of one sun (100 mW/cm²), the quantum-dot-sensitized solar cell based on Ti porous film-supported NiCo₂S₄ nanotubes counter electrode achieved a power conversion efficiency of 3.14%, which is superior to the cell based on FTO/Pt counter electrode (1.3%).

Pt/Pd electrocatalyst electrons for fuel cells

DOEpatents

Stonehart, P.

1981-11-03

This invention relates to improved electrochemical cells and to novel electrodes for use therein. In particular, the present invention comprises a fuel cell used primarily for the consumption of impure hydrogen fuels containing carbon monoxide or carbonaceous fuels where the electrode in contact with the fuel is not substantially poisoned by carbon monoxide. The anode of the fuel cell comprises a Pd/Pt alloy supported on a graphitized or partially graphitized carbon material. Fuel cells which comprise as essential elements a fuel electrode, an oxidizing electrode, and an electrolyte between said electrodes are devices for the direct production of electricity through the electrochemical combustion of a fuel and oxidant. These devices are recognized for their high efficiency as energy conversion units, since unlike conventional combustion engines, they are not subject to the limitations of the Carnot heat cycle. It is the primary object of the present invention to provide an electrode having high electrochemical activity for an electrochemical cell. It is another object of the present invention to provide an electrode having an electro-catalyst which is highly resistant to the corrosive environment of an electrochemical cell.

Graphene-metallic nanocomposites as modifiers in electrochemical glucose biosensor transducers

NASA Astrophysics Data System (ADS)

Altuntas, Derya Bal; Tepeli, Yudum; Anik, Ulku

2016-09-01

Graphene sheets and three different graphene-metallic nanocomposites including graphene-copper (graphene-Cu), graphene-nickel (graphene-Ni) and graphene-platinum (graphene-Pt) were prepared and characterized in the first place. Then the electrochemical performances of these nanocomposites were tested in glucose biosensor transducers, which were formed by combining these metallic nanocomposites with glucose oxidase enzyme and glassy carbon paste electrode (GCPE). This is the first work that includes the usage of these graphene-Me nanocomposites as a part of glucose biosensor transducer. Fabricated amperometric biosensors linear ranges were obtained as follow: For the plain graphene, the linear range was found in the concentration range between 50 μM and 800 μM with the RSD (n = 3 for 50 μM glucose) value of 12.86% and LOD value of 7.2 μM. For graphene-Pt modified glucose biosensor, the linear range was between 10 μM and 600 μM with the RSD (n = 3 for 50 μM glucose) value of 3.45% and LOD value of 3.06 μM. In the case of graphene-Ni modified glucose biosensor, the values were 25 μM to 600 μM with the RSD (n = 3 for 50 μM glucose) value of 8.76% and LOD value of 24.71 μM and for graphene-Cu modified glucose biosensor linear range was 25 μM to 400 μM with the RSD (n = 3 for 50 μM glucose) value of 3.93% and LOD value of 2.87 μM.

Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

NASA Astrophysics Data System (ADS)

Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

2017-09-01

The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

Real-Time Optical Monitoring of Pt Catalyst Under the Potentiodynamic Conditions

NASA Astrophysics Data System (ADS)

Song, Hyeon Don; Lee, Minzae; Kim, Gil-Pyo; Choi, Inhee; Yi, Jongheop

2016-12-01

In situ monitoring of electrode materials reveals detailed physicochemical transition in electrochemical device. The key challenge is to explore the localized features of electrode surfaces, since the performance of an electrochemical device is determined by the summation of local architecture of the electrode material. Adaptive in situ techniques have been developed for numerous investigations; however, they require restricted measurement environments and provide limited information, which has impeded their widespread application. In this study, we realised an optics-based electrochemical in situ monitoring system by combining a dark-field micro/spectroscopy with an electrochemical workstation to investigate the physicochemical behaviours of Pt catalyst. We found that the localized plasmonic trait of a Pt-decorated Au nanoparticle as a model system varied in terms of its intensity and wavelength during the iterations of a cyclic voltammetry test. Furthermore, we show that morphological and compositional changes of the Pt catalyst can be traced in real time using changes in quantified plasmonic characteristics, which is a distinct advantage over the conventional electrochemistry-based in situ monitoring systems. These results indicate the substantial promise of online operando observation in a wide range of electrical energy conversion systems and electrochemical sensing areas.

Nanostructured aptamer-based sensing platform for highly sensitive recognition of myoglobin.

PubMed

Nia, Neda Ghafori; Azadbakht, Azadeh

2018-06-21

A composite was prepared from PtSn nanoparticles and carbon nanotubes (PtSnNP/CNTs) and applied to the electrochemical determination of myoglobin (Mb). An Mb-aptamer was immobilized on a glassy carbon electrode (GCE), and hexcyanoferrate was used as an electrochemical probe. The PtSnNP/CNTs were synthesized by a microwave-aided ethylene glycol reduction method. Detection is based on electron transfer inhibition that is caused by the folding and conformational change of the Mb-aptamer in the presence of Mb. The amperometric signal for hexacyanoferrate, best measured at 0.2 V vs. Ag/AgCl depends on the concentration of Mb that interacts with the aptamer on the GCE. This approach is selective and sensitive for Mb due to (a) the highly specific recognition ability of the aptamer for Mb, (b) the powerful electronic properties of carbon nanotubes, (c) the arranged decoration of CNTs with PtSnNPs, and (d), the superior electron transfer to hexacyanoferrate. The assay is highly selective, with linear relationships from 0.01-1 nM and 10 nM-200 nM, and a limit of detection as low as 2.2 ± 0.1 pM. The modified GCE was applied to the quantitation of Mb in spiked human serum samples. Graphical abstract Schematic illustration of the method for Mb detection.

Synthesis of Pt nanoparticles as catalysts of oxygen reduction with microbubble-assisted low-voltage and low-frequency solution plasma processing

NASA Astrophysics Data System (ADS)

Horiguchi, Genki; Chikaoka, Yu; Shiroishi, Hidenobu; Kosaka, Shinpei; Saito, Morihiro; Kameta, Naohiro; Matsuda, Naoki

2018-04-01

In the preparation of metallic nanoparticles by conventional solution plasma (SP) techniques, unstable plasma emission becomes an issue when the voltage and frequency of the waves applied between two electrodes placed in solution are lowered to avoid the boiling of the solution. In this study, we confirm that, in the presence of microbubbles, plasma is generated stably at low voltage (440 V) and low frequency (50-100 Hz) and small-size (≤10 nm) Pt nanoparticles (PtNPs) are synthesized in succession using a flow cell. The smallest PtNPs, ∼3.3 nm in diameter, are obtained using half-wave rectification, a tungsten wire anode, and a platinum wire cathode. The PtNPs are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimeter-differential thermal analysis. The oxygen reduction reaction (ORR) is investigated in 0.1 M HClO4 solution on carbon-supported PtNPs using a rotating ring-disk electrode. The catalytic activities per initial electrochemical active surface area of the carbon-supported PtNPs synthesized employing the low-voltage, low-frequency (LVLF)-SP technique is higher than that of the commercially available 20 wt% Pt on Vulcan XC-72R. These results indicate that the LVLF-SP technique is a promising approach to producing carbon-supported PtNPs that catalyze ORR with low energy consumption.

ELECTRODE MEASUREMENT OF REDOX POTENTIAL IN ANAEROBIC FERRIC/FERROUS CHLORIDE SYSTEMS

EPA Science Inventory

The behaviour of two inert redox electrodes (Pt and wax-impregnated graphite) was investigated in anaerobic ferrous and ferric chloride solutions in order to establish if these electrodes respond to the Fe³⁺/Fe²⁺ couple in a Nernstian manner. A new method fo...

Combinatorial study of Ni-Ti-Pt ternary metal gate electrodes on HfO{sub 2} for the advanced gate stack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, K.-S.; Green, M. L.; Suehle, J.

2006-10-02

The authors have fabricated combinatorial Ni-Ti-Pt ternary metal gate thin film libraries on HfO{sub 2} using magnetron co-sputtering to investigate flatband voltage shift ({delta}V{sub fb}), work function ({phi}{sub m}), and leakage current density (J{sub L}) variations. A more negative {delta}V{sub fb} is observed close to the Ti-rich corner than at the Ni- and Pt-rich corners, implying smaller {phi}{sub m} near the Ti-rich corners and higher {phi}{sub m} near the Ni- and Pt-rich corners. In addition, measured J{sub L} values can be explained consistently with the observed {phi}{sub m} variations. Combinatorial methodologies prove to be useful in surveying the large compositionalmore » space of ternary alloy metal gate electrode systems.« less

Electrochemical quartz crystal microbalance study of polyelectrolyte film growth under anodic conditions

NASA Astrophysics Data System (ADS)

Nilsson, Sara; Björefors, Fredrik; Robinson, Nathaniel D.

2013-09-01

Coating hard materials such as Pt with soft polymers like poly-L-lysine is a well-established technique for increasing electrode biocompatibility. We have combined quartz crystal microgravimetry with dissipation with electrochemistry (EQCM-D) to study the deposition of PLL onto Pt electrodes under anodic potentials. Our results confirm the change in film growth over time previously reported by others. However, the dissipation data suggest that, after the short initial phase of the process, the rigidity of the film increases with time, rather than decreasing, as previously proposed. In addition to these results, we discuss how gas evolution from water electrolysis and Pt etching in electrolytes containing Cl- affect EQCM-D measurements, how to recognize these effects, and how to reduce them. Despite the challenges of using Pt as an anode in this system, we demonstrate that the various electrochemical processes can be understood and that PLL coatings can be successfully electrodeposited.

Electrochemically assisted localized etching of ZnO single crystals in water using a catalytically active Pt-coated atomic force microscopy probe

NASA Astrophysics Data System (ADS)

Shibata, Takayuki; Yamamoto, Kota; Sasano, Junji; Nagai, Moeto

2017-09-01

This paper presents a nanofabrication technique based on the electrochemically assisted chemical dissolution of zinc oxide (ZnO) single crystals in water at room temperature using a catalytically active Pt-coated atomic force microscopy (AFM) probe. Fabricated grooves featured depths and widths of several tens and several hundreds of nanometers, respectively. The material removal rate of ZnO was dramatically improved by controlling the formation of hydrogen ions (H+) on the surface of the catalytic Pt-coated probe via oxidation of H2O molecules; this reaction can be enhanced by applying a cathodic potential to an additional Pt-wire working electrode in a three-electrode configuration. Consequently, ZnO can be dissolved chemically in water as a soluble Zn2+ species via a reaction with H+ species present in high concentrations in the immediate vicinity of the AFM tip apex.

Chemistry of vinylidene complexes. XXIV. A new μ-vinylidene complex containing RePt core, and platinum-bound carbonyl ligand. Spectroscopic, structural and electrochemical study

NASA Astrophysics Data System (ADS)

Verpekin, Victor V.; Vasiliev, Alexander D.; Kondrasenko, Alexander A.; Burmakina, Galina V.; Chudin, Oleg S.; Pavlenko, Nina I.; Zimonin, Dmitry V.; Rubaylo, Anatoly I.

2018-07-01

The novel heterobinuclear μ-vinylidene complex [Cp(CO)2Re(μ-C=CHPh)Pt(PPh3)(CO)] (1) was isolated from the reaction mixture of [Cp(CO)2Re(μ-C=CHPh)Fe(CO)4] and Pt(PPh3)4 for the first time. Alternative high-yield synthetic approaches to 1 were developed including the reactions of [Cp(CO)2Re(μ-C=CHPh)Pt(PPh3)2] (2) with Co2(CO)8 and Rh(acac)(CO)2. The complex was characterized by IR and 1H, 13C and 31P NMR spectroscopy, a molecular structure of 1 was determined by X-ray diffraction analysis. The electrochemical behavior of the new complex was studied by cyclic voltammetry at platinum or glassed carbon electrodes and by dc polarography at a dropping mercury electrode.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: II. Influence of Ink Formulation, Catalyst Layer Uniformity and Thickness

DOE PAGES

Shinozaki, Kazuma; Zack, Jason W.; Pylypenko, Svitlana; ...

2015-09-17

Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mgPt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mgPt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1more » M HClO 4, 20 mV/s, 100 kPa O 2 and 23±2°C. An enhancement factor of 2.8 in themeasured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (~4.5 μg/cm 2 Pt) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m2/gPt) and Pt/V (65 ± 5 m 2/gPt) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.« less

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: II. Influence of Ink Formulation, Catalyst Layer Uniformity and Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinozaki, Kazuma; Zack, Jason W.; Pylypenko, Svitlana

Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mgPt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mgPt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1more » M HClO 4, 20 mV/s, 100 kPa O 2 and 23±2°C. An enhancement factor of 2.8 in themeasured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (~4.5 μg/cm 2 Pt) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m2/gPt) and Pt/V (65 ± 5 m 2/gPt) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Taehoon; Jung, Yong Chan; Seong, Sejong

The metal gate electrodes of Ni, W, and Pt have been investigated for their scavenging effect: a reduction of the GeO{sub x} interfacial layer (IL) between HfO{sub 2} dielectric and Ge substrate in metal/HfO{sub 2}/GeO{sub x}/Ge capacitors. All the capacitors were fabricated using the same process except for the material used in the metal electrodes. Capacitance-voltage measurements, scanning transmission electron microscopy, and electron energy loss spectroscopy were conducted to confirm the scavenging of GeO{sub x} IL. Interestingly, these metals are observed to remotely scavenge the interfacial layer, reducing its thickness in the order of Ni, W, and then Pt. Themore » capacitance equivalent thickness of these capacitors with Ni, W, and Pt electrodes are evaluated to be 2.7 nm, 3.0 nm, and 3.5 nm, and each final remnant physical thickness of GeO{sub x} IL layer is 1.1 nm 1.4 nm, and 1.9 nm, respectively. It is suggested that the scavenging effect induced by the metal electrodes is related to the concentration of oxygen vacancies generated by oxidation reaction at the metal/HfO{sub 2} interface.« less

Low-Temperature Co-Fired Unipoled Multilayer Piezoelectric Transformers.

PubMed

Gao, Xiangyu; Yan, Yongke; Carazo, Alfredo Vazquez; Dong, Shuxiang; Priya, Shashank

2018-03-01

The reliability of piezoelectric transformers (PTs) is dependent upon the quality of fabrication technique as any heterogeneity, prestress, or misalignment can lead to spurious response. In this paper, unipoled multilayer PTs were investigated focusing on high-power composition and co-firing profile in order to provide low-temperature synthesized high-quality device measured in terms of efficiency and power density. The addition of 0.2 wt% CuO into Pb 0.98 Sr 0.02 (Mg 1/3 Nb 2/3 ) 0.06 (Mn 1/3 Nb 2/3 ) 0.06 (Zr 0.48 Ti 0.52 ) 0.88 O 3 (PMMnN-PZT) reduces the co-firing temperature from 1240 °C to 930 °C, which allows the use of Ag/Pd inner electrode instead of noble Pt inner electrode. Low-temperature synthesized material was found to exhibit excellent piezoelectric properties ( , , %, pC/N, and °C). The performance of the PT co-fired with Ag/Pd electrode at 930 °C was similar to that co-fired at 1240 °C with Pt electrode (25% reduction in sintering temperature). Both high- and low-temperature synthesized PTs demonstrated 5-W output power with >90% efficiency and 11.5 W/cm 3 power density.

A Comparative evaluation of Graphene oxide based materials for Electrochemical non-enzymatic sensing of Curcumin

NASA Astrophysics Data System (ADS)

Dey, Nibedita; Devasena, T.; Sivalingam, Tamilarasu

2018-02-01

This work reports a comparative study on the development of a sensitive voltammetric method for the assay of diferuloylmethane which is fabricated using cost-effective sensing material graphene oxide (GO modified electrode) and reduced graphene oxide (rGO modified electrode) modified on glassy carbon electrode respectively. The prepared materials were characterized using SEM, XRD, FTIR, and Raman techniques to understand the formation. Between the both modified electrodes, rGO modified electrode demonstrated a lower limit detection of 0.9 pM and good signal quality. But, the better linear dynamic range for detection was found to be 1 nm to 100 nM for GO and 0.1 nM to 10 nM for rGO modified electrodes respectively. The repeatability is checked for seven cycles and interference studies were also performed for checking the sensors’ selectivity to curcumin. rGO modified electrode and GO modified electrode both shows specific signals for Diferuloylmethane under conditions similar to physiology. But, with better properties over GO modified electrode, rGO modified electrode is suggested a better candidate for real-time usability in sensing. The detection limit reported is the lowest till date for the given plant drug using any sensing assay.

Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity.

PubMed

Eckhard, Kathrin; Chen, Xingxing; Turcu, Florin; Schuhmann, Wolfgang

2006-12-07

In order to locally analyse catalytic activity on modified surfaces a transient redox competition mode of scanning electrochemical microscopy (SECM) has been developed. In a bi-potentiostatic experiment the SECM tip competes with the sample for the very same analyte. This leads to a current decrease at the SECM tip, if it is positioned in close proximity to an active catalyst site on the surface. Specifically, local catalytic activity of a Pt-catalyst modified sample with respect to the catalytic reduction of molecular oxygen was investigated. At higher local catalytic activity the local 02 partial pressure within the gap between accurately positioned SECM tip and sample is depleted, leading to a noticeable tip current decrease over active sites. A flexible software module has been implemented into the SECM to adapt the competition conditions by proper definition of tip and sample potentials. A potential pulse profile enables the localised electrochemically induced generation of molecular oxygen prior to the competition detection. The current decay curves are recorded over the entire duration of the applied reduction pulse. Hence, a time resolved processing of the acquired current values provides movies of the local oxygen concentration against x,y-position. The SECM redox competition mode was verified with a macroscopic Pt-disk electrode as a test sample to demonstrate the feasibility of the approach. Moreover, highly dispersed electro-deposited spots of gold and platinum on glassy carbon were visualised using the redox competition mode of SECM. Catalyst spots of different nature as well as activity inhomogeneities within one spot caused by local variations in Pt-loading were visualised successfully.

Control of crystallographic texture and surface morphology of Pt/Tio2 templates for enhanced PZT thin film texture.

PubMed

Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan

2015-01-01

Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf2N ionic liquid

PubMed Central

Sandoval, Andrea P; Suárez-Herrera, Marco F

2015-01-01

Summary Thin films of PEDOT synthesized on platinum single electrodes in contact with the ionic liquid 1-ethyl-2,3-dimethylimidazolium triflimide ([EMMIM]Tf2N) were studied by cyclic voltammetry, chronoamperometry, infrared spectroscopy and atomic force microscopy. It was found that the polymer grows faster on Pt(111) than on Pt(110) or Pt(100) and that the redox reactions associated with the PEDOT p-doping process are much more reversible in [EMMIM]Tf2N than in acetonitrile. Finally, the ion exchange and charge carriers’ formation during the p-doping reaction of PEDOT were studied using in situ FTIR spectroscopy. PMID:25815089

Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations

PubMed Central

Meneses, Diogenes; Gunasekara, Dulan B.; Pichetsurnthorn, Pann; da Silva, José A. F.; de Abreu, Fabiane C.; Lunte, Susan M.

2015-01-01

In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration. PMID:25256669

Fuel cell with Pt/Pd electrocatalyst electrode

DOEpatents

Stonehart, Paul

1983-01-01

An electrode for use in a phosphoric acid fuel cell comprising a graphitized or partially graphitized carbon support having a platinum/palladium electrocatalyst thereon. Preferably, the platinum/palladium catalyst comprises 20 to 65 weight percent palladium.

A novel non-invasive detection method for the FGFR3 gene mutation in maternal plasma for a fetal achondroplasia diagnosis based on signal amplification by hemin-MOFs/PtNPs.

PubMed

Chen, Jun; Yu, Chao; Zhao, Yilin; Niu, Yazhen; Zhang, Lei; Yu, Yujie; Wu, Jing; He, Junlin

2017-05-15

The small amount of cell-free fetal DNA (cffDNA) can be a useful biomarker for early non-invasive prenatal diagnosis (NIPD) of achondroplasia. In this study, a novel non-invasive electrochemical DNA sensor for ultrasensitive detecting FGFR3 mutation gene, a pathogenic gene of achondroplasia, based on biocatalytic signal materials and the biotin-streptavidin system are presented. Notably encapsulation of hemin in metal-organic frameworks-based materials (hemin-MOFs) and platinum nanoparticles (PtNPs) were used to prepare hemin-MOFs/PtNPs composites via a one-beaker-one-step reduction. We utilized hemin-MOFs/PtNPs for signal amplification because the promising hemin-MOFs/PtNPs nanomaterial has remarkable ability of catalyze H 2 O 2 as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA), gold nanoparticles and streptavidin were selected for modification of the electrode to enhance the conductivity and immobilize more biotin-modified capture probe (Bio-CP) through the high specificity and superior affinity between streptavidin and biotin. The electrochemical signal was primarily derived from the synergistic catalysis of H 2 O 2 by hemin and PtNPs and recorded by Chronoamperometry. Under the optimal conditions, this newly designed biosensor exhibited sensitive detection of FGFR3 from 0.1fM to 1nM with a low detection limit of 0.033fM (S/N=3). We proposed that this ultrasensitive biosensor is useful for the early non-invasive prenatal diagnosis of achondroplasia. Copyright © 2016 Elsevier B.V. All rights reserved.

Photoelectrochemical biosensor for HEN1 RNA methyltransferase detection using peroxidase mimics PtCu NFs and poly(U) polymerase-mediated RNA extension.

PubMed

Wang, Haiyan; Zhu, Libang; Duan, Junling; Wang, Minghui; Yin, Huanshun; Wang, Po; Ai, Shiyun

2018-04-30

2'-O-methyl group on the 3' terminal nucleotide in plant microRNAs, as one kind of RNA methylations, is caused by HEN1 RNA methyltransferase (HENMT1), which is thought to be crucial for ribosome biogenesis and function. Herein, a simple and label-free PEC biosensing method was proposed for assay of HENMT1 activity and inhibitor screening based on peroxidase mimic PtCu nanoframes (PtCu NFs) catalytic signal amplification. In this work, MoS 2 @Graphene quantum dots/Phosphorus-doped rodlike carbon nitride (MoS 2 @GQDs/P-RCN) heterojunction was used as photoactive materials. With the doping of GQDs and the formation of heterojunction, the photoactivity of MoS 2 is greatly improved. After the double-stranded RNA (dsRNA) with 2 nt 3' overhangs was treated with HENMT1 in the presence of S-adenosyl-L-methionine, the 3' terminal nucleotide of the unmethylated dsRNA could be extended under the catalysis of the poly(U) polymerase in the existence of UTP. Poly(A) nucleotide chain modified with carboxyl group was captured on the electrode surface through hybridization reaction and acted as a bridge for the immobilization of reticular DNA-functionalized PtCu NFs (PtCu@DNA). Under the catalysis effect of peroxidase mimics PtCu@DNA towards hydrogen peroxide, O 2- was in situ generated as electron donor and a strong photocurrent was obtained. The proposed PEC bioassay exhibited high selectivity and low detection limit of 3.36ng/mL for HENMT1 activity assay. Furthermore, the inhibition research indicated that chlorpyrifos could inhibit the HENMT1 activity with the IC 50 value of 48.32nM. Copyright © 2017 Elsevier B.V. All rights reserved.

Redox and catalysis 'all-in-one' infinite coordination polymer for electrochemical immunosensor of tumor markers.

PubMed

Zhang, Bing; Liu, Bingqian; Chen, Guonan; Tang, Dianping

2015-02-15

Prostate-specific antigen (PSA), as a glycoprotein enzyme encoded in humans by the KLK3 gene, is one of the most important biomarkers for the diagnosis and prognosis of prostate cancer. Herein, a new electrochemical immunosensor for sensitive determination of PSA was designed by using redox and catalysis 'all-in-one' infinite coordination polymer (PtNP@ICP) as signal tag on the polyamidoamine dendrimers modified electrode interface. To construct such 'all-in-one' PtNP@ICP nanostructures, the coordination polymerization was fully carried between metal ions and polydentate bridging ligands, and the PtNP was encapsulated into the ICP in the process of polymerization. The prepared PtNP@ICP nanocatalyst was characterized by transmission electron microscope (TEM), energy dispersive X-ray spectrometry (EDX), ultraviolet and visible (UV-vis) spectrophotometry and Fourier transform infrared spectroscope (FTIR). And the synthesized PtNP@ICP was utilized as signal tag for the label of PSA. With a sandwich-type immunoassay format, the conjugated signal tag on the transducer increased with the increasing PSA concentration in the sample thus enhancing the signal of the electrochemical immunosensor due to the catalytic reduction toward H2O2 of the enveloped PtNP. Under optimal conditions, the current was proportional to the logarithm of PSA concentration ranging from 0.001 to 60 ng/mL. The detection limit (LOD) was 0.3 pg/mL at 3 sB. The immunosensor displayed an acceptable reproducibility, stability and selectivity. In addition, the methodology was evaluated with human serum specimens receiving good correlation with results from commercialized enzyme-linked immunosorbent assay (ELISA) method. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanoparticles of Ag with a Pt and Pd rich surface supported on carbon as a new catalyst for the oxygen electroreduction reaction (ORR) in acid electrolytes: Part 1

NASA Astrophysics Data System (ADS)

Pech-Pech, I. E.; Gervasio, Dominic F.; Godínez-Garcia, A.; Solorza-Feria, O.; Pérez-Robles, J. F.

2015-02-01

Silver (Ag) nanoparticles enriched with platinum (Pt) and palladium (Pd) on their surfaces (Ag@Pt0.1Pd0.1) are supported on Vulcan XC-72 carbon (C) to form a new catalyst (Ag@Pt0.1Pd0.1/C) for the oxygen reduction reaction (ORR) in acid electrolytes. This catalyst is prepared in one pot by reducing Ag and then Pt and Pd metal salts with sodium borohydride in the presence of trisodium citrate then adding XC-72 while applying intense ultrasound. The metallic Ag@Pt0.1Pd0.1 nanoparticles contain 2 weight percent of Pt, are spherical and have an average size less than 10 nm as determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). At the ORR potentials, Ag nanoparticles on carbon (Ag/C) rapidly lose Ag by dissolution and show no more catalytic activity for the ORR than the carbon support, whereas Ag@Pt0.1Pd0.1/C is a stable catalyst and exhibits 1.4 and 1.6 fold greater specific activity, also 3.6 and 2.8 fold greater mass activity for ORR in 0.5 M H2SO4 solution than comparable Pt/C and Pt0.5Pd0.5/C catalysts with the same Pt loading as determined for thin-films of these catalysts on a rotating-disk electrode (TF-RDE). Using silver nanoparticles increases Pt utilization and therefore decreases Pt-loading and cost of a catalyst for a proton exchange membrane fuel cell (PEMFC) electrode.

Bioelectricity generation in continuously-fed microbial fuel cell: effects of anode electrode material and hydraulic retention time.

PubMed

Akman, Dilek; Cirik, Kevser; Ozdemir, Sebnem; Ozkaya, Bestamin; Cinar, Ozer

2013-12-01

The main aim of this study is to investigate the bioelectricity production in continuously-fed dual chambered microbial fuel cell (MFC). Initially, MFC was operated with different anode electrode material at constant hydraulic retention time (HRT) of 2d to evaluate the effect of electrode material on electricity production. Pt electrode yielded about 642 mW/m(2) power density, which was 4 times higher than that of the MFC with the mixed metal oxide titanium (Ti-TiO2). Further, MFC equipped with Pt electrode was operated at varying HRT (2-0.5d). The power density generation increased with decreasing HRT, corresponding to 1313 mW/m(2) which was maximum value obtained during this study. Additionally, decreasing HRT from 2 to 0.5d resulted in increasing effluent dissolved organic carbon (DOC) concentration from 1.92 g/L to 2.23 g/L, corresponding to DOC removal efficiencies of 46% and 38%, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Soo Kang, Jin; Park, Min-Ah; Kim, Jae-Yup; Ha Park, Sun; Young Chung, Dong; Yu, Seung-Ho; Kim, Jin; Park, Jongwoo; Choi, Jung-Woo; Jae Lee, Kyung; Jeong, Juwon; Jae Ko, Min; Ahn, Kwang-Soon; Sung, Yung-Eun

2015-05-01

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.

Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing.

PubMed

Pootawang, Panuphong; Saito, Nagahiro; Takai, Osamu; Lee, Sang-Yul

2012-10-05

Arc discharge in solution, generated by applying a high voltage of unipolar pulsed dc to electrodes of Ag and Pt, was used as a method to form Ag/Pt bimetallic nanocomposites via electrode erosion by the effects of the electric arc at the cathode (Ag rod) and the sputtering at the anode (Pt rod). Ag/Pt bimetallic nanocomposites were formed as colloidal particles dispersed in solution via the reduction of hydrogen radicals generated during discharge without the addition of chemical precursor or reducing agent. At a discharge time of 30 s, the fine bimetallic nanoparticles with a mean particle size of approximately 5 nm were observed by transmission electron microscopy (TEM). With increasing discharge time, the bimetallic nanoparticle size tended to increase by forming an agglomeration. The presence of the relatively small amount of Pt dispersed in the Ag matrix could be observed by the analytical mapping mode of energy-dispersive x-ray spectroscopy and high-resolution TEM. This demonstrated that the synthesized particle was in the form of a nanocomposite. No contamination of other chemical substances was detected by x-ray photoelectron spectroscopy. Hence, solution plasma could be a clean and simple process to effectively synthesize Ag/Pt bimetallic nanocomposites and it is expected to be widely applicable in the preparation of several types of nanoparticle.

Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

NASA Astrophysics Data System (ADS)

Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

2014-09-01

In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

NASA Astrophysics Data System (ADS)

Alonso, Jose Maria; Bielen, Abraham A. M.; Olthuis, Wouter; Kengen, Servé W. M.; Zuilhof, Han; Franssen, Maurice C. R.

2016-10-01

Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (NHS) ester-derived groups, to provide anchoring points for enzyme immobilization. The functionalized Pt surfaces were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (CA), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Glucose oxidase (GOX) was covalently attached to the functionalized Pt electrodes, either with or without additional glutaraldehyde crosslinking. The responses of the acquired sensors to glucose concentrations ranging from 0.5 to 100 mM were monitored by chronoamperometry. Furthermore, lactate oxidase (LOX) and human hydroxyacid oxidase (HAOX) were successfully immobilized onto the PtOx surface platform. The performance of the resulting lactate sensors was investigated for lactate concentrations ranging from 0.05 to 20 mM. The successful attachment of active enzymes (GOX, LOX and HAOX) on Pt electrodes demonstrates that covalently functionalized PtOx surfaces provide a universal platform for the development of oxidase enzyme-based sensors.

Directly deposited current collecting grids for alkali metal thermal-to-electric converter electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryan, M.A.; Jeffries-Nakamura, B.; Williams, R.M.

1995-12-01

Current collection in porous thin film electrodes on solid electrolytes has been improved by using thick film grids to decrease sheet and contact resistance in RhW and PtW electrodes. The grids are directly deposited on the solid electrolyte either by sputter- or photodeposition and the electrode deposited over the grid. Comparison of the performance of electrodes having such underlying grids with that of electrodes without such grids has shown performance, as measured by current or power produced, to be improved by 10--30% in electrodes with grids.

Directly Deposited Current Collecting Grids for Alkali Metal Thermal-to-Electric Converter Electrodes

NASA Technical Reports Server (NTRS)

Ryan, M. A.; Jeffries-Nakamura, B.; Williams, R. M.; Underwood, M. L.; OConnor, D.; Kikkert, S.

1995-01-01

Current collection in porous thin film electrodes on solid electrolytes has been improved by using thick film grids to decrease sheet and contact resistance in RhW and PtW electrodes. The grids are directly deposited on the solid electrolyte either by sputter- or photodeposition, and the electrode deposited over the grid. Comparison of the performance of electrodes having such underlying grids with that of electrodes without such grids has shown performance, as measured by current or power produced, to be improved by 10-30% in electrodes with grids.

Pt/Ceria-based Catalysts for Small Alcohol Electrooxidation

NASA Astrophysics Data System (ADS)

Menendez-Mora, Christian L.

High emissions of fossil-based energy sources have led to scientists around the world to develop new alternatives for the future. In this sense, fuel cells are a remarkable and promising energy option with less environmental impact. The most used fuels for this technology are hydrogen and small chain alcohols, which can be oxidized to transform their chemical energy into electrical power. To do this, fuel cells need catalysts that will act as an active surface where the oxidation can take place. The problem with platinum catalysts is its possible CO poisoning with intermediates that are produced before the complete oxidation of alcohol to CO2. Different approaches have been taken to try to resolve this issue. In this case, cerium oxide (ceria) was selected as a co-catalyst to mitigate the effect of CO poisoning of platinum. Ceria is a compound that has the ability to work as an "oxygen tank" and can donate oxygen to carbon monoxide that is strongly adsorbed at platinum surface to produce CO2 (carbon dioxide), regenerating the Pt surface for further alcohol oxidation. Therefore, enhancing the current density as well as the power output of a fuel cell. First, an occlusion deposition technique was used to prepare platinum/ceria composite electrodes and tested them towards small chain alcohol oxidation such as methanol oxidation reaction in acidic and alkaline media. The preliminary results demonstrated that the Pt/ceria electrodes were more efficient towards methanol electrooxidation when compared to Pt electrodes. This enhancement was attributed to the presence of ceria. A second preparation method was selected for the synthesis of ceria/Pt catalysts. In this case, a hydrothermal method was used and the catalysis were studied for the effect of MeOH, EtOH and n-BuOH oxidation. The observed effect was that electrodes made of Pt/Pt:CeO2-x showed better catalytic effect than Pt/ceria and platinum electrodes. Moreover, a comparison between ceria nanorods versus nanoparticles as substrates was done. The general result was that ceria nanoparticles showed better electrocatalytic behavior towards the oxidation of methanol in alkaline medium. Finally, as an outreach activity, an educational module to reinforce the electrochemical concepts in the General Chemistry Laboratory course at UPR-RP was developed. The module was based on Volta's Experiment and an improvement on students learning was detected when comparing this activity with the normal Daniel's cell experience that is used in most Universities at the undergraduate level. In summary, the findings of this thesis conclude that ceria is a compound that may enhance platinum catalytic activity by CO oxidation, promoting the oxidation of alcohols in acidic and alkaline medium. Moreover, catalysis depends on the morphology of the ceria that is used as the catalysts support.

Conformable liquid metal printed epidermal electronics for smart physiological monitoring and simulation treatment

NASA Astrophysics Data System (ADS)

Wang, Xuelin; Zhang, Yuxin; Guo, Rui; Wang, Hongzhang; Yuan, Bo; Liu, Jing

2018-03-01

Conformable epidermal printed electronics enabled from gallium-based liquid metals (LMs), highly conductive and low-melting-point alloys, are proposed as the core to achieving immediate contact between skin surface and electrodes, which can avoid the skin deformation often caused by conventional rigid electrodes. When measuring signals, LMs can eliminate resonance problems with shorter time to reach steady state than Pt and gelled Pt electrodes. By comparing the contact resistance under different working conditions, it is demonstrated that both ex vivo and in vivo LM electrode-skin models have the virtues of direct and immediate contact with skin surface without the deformation encountered with conventional rigid electrodes. In addition, electrocardio electrodes composed of conformable LM printed epidermal electronics are adopted as smart devices to monitor electrocardiogram signals of rabbits. Furthermore, simulation treatment for smart defibrillation offers a feasible way to demonstrate the effect of liquid metal electrodes (LMEs) on the human body with less energy loss. The remarkable features of soft epidermal LMEs such as high conformability, good conductivity, better signal stability, and fine biocompatibility represent a critical step towards accurate medical monitoring and future smart treatments.

Spatiotemporal norepinephrine mapping using a high-density CMOS microelectrode array.

PubMed

Wydallis, John B; Feeny, Rachel M; Wilson, William; Kern, Tucker; Chen, Tom; Tobet, Stuart; Reynolds, Melissa M; Henry, Charles S

2015-10-21

A high-density amperometric electrode array containing 8192 individually addressable platinum working electrodes with an integrated potentiostat fabricated using Complementary Metal Oxide Semiconductor (CMOS) processes is reported. The array was designed to enable electrochemical imaging of chemical gradients with high spatiotemporal resolution. Electrodes are arranged over a 2 mm × 2 mm surface area into 64 subarrays consisting of 128 individual Pt working electrodes as well as Pt pseudo-reference and auxiliary electrodes. Amperometric measurements of norepinephrine in tissue culture media were used to demonstrate the ability of the array to measure concentration gradients in complex media. Poly(dimethylsiloxane) microfluidics were incorporated to control the chemical concentrations in time and space, and the electrochemical response at each electrode was monitored to generate electrochemical heat maps, demonstrating the array's imaging capabilities. A temporal resolution of 10 ms can be achieved by simultaneously monitoring a single subarray of 128 electrodes. The entire 2 mm × 2 mm area can be electrochemically imaged in 64 seconds by cycling through all subarrays at a rate of 1 Hz per subarray. Monitoring diffusional transport of norepinephrine is used to demonstrate the spatiotemporal resolution capabilities of the system.

Few-layer MoSe₂ possessing high catalytic activity towards iodide/tri-iodide redox shuttles.

PubMed

Lee, Lawrence Tien Lin; He, Jian; Wang, Baohua; Ma, Yaping; Wong, King Young; Li, Quan; Xiao, Xudong; Chen, Tao

2014-02-14

Due to the two-dimensional confinement of electrons, single- and few-layer MoSe₂ nanostructures exhibit unusual optical and electrical properties and have found wide applications in catalytic hydrogen evolution reaction, field effect transistor, electrochemical intercalation, and so on. Here we present a new application in dye-sensitized solar cell as catalyst for the reduction of I₃(-) to I(-) at the counter electrode. The few-layer MoSe₂ is fabricated by surface selenization of Mo-coated soda-lime glass. Our results show that the few-layer MoSe₂ displays high catalytic efficiency for the regeneration of I(-) species, which in turn yields a photovoltaic energy conversion efficiency of 9.00%, while the identical photoanode coupling with "champion" electrode based on Pt nanoparticles on FTO glass generates efficiency only 8.68%. Thus, a Pt- and FTO-free counter electrode outperforming the best conventional combination is obtained. In this electrode, Mo film is found to significantly decrease the sheet resistance of the counter electrode, contributing to the excellent device performance. Since all of the elements in the electrode are of high abundance ratios, this type of electrode is promising for the fabrication of large area devices at low materials cost.

3D Printed Microfluidic Devices with Integrated Versatile and Reusable Electrodes

PubMed Central

Erkal, Jayda L.; Selimovic, Asmira; Gross, Bethany C.; Lockwood, Sarah Y.; Walton, Eric L.; McNamara, Stephen; Martin, R. Scott; Spence, Dana M.

2014-01-01

We report two 3D printed devices that can be used for electrochemical detection. In both cases, the electrode is housed in commercially available, polymer-based fittings so that the various electrode materials (platinum, platinum black, carbon, gold, silver) can be easily added to a threaded receiving port printed on the device; this enables a module-like approach to the experimental design, where the electrodes are removable and can be easily repolished for reuse after exposure to biological samples. The first printed device represents a microfluidic platform with a 500 × 500 μm channel and a threaded receiving port to allow integration of either polyetheretherketone (PEEK) nut-encased glassy carbon or platinum black (Pt-black) electrodes for dopamine and nitric oxide (NO) detection, respectively. The embedded 1 mm glassy carbon electrode had a limit of detection (LOD) of 500 nM for dopamine and a linear response (R2= 0.99) for concentrations between 25-500 μM. When the glassy carbon electrode was coated with 0.05% Nafion, significant exclusion of nitrite was observed when compared to signal obtained from equimolar injections of dopamine. When using flow injection analysis with a Pt/Pt-black electrode and standards derived from NO gas, a linear correlation (R2 = 0.99) over a wide range of concentrations (7.6 - 190 μM) was obtained, with the LOD for NO being 1 μM. The second application showcases a 3D printed fluidic device that allows collection of the biologically relevant analyte adenosine triphosphate (ATP) while simultaneously measuring the release stimulus (reduced oxygen concentration). The hypoxic sample (4.76 ± 0.53 ppm oxygen) released 2.37 ± 0.37 times more ATP than the normoxic sample (8.22 ± 0.60 ppm oxygen). Importantly, the results reported here verify the reproducible and transferable nature of using 3D printing as a fabrication technique, as devices and electrodes were moved between labs multiple times during completion of the study. PMID:24763966

In situ prepared transparent polyaniline electrode and its application in bifacial dye-sensitized solar cells.

PubMed

Tai, Qidong; Chen, Bolei; Guo, Feng; Xu, Sheng; Hu, Hao; Sebo, Bobby; Zhao, Xing-Zhong

2011-05-24

Highly uniform and transparent polyaniline (PANI) electrodes that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) were prepared by a facile in situ polymerization method. They were used to fabricate a novel bifacially active transparent DSSC, which showed conversion efficiencies of 6.54 and 4.26% corresponding to front- and rear-side illumination, respectively. Meanwhile, the efficiency of the same photoanode employing a Pt counter electrode was 6.69%. Compared to conventional Pt-based DSSCs, the design of the bifacial DSSC fabricated in this work would help to bring down the cost of energy production due to the lower cost of the materials and the higher power-generating efficiency of such devices for their capabilities of utilizing the light from both sides. These promising results highlight the potential application of PANI in cost-effective, transparent DSSCs.

Toward a chemiresistive ammonia (NH3) gas sensor based on viral-templated gold nanoparticles embedded in polypyrrole nanowires

NASA Astrophysics Data System (ADS)

Yan, Yiran; Zhang, Miluo; Su, Heng Chia; Myung, Nosang V.; Haberer, Elaine D.

2014-08-01

Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating of gold nanoparticles and PPy electrodeposition via cyclic voltammetry are the focus of this investigation. A gold-binding M13 bacteriophage was used as a bio-template to assemble continuous chains of gold nanoparticles on interdigitated Pt working electrodes. The dimensions of the resulting nanowire-like structures were examined and the electrical resistance measured. PPy films were electropolymerized using an interdigitated planar, Pt electrode integrated counter and reference electrode. Morphological characterization of the polymer films was completed.

Long-term hydrogen oxidation catalysts in alkaline fuel cells

NASA Astrophysics Data System (ADS)

Kiros, Y.; Schwartz, S.

Pt/Pd bimetallic combination and Raney Ni catalysts were employed in long-term electrochemical assessment of the hydrogen oxidation reaction (HOR) in 6 M KOH. Steady-state current vs. potential measurements of the gas diffusion electrodes have shown high activity for these types of catalysts. Durability tests of the electrodes have shown increased stability for the Pt/Pd-based catalysts than the Raney Ni at a constant load of 100 mA/cm 2 and at temperatures of 55°C and 60°C, respectively. Surface, structural and chemical analyses by BET surface area, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to characterize the composite electrode/catalyst both before and after the electrochemical testing.

Multi-spot porous silicon chip prepared from asymmetric electrochemical etching for human immunoglobin G sensor.

PubMed

Um, Sungyong; Cho, Bomin; Woo, Hee-Gweon; Sohn, Honglae

2011-08-01

Multi-spot porous silicon (MSPS)-based optical biosensor was developed to specify the biomolecules. MSPS chip was generated by an electrochemical etching of silicon wafer using an asymmetric electrode configuration in aqueous ethanolic HF solution and constituted with nine arrayed porous silicon. MSPS prepared from anisotropic etching conditions displayed the Fabry-Pérot fringe patterns which varied spatially across the porous silicon (PS). Each spot displayed different reflection resonances and different pore characteristics as a function of the lateral distance from the Pt counter electrode. The sensor system consists of the 3 x 3 spot array of porous silicon modified with Protein A. The system was probed with various fragments of an aqueous Human Immunoglobin G (Ig G) analyte. The sensor operated by measurement of the reflection patterns in the white light reflection spectrum of MSPS. Molecular binding and specificity was detected as a shift in wavelength of these Fabry-Pérot fringe patterns.

Enlarging photovoltaic effect: combination of classic photoelectric and ferroelectric photovoltaic effects

PubMed Central

Zhang, Jingjiao; Su, Xiaodong; Shen, Mingrong; Dai, Zhihua; Zhang, Lingjun; He, Xiyun; Cheng, Wenxiu; Cao, Mengyu; Zou, Guifu

2013-01-01

Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm2) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials. PMID:23811832

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

NASA Astrophysics Data System (ADS)

Zhu, Zhigang; Song, Wenhui; Burugapalli, Krishna; Moussy, Francis; Li, Ya-Li; Zhong, Xiao-Hua

2010-04-01

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 µm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 °C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 µM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.

Hierarchically structured Co₃O₄@Pt@MnO₂ nanowire arrays for high-performance supercapacitors.

PubMed

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-17

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

Hydrogen peroxide sensor based on carbon nanowalls grown by plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Tomatsu, Masakazu; Hiramatsu, Mineo; Foord, John S.; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Takeda, Keigo; Hori, Masaru

2017-06-01

Fabrication of an electrochemical sensor for hydrogen peroxide (H2O2) detection was demonstrated. H2O2 is a major messenger molecule in various redox-dependent cellular signaling transductions. Therefore, sensitive detection of H2O2 is greatly important in health inspection and environmental protection. Carbon nanowalls (CNWs) are composed of few-layer graphenes standing almost vertically on a substrate forming a three-dimensional structure. In this work, CNWs were used as a platform for H2O2 sensing, which is based on the large surface area of conducting carbon and surface decoration with platinum (Pt) nanoparticles (NPs). CNWs were grown on carbon fiber paper (CFP) by inductively coupled plasma-enhanced chemical vapor deposition to increase the surface area. Then, the CNW surface was decorated with Pt-NPs by the reduction of H2PtCl6. Cyclic voltammetry results indicate that the Pt-decorated CNW/CFP electrode possesses excellent electrocatalytic activity for the reduction of H2O2. Amperometric responses indicate the high-sensitivity detection capability of the Pt-decorated CNW/CFP electrode for H2O2.

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells

PubMed Central

Kim, Jiyoung; Jang, Jin-Sung; Peck, Dong-Hyun; Lee, Byungrok; Yoon, Seong-Ho; Jung, Doo-Hwan

2016-01-01

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected. PMID:28335275

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells.

PubMed

Kim, Jiyoung; Jang, Jin-Sung; Peck, Dong-Hyun; Lee, Byungrok; Yoon, Seong-Ho; Jung, Doo-Hwan

2016-08-15

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF-supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

Effects of Thickness, Pulse Duration, and Size of Strip Electrode on Ferroelectric Electron Emission of Lead Zirconate Titanate Films

NASA Astrophysics Data System (ADS)

Yaseen, Muhammad; Ren, Wei; Chen, Xiaofeng; Feng, Yujun; Shi, Peng; Wu, Xiaoqing

2018-02-01

Sol-gel-derived lead zirconate titanate (PZT) thin-film emitters with thickness up to 9.8 μm have been prepared on Pt/TiO2/SiO2/Si wafer via chemical solution deposition with/without polyvinylpyrrolidone (PVP) modification, and the relationship between the film thickness and electron emission investigated. Notable electron emission was observed on application of a trigger voltage of 120 V for PZT film with thickness of 1.1 μm. Increasing the film thickness decreased the threshold field to initiate electron emission for non-PVP-modified films. In contrast, the electron emission behavior of PVP-modified films did not show significant dependence on film thickness, probably due to their porous structure. The emission current increased with decreasing strip width and space between strips. Furthermore, it was observed that increasing the duration of the applied pulse increased the magnitude of the emission current. The stray field on the PZT film thickness was also calculated and found to increase with increasing ferroelectric sample thickness. The PZT emitters were found to be fatigue free up to 105 emission cycles. Saturated emission current of around 25 mA to 30 mA was achieved for the electrode pattern used in this work.

Porous carbon-coated graphite electrodes for energy production from salinity gradient using reverse electrodialysis

NASA Astrophysics Data System (ADS)

Lee, Su-Yoon; Jeong, Ye-Jin; Chae, So-Ryong; Yeon, Kyeong-Ho; Lee, Yunkyu; Kim, Chan-Soo; Jeong, Nam-Jo; Park, Jin-Soo

2016-04-01

Performance of graphite foil electrodes coated by porous carbon black (i.e., Vulcan) was investigated in comparison with metal electrodes for reverse electrodialysis (RED) application. The electrode slurry that was used for fabrication of the porous carbon-coated graphite foil is composed of 7.2 wt% of carbon black (Vulcan X-72), 0.8 wt% of a polymer binder (polyvinylidene fluoride, PVdF), and 92.0 wt% of a mixing solvent (dimethylacetamide, DMAc). Cyclic voltammograms of both the porous carbon (i.e., Vulcan)-coated graphite foil electrode and the graphite foil electrode without Vulcan showed good reversibility in the hexacyanoferrate(III) (i.e., Fe(CN)63-) and hexacyanoferrate(II) (i.e., Fe(CN)64-) redox couple and 1 M Na2SO4 at room temperature. However, anodic and cathodic current of the Vulcan-coated graphite foil electrode was much higher than those of the graphite foil electrode. Using a bench-scale RED stack, the current-voltage polarization curve of the Vulcan-coated graphite electrode was compared to that of metal electrodes such as iridium (Ir) and platinum (Pt). From the results, it was confirmed that resistance of four different electrodes increased with the following order: the Vulcan-coated graphite foil

Optimization of PZT Thin Film Crystalline Orientation Through Optimization of TiO2/Pt Templates

DTIC Science & Technology

2011-01-01

with 90% textured volume fraction, which is expected to improve electrical properties of the PZT films. 15. SUBJECT TERMS Sputter film, Pt...INTENTIONALLY LEFT BLANK. 1 1. Introduction A wide variety of the physical properties of materials ...device fabrication. Because the Pt electrode crystallographic texture acts as a template for PZT film growth, the properties of ferroelectric PZT

Air-Coupled Ultrasonic Receivers with High Electromechanical Coupling PMN-32%PT Strip-Like Piezoelectric Elements

PubMed Central

Kazys, Rymantas J.; Sliteris, Reimondas; Sestoke, Justina

2017-01-01

For improvement of the efficiency of air-coupled ultrasonic transducers PMN-32%PT piezoelectric crystals which possess very high piezoelectric properties may be used. The electromechanical coupling factor of such crystals for all main vibration modes such as the thickness extension and transverse extension modes is more than 0.9. Operation of ultrasonic transducers with such piezoelectric elements in transmitting and receiving modes is rather different. Therefore, for transmission and reception of ultrasonic signals, separate piezoelectric elements with different dimensions must be used. The objective of this research was development of novel air-coupled ultrasonic receivers with PMN-32%PT strip-like piezoelectric elements vibrating in a transverse-extension mode with electromechanically controlled operation and suitable for applications in ultrasonic arrays. Performance of piezoelectric receivers made of the PMN-32%PT strip-like elements vibrating in this mode may be efficiently controlled by selecting geometry of the electrodes covering side surfaces of the piezoelectric element. It is equivalent to introduction of electromechanical damping which does not require any additional backing element. For this purpose; we have proposed the continuous electrodes to divide into two pairs of electrodes. The one pair is used to pick up the electric signal; another one is exploited for electromechanical damping. Two types of electrodes may be used—rectangular or non-rectangular—with a gap between them directed at some angle, usually 45°. The frequency bandwidth is wider (up to 9 kHz) in the case of non-rectangular electrodes. The strip-like acoustic matching element bonded to the tip of the PMN-32%PT crystal may significantly enhance the performance of the ultrasonic receiver. It was proposed to use for this purpose AIREX T10.110 rigid polymer foam, the acoustic impedance of which is close to the optimal value necessary for matching with air. It was found that in order to get a wide bandwidth the length of the matching strip should be selected not a quarter wavelength λ/4 at the antiresonance frequency but at lower frequency. It allowed achieving the frequency bandwidth (14–18)% with respect to the central frequency at −3 dB level. PMID:29035348

Air-Coupled Ultrasonic Receivers with High Electromechanical Coupling PMN-32%PT Strip-Like Piezoelectric Elements.

PubMed

Kazys, Rymantas J; Sliteris, Reimondas; Sestoke, Justina

2017-10-16

For improvement of the efficiency of air-coupled ultrasonic transducers PMN-32%PT piezoelectric crystals which possess very high piezoelectric properties may be used. The electromechanical coupling factor of such crystals for all main vibration modes such as the thickness extension and transverse extension modes is more than 0.9. Operation of ultrasonic transducers with such piezoelectric elements in transmitting and receiving modes is rather different. Therefore, for transmission and reception of ultrasonic signals, separate piezoelectric elements with different dimensions must be used. The objective of this research was development of novel air-coupled ultrasonic receivers with PMN-32%PT strip-like piezoelectric elements vibrating in a transverse-extension mode with electromechanically controlled operation and suitable for applications in ultrasonic arrays. Performance of piezoelectric receivers made of the PMN-32%PT strip-like elements vibrating in this mode may be efficiently controlled by selecting geometry of the electrodes covering side surfaces of the piezoelectric element. It is equivalent to introduction of electromechanical damping which does not require any additional backing element. For this purpose; we have proposed the continuous electrodes to divide into two pairs of electrodes. The one pair is used to pick up the electric signal; another one is exploited for electromechanical damping. Two types of electrodes may be used-rectangular or non-rectangular-with a gap between them directed at some angle, usually 45°. The frequency bandwidth is wider (up to 9 kHz) in the case of non-rectangular electrodes. The strip-like acoustic matching element bonded to the tip of the PMN-32%PT crystal may significantly enhance the performance of the ultrasonic receiver. It was proposed to use for this purpose AIREX T10.110 rigid polymer foam, the acoustic impedance of which is close to the optimal value necessary for matching with air. It was found that in order to get a wide bandwidth the length of the matching strip should be selected not a quarter wavelength λ/4 at the antiresonance frequency but at lower frequency. It allowed achieving the frequency bandwidth (14-18)% with respect to the central frequency at -3 dB level.

Surface area loss mechanisms of Pt3Co nanocatalysts in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Rasouli, S.; Ortiz Godoy, R. A.; Yang, Z.; Gummalla, M.; Ball, S. C.; Myers, D.; Ferreira, P. J.

2017-03-01

Pt3Co catalyst nanoparticles of 4.9 nm size present on the cathode side of a PEMFC membrane-electrode assembly (MEA) were analyzed by transmission electron microscopy after 10 K voltage cycles under different operating conditions. The operating conditions include baseline (0.4-0.95 V, 80° C, 100% Relative Humidity (RH)), high potential (0.4-1.05 V, 80° C, 100% RH), high temperature (0.4-0.95 V, 90° C, 100% RH), and low humidity (0.4-0.95 V, 80° C, 30% RH). Particle growth and particle loss to the membrane is more severe in the high potential sample than in the high temperature and baseline MEAs, while no significant particle growth and particle precipitation in the membrane can be observed in the low humidity sample. Particles with different morphologies were seen in the cathode including: 1-Spherical individual particles resulting from modified electro-chemical Ostwald ripening and 2-aggregated and coalesced particles resulting from either necking of two or more particles or preferential deposition of Pt between particles with consequent bridging. The difference in the composition of these morphologies results in composition variations through the cathode from cathode/diffusion media (DM) to the cathode/membrane interface.

Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

NASA Astrophysics Data System (ADS)

Jia, Hongmei; Chang, Gang; Lei, Ming; He, Hanping; Liu, Xiong; Shu, Honghui; Xia, Tiantian; Su, Jie; He, Yunbin

2016-10-01

Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the oxidation of glucose because of excellent synergetic effects between gold and platinum species and the increased electrochemical active area from Pt nanoparticles loading. The non-enzymatic glucose biosensor based on Pt/DGNs/GC showed a rapid respond time (within 2 s), wide linear range (from 0.1 mM to 14 mM), low detection limit (0.01 mM), supernal sensitivity (275.44 μA cm-2 mM-1, R = 0.993), satisfactory reproducibility and good stability for glucose sensing. It was demonstrated that Pt/DGNs/GC could work as promising candidate for factual non-enzymatic glucose detection.

Metal-air batteries: from oxygen reduction electrochemistry to cathode catalysts.

PubMed

Cheng, Fangyi; Chen, Jun

2012-03-21

Because of the remarkably high theoretical energy output, metal-air batteries represent one class of promising power sources for applications in next-generation electronics, electrified transportation and energy storage of smart grids. The most prominent feature of a metal-air battery is the combination of a metal anode with high energy density and an air electrode with open structure to draw cathode active materials (i.e., oxygen) from air. In this critical review, we present the fundamentals and recent advances related to the fields of metal-air batteries, with a focus on the electrochemistry and materials chemistry of air electrodes. The battery electrochemistry and catalytic mechanism of oxygen reduction reactions are discussed on the basis of aqueous and organic electrolytes. Four groups of extensively studied catalysts for the cathode oxygen reduction/evolution are selectively surveyed from materials chemistry to electrode properties and battery application: Pt and Pt-based alloys (e.g., PtAu nanoparticles), carbonaceous materials (e.g., graphene nanosheets), transition-metal oxides (e.g., Mn-based spinels and perovskites), and inorganic-organic composites (e.g., metal macrocycle derivatives). The design and optimization of air-electrode structure are also outlined. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of metal-air batteries (219 references).

Hierarchical Ni-Mo-S nanosheets on carbon fiber cloth: A flexible electrode for efficient hydrogen generation in neutral electrolyte.

PubMed

Miao, Jianwei; Xiao, Fang-Xing; Yang, Hong Bin; Khoo, Si Yun; Chen, Jiazang; Fan, Zhanxi; Hsu, Ying-Ya; Chen, Hao Ming; Zhang, Hua; Liu, Bin

2015-08-01

A unique functional electrode made of hierarchal Ni-Mo-S nanosheets with abundant exposed edges anchored on conductive and flexible carbon fiber cloth, referred to as Ni-Mo-S/C, has been developed through a facile biomolecule-assisted hydrothermal method. The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity. The Ni-Mo-S/C electrode exhibits a large cathodic current and a low onset potential for hydrogen evolution reaction in neutral electrolyte (pH ~7), for example, current density of 10 mA/cm(2) at a very small overpotential of 200 mV. Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes. Scanning and transmission electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy were used to understand the formation process and electrocatalytic properties of Ni-Mo-S/C. The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

Alkaline fuel cell: carbon nanobeads coated with metal catalyst over porous ceramic for hydrogen electrode

NASA Astrophysics Data System (ADS)

Chatterjee, A. K.; Sharon, Maheshwar; Banerjee, Rangan

The development of a hydrogen electrode using a porous ceramic coated with carbon nanobeads for an alkaline fuel cell (AFC) is reported. This electrode can provide necessary strength and porosity to enable hydrogen to diffuse without allowing electrolyte to percolate inside the electrode. Various catalysts (Pt, Ni, Co and Fe) are electrochemically dispersed over the carbon nanobeads to examine their performance in the alkaline fuel cell. Turpentine oil has been used as a precursor for preparing the carbon nanobeads by a chemical vapour deposition technique. Scanning electron microscopic and transmission electron microscopic images show that the carbon nanobeads have sizes between 500 and 650 nm and are spread uniformly over the entire ceramic substrate. X-ray diffraction (XRD) patterns indicate that the nanobeads are graphitic in nature. Thus, the electrode is highly conductive. The current-voltage characteristics and chronopotentiometry of a half cell (i.e. hydrogen electrode coated with different electrocatalysts) and a full cell (using both hydrogen and oxygen electrodes) with 30% KOH solution are measured. About 93% of the theoretical hydrogen dissociation voltage is obtained with Ni and Pt catalyst. All other metals (Co and Fe) give a lower voltage. Ni-coated carbon nanobeads deposited over a ceramic oxide can be used in place of Raney nickel electrode as their characteristics are similar to those of a platinum electrode.

Synthesis of Magnetite Nanoparticles and Its Application As Electrode Material for the Electrochemical Oxidation of Methanol

NASA Astrophysics Data System (ADS)

Shah, Muhammad Tariq; Balouch, Aamna; Panah, Pirah; Rajar, Kausar; Mahar, Ali Muhammad; Khan, Abdullah; Jagirani, Muhammad Saqaf; Khan, Humaira

2018-06-01

In this study, magnetite (Fe3O4) nanoparticles were synthesized by a simple and facile chemical co-precipitation method at ambient laboratory conditions. The synthesized Fe3O4 nanostructures were characterized for their morphology, size, crystalline structure and component analysis using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, x-ray diffraction and electron dispersive x-ray spectroscopy. The Fe3O4 nanoparticles showed semi-spherical geometry with an average particle diameter up to 14 nm. The catalytic properties of Fe3O4 nanoparticles were evaluated for electrochemical oxidation of methanol. For this purpose, the magnetite NPs were coated on the surface of an indium tin oxide (ITO) electrode and used as a working electrode in the electrochemical oxidation of methanol. The effect of potential scan rate, the concentration of methanol, the volume of electrolyte and catalyst (Fe3O4 NPs) deposition volume was studied to get high peak current densities for methanol oxidation. The stability and selectivity of the fabricated electrode (Fe3O4/ITO) were also assessed during the electrochemical process. This study revealed that the Fe3O4/ITO electrode was highly stable and selective towards methanol electrochemical oxidation in basic (KOH) media. Bare ITO and Fe3O4 NPs modified glassy (Fe3O4/GCE) electrodes were also tested in the electro-oxidation study of methanol, but their peak current density responses were very low as compared to the Fe3O4/ITO electrode, which showed high electrocatalytic activity towards methanol oxidation under similar conditions. We hope that Fe3O4 nanoparticles (NPs) will be an alternative for methanol oxidation as compared to the expensive noble metals (Pt, Au, and Pd) for energy generation processes.

An electrochemical sulfite biosensor based on gold coated magnetic nanoparticles modified gold electrode.

PubMed

Rawal, Rachna; Chawla, Sheetal; Pundir, Chandra Shekhar

2012-01-15

A sulfite oxidase (SO(X)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto carboxylated gold coated magnetic nanoparticles (Fe(3)O(4)@GNPs) electrodeposited onto the surface of a gold (Au) electrode through N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC)-N-hydroxy succinimide (NHS) chemistry. An amperometric sulfite biosensor was fabricated using SO(X)/Fe(3)O(4)@GNPs/Au electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode. The working electrode was characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) before and after immobilization of SO(X). The biosensor showed optimum response within 2s when operated at 0.2V (vs. Ag/AgCl) in 0.1 M Tris-HCl buffer, pH 8.5 and at 35 °C. Linear range and detection limit were 0.50-1000 μM and 0.15 μM (S/N=3) respectively. Biosensor was evaluated with 96.46% recovery of added sulfite in red wine and 1.7% and 3.3% within and between batch coefficients of variation respectively. Biosensor measured sulfite level in red and white wines. There was good correlation (r=0.99) between red wines sulfite value by standard DTNB (5,5'-dithio-bis-(2-nitrobenzoic acid)) method and the present method. Enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C. Biosensor has advantages over earlier biosensors that it has excellent electrocatalysis towards sulfite, lower detection limit, higher storage stability and no interference by ascorbate, cysteine, fructose and ethanol. Copyright © 2011 Elsevier B.V. All rights reserved.

Dual role of TiO2 buffer layer in Pt catalyzed BiFeO3 photocathodes: Efficiency enhancement and surface protection

NASA Astrophysics Data System (ADS)

Shen, Huanyu; Zhou, Xiaoxue; Dong, Wen; Su, Xiaodong; Fang, Liang; Wu, Xi; Shen, Mingrong

2017-09-01

Polycrystalline ferroelectric BiFeO3 (BFO) films deposited on transparent indium tin oxide (ITO) electrodes have shown to be an interesting photocathode for photoelectrochemical (PEC) water splitting; however, its PEC performance and stability are far from perfection. Herein, we reported an amorphous TiO2 buffer layer, inserted between BFO and Pt catalyst, improves significantly both its PEC activity and stability. A photocathodic current density of -460 μA/cm2 at 0 V vs. reversible hydrogen electrode (RHE) and an onset potential of 1.25 V vs. RHE were obtained in ITO/BFO/TiO2/Pt photocathode under 100 mW/cm2 Xe-lamp illumination. TiO2 functions as a buffer layer to remove the upward barrier between BFO and Pt, and makes the photogenerated carriers separate efficiently. The photocathode also shows high stability in acid solution after a 10-h PEC continuous testing.

Selective electrocatalysts toward a prototype of the membraneless direct methanol fuel cell.

PubMed

Feng, Yan; Yang, Jinhua; Liu, Hui; Ye, Feng; Yang, Jun

2014-01-22

Mastery over the structure of nanomaterials enables control of their properties to enhance their performance for a given application. Herein we demonstrate the design and fabrication of Pt-based nanomaterials with enhanced catalytic activity and superior selectivity toward the reactions in direct methanol fuel cells (DMFCs) upon the deep understanding of the mechanisms of these electrochemical reactions. In particular, the ternary Au@Ag2S-Pt nanocomposites display superior methanol oxidation reaction (MOR) selectivity due to the electronic coupling effect among different domains of the nanocomposites, while the cage-bell structured Pt-Ru nanoparticles exhibit excellent methanol tolerance for oxygen reduction reaction (ORR) at the cathode because of the differential diffusion of methanol and oxygen in the porous Ru shell of the cage-bell nanoparticles. The good catalytic selectivity of these Pt-based nanomaterials via structural construction enables a DMFC to be built without a proton exchange membrane between the fuel electrode and the oxygen electrode.

Selective electrocatalysts toward a prototype of the membraneless direct methanol fuel cell

PubMed Central

Feng, Yan; Yang, Jinhua; Liu, Hui; Ye, Feng; Yang, Jun

2014-01-01

Mastery over the structure of nanomaterials enables control of their properties to enhance their performance for a given application. Herein we demonstrate the design and fabrication of Pt-based nanomaterials with enhanced catalytic activity and superior selectivity toward the reactions in direct methanol fuel cells (DMFCs) upon the deep understanding of the mechanisms of these electrochemical reactions. In particular, the ternary Au@Ag2S-Pt nanocomposites display superior methanol oxidation reaction (MOR) selectivity due to the electronic coupling effect among different domains of the nanocomposites, while the cage-bell structured Pt-Ru nanoparticles exhibit excellent methanol tolerance for oxygen reduction reaction (ORR) at the cathode because of the differential diffusion of methanol and oxygen in the porous Ru shell of the cage-bell nanoparticles. The good catalytic selectivity of these Pt-based nanomaterials via structural construction enables a DMFC to be built without a proton exchange membrane between the fuel electrode and the oxygen electrode. PMID:24448514

A combination of CoO and Co nanoparticles supported on electrospun carbon nanofibers as highly stable air electrodes

NASA Astrophysics Data System (ADS)

Alegre, Cinthia; Busacca, Concetta; Di Blasi, Orazio; Antonucci, Vincenzo; Aricò, Antonino Salvatore; Di Blasi, Alessandra; Baglio, Vincenzo

2017-10-01

Bifunctional materials able to catalyze both the oxygen reduction (ORR) and the oxygen evolution (OER) reactions in alkaline media are still a challenge for the progress of energy conversion and storage devices such as metal-air batteries or unitized regenerative fuel cells. In this work, carbon nanofibers synthesized by electrospinning are modified with a combination of cobalt oxide and metallic cobalt (CoO-Co/CNF) and studied as a bifunctional air electrode for metal-air batteries. The performance of CoO-Co/CNF for both reactions is compared with state-of-the-art catalysts such as Pt/C and IrO2. The combination of cobalt oxide and metallic cobalt, finely distributed on the surface of graphitic carbon nanofibers, leads to a bifunctional catalyst with a half-wave potential for the ORR slightly better than Pt/C and a reversibility (ΔEOER-ORR) of 809 mV. The stability of CoO-Co/CNF is assessed by means of different stress tests: polarizations at high electrochemical potentials (2 V vs. RHE), rapid charge-discharge cycles at ±80 mA cm-2 and long durability tests by charging for 12 h at 60 mA cm-2 and discharging for 8 h at -80 mA cm-2. CoO-Co/CNF shows a remarkable stability, maintaining, at least, an 82% of its performance for the ORR after the stress tests, even when cycled for more than 100 h.

Design of ultrasensitive bisphenol A-aptamer based on platinum nanoparticles loading to polyethyleneimine-functionalized carbon nanotubes.

PubMed

Derikvandi, Zeinab; Abbasi, Amir Reza; Roushani, Mahmoud; Derikvand, Zohreh; Azadbakht, Azadeh

2016-11-01

Here, a highly sensitive electrochemical aptasensor based on a novel signal amplification strategy for the determination of bisphenol A (BPA) was developed. Construction of the aptasensor began with the deposition of highly dispersed platinum nanoparticles (PtNPs)/acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI) at the surface of glassy carbon (PtNPs/PEI/CNTs-COOH/GC) electrode. After immobilizing the amine-capped capture probe (ssDNA1) through the covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides, we employed a designed complementary BPA-aptamer (ssDNA2) as a detection probe to hybridize with the ssDNA1. By adding BPA as a target, the aptamer specifically bound to BPA and its end folded into a BPA-binding junction. Because of steric/conformational restrictions caused by aptamer-BPA complex formation at the surface of modified electrode, the interfacial electron transfer of [Fe(CN)6](3-/4-) as a probe was blocked. Sensitive quantitative detection of BPA was carried out by monitoring the decrease of differential pulse voltammetric responses of [Fe(CN)6](3-/4-) peak current with increasing BPA concentrations. The newly developed aptasensor embraced a number of attractive features such as ease of fabrication, low detection limit, excellent selectivity, good stability and a wide linear range with respect to BPA. Copyright © 2016 Elsevier Inc. All rights reserved.

Surface modification of amine-functionalised graphite for preparation of cobalt hexacyanoferrate (CoHCF)-modified electrode: an amperometric sensor for determination of butylated hydroxyanisole (BHA).

PubMed

Prabakar, S J Richard; Narayanan, S Sriman

2006-12-01

A cobalt hexacyanoferrate (CoHCF)-modified graphite paraffin wax composite electrode was prepared by a new approach. An amine-functionalised graphite powder was used for the fabrication of the electrode. A functionalised graphite paraffin wax composite electrode was prepared and the surface of the electrode was modified with a thin film of CoHCF. Various parameters that influence the electrochemical behaviour of the modified electrode were studied by varying the background electrolytes, scan rates and pH. The modified electrode showed good electrocatalytic activity towards the oxidation of butylated hydroxyanisole (BHA) under optimal conditions and showed a linear response over the range from 7.9 x 10(-7) to 1.9 x 10(-4) M of BHA with a correlation coefficient of 0.9988. The limit of detection was 1.9 x 10(-7) M. Electrocatalytic oxidation of BHA was effective at the modified electrode at a significantly reduced potential and at a broader pH range. The utility of the modified electrode as an amperometric sensor for the determination of BHA in flow systems was evaluated by carrying out hydrodynamic and chronoamperometric experiments. The modified electrode showed very good stability and a longer shelf life. The modified electrode was applied for the determination of BHA in spiked samples of chewing gum and edible sunflower oil. The advantage of this method is the ease of electrode fabrication, good stability, longer shelf life, low cost and its diverse application for BHA determination.

Site-Dependent Vibrational Coupling of CO Adsorbates on Well-Defined Step and Terrace Sites of Monocrystalline Platinum: Mixed-Isotope Studies at Pt(335) and Pt(111) in the Aqueous Electrochemical Environment

DTIC Science & Technology

1994-09-15

and Terrace Sites of Monocrystalline Platinum: Mixed-Isotope Studies at Pt(335) and Pt(1 11) in the Aqueous Electrochemical Environment by Chung S. Kim... monocrystalline metals. These materials have structurally well-defined step and kink structures, which serve as models for the surface defect sites found on...and molecular interactions at stepped monocrystalline electrode surfaces [3,4]. A notable property of Pt(335)/CO is that the CO occupancy at step and

Protic ionic liquid modified electrocatalyst enables robust anode under cell reversal condition

NASA Astrophysics Data System (ADS)

Zhu, Zhengyu; Yan, Xiaocong; Tang, Haolin; Cai, Haopeng; Pan, Mu; Zhang, Haining; Luo, Jiangshui

2017-05-01

Pt/C has been commercially used as anode electrocatalyst for fuel cells but generally exhibits limited durability under conditions of fuel starvation and subsequent cell reversal. Herein we report an improved scaffold concept to simultaneously stabilize the catalyst against particle growth and reduce the adverse effects of cell reversal by modifying Pt/C with suitable protic ionic liquids (PILs). The modified Pt/C catalysts show enhanced cell reversal tolerance because of their high activity towards oxygen evolution reaction (OER), up to 300 mV lower overpotential compared to the unmodified Pt/C. Moreover, the PIL modified catalysts show better resistance to the loss of electrochemical surface area (ECSA) under simulated cell reversal conditions. The results indicate that modification of Pt/C catalysts with PILs is a promising strategy to enhance the stability and durability of electrocatalysts in fuel cell applications with the risk of frequent fuel starvation events, such as automotive fuel cells.

Synthesis, characterization and optimization of platinum-alloy nanoparticle catalysts in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Srivastava, Ratndeep

Renewable hydrogen-fuelled proton exchange membrane (PEMFC) fuel cells have consistently demonstrated great promise as a future source of energy due to their high conversion efficiency, lower temperature of operation and lack of greenhouse emissions. One of the major impediments in the commercialization of polymer electrolyte membrane fuel cells is the insufficient catalytic reactivity and higher cost of Pt electrocatalysts which are utilized for the electroreduction of oxygen from air. This dissertation focuses primarily on a family of Pt alloy fuel cell electrocatalysts referred to as de-alloyed core-shell electrocatalysts. These materials are bimetallic or multimetallic nanoparticles, mostly supported on conductive supports which were first described in a dissertation by Dr. S. Koh earlier in 2009.1 De-alloyed Pt nanoparticle electrocatalysts are formed from base metal rich binary Pt-M and ternary Pt-M1-M 2 (M, M1, M2 = Cu, Co, Ni, Fe and Cr) alloy nanoparticle precursors. The precursors are transformed and activated by electrochemical selective dissolution of the less noble metal component of the precursors (de-alloying). They have shown exceptional activity for oxygen reduction reaction (ORR) in idealized electrochemical half cell measurements, in particular rotating disk electrode experiments. However, these materials were never tested or implemented in realistic Membrane Electrode Assemblies (MEA) and single PEM fuel cells. The objective of this work was to implement de-alloyed Pt particle catalysts in realistic fuel cell electrode layers as well as a detailed characterization of their behavior and stability. The major challenges of MEA implementation consists of the behavior of the new nanostructured electrocatalysts inside the complex three-phase interface of polymer membrane ionomer, liquid water, metal catalyst, support, and reactant gas. Activity measurements were followed by medium and long-term durability analysis by potential cycling of the membrane electrode assemblies to high potentials. These de-alloyed catalysts show improved resistance to electro-chemical surface area degradation as compared to state of the art available commercial Pt/C catalysts. TEM imaging with combination of electrochemical characterization helps in determining the mechanisms for particle growth and failures. Anomalous small angle x-ray scattering (ASAXS) and x-ray diffraction (XRD) techniques were also used in the characterization of these materials.

Chemical vapor deposited carbon nanotubes for aqueous H2-Cl2 fuel cells.

PubMed

Suryavanshi, U B; Bhosale, C H

2010-06-01

Carbon nanotubes having large surface area is an interesting material to develop H2-Cl2 fuel cell electrodes. The attempts were made to deposit carbon nanotubes on porous substrates by chemical vapour deposition. Turpentine oil (C10H16) was used as a precursor, decomposed at 1100 degrees C reactor temperature. Nickel, platinum, tin, Ni-Pt, Ni-Sn, Pt-Sn, Ni-Pt-Sn catalysts were used to grow carbon nanotubes. Nickel was deposited with electrodeposition, platinum with sputter coater and tin with vacuum deposition technique. The developed electrodes were characterized by XRD, SEM, TEM, FTIR, and resistivity by van-der Pauw method. Carbon nanotubes have been formed for 0.25 N nickel deposited for 45 and 60 min; 0.5 N, 0.75 N and 1 N nickel deposited for 15 to 60 min, at the interval of 15. Ni-Pt, Ni-Sn, Pt-Sn and Ni-Pt-Sn activated carbon also shows the well grown CNTs. Aqueous H2-Cl2 fuel cell performance was tested with these grown carbon nanotubes. 40% KCl with 1067 mohm(-1) cm(-1) conductivity was used as electrolyte. Linear sweep voltametry shows reduction potential for hydrogen gas. Chronoamperometry results show better half cell performance for nickel, deposited with 1 N, 45 min deposition time period; and combination of Ni-Pt-Sn with 140, and 110-100 mA/cm2 stable current density respectively.

The role of water management on the oxygen transport resistance in polymer electrolyte fuel cell with ultra-low precious metal loading

NASA Astrophysics Data System (ADS)

Srouji, A. K.; Zheng, L. J.; Dross, R.; Aaron, D.; Mench, M. M.

2017-10-01

Limiting current measurements are used to evaluate oxygen transport resistance in the catalyst layer of a polymer electrolyte fuel cell (PEFC). The pressure independent oxygen transport resistance in the electrode is quantified for two cell architectures and two cathode Pt loadings (0.4 and 0.07 mgPt.cm-2). The compounded effect of the flow field and Pt loading is used to shed light on the nature of the observed transport resistance, especially its response to fundamentally different flow fields, which is shown to directly or indirectly scale with Pt loading in the open literature. By varying gas pressure and using low oxygen concentrations, the total oxygen transport resistance is divided into intermolecular gas diffusion (a pressure-dependent component) and a pressure independent component, which can be attributed to Knudsen diffusion or dissolution film resistance. The pressure-independent oxygen transport resistance in the catalyst layer varies between 13.3 and 34.4 s/m. It is shown that the pressure independent oxygen transport resistance increases with reduced Pt loading, but that effect is greatly exacerbated by using conventional channel/lands. The results indicate that open metallic element architecture improves the oxygen transport resistance in ultra-low Pt loading electrodes, likely due to enhanced water management at the catalyst layer.

Influence of metal electrode on the performance of ZnO based resistance switching memories

NASA Astrophysics Data System (ADS)

Wang, Xueting; Qian, Haolei; Guan, Liao; Wang, Wei; Xing, Boran; Yan, Xiaoyuan; Zhang, Shucheng; Sha, Jian; Wang, Yewu

2017-10-01

Resistance random access memory (RRAM) is considered a promising candidate for the next generation of non-volatile memory. In this work, we fabricate metal (Ag, Ti, or Pt)/ZnO/Pt RRAM cells and then systematically investigate the effects of different top electrodes and their performance. With the formation and rupture of Ag-bridge and the shapeless oxygen vacancy filaments under a series of positive and negative bias, the set and reset processes have been successfully conducted in the Ag/ZnO/Pt device with very low work voltage, high on-off ratio, and good endurance. When applying the voltage bias to the Ti/ZnO/Pt device, the interfacial oxygen ions' migration causes the redox reaction of the conducting filament's oxygen vacancies, leading to the formation and rupture of the conducting filaments but in a relatively poor endurance. At the same time, for the Pt/ZnO/Pt device, once the filaments in the functional layer consisting of oxygen vacancies are formed, it is difficult to disrupt, resulting in the permanent low resistance state after a forming-like process. The results demonstrated that the devices with a metallic conductive bridge mechanism show much better switching behaviors than those with an oxygen ion/vacancy filament mechanism.

Nonlocal magnon spin transport in yttrium iron garnet with tantalum and platinum spin injection/detection electrodes

NASA Astrophysics Data System (ADS)

Liu, J.; Cornelissen, L. J.; Shan, J.; van Wees, B. J.; Kuschel, T.

2018-06-01

We study the magnon spin transport in the magnetic insulator yttrium iron garnet (YIG) in a nonlocal experiment and compare the magnon spin excitation and detection for the heavy metal paramagnetic electrodes platinum (Pt|YIG|Pt) and tantalum (Ta|YIG|Ta). The electrical injection and detection processes rely on the (inverse) spin Hall effect in the heavy metals and the conversion between the electron spin and magnon spin at the heavy metal|YIG interface. Pt and Ta possess opposite signs of the spin Hall angle. Furthermore, their heterostructures with YIG have different interface properties, i.e. spin mixing conductances. By varying the distance between injector and detector, the magnon spin transport is studied. Using a circuit model based on the diffusion-relaxation transport theory, a similar magnon relaxation length of  ∼10 μm was extracted from both Pt and Ta devices. By changing the injector and detector material from Pt to Ta, the influence of interface properties on the magnon spin transport has been observed. For Ta devices on YIG the spin mixing conductance is reduced compared with Pt devices, which is quantitatively consistent when comparing the dependence of the nonlocal signal on the injector-detector distance with the prediction from the circuit model.

Charge Transfer in Multiple Site Chemical Systems.

DTIC Science & Technology

1985-05-30

oxidation either chemically (using excess Ce+(IV)) or electrochemically (using a reticulated vitreous carbon electrode potentiostated at +1.20 V vs.. SCE...The resulting polymers form fairly stable, electrochemically active films on the cxidizing electrode, which can be Pt, SnO2 or vitreous carbon ...surface, including platinum and glassy carbon electrodes. The redox couples incorporated include polypyrydyl omplexes of iron, ruthenium and osmium

Effective immobilization of glucose oxidase on chitosan submicron particles from gladius of Todarodes pacificus for glucose sensing.

PubMed

Anusha, J R; Fleming, Albin T; Kim, Hee-Je; Kim, Byung Chul; Yu, Kook-Hyun; Raj, C Justin

2015-08-01

An effective enzymatic glucose biosensor was developed by immobilizing glucose oxidase on chitosan submicron particles synthesized from the gladius of Todarodes pacificus (GCSP). The chemically synthesized chitosan from gladius was pulverized to submicron particles by ball milling technique, which was further characterized and compared with the standard chitosan (SCS). The degree of deacetylation of GCSP was determined using FTIR spectroscopy which was comparable to the value of standard chitosan. The glucose oxidase (GOx) was immobilized over GCSP on porous zinc oxide/platinum nanoparticle (ZnO/Pt) based electrode. The morphological and structural properties of the electrodes were analyzed using scanning electron microscopy and X-ray diffraction analysis. The glucose sensing behavior of electrode was estimated using electrochemical analysis and showed an excellent analytical performance. The electrode ZnO/Pt/GCSP conjugated with GOx displayed high sensitivity (88.76 μA mM(-1) cm(-2)) with low detection limit in short response time. In addition, the very low value of Michaelis-Menten constant for GCSP based electrode contributes a better affinity of the electrode surface towards glucose oxidase. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports

NASA Astrophysics Data System (ADS)

Parambath Vinayan, Bhaghavathi; Nagar, Rupali; Ramaprabhu, Sundara

2016-09-01

We investigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets (f-G), multi-walled carbon nanotubes (f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support (f-G-MWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half- and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-G-MWNTs cathode electrocatalyst yield a maximum power density of 319 mW cm-2 at 60 °C without any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The high ORR and MOR activity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.

Few-Layer MoSe2 Possessing High Catalytic Activity towards Iodide/Tri-iodide Redox Shuttles

PubMed Central

Lee, Lawrence Tien Lin; He, Jian; Wang, Baohua; Ma, Yaping; Wong, King Young; Li, Quan; Xiao, Xudong; Chen, Tao

2014-01-01

Due to the two-dimensional confinement of electrons, single- and few-layer MoSe2 nanostructures exhibit unusual optical and electrical properties and have found wide applications in catalytic hydrogen evolution reaction, field effect transistor, electrochemical intercalation, and so on. Here we present a new application in dye-sensitized solar cell as catalyst for the reduction of I3− to I− at the counter electrode. The few-layer MoSe2 is fabricated by surface selenization of Mo-coated soda-lime glass. Our results show that the few-layer MoSe2 displays high catalytic efficiency for the regeneration of I− species, which in turn yields a photovoltaic energy conversion efficiency of 9.00%, while the identical photoanode coupling with “champion” electrode based on Pt nanoparticles on FTO glass generates efficiency only 8.68%. Thus, a Pt- and FTO-free counter electrode outperforming the best conventional combination is obtained. In this electrode, Mo film is found to significantly decrease the sheet resistance of the counter electrode, contributing to the excellent device performance. Since all of the elements in the electrode are of high abundance ratios, this type of electrode is promising for the fabrication of large area devices at low materials cost. PMID:24525919

Comparative studies in electrochemical degradation of sulfamethoxazole and diclofenac in water by using various electrodes and phosphate and sulfate supporting electrolytes.

PubMed

Sifuna, Fred W; Orata, Francis; Okello, Veronica; Jemutai-Kimosop, Selly

2016-09-18

In this study, the electro-oxidation capacities of Na2SO4 and potassium phosphate buffer supporting electrolytes were tested and compared for destruction of the sulfamethoxazole (SMX) and diclofenac (DCF) on platinum (Pt) electrode and graphite carbon electrode in aqueous medium. The suitability of pharmaceutical active compounds (PhACs) for electrochemical oxidation was tested by cyclic voltammetry (CV) technique performed in the potential range -1.5 to +1.5 V versus Ag/AgCl, which confirmed the electro-activity of the selected PhACs. The degradation and mineralization were monitored by ultraviolet (UV)-Vis spectrophotometry and HPLC. 0.1 M Na2SO4 supporting electrolyte was found to be more effective for mineralization of SMX and DCF, with efficiency of 15-30% more than the 0.1 M phosphate buffer supporting electrolyte on the platinum (Pt) and carbon electrodes. The Pt electrode showed better performance in the degradation of the two PhACs while under the same conditions than the carbon electrode for both 0.1 M Na2SO4 and 0.1 M potassium phosphate buffer supporting electrolytes. The SMX and DCF degradation kinetics best fitted the second-order reaction, with rate constants ranging between 0.000389 and 0.006 mol(2) L(-2) min(-1) and correlation coefficient (R(2)) above 0.987. The second-order degradation kinetics indicated that the rate-determining step in the degradation could be a chemical process, thus suggesting the active involvement of electrolyte radical species in the degradation of SMX and DCF. Results obtained from a real field sample showed a more than 98% removal of the PhACs from the wastewater by electrochemical degradation.

Design and Characterization of a Sensorized Microfluidic Cell-Culture System with Electro-Thermal Micro-Pumps and Sensors for Cell Adhesion, Oxygen, and pH on a Glass Chip.

PubMed

Bonk, Sebastian M; Stubbe, Marco; Buehler, Sebastian M; Tautorat, Carsten; Baumann, Werner; Klinkenberg, Ernst-Dieter; Gimsa, Jan

2015-07-30

We combined a multi-sensor glass-chip with a microfluidic channel grid for the characterization of cellular behavior. The grid was imprinted in poly-dimethyl-siloxane. Mouse-embryonal/fetal calvaria fibroblasts (MC3T3-E1) were used as a model system. Thin-film platinum (Pt) sensors for respiration (amperometric oxygen electrode), acidification (potentiometric pH electrodes) and cell adhesion (interdigitated-electrodes structures, IDES) allowed us to monitor cell-physiological parameters as well as the cell-spreading behavior. Two on-chip electro-thermal micro-pumps (ETμPs) permitted the induction of medium flow in the system, e.g., for medium mixing and drug delivery. The glass-wafer technology ensured the microscopic observability of the on-chip cell culture. Connecting Pt structures were passivated by a 1.2 μm layer of silicon nitride (Si3N4). Thin Si3N4 layers (20 nm or 60 nm) were used as the sensitive material of the pH electrodes. These electrodes showed a linear behavior in the pH range from 4 to 9, with a sensitivity of up to 39 mV per pH step. The oxygen sensors were circular Pt electrodes with a sensor area of 78.5 μm(2). Their sensitivity was 100 pA per 1% oxygen increase in the range from 0% to 21% oxygen (air saturated). Two different IDES geometries with 30- and 50-μm finger spacings showed comparable sensitivities in detecting the proliferation rate of MC3T3 cells. These cells were cultured for 11 days in vitro to test the biocompatibility, microfluidics and electric sensors of our system under standard laboratory conditions.

Cobalt Phthalocyanine Modified Electrodes Utilised in Electroanalysis: Nano-Structured Modified Electrodes vs. Bulk Modified Screen-Printed Electrodes

PubMed Central

Foster, Christopher W.; Pillay, Jeseelan; Metters, Jonathan P.; Banks, Craig E.

2014-01-01

Cobalt phthalocyanine (CoPC) compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC) onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes l-ascorbic acid, oxygen and hydrazine. It is found that no “electrocatalysis” is observed towards l-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where “electrocatalysis” has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate. PMID:25414969

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

PubMed Central

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-01-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

Ultrahigh PEMFC performance of a thin-film, dual-electrode assembly with tailored electrode morphology.

PubMed

Jung, Chi-Young; Kim, Tae-Hyun; Yi, Sung-Chul

2014-02-01

A dual-electrode membrane electrode assembly (MEA) for proton exchange membrane fuel cells with enhanced polarization under zero relative humidity (RH) is fabricated by introducing a phase-separated morphology in an agglomerated catalyst layer of Pt/C (platinum on carbon black) and Nafion. In the catalyst layer, a sufficient level of phase separation is achieved by dispersing the Pt catalyst and the Nafion dispersion in a mixed-solvent system (propane-1,2,3-triol/1-methyl-2-pyrrolidinone).The high polymer chain mobility results in improved water uptake and regular pore-size distribution with small pore diameters. The electrochemical performance of the dual-film electrode assembly with different levels of phase separation is compared to conventional electrode assemblies. As a result, good performance at 0 % RH is obtained because self-humidification is dramatically improved by attaching this dense and phase-separated catalytic overlayer onto the conventional catalyst layer. A MEA prepared using the thin-film, dual-layered electrode exhibits 39-fold increased RH stability and 28-fold improved start-up recovery time during the on-off operation relative to the conventional device. We demonstrate the successful operation of the dual-layered electrode comprised of discriminatively phase-separated agglomerates with an ultrahigh zero RH fuel-cell performance reaching over 95 % performance of a fully humidified MEA. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomic scale deposition of Pt around Au nanoparticles to achieve much enhanced electrocatalysis of Pt

DOE PAGES

Xi, Zheng; Lv, Haifeng; Erdosy, Daniel P.; ...

2017-05-07

Here, we report an electrochemical method to deposit atomic scale Pt on a 5 nm Au nanoparticle (NP) surface in N 2-saturated 0.5 M H 2SO 4. Furthermore, Pt is provided by the Pt wire counter electrode via one-step Pt wire oxidation, dissolution, and deposition realized by controlled electrochemical scanning. Scanning from 0.6–1.0 V (vs. RHE) for 10 000 cycles gives Au 98.2Pt 1.8, which serves as an excellent catalyst for the formic acid oxidation reaction, showing 41 times higher specific activity (20.19 mA cm -2) and 25 times higher mass activity (10.80 A mg Pt -1) with much bettermore » CO-tolerance and stability than commercial Pt. This work demonstrates a unique strategy to minimize the use of Pt as a catalyst for electrochemical reactions.« less

Atomic scale deposition of Pt around Au nanoparticles to achieve much enhanced electrocatalysis of Pt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, Zheng; Lv, Haifeng; Erdosy, Daniel P.

Here, we report an electrochemical method to deposit atomic scale Pt on a 5 nm Au nanoparticle (NP) surface in N 2-saturated 0.5 M H 2SO 4. Furthermore, Pt is provided by the Pt wire counter electrode via one-step Pt wire oxidation, dissolution, and deposition realized by controlled electrochemical scanning. Scanning from 0.6–1.0 V (vs. RHE) for 10 000 cycles gives Au 98.2Pt 1.8, which serves as an excellent catalyst for the formic acid oxidation reaction, showing 41 times higher specific activity (20.19 mA cm -2) and 25 times higher mass activity (10.80 A mg Pt -1) with much bettermore » CO-tolerance and stability than commercial Pt. This work demonstrates a unique strategy to minimize the use of Pt as a catalyst for electrochemical reactions.« less

Hot corrosion behavior of platinum-modified nickel- and cobalt-based alloys and coatings

NASA Astrophysics Data System (ADS)

Deodeshmukh, Vinay Prakash

High temperature degradation by hot corrosion (650-1000°C) and/or oxidation (>1000°C) can severely reduce the longevity of advanced gas turbine engine components. The protection of high-temperature components against hot corrosion or oxidation is typically conferred by the application of either a diffusion or overlay metallic coating that is able to form a continuous, adherent, and slow-growing oxide scale. There are currently no coatings that provide adequate protection to both hot corrosion and oxidation. Indeed, there is a particular need for such protective coatings because many advanced aero, marine, and industrial gas-turbines operate in both hot corrosion and oxidation regimes in their duty cycle. Recent work at Iowa State University (ISU) has showed that a wide range Pt+Hf-modified gamma'-Ni3Al + gamma-Ni alloy compositions form a very adherent and slow-growing Al 2O3 scale. In fact, the results reported suggest that Pt+Hf-modified gamma' + gamma coatings offer a viable superior alternative to beta-NiAl(Pt)-based coatings. The main thrust of this study was to assess and establish optimum target gamma' + gamma coating compositions for extending the service life of high-temperature gas turbine components exposed to hot corrosion and oxidation conditions. Both high temperature hot-corrosion (HTHC-900°C) and low temperature hot-corrosion (LTHC-705°C) behaviors of the Pt+Hf-modified gamma' + gamma alloys were assessed. The salt used to bring about hot corrosion was Na 2SO4. Quite interestingly, it was found that the HTHC resistance of gamma' + gamma alloys improved with up to about 10 at.% Pt addition, but then decreased significantly with increasing Pt content up to 30 at.% (the maximum level studied); however, under LTHC conditions the resistance of gamma' + gamma alloys improved with increasing Pt content up to 30 at.%. To further improve hot corrosion resistance of Pt+Hf-modified gamma' + gamma alloys, the effects of systematic additions of Cr, Si, and Cr+Si were assessed. The effects pre-oxidation treatments were also studied to further improve the hot corrosion resistance. In addition, high-temperature oxidation behavior of various modified of gamma' + gamma alloys was studied in air at 1150°C under both isothermal and cyclic oxidation conditions. Certain modified versions of gamma' + gamma coating composition(s) exhibited excellent resistance to both hot corrosion and oxidation. Finally, the HTHC and LTHC resistance of novel Pt+Hf-modified gamma' + gamma-based diffusion coatings using a pack cementation process developed at ISU were studied and compared with state-of-the-art commercial coatings. It was found that the Pt+Hf-modified gamma' + gamma coating exhibited superior resistance to both types of hot corrosion with the preoxidation treatment; while, only Pt-modified beta exhibited excellent LTHC resistance with no pre-oxidation treatment. This study also involved evaluating the hot corrosion resistance of various commercially available Pt-modified beta-NiAl diffusion aluminides and CoCrAlY-based overlay coatings for marine gas turbine engine components under both HTHC and LTHC conditions. The Al-Pt-rich beta aluminide exhibited improved resistance to both types of hot corrosion compared to the various Ni-rich beta aluminide and CoCrAlY coatings.

Single-wire dye-sensitized solar cells wrapped by carbon nanotube film electrodes.

PubMed

Zhang, Sen; Ji, Chunyan; Bian, Zhuqiang; Liu, Runhua; Xia, Xinyuan; Yun, Daqin; Zhang, Luhui; Huang, Chunhui; Cao, Anyuan

2011-08-10

Conventional fiber-shaped polymeric or dye-sensitized solar cells (DSSCs) are usually made into a double-wire structure, in which a secondary electrode wire (e.g., Pt) was twisted along the primary core wire consisting of active layers. Here, we report highly flexible DSSCs based on a single wire, by wrapping a carbon nanotube film around Ti wire-supported TiO(2) tube arrays as the transparent electrode. Unlike a twisted Pt electrode, the CNT film ensures full contact with the underlying active layer, as well as uniform illumination along circumference through the entire DSSC. The single-wire DSSC shows a power conversion efficiency of 1.6% under standard illumination (AM 1.5, 100 mW/cm(2)), which is further improved to more than 2.6% assisted by a second conventional metal wire (Ag or Cu). Our DSSC wires are stable and can be bent to large angles up to 90° reversibly without performance degradation.

Methanol-tolerant cathode catalyst composite for direct methanol fuel cells

DOEpatents

Zhu, Yimin; Zelenay, Piotr

2006-09-05

A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of Pt.sub.3Cr/C so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

Exploration of the Ionizable Metal Cluster-Electrode Surface Analogy: Infrared Spectroelectrochemistry of (Pt24(CO)30)n, (Pt26(CO)32)n, and (Pt38(CO) 44)n (n=0 to -10), and Comparisons with Potential-Dependent Spectra of CO adlayers on Platinum Surfaces

DTIC Science & Technology

1992-05-01

100"C under vacuum for 24 hours. The corresponding tetraethylammonium hexafluorophosphate (TEAH) was prepared similarly by using ammonium...the four electrolytes examined in acetonitrile (Table III). Nevertheless, use of lithium perchlorate in acetonitrile restricted the range of cluster

N, P-codoped Mesoporous Carbon Supported PtCox Nanoparticles and Their Superior Electrochemical toward Methanol Oxidation

NASA Astrophysics Data System (ADS)

Cui, Hangjun; Li, Yueming; Liu, Shimin

2018-03-01

In this report, a novel strategy by using the N, P co-doped mesoporous carbon structure as catalyst support to enhance the electrochemical catalytic activity of Pt-based catalysts is proposed. The as-synthesized PtCox@N, P-doped mesoporous carbon nanocomposties have been studied as an anode catalyst toward methanol oxidation, exhibiting greatly improved electrochemical activity and stability compared with Pt@mesoporous carbon. The synergistic effects of N, P dual-doping and porous carbon structure help to achieve better electron transport at the electrode surface, which eventually leads to greatly enhanced catalytic activity compared to the pristine Pt/mesoporous carbon.…

Improvement of the electrochromic response of a low-temperature sintered dye-modified porous electrode using low-resistivity indium tin oxide nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Yuichi, E-mail: yuichi.watanabe@aist.go.jp; Suemori, Kouji; Hoshino, Satoshi

2016-06-15

An indium tin oxide (ITO) nanoparticle-based porous electrode sintered at low temperatures was investigated as a transparent electrode for electrochromic displays (ECDs). The electrochromic (EC) response of the dye-modified ITO porous electrode sintered at 150 °C, which exhibited a generally low resistivity, was markedly superior to that of a conventional dye-modified TiO{sub 2} porous electrode sintered at the same temperature. Moreover, the EC characteristics of the dye-modified ITO porous electrode sintered at 150 °C were better than those of the high-temperature (450 °C) sintered conventional dye-modified TiO{sub 2} porous electrode. These improvements in the EC characteristics of the dye-modified ITO porous electrode aremore » attributed to its lower resistivity than that of the TiO{sub 2} porous electrodes. In addition to its sufficiently low resistivity attained under the sintering conditions required for flexible ECD applications, the ITO porous film had superior visible-light transparency and dye adsorption capabilities. We conclude that the process temperature, resistivity, optical transmittance, and dye adsorption capability of the ITO porous electrode make it a promising transparent porous electrode for flexible ECD applications.« less

Electrochemical modification of properties of ZnO films

NASA Astrophysics Data System (ADS)

Abe, Koji; Okubo, Takamasa; Ishikawa, Hirohito

2017-12-01

The properties of Al-doped ZnO films and Li- and Al-doped ZnO films were modified by electrochemical treatment. A constant current was applied between a ZnO film and a Pt electrode in an electrolyte solution. The sheet resistance of the ZnO film increased and decreased depending on the direction of current flow during the electrochemical treatment. When the ZnO film was used as a cathode (forward biased condition), the sheet resistance of the ZnO film decreased with increasing treatment time. The optical bandgap of the H2-annealed ZnO film also depended on the direction of current flow and increased under the forward biased condition. The electrochemical treatment caused the Burstein-Moss effect.

The impact of electrode materials on 1/f noise in piezoelectric AlN contour mode resonators

NASA Astrophysics Data System (ADS)

Kim, Hoe Joon; Jung, Soon In; Segovia-Fernandez, Jeronimo; Piazza, Gianluca

2018-05-01

This paper presents a detailed analysis on the impact of electrode materials and dimensions on flicker frequency (1/f) noise in piezoelectric aluminum nitride (AlN) contour mode resonators (CMRs). Flicker frequency noise is a fundamental noise mechanism present in any vibrating mechanical structure, whose sources are not generally well understood. 1 GHz AlN CMRs with three different top electrode materials (Al, Au, and Pt) along with various electrode lengths and widths are fabricated to control the overall damping acting on the device. Specifically, the use of different electrode materials allows control of thermoelastic damping (TED), which is the dominant damping mechanism for high frequency AlN CMRs and largely depends on the thermal properties (i.e. thermal diffusivities and expansion coefficients) of the metal electrode rather than the piezoelectric film. We have measured Q and 1/f noise of 68 resonators and the results show that 1/f noise decreases with increasing Q, with a power law dependence that is about 1/Q4. Interestingly, the noise level also depends on the type of electrode materials. Devices with Pt top electrode demonstrate the best noise performance. Our results help unveiling some of the sources of 1/f noise in these resonators, and indicate that a careful selection of the electrode material and dimensions could reduce 1/f noise not only in AlN-CMRs, but also in various classes of resonators, and thus enable ultra-low noise mechanical resonators for sensing and radio frequency applications.

Biaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis

DOE PAGES

Bu, Lingzheng; Zhang, Nan; Guo, Shaojun; ...

2016-12-16

Compressive surface strains have been necessary to boost oxygen reduction reaction (ORR) activity in core/shell M/Pt catalysts (where M can be Ni, Co, Fe). We report a class of PtPb/Pt core/shell nanoplate catalysts that exhibit large biaxial tensile strains. The stable Pt (110) facets of the nanoplates have high ORR specific and mass activities that reach 7.8 milliampere per centimeter square and 4.3 ampere per milligram of platinum at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. Density functional theory calculations revealed that the edge-­Pt and top (bottom)-Pt (110) facets undergo large tensile strains that help optimize the Pt-­Omore » bond strength. The intermetallic core and uniform 4 layers of Pt shell of the PtPb/Pt nanoplates appear to underlie the high endurance of these catalysts, which can undergo 50,000 voltage cycles with negligible activity decay and no apparent structure and composition changes.« less

Biaxially strained PtPb/Pt core/shell nanoplate boosts oxygen reduction catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bu, Lingzheng; Zhang, Nan; Guo, Shaojun

Compressive surface strains have been necessary to boost oxygen reduction reaction (ORR) activity in core/shell M/Pt catalysts (where M can be Ni, Co, Fe). We report a class of PtPb/Pt core/shell nanoplate catalysts that exhibit large biaxial tensile strains. The stable Pt (110) facets of the nanoplates have high ORR specific and mass activities that reach 7.8 milliampere per centimeter square and 4.3 ampere per milligram of platinum at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. Density functional theory calculations revealed that the edge-­Pt and top (bottom)-Pt (110) facets undergo large tensile strains that help optimize the Pt-­Omore » bond strength. The intermetallic core and uniform 4 layers of Pt shell of the PtPb/Pt nanoplates appear to underlie the high endurance of these catalysts, which can undergo 50,000 voltage cycles with negligible activity decay and no apparent structure and composition changes.« less

Preparation of Fe2O3-Clorprenaline/Tetraphenylborate Nanospheres and Their Application as Ion Selective Electrode for Determination of Clorprenaline in Pork

NASA Astrophysics Data System (ADS)

Shao, Xintian; Zhang, Jing; Li, Donghui; Yue, Jingli; Chen, Zhenhua

2016-04-01

A novel modified ion selective electrode based on Fe2O3-clorprenaline/tetraphenylborate nanospheres (Fe2O3-CLPT NSs) as electroactive materials for the determination of clorprenaline hydrochloride (CLP) is described. The α-Fe2O3 nanoparticles (NPs) were prepared by hydrothermal synthesis, then self-assembled on CLP/tetraphenylborate (TPB) to form Fe2O3-CLPT NSs, which were used as a potentiometric electrode for analyte determination innovatively. The Fe2O3-CLPT NSs modified electrode exhibited a wider concentration range from 1.0 × 10-7 to 1.0 × 10-1 mol/L and a lower detection limit of 3.7 × 10-8 mol/L compared with unmodified electrodes. The selectivity of the modified electrode was evaluated by fixed interference method. The good performance of the modified electrode such as wide pH range (2.4-6.7), fast response time (15 s), and adequate lifetime (14 weeks) indicate the utility of the modified electrode for evaluation of CLP content in various real samples. Finally, the modified electrode was successfully employed to detect CLP in pork samples with satisfactory results. These results demonstrated the Fe2O3-CLPT NSs modified electrode to be a functional and convenient method to the field of potentiometry determination of CLP in real samples.

Direct synthesis of few-layer graphene supported platinum nanocatalyst for methanol oxidation

NASA Astrophysics Data System (ADS)

Tan, Hong; Ma, Xiaohui; Sheng, Leimei; An, Kang; Yu, Liming; Zhao, Hongbin; Xu, Jiaqiang; Ren, Wei; Zhao, Xinluo

2014-11-01

High-crystalline few-layer graphene supported Pt nanoparticles have been synthesized by arc discharge evaporation of carbon electrodes containing Pt element. A high-temperature treatment under hydrogen atmosphere has been carried out to obtain a new type of Pt/graphene catalyst for methanol oxidation in direct methanol fuel cell. The morphology and structure characterizations of as-grown few-layer graphene supported Pt nanoparticles and Pt/graphene catalysts have been studied by Raman spectroscopy, scanning electron microscopy with energy-dispersive spectroscopy, and high-resolution transmission electron microscopy. Cyclic voltammograms and chronoamperometric curves show that our present Pt/graphene catalysts have larger current density for methanol oxidation, higher tolerance to carbon monoxide poisoning, and better stability during the operating procedure, compared to commercial Pt/C catalysts.

Direct methanol fuel cell with extended reaction zone anode: PtRu and PtRuMo supported on graphite felt

NASA Astrophysics Data System (ADS)

Bauer, Alex; Gyenge, Előd L.; Oloman, Colin W.

Pressed graphite felt (thickness ∼350 μm) with electrodeposited PtRu (43 g m -2, 1.4:1 atomic ratio) or PtRuMo (52 g m -2, 1:1:0.3 atomic ratio) nanoparticle catalysts was investigated as an anode for direct methanol fuel cells. At temperatures above 333 K the fuel cell performance of the PtRuMo catalyst was superior compared to PtRu. The power density was 2200 W m -2 with PtRuMo at 5500 A m -2 and 353 K while under the same conditions PtRu yielded 1925 W m -2. However, the degradation rate of the Mo containing catalyst formulation was higher. Compared to conventional gas diffusion electrodes with comparable PtRu catalyst composition and load, the graphite felt anodes gave higher power densities mainly due to the extended reaction zone for methanol oxidation.

Nonvolatile resistive switching in metal/La-doped BiFeO3/Pt sandwiches.

PubMed

Li, Mi; Zhuge, Fei; Zhu, Xiaojian; Yin, Kuibo; Wang, Jinzhi; Liu, Yiwei; He, Congli; Chen, Bin; Li, Run-Wei

2010-10-22

The resistive switching (RS) characteristics of a Bi(0.95)La(0.05)FeO(3) (La-BFO) film sandwiched between a Pt bottom electrode and top electrodes (TEs) made of Al, Ag, Cu, and Au have been studied. Devices with TEs made of Ag and Cu showed stable bipolar RS behaviors, whereas those with TEs made of Al and Au exhibited unstable bipolar RS. The Ag/La-BFO/Pt structure showed an on/off ratio of 10(2), a retention time > 10(5) s, and programming voltages < 1 V. The RS effect can be attributed to the formation/rupture of nanoscale metal filaments due to the diffusion of the TEs under a bias voltage. The maximum current before the reset process (on-to-off switching) was found to increase linearly with the current compliance applied during the set process (off-to-on switching).

The mechanical properties of ionic polymer-metal composites

NASA Astrophysics Data System (ADS)

Park, Il-Seok; Kim, Sang-Mun; Kim, Doyeon; Kim, Kwang J.

2007-04-01

In this study, we investigated the mechanical properties of various type ionic polymer-metal composites (IPMCs) and Pt, Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5~7 μm doped layer and nano-sized Au particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in a dried condition. In a thermal behavior, Au IPMC has the highest T g (153°C) and T m (263°C) in both the DMA and DSC results. The fracture behavior of various types IPMCs followed base material's behavior, Nafion TM, which is represented as the semicrystalline polymer characteristic.

Investigation of nanoporous platinum thin films fabricated by reactive sputtering: Application as micro-SOFC electrode

NASA Astrophysics Data System (ADS)

Jung, WooChul; Kim, Jae Jin; Tuller, Harry L.

2015-02-01

Highly porous Pt thin films, with nano-scale porosity, were fabricated by reactive sputtering. The strategy involved deposition of thin film PtOx at room temperature, followed by the subsequent decomposition of the oxide by rapid heat treatment. The resulting films exhibited percolating Pt networks infiltrated with interconnected nanosized pores, critical for superior solid oxide fuel cell cathode performance. This approach is particularly attractive for micro-fabricated solid oxide fuel cells, since it enables fabrication of the entire cell stack (anode/electrolyte/cathode) within the sputtering chamber, without breaking vacuum. In this work, the morphological, crystallographic and chemical properties of the porous electrode were systematically varied by control of deposition conditions. Oxygen reduction reaction kinetics were investigated by means of electrochemical impedance spectroscopy, demonstrating the critical role of nano-pores in achieving satisfactory micro-SOFC cathode performance.

Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

NASA Astrophysics Data System (ADS)

Long, Shibing; Liu, Qi; Lv, Hangbing; Li, Yingtao; Wang, Yan; Zhang, Sen; Lian, Wentai; Zhang, Kangwei; Wang, Ming; Xie, Hongwei; Liu, Ming

2011-03-01

Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO2 film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO2:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I- V relationship of low resistance state (LRS) and the dependence of LRS resistance ( R ON) and reset current ( I reset) on the set current compliance ( I comp) indicate that the observed resistive switching characteristics of the Ag/ZrO2:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.

Accurate Assessment of the Oxygen Reduction Electrocatalytic Activity of Mn/Polypyrrole Nanocomposites Based on Rotating Disk Electrode Measurements, Complemented with Multitechnique Structural Characterizations

PubMed Central

Sánchez, Carolina Ramírez; Taurino, Antonietta; Bozzini, Benedetto

2016-01-01

This paper reports on the quantitative assessment of the oxygen reduction reaction (ORR) electrocatalytic activity of electrodeposited Mn/polypyrrole (PPy) nanocomposites for alkaline aqueous solutions, based on the Rotating Disk Electrode (RDE) method and accompanied by structural characterizations relevant to the establishment of structure-function relationships. The characterization of Mn/PPy films is addressed to the following: (i) morphology, as assessed by Field-Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscope (AFM); (ii) local electrical conductivity, as measured by Scanning Probe Microscopy (SPM); and (iii) molecular structure, accessed by Raman Spectroscopy; these data provide the background against which the electrocatalytic activity can be rationalised. For comparison, the properties of Mn/PPy are gauged against those of graphite, PPy, and polycrystalline-Pt (poly-Pt). Due to the literature lack of accepted protocols for precise catalytic activity measurement at poly-Pt electrode in alkaline solution using the RDE methodology, we have also worked on the obtainment of an intralaboratory benchmark by evidencing some of the time-consuming parameters which drastically affect the reliability and repeatability of the measurement. PMID:28042491

Properties of epitaxial, (001)- and (110)-oriented (PbMg1/3Nb2/3O3)2/3-(PbTiO3)1/3 films on silicon described by polarization rotation

PubMed Central

Boota, Muhammad; Houwman, Evert P.; Dekkers, Matthijn; Nguyen, Minh D.; Vergeer, Kurt H.; Lanzara, Giulia; Koster, Gertjan; Rijnders, Guus

2016-01-01

Abstract Epitaxial (PbMg1/3Nb2/3O3)2/3-(PbTiO3)1/3 (PMN-PT) films with different out-of-plane orientations were prepared using a CeO2/yttria stabilized ZrO2 bilayer buffer and symmetric SrRuO3 electrodes on silicon substrates by pulsed laser deposition. The orientation of the SrRuO3 bottom electrode, either (110) or (001), was controlled by the deposition conditions and the subsequent PMN-PT layer followed the orientation of the bottom electrode. The ferroelectric, dielectric and piezoelectric properties of the (SrRuO3/PMN-PT/SrRuO3) ferroelectric capacitors exhibit orientation dependence. The properties of the films are explained in terms of a model based on polarization rotation. At low applied fields domain switching dominates the polarization change. The model indicates that polarization rotation is easier in the (110) film, which is ascribed to a smaller effect of the clamping on the shearing of the pseudo-cubic unit cell compared to the (001) case. PMID:27877857

A novel differential electrochemical mass spectrometry method to determine the product distribution from parasitic Methanol oxidation reaction on oxygen reduction reaction catalysts

NASA Astrophysics Data System (ADS)

Jurzinsky, Tilman; Kurzhals, Philipp; Cremers, Carsten

2018-06-01

The oxygen reduction reaction is in research focus since several decades due to its importance for the overall fuel cell performance. In direct methanol fuel cells, the crossover of methanol and its subsequent parasitic oxidation are main issues when it comes to preventing fuel cell performance losses. In this work, we present a novel differential electrochemical mass spectrometry method to evaluate oxygen reduction reaction catalysts on their tolerance to methanol being present at the cathode. Besides this, the setup allows to measure under more realistic fuel cell conditions than typical rotating disc electrode measurements, because the oxygen reduction reaction is evaluated in gaseous phase and a gas diffusion electrode is used as working electrode. Due to the new method, it was possible to investigate the oxygen reduction reaction on two commonly used catalysts (Pt/C and Pt3Co/C) in absence and presence of methanol. It was found, that Pt3Co/C is less prone to parasitic current losses due to methanol oxidation reaction. By connecting a mass spectrometer to the electrochemical cell, the new method allows to determine the products formed on the catalysts due to parasitic methanol electrooxidation.

Enhanced electrodes for solid state gas sensors

DOEpatents

Garzon, Fernando H.; Brosha, Eric L.

2001-01-01

A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

Unraveling micro- and nanoscale degradation processes during operation of high-temperature polymer-electrolyte-membrane fuel cells

NASA Astrophysics Data System (ADS)

Hengge, K.; Heinzl, C.; Perchthaler, M.; Varley, D.; Lochner, T.; Scheu, C.

2017-10-01

The work in hand presents an electron microscopy based in-depth study of micro- and nanoscale degradation processes that take place during the operation of high-temperature polymer-electrolyte-membrane fuel cells (HT-PEMFCs). Carbon supported Pt particles were used as cathodic catalyst material and the bimetallic, carbon supported Pt/Ru system was applied as anode. As membrane, cross-linked polybenzimidazole was used. Scanning electron microscopy analysis of cross-sections of as-prepared and long-term operated membrane-electrode-assemblies revealed insight into micrometer scale degradation processes: operation-caused catalyst redistribution and thinning of the membrane and electrodes. Transmission electron microscopy investigations were performed to unravel the nanometer scale phenomena: a band of Pt and Pt/Ru nanoparticles was detected in the membrane adjacent to the cathode catalyst layer. Quantification of the elemental composition of several individual nanoparticles and the overall band area revealed that they stem from both anode and cathode catalyst layers. The results presented do not demonstrate any catastrophic failure but rather intermediate states during fuel cell operation and indications to proceed with targeted HT-PEMFC optimization.

Platinized Graphene/ceramics Nano-sandwiched Architectures and Electrodes with Outstanding Performance for PEM Fuel Cells

PubMed Central

Chen, Xu; He, Daping; Wu, Hui; Zhao, Xiaofeng; Zhang, Jian; Cheng, Kun; Wu, Peng; Mu, Shichun

2015-01-01

For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets (GNS) is tailored by platinizing graphene in advance to shorten the difference in the specific gravity between carbon and SiC materials, and then nano-SiC is well intercalated into GNS interlayers. This nano-architecture with highly dispersed Pt nanoparticles exhibits a very high oxygen reduction reaction (ORR) activity and polymer electrolyte membrane (PEM) fuel cell performance. The mass activity of half cells is 1.6 times of that of the GNS supported Pt, and 2.4 times that of the commercial Pt/C catalyst, respectively. Moreover, after an accelerated stress test our catalyst shows a predominantly electrochemical stability compared with benchmarks. Further fuel cell tests show a maximum power density as high as 747 mW/cm2 at low Pt loading, which is more than 2 times higher than that of fuel cells with the pristine graphene electrode. PMID:26538366

Platinized Graphene/ceramics Nano-sandwiched Architectures and Electrodes with Outstanding Performance for PEM Fuel Cells.

PubMed

Chen, Xu; He, Daping; Wu, Hui; Zhao, Xiaofeng; Zhang, Jian; Cheng, Kun; Wu, Peng; Mu, Shichun

2015-11-05

For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets (GNS) is tailored by platinizing graphene in advance to shorten the difference in the specific gravity between carbon and SiC materials, and then nano-SiC is well intercalated into GNS interlayers. This nano-architecture with highly dispersed Pt nanoparticles exhibits a very high oxygen reduction reaction (ORR) activity and polymer electrolyte membrane (PEM) fuel cell performance. The mass activity of half cells is 1.6 times of that of the GNS supported Pt, and 2.4 times that of the commercial Pt/C catalyst, respectively. Moreover, after an accelerated stress test our catalyst shows a predominantly electrochemical stability compared with benchmarks. Further fuel cell tests show a maximum power density as high as 747 mW/cm(2) at low Pt loading, which is more than 2 times higher than that of fuel cells with the pristine graphene electrode.

Platinized Graphene/ceramics Nano-sandwiched Architectures and Electrodes with Outstanding Performance for PEM Fuel Cells

NASA Astrophysics Data System (ADS)

Chen, Xu; He, Daping; Wu, Hui; Zhao, Xiaofeng; Zhang, Jian; Cheng, Kun; Wu, Peng; Mu, Shichun

2015-11-01

For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets (GNS) is tailored by platinizing graphene in advance to shorten the difference in the specific gravity between carbon and SiC materials, and then nano-SiC is well intercalated into GNS interlayers. This nano-architecture with highly dispersed Pt nanoparticles exhibits a very high oxygen reduction reaction (ORR) activity and polymer electrolyte membrane (PEM) fuel cell performance. The mass activity of half cells is 1.6 times of that of the GNS supported Pt, and 2.4 times that of the commercial Pt/C catalyst, respectively. Moreover, after an accelerated stress test our catalyst shows a predominantly electrochemical stability compared with benchmarks. Further fuel cell tests show a maximum power density as high as 747 mW/cm2 at low Pt loading, which is more than 2 times higher than that of fuel cells with the pristine graphene electrode.

Understanding interaction of curcumin and metal ions on electrode surfaces using EDXRF

NASA Astrophysics Data System (ADS)

Joseph, Daisy; Kumar, K. Krishna; Narayanan, S. Sriman

2018-04-01

A chemically modified electrode was developed for determination of metal ions (Cd, Pb, Zn, Co, Hg). The modifier used for the study was Curcumin. Curcumin acts as a complexing agent at the surface of the electrode for preconcentration of metal ions from electrolyte to electrode surface and stripped back to electrolyte during analysis. EDXRF was used to analyze these electrodes and it was concluded that the PCR modified electrode favored effective chelation for lead and mercury.

Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores.

PubMed

Pardon, Gaspard; Gatty, Hithesh K; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

2013-01-11

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al(2)O(3)) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al(2)O(3) layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al(2)O(3) using ALD.

Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

NASA Astrophysics Data System (ADS)

Pardon, Gaspard; Gatty, Hithesh K.; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

2013-01-01

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

M13 Virus-Incorporated Biotemplates on Electrode Surfaces To Nucleate Metal Nanostructures by Electrodeposition.

PubMed

Manivannan, Shanmugam; Kang, Inhak; Seo, Yeji; Jin, Hyo-Eon; Lee, Seung-Wuk; Kim, Kyuwon

2017-09-27

We report a virus-incorporated biological template (biotemplate) on electrode surfaces and its use in electrochemical nucleation of metal nanocomposites as an electrocatalytic material for energy applications. The biotemplate was developed with M13 virus (M13) incorporated in a silicate sol-gel matrix as a scaffold to nucleate Au-Pt alloy nanostructures by electrodeposition, together with reduced graphene oxide (rGO). The phage when engineered with Y3E peptides could nucleate Au-Pt alloy nanostructures, which ensured adequate packing density, simultaneous stabilization of rGO, and a significantly increased electrochemically active surface area. Investigation of the electrocatalytic activity of the resulting sol-gel composite catalyst toward methanol oxidation in an alkaline medium showed that this catalyst had mass activity greater than that of the biotemplate containing wild-type M13 and that of monometallic Pt and other Au-Pt nanostructures with different compositions and supports. M13 in the nanocomposite materials provided a close contact between the Au-Pt alloy nanostructures and rGO. In addition, it facilitated the availability of an OH - -rich environment to the catalyst. As a result, efficient electron transfer and a synergistic catalytic effect of the Au and Pt in the alloy nanostructures toward methanol oxidation were observed. Our nanocomposite synthesis on the novel biotemplate and its application might be useful for developing novel clean and green energy-generating and energy-storage materials.

Dissolution of Pt during Oxygen Reduction Reaction Produces Pt Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bae, Je Hyun; Brocenschi, Ricardo F.; Kisslinger, Kim

The loss of Pt during the oxygen reduction reaction (ORR) affects the performance and economic viability of fuel cells and sensors. Our group previously observed the dissolution of Pt nanoelectrodes at moderately negative potentials during the ORR. Here we report a more detailed study of this process and identify its product. The nanoporous Pt surface formed during the ORR was visualized by AFM and high-resolution SEM, which also showed ~5 nm sized Pt particles on the glass surface surrounding the electrode. Furthermore, the release of these nanoparticles into the solution was confirmed by monitoring their catalytically amplified collisions with amore » Hg-coated microelectrode used as the tip in the scanning electrochemical microscope (SECM).« less

Dissolution of Pt during Oxygen Reduction Reaction Produces Pt Nanoparticles

DOE PAGES

Bae, Je Hyun; Brocenschi, Ricardo F.; Kisslinger, Kim; ...

2017-11-15

The loss of Pt during the oxygen reduction reaction (ORR) affects the performance and economic viability of fuel cells and sensors. Our group previously observed the dissolution of Pt nanoelectrodes at moderately negative potentials during the ORR. Here we report a more detailed study of this process and identify its product. The nanoporous Pt surface formed during the ORR was visualized by AFM and high-resolution SEM, which also showed ~5 nm sized Pt particles on the glass surface surrounding the electrode. Furthermore, the release of these nanoparticles into the solution was confirmed by monitoring their catalytically amplified collisions with amore » Hg-coated microelectrode used as the tip in the scanning electrochemical microscope (SECM).« less

Applications of Graphene-Modified Electrodes in Microbial Fuel Cells

PubMed Central

Yu, Fei; Wang, Chengxian; Ma, Jie

2016-01-01

Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy. PMID:28773929

Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode

NASA Astrophysics Data System (ADS)

Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

2016-01-01

A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light ( λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system.

Surface modifications of chalcopyrite CuInS2 thin films for photochatodes in photoelectrochemical water splitting under sunlight irradiation

NASA Astrophysics Data System (ADS)

Gunawan; Haris, A.; Widiyandari, H.; Septina, W.; Ikeda, S.

2017-02-01

Copper chalcopyrite semiconductors include a wide range of compounds that are of interest for photoelectrochemical water splitting which enables them to be used as photochatodes for H2 generation. Among them, CuInS2 is one of the most important materials due to its optimum band gap energy for sunlight absorption. In the present study, we investigated the application of CuInS2 fabricated by electrodeposition as photochatodes for water splitting. Thin film of CuInS2 chalcopyrite was formed on Mo-coated glass substrate by stacked electrodeposition of copper and indium followed by sulfurization under H2S flow. The films worked as a H2 liberation electrode under cathodic polarization from a solution containing Na2SO4 after loading Pt deposits on the film. Introduction of an n-type CdS layer by chemical bath deposition on the CuInS2 surface before the Pt loading resulted appreciable improvements of H2 liberation efficiency and a higher photocurrent onset potential. Moreover, the use of In2S3 layer as an alternative n-type layer to the CdS significantly improved the H2 liberation performance: the CuInS2 film modified with In2S3 and Pt deposits worked as an efficient photocathode for photoelectrochemical water splitting.

Novel electrochemical biosensor based on cationic peptide modified hemin/G-quadruples enhanced peroxidase-like activity.

PubMed

Yu, Qian; Wu, Yongmei; Liu, Zi; Lei, Sheng; Li, Gaiping; Ye, Baoxian

2018-06-01

This work designed an artificial substrate peptide to synthesize peptide-hemin/G-quadruplex (peptide-DNAzyme) conjugates. In addition to enhancing catalytic activity of hemin/G-quadruplex, the peptide could also be induced and cleaved by prostate specific antigen (PSA). It was the first report on peptide-DNAzyme conjugates in application of the peptide biosensor. The polyethyleneimine-reduced graphene oxide@hollow platinum nanotubes (PEI-rGO@PtNTs) nanocomposites were cast on the glassy carbon electrode in order to form the interface of biocompatibility and huge surface area for bioprobes immobilization. In absence of PSA, the peptide-DNAzyme conjugates retained intact on the surface of the electrode to produce a strong response signal. But in presence of PSA, the peptide-DNAzyme conjugates were destroyed to release electron mediators, resulting in dramatical decrease of the electrochemicl signal. Therefore, the method had high sensitivity and super selectivity with the limit of detection calculated as 2.0 fg/mL. Furthermore, the strategy would be promising to apply for other proteases by transforming the synthetic peptide module of target. Copyright © 2018 Elsevier B.V. All rights reserved.

Functional design of electrolytic biosensor

NASA Astrophysics Data System (ADS)

Gamage Preethichandra, D. M.; Mala Ekanayake, E. M. I.; Onoda, M.

2017-11-01

A novel amperometric biosensbased on conjugated polypyrrole (PPy) deposited on a Pt modified ITO (indium tin oxide) conductive glass substrate and their performances are described. We have presented a method of developing a highly sensitive and low-cost nano-biosensor for blood glucose measurements. The fabrication method proposed decreases the cost of production significantly as the amount of noble metals used is minimized. A nano-corrugated PPy substrate was developed through pulsed electrochemical deposition. The sensitivity achieved was 325 mA/(Mcm2) and the linear range of the developed sensor was 50-60 mmol/l. Then the application of the electrophoresis helps the glucose oxidase (GOx) on the PPy substrate. The main reason behind this high enzyme loading is the high electric field applied across the sensor surface (working electrode) and the counter electrode where that pushes the nano-scale enzyme particles floating in the phosphate buffer solution towards the substrate. The novel technique used has provided an extremely high sensitivities and very high linear ranges for enzyme (GOx) and therefore can be concluded that this is a very good technique to load enzyme onto the conducting polymer substrates.

Iridium oxide pH sensor for biomedical applications. Case urea-urease in real urine samples.

PubMed

Prats-Alfonso, Elisabet; Abad, Llibertat; Casañ-Pastor, Nieves; Gonzalo-Ruiz, Javier; Baldrich, Eva

2013-01-15

This work demonstrates the implementation of iridium oxide films (IROF) grown on silicon-based thin-film platinum microelectrodes, their utilization as a pH sensor, and their successful formatting into a urea pH sensor. In this context, Pt electrodes were fabricated on Silicon by using standard photolithography and lift-off procedures and IROF thin films were growth by a dynamic oxidation electrodeposition method (AEIROF). The AEIROF pH sensor reported showed a super-Nerstian (72.9±0.9mV/pH) response between pH 3 and 11, with residual standard deviation of both repeatability and reproducibility below 5%, and resolution of 0.03 pH units. For their application as urea pH sensors, AEIROF electrodes were reversibly modified with urease-coated magnetic microparticles (MP) using a magnet. The urea pH sensor provided fast detection of urea between 78μM and 20mM in saline solution, in sample volumes of just 50μL. The applicability to urea determination in real urine samples is discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

Cell attachment functionality of bioactive conducting polymers for neural interfaces.

PubMed

Green, Rylie A; Lovell, Nigel H; Poole-Warren, Laura A

2009-08-01

Bioactive coatings for neural electrodes that are tailored for cell interactions have the potential to produce superior implants with improved charge transfer capabilities. In this study synthetically produced anionically modified laminin peptides DEDEDYFQRYLI and DCDPGYIGSR were used to dope poly(3,4-ethylenedioxythiophene) (PEDOT) electrodeposited on platinum (Pt) electrodes. Performance of peptide doped films was compared to conventional polymer PEDOT/paratoluene sulfonate (pTS) films using SEM, XPS, cyclic voltammetry, impedance spectroscopy, mechanical hardness and adherence. Bioactivity of incorporated peptides and their affect on cell growth was assessed using a PC12 neurite outgrowth assay. It was demonstrated that large peptide dopants produced softer PEDOT films with a minimal decrease in electrochemical stability, compared to the conventional dopant, pTS. Cell studies revealed that the YFQRYLI ligand retained neurite outgrowth bioactivity when DEDEDYFQRYLI was used as a dopant, but the effect was strongly dependant on initial cell attachment. Alternate peptide dopant, DCDPGYIGSR was found to impart superior cell attachment properties when compared to DEDEDYFQRYLI, but attachment on both peptide doped polymers could be enhanced by coating with whole native laminin.

Microfluidic Device with Tunable Post Arrays and Integrated Electrodes for Studying Cellular Release

PubMed Central

Selimovic, Asmira; Erkal, Jayda L.; Spence, Dana M.; Martin, R. Scott

2015-01-01

In this paper, we describe the development of a planar, pillar array device that can be used to image either side of a tunable membrane, as well as sample and detect small molecules in a cell-free region of the microchip. The pores are created by sealing two parallel PDMS microchannels (a cell channel and a collector channel) over a gold pillar array (5 or 10 µm in height), with the device being characterized and optimized for small molecule cross-over while excluding a flowing cell line (here, red blood cells, RBCs). The device was characterized in terms of the flow rate dependence of cross-over of analyte and cell exclusion as well as the ability to perform amperometric detection of catechol and nitric oxide (NO) as they cross-over into the collector channel. Using catechol as the test analyte, the limits of detection (LOD) of the cross-over for the 10 µm and 5 µm pillar array heights were shown to be 50 nM and 106 nM, respectively. Detection of NO was made possible with a glassy carbon detection electrode (housed in the collector channel) modified with Pt-black and Nafion, to enhance sensitivity and selectivity, respectively. Reproducible cross-over of NO as a function of concentration resulted in a linear correlation (r2 = 0.995, 7.6 µM - 190 µM), with an LOD for NO of 230 nM on the glassy carbon-Pt-black-0.05% Nafion electrode. The applicability of the device was demonstrated by measuring the NO released from hypoxic RBCs, with the device allowing the released NO to cross-over into a cell free channel where it was detected in close to real-time. This type of device is an attractive alternative to the use of 3-dimensional devices with polycarbonate membranes, as either side of the membrane can be imaged and facile integration of electrochemical detection is possible. PMID:25105251

High energy efficiency and high power density proton exchange membrane fuel cells: Electrode kinetics and mass transport

NASA Technical Reports Server (NTRS)

Srinivasan, Supramaniam; Velev, Omourtag A.; Parthasathy, Arvind; Manko, David J.; Appleby, A. John

1991-01-01

The development of proton exchange membrane (PEM) fuel cell power plants with high energy efficiencies and high power densities is gaining momentum because of the vital need of such high levels of performance for extraterrestrial (space, underwater) and terrestrial (power source for electric vehicles) applications. Since 1987, considerable progress has been made in achieving energy efficiencies of about 60 percent at a current density of 200 mA/sq cm and high power densities (greater than 1 W/sq cm) in PEM fuel cells with high (4 mg/sq cm) or low (0.4 mg/sq cm) platinum loadings in electrodes. The following areas are discussed: (1) methods to obtain these high levels of performance with low Pt loading electrodes - by proton conductor impregnation into electrodes, localization of Pt near front surface; (2) a novel microelectrode technique which yields electrode kinetic parameters for oxygen reduction and mass transport parameters; (3) demonstration of lack of water transport from anode to cathode; (4) modeling analysis of PEM fuel cell for comparison with experimental results and predicting further improvements in performance; and (5) recommendations of needed research and development for achieving the above goals.

Low-Cost Flexible Nano-Sulfide/Carbon Composite Counter Electrode for Quantum-Dot-Sensitized Solar Cell

PubMed Central

2010-01-01

Cu2S nanocrystal particles were in situ deposited on graphite paper to prepare nano-sulfide/carbon composite counter electrode for CdS/CdSe quantum-dot-sensitized solar cell (QDSC). By optimization of deposition time, photovoltaic conversion efficiency up to 3.08% was obtained. In the meantime, this composite counter electrode was superior to the commonly used Pt, Au and carbon counter electrodes. Electrochemical impedance spectra further confirmed that low charge transfer resistance at counter electrode/electrolyte interface was responsible for this, implied the potential application of this composite counter electrode in high-efficiency QDSC. PMID:20672135

A methodology for investigating new nonprecious metal catalysts for PEM fuel cells.

PubMed

Susac, D; Sode, A; Zhu, L; Wong, P C; Teo, M; Bizzotto, D; Mitchell, K A R; Parsons, R R; Campbell, S A

2006-06-08

This paper reports an approach to investigate metal-chalcogen materials as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. The methodology is illustrated with reference to Co-Se thin films prepared by magnetron sputtering onto a glassy-carbon substrate. Scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) have been used, in parallel with electrochemical activity and stability measurements, to assess how the electrochemical performance relates to chemical composition. It is shown that Co-Se thin films with varying Se are active for oxygen reduction, although the open circuit potential (OCP) is lower than for Pt. A kinetically controlled process is observed in the potential range 0.5-0.7 V (vs reversible hydrogen electrode) for the thin-film catalysts studied. An initial exposure of the thin-film samples to an acid environment served as a pretreatment, which modified surface composition prior to activity measurements with the rotating disk electrode (RDE) method. Based on the SAM characterization before and after electrochemical tests, all surfaces demonstrating activity are dominated by chalcogen. XRD shows that the thin films have nanocrystalline character that is based on a Co(1-x)Se phase. Parallel studies on Co-Se powder supported on XC72R carbon show comparable OCP, Tafel region, and structural phase as for the thin-film model catalysts. A comparison for ORR activity has also been made between this Co-Se powder and a commercial Pt catalyst.

Laterally configured resistive switching device based on transition-metal nano-gap electrode on Gd oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakita, Masatoshi; Okabe, Kyota; Kimura, Takashi

2016-01-11

We have developed a fabrication process for a laterally configured resistive switching device based on a Gd oxide. A nano-gap electrode connected by a Gd oxide with the ideal interfaces has been created by adapting the electro-migration method in a metal/GdO{sub x} bilayer system. Bipolar set and reset operations have been clearly observed in the Pt/GdO{sub x} system similarly in the vertical device based on GdO{sub x}. Interestingly, we were able to observe a clear bipolar switching also in a ferromagnetic CoFeB nano-gap electrode with better stability compared to the Pt/GdO{sub x} device. The superior performance of the CoFeB/GdO{sub x}more » device implies the importance of the spin on the resistive switching.« less

The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

NASA Technical Reports Server (NTRS)

Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

1992-01-01

The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

Combinatorial electrochemical synthesis and screening of Pt-WO3 catalysts for electro-oxidation of methanol

NASA Astrophysics Data System (ADS)

Jayaraman, Shrisudersan; Baeck, Sung-Hyeon; Jaramillo, Thomas F.; Kleiman-Shwarsctein, Alan; McFarland, Eric W.

2005-06-01

An automated system for high-throughput electrochemical synthesis and screening of fuel cell electro-oxidation catalysts is described. This system consists of an electrode probe that contains counter and reference electrodes that can be positioned inside an array of electrochemical cells created within a polypropylene block. The electrode probe is attached to an automated of X-Y-Z motion system. An externally controlled potentiostat is used to apply the electrochemical potential to the catalyst substrate. The motion and electrochemical control are integrated using a user-friendly software interface. During automated synthesis the deposition potential and/or current may be controlled by a pulse program triggered by the software using a data acquisition board. The screening includes automated experiments to obtain cyclic voltammograms. As an example, a platinum-tungsten oxide (Pt-WO3) library was synthesized and characterized for reactivity towards methanol electro-oxidation.

Effect of Organic Cations on Hydrogen Oxidation Reaction of Carbon Supported Platinum

DOE PAGES

Chung, Hoon Taek; Choe, Yong-Kee; Martinez, Ulises; ...

2016-11-02

Effect of organic cations on hydrogen oxidation reaction (HOR) of carbon supported platinum (Pt/C) is investigated using three 0.1 M alkaline electrolytes, tetramethylammonium hydroxide (TMAOH), tetrabutylammonium hydroxide (TBAOH) and tetrabutylphosphonium hydroxide (TBPOH). Rotating disk electrode experiments indicate that the HOR of Pt/C is adversely impacted by time-dependent and potential-driven chemisorption of organic cations. In-situ infrared reflection adsorption spectroscopy experiments indicated that the specific chemisorption of organic cations drives the hydroxide co-adsorption on Pt surface. The co-adsorption of TMA + and hydroxide at 0.1 V vs. reversible hydrogen electrode is the strongest; consequently, complete removal of the co-adsorbed layer from Ptmore » surface is difficult even after exposure the Pt surface to 1.2 V. Conversely, the chemisorption of TBP+ is the weakest, yet notable decrease of HOR current density is still observed. The adsorption energies, ΔE, for TMA +, TBA +, and TBP + on Pt (111) surface from density functional theory are computed to be -2.79, -2.42 and -2.00 eV, respectively. The relatively low adsorption energy of TBP + is explained by the steric hindrance and electronic effect. This study emphasizes the importance of cationic group on HOR activity of alkaline anion exchange membrane fuel cells.« less

Chlorobenzene Poisoning and Recovery of Platinum-Based Cathodes in Proton Exchange Membrane Fuel Cells

PubMed Central

Zhai, Yunfeng; Baturina, Olga; Ramaker, David; Farquhar, Erik; St-Pierre, Jean; Swider-Lyons, Karen

2015-01-01

The platinum electrocatalysts found in proton exchange membrane fuel cells are poisoned both reversibly and irreversibly by air pollutants and residual manufacturing contaminants. In this work, the poisoning of a Pt/C PEMFC cathode was probed by a trace of chlorobenzene in the air feed. Chlorobenzene inhibits the oxygen reduction reaction and causes significant cell performance loss. The performance loss is largely restored by neat air operation and potential cycling between 0.08 V and 1.2 V under H2/N2 (anode/cathode). The analysis of emissions, in situ X-ray absorption spectroscopy and electrochemical impedance spectra show the chlorobenzene adsorption/reaction and molecular orientation on Pt surface depend on the electrode potential. At low potentials, chlorobenzene deposits either on top of adsorbed H atoms or on the Pt surface via the benzene ring and is converted to benzene (ca. 0.1 V) or cyclohexane (ca. 0 V) upon Cl removal. At potentials higher than 0.2 V, chlorobenzene binds to Pt via the Cl atom and can be converted to benzene (less than 0.3 V) or desorbed. Cl− is created and remains in the membrane electrode assembly. Cl− binds to the Pt surface much stronger than chlorobenzene, but can slowly be flushed out by liquid water. PMID:26388963

Highly Oriented Growth of Piezoelectric Thin Films on Silicon Using Two-Dimensional Nanosheets as Growth Template Layer.

PubMed

Nguyen, Minh D; Yuan, Huiyu; Houwman, Evert P; Dekkers, Matthijn; Koster, Gertjan; Ten Elshof, Johan E; Rijnders, Guus

2016-11-16

Ca 2 Nb 3 O 10 (CNOns) and Ti 0.87 O 2 (TiOns) metal oxide nanosheets (ns) are used as a buffer layer for epitaxial growth of piezoelectric capacitor stacks on Si and Pt/Ti/SiO 2 /Si (Pt/Si) substrates. Highly (001)- and (110)-oriented Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) films are achieved by utilizing CNOns and TiOns, respectively. The piezoelectric capacitors are characterized by polarization and piezoelectric hysteresis loops and by fatigue measurements. The devices fabricated with SrRuO 3 top and bottom electrodes directly on nanosheets/Si have ferroelectric and piezoelectric properties well comparable with devices that use more conventional oxide buffer layers (stacks) such as YSZ, CeO 2 /YSZ, or SrTiO 3 on Si. The devices grown on nanosheets/Pt/Si with Pt top electrodes show significantly improved polarization fatigue properties over those of similar devices grown directly on Pt/Si. The differences in properties are ascribed to differences in the crystalline structures and the density of the films. These results show a route toward the fabrication of single crystal piezoelectric thin films and devices with high quality, long-lifetime piezoelectric capacitor structures on nonperovskite and even noncrystalline substrates such as glass or polished metal surfaces.

Simultaneous determination of hydroxylamine and phenol using a nanostructure-based electrochemical sensor.

PubMed

Moghaddam, Hadi Mahmoudi; Beitollahi, Hadi; Tajik, Somayeh; Malakootian, Mohammad; Maleh, Hassan Karimi

2014-11-01

The electrochemical oxidation of hydroxylamine on the surface of a carbon paste electrode modified with carbon nanotubes and 2,7-bis(ferrocenyl ethyl)fluoren-9-one is studied. The electrochemical response characteristics of the modified electrode toward hydroxylamine and phenol were investigated. The results showed an efficient catalytic activity of the electrode for the electro-oxidation of hydroxylamine, which leads to lowering its overpotential. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for hydroxylamine and phenol. Also, the modified electrode was used for determination of hydroxylamine and phenol in some real samples.

Chemically modified graphite for electrochemical cells

DOEpatents

Greinke, R.A.; Lewis, I.C.

1998-05-26

This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (1) the electrode, (2) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (3) a counter electrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes. 3 figs.

High Temperature and High Sensitive NOx Gas Sensor with Hetero-Junction Structure using Laser Ablation Method

NASA Astrophysics Data System (ADS)

Gao, Wei; Shi, Liqin; Hasegawa, Yuki; Katsube, Teruaki

In order to develop a high temperature (200°C˜400°C) and high sensitive NOx gas sensor, we developed a new structure of SiC-based hetero-junction device Pt/SnO2/SiC/Ni, Pt/In2O3/SiC/Ni and Pt/WO3/SiC/Ni using a laser ablation method for the preparation of both metal (Pt) electrode and metal-oxide film. It was found that Pt/In2O3/SiC/Ni sensor shows higher sensitivity to NO2 gas compared with the Pt/SnO2/SiC/Ni and Pt/WO3/SiC/Ni sensor, whereas the Pt/WO3/SiC/Ni sensor had better sensitivity to NO gas. These results suggest that selective detection of NO and NO2 gases may be obtained by choosing different metal oxide films.

New Electrochemical Methods for Studying Nanoparticle Electrocatalysis and Neuronal Exocytosis

NASA Astrophysics Data System (ADS)

Cox, Jonathan T.

This dissertation presents the construction and application of micro and nanoscale electrodes for electroanalytical analysis. The studies presented herein encompass two main areas: electrochemical catalysis, and studies of the dynamics of single cell exocytosis. The first portion of this dissertation engages the use of Pt nanoelectrodes to study the stability and electrocatalytic properties of materials. A single nanoparticle electrode (SNPE) was fabricated by immobilizing a single Au nanoparticle on a Pt disk nanoelectrode via an amine-terminated silane cross linker. In this manner we were able to effectively study the electrochemistry and electrocatalytic activity of single Au nanoparticles and found that the electrocatalytic activity is dependent on nanoparticle size. This study can further the understanding of the structure-function relationship in nanoparticle based electrocatalysis. Further work was conducted to probe the stability of Pt nanoelectrodes under conditions of potential cycling. Pt based catalysts are known to deteriorate under such conditions due to losses in electrochemical surface area and Pt dissolution. By using Pt disk nanoelectrodes we were able to study Pt dissolution via steady-state voltammetry. We observed an enhanced dissolution rate and higher charge density on nanoelectrodes than that previously found on macro scale electrodes. The goal of the second portion of this dissertation is to develop new analytical methods to study the dynamics of exocytosis from single cells. The secretion of neurotransmitters plays a key role in neuronal communication, and our studies highlight how bipolar electrochemistry can be employed to enhance detection of neurotransmitters from single cells. First, we developed a theory to quantitatively characterize the voltammetric behavior of bipolar carbon fiber microelectrodes and secondly applied those principles to single cell detection. We showed that by simply adding an additional redox mediator to the back-fill solution of a carbon fiber microelectrode, there is a significant enhancement in detection. Additionally we used solid state nanopores to detect individual phospholipid vesicles in solution. Vesicles are key cellular components that play essential biological roles especially in neurotransmission. This work represents preliminary studies in detection and size determination from vesicles isolated from individual cells.

Improvement on the Repair Effect of Electrochemical Chloride Extraction Using a Modified Electrode Configuration

PubMed Central

Feng, Wei; Xu, Jinxia; Jiang, Linhua; Song, Yingbin; Cao, Yalong; Tan, Qiping

2018-01-01

To improve the repair effect of electrochemical chloride extraction, a modified electrode configuration is applied in this investigation. In this configuration, two auxiliary electrodes placed in the anodic and cathodic electrolytes were used as the anode and cathode, respectively. Besides this, the steel in the mortar was grounded to protect it from corrosion. By a comparative experiment, the potential evolution, various ions concentrations (Cl−, OH−, Na+, and K+) in different mortar depths, the corrosion potential, and the current density of the steel were measured. The results indicate that compared to electrochemical chloride extraction with the traditional electrode configuration, this electrochemical chloride extraction method with a modified electrode configuration has a similar chloride removal ratio. Besides this, potential of steel is just about 800 mV for a saturated calomel electrode (SCE) during the treatment, which did not reach the hydrogen evolution potential. The phenomenon of the accumulation of OH−, Na+, and K+ did not occur when the modified electrode configuration is applied. Additionally, higher corrosion potentials and lower corrosion current rates were measured after performing electrochemical chloride extraction with the modified electrode configuration. Additionally, it is a short period of time for the steel to go from activation to passivation. On this basis, the modified electrode configuration may overcome the drawbacks of electrochemical chloride extraction. PMID:29389855

Diamond-like carbon (DLC) thin film bioelectrodes: effect of thermal post-treatments and the use of Ti adhesion layer.

PubMed

Laurila, Tomi; Rautiainen, Antti; Sintonen, Sakari; Jiang, Hua; Kaivosoja, Emilia; Koskinen, Jari

2014-01-01

The effect of thermal post-treatments and the use of Ti adhesion layer on the performance of thin film diamond like carbon bioelectrodes (DLC) have been investigated in this work. The following results were obtained: (i) The microstructure of the DLC layer after the deposition was amorphous and thermal annealing had no marked effect on the structure, (ii) formation of oxygen containing SiOx and Ti[O,C] layers were detected at the Si/Ti and Ti/DLC interfaces with the help of transmission electron microscope (TEM), (iii) thermal post-treatments increased the polar fraction of the surface energy, (iv) cyclic voltammetry (CV) measurements showed that the DLC films had wide water windows and were stable in contact with dilute sulphuric acid and phosphate buffered saline (PBS) solutions, (v) use of Ti interlayer between Pt(Ir) microwire and DLC layer was crucial for the electrodes to survive the electrochemical measurements without the loss of adhesion of the DLC layer, (vi) DLC electrodes with small exposed Pt areas were an order of magnitude more sensitive towards dopamine than Pt electrodes and (vii) thermal post-treatments did not markedly change the electrochemical behavior of the electrodes despite the significant increase in the polar nature of the surfaces. It can be concluded that thin DLC bioelectrodes are stable under physiological conditions and can detect dopamine in micro molar range, but their sensitivity must be further improved. © 2013 Elsevier B.V. All rights reserved.

Fabrication, characterisation and voltammetric studies of gold amalgam nanoparticle modified electrodes.

PubMed

Welch, Christine M; Nekrassova, Olga; Dai, Xuan; Hyde, Michael E; Compton, Richard G

2004-09-20

The tabrication, characterisation, and electroanalytical application of gold and gold amalgam nanoparticles on glassy carbon electrodes is examined. Once the deposition parameters for gold nanoparticle electrodes were optimised, the analytical utility of the electrodes was examined in CrIII electroanalysis. It was found that gold nanoparticle modified (Au-NM) electrodes possess higher sensitivity than gold macroelectrodes. In addition, gold amalgam nanoparticle modified (AuHg-NM) electrodes were fabricated and characterised. The response of those electrodes was recorded in the presence of important environmental analytes (heavy metal cations). It was found AuHg-NM electrodes demonstrate a unique voltammetric behaviour and can be applied for electroanalysis when enhanced sensitivity is crucial.

CHROMIUM ELECTROANALYSIS AT SCREEN PRINTED ELECTRODE MODIFIED BY THIN FILMS OF NICKEL

EPA Science Inventory

A rapid and potentially cost-effective electrochemical method is reported for analysis of chromium (VI) and Chromium(III) using a nickel modified screen printed carbon ink electrode. Electrochemical characteristics of nickel modified electrode as well voltammetric behavior f...

Ferroelectric enhancement in heterostructured ZnO /BiFeO3-PbTiO3 film

NASA Astrophysics Data System (ADS)

Yu, Shengwen; Chen, Rui; Zhang, Guanjun; Cheng, Jinrong; Meng, Zhongyan

2006-11-01

The authors have prepared heterostructured ZnO /BiFeO3-PbTiO3 (BFO-PT) composite film and BFO-PT film on Pt /Ti/SiO2/Si substrates by pulsed-laser deposition. The structure and morphologies of the films were characterized by x-ray diffraction (XRD) and scanning electron microscope. XRD results show that both films are perovskite structured last with different orientations. The leakage current density in the ZnO /BFO-PT film was found to be nearly two orders of magnitude lower. This could be due to the introduced ZnO layer behaving as a Schottky barrier between the BFO-PT film and top electrodes. The dramatic ferroelectric enhancement in ZnO /BFO-PT film is mostly ascribed to the improved insulation.

Negative differential resistance effect induced by metal ion implantation in SiO2 film for multilevel RRAM application

NASA Astrophysics Data System (ADS)

Wu, Facai; Si, Shuyao; Shi, Tuo; Zhao, Xiaolong; Liu, Qi; Liao, Lei; Lv, Hangbing; Long, Shibing; Liu, Ming

2018-02-01

Pt/SiO2:metal nanoparticles/Pt sandwich structure is fabricated with the method of metal ion (Ag) implantation. The device exhibits multilevel storage with appropriate R off/R on ratio, good endurance and retention properties. Based on transmission electron microscopy and energy dispersive spectrometer analysis, we confirm that Pt nanoparticles are spurted into SiO2 film from Pt bottom electrode by Ag implantation; during electroforming, the local electric field can be enhanced by these Pt nanoparticles, meanwhile the Ag nanoparticles constantly migrate toward the Pt nanoparticles. The implantation induced nanoparticles act as trap sites in the resistive switching layer and play critical roles in the multilevel storage, which is evidenced by the negative differential resistance effect in the current-voltage (I-V) measurements.

Optically transparent FTO-free cathode for dye-sensitized solar cells.

PubMed

Kavan, Ladislav; Liska, Paul; Zakeeruddin, Shaik M; Grätzel, Michael

2014-12-24

The woven fabric containing electrochemically platinized tungsten wire is an affordable flexible cathode for liquid-junction dye-sensitized solar cells with the I3(-)/I(-) redox mediator and electrolyte solution consisting of ionic liquids and propionitrile. The fabric-based electrode outperforms the thermally platinized FTO in serial ohmic resistance and charge-transfer resistance for triiodide reduction, and it offers comparable or better optical transparency in the visible and particularly in the near-IR spectral region. The electrode exhibits good stability during electrochemical loading and storage at open circuit. The dye-sensitized solar cells with a C101-sensitized titania photoanode and either Pt-W/PEN or Pt-FTO cathodes show a comparable performance.

Electrochemical detection of dopamine in the presence of ascorbic acid using graphene modified electrodes.

PubMed

Kim, Yang-Rae; Bong, Sungyool; Kang, Yeon-Joo; Yang, Yongtak; Mahajan, Rakesh Kumar; Kim, Jong Seung; Kim, Hasuck

2010-06-15

Dopamine plays a significant role in the function of human metabolism. It is important to develop sensitive sensor for the determination of dopamine without the interference by ascorbic acid. This paper reports the synthesis of graphene using a modified Hummer's method and its application for the electrochemical detection of dopamine. Electrochemical measurements were performed at glassy carbon electrode modified with graphene via drop-casting method. Cyclic voltammogram of ferri/ferrocyanide redox couple at graphene modified electrode showed an increased current intensity compared with glassy carbon electrode and graphite modified electrode. The decrease of charge transfer resistance was also analyzed by electrochemical impedance spectroscopy. The capacity of graphene modified electrode for selective detection of dopamine was confirmed in a sufficient amount of ascorbic acid (1 mM). The observed linear range for the determination of dopamine concentration was from 4 microM to 100 microM. The detection limit was estimated to be 2.64 microM. Copyright 2010 Elsevier B.V. All rights reserved.

A Palladium-Tin Modified Microband Electrode Array for Nitrate Determination

PubMed Central

Fu, Yexiang; Bian, Chao; Kuang, Jian; Wang, Jinfen; Tong, Jianhua; Xia, Shanhong

2015-01-01

A microband electrode array modified with palladium-tin bimetallic composite has been developed for nitrate determination. The microband electrode array was fabricated by Micro Electro-Mechanical System (MEMS) technique. Palladium and tin were electrodeposited successively on the electrode, forming a double-layer structure. The effect of the Pd-Sn composite was investigated and its enhancement of catalytic activity and lifetime was revealed. The Pd-Sn modified electrode showed good linearity (R2 = 0.998) from 1 mg/L to 20 mg/L for nitrate determination with a sensitivity of 398 μA/(mg∙L−1∙cm2). The electrode exhibited a satisfying analytical performance after 60 days of storage, indicating a long lifetime. Good repeatability was also displayed by the Pd-Sn modified electrodes. The results provided an option for nitrate determination in water. PMID:26389904

Stabilization of electrogenerated copper species on electrodes modified with quantum dots.

PubMed

Martín-Yerga, Daniel; Costa-García, Agustín

2017-02-15

Quantum dots (QDs) have special optical, surface, and electronic properties that make them useful for electrochemical applications. In this work, the electrochemical behavior of copper in ammonia medium is described using bare screen-printed carbon electrodes and the same modified with CdSe/ZnS QDs. At the bare electrodes, the electrogenerated Cu(i) and Cu(0) species are oxidized by dissolved oxygen in a fast coupled chemical reaction, while at the QDs-modified electrode, the re-oxidation of Cu(i) and Cu(0) species can be observed, which indicates that they are stabilized by the nanocrystals present on the electrode surface. A weak adsorption is proposed as the main cause for this stabilization. The electrodeposition on electrodes modified with QDs allows the generation of random nanostructures with copper nanoparticles, avoiding the preferential nucleation onto the most active electrode areas.

Same-View Nano-XAFS/STEM-EDS Imagings of Pt Chemical Species in Pt/C Cathode Catalyst Layers of a Polymer Electrolyte Fuel Cell.

PubMed

Takao, Shinobu; Sekizawa, Oki; Samjeské, Gabor; Nagamatsu, Shin-ichi; Kaneko, Takuma; Yamamoto, Takashi; Higashi, Kotaro; Nagasawa, Kensaku; Uruga, Tomoya; Iwasawa, Yasuhiro

2015-06-04

We have made the first success in the same-view imagings of 2D nano-XAFS and TEM/STEM-EDS under a humid N2 atmosphere for Pt/C cathode catalyst layers in membrane electrode assemblies (MEAs) of polymer electrolyte fuel cells (PEFCs) with Nafion membrane to examine the degradation of Pt/C cathodes by anode gas exchange cycles (start-up/shut-down simulations of PEFC vehicles). The same-view imaging under the humid N2 atmosphere provided unprecedented spatial information on the distribution of Pt nanoparticles and oxidation states in the Pt/C cathode catalyst layer as well as Nafion ionomer-filled nanoholes of carbon support in the wet MEA, which evidence the origin of the formation of Pt oxidation species and isolated Pt nanoparticles in the nanohole areas of the cathode layer with different Pt/ionomer ratios, relevant to the degradation of PEFC catalysts.

Cathodic and anodic biofilms in Single Chamber Microbial Fuel Cells.

PubMed

Cristiani, P; Carvalho, M L; Guerrini, E; Daghio, M; Santoro, C; Li, B

2013-08-01

The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation. Copyright © 2012 Elsevier B.V. All rights reserved.

Sustained Resistive Switching in a Single Cu:7,7,8,8-tetracyanoquinodimethane Nanowire: A Promising Material for Resistive Random Access Memory

PubMed Central

Basori, Rabaya; Kumar, Manoranjan; Raychaudhuri, Arup K.

2016-01-01

We report a new type of sustained and reversible unipolar resistive switching in a nanowire device made from a single strand of Cu:7,7,8,8-tetracyanoquinodimethane (Cu:TCNQ) nanowire (diameter <100 nm) that shows high ON/OFF ratio (~103), low threshold voltage of switching (~3.5 V) and large cycling endurance (>103). This indicates a promising material for high density resistive random access memory (ReRAM) device integration. Switching is observed in Cu:TCNQ single nanowire devices with two different electrode configuration: symmetric (C-Pt/Cu:TCNQ/C-Pt) and asymmetric (Cu/Cu:TCNQ/C-Pt), where contacts connecting the nanowire play an important role. This report also developed a method of separating out the electrode and material contributions in switching using metal-semiconductor-metal (MSM) device model along with a direct 4-probe resistivity measurement of the nanowire in the OFF as well as ON state. The device model was followed by a phenomenological model of current transport through the nanowire device which shows that lowering of potential barrier at the contacts likely occur due to formation of Cu filaments in the interface between nanowire and contact electrodes. We obtain quantitative agreement of numerically analyzed results with the experimental switching data. PMID:27245099

Glucose sensing based on Pt-MWCNT and MWCNT

NASA Astrophysics Data System (ADS)

Aryasomayajula, Lavanya; Xie, Jining; Wang, Shouyan; Varadan, Vijay K.

2007-04-01

It is known that multi walled carbon nanotubes (MWCNTs) is an excellent materials for biosensing applications and with the introduction of Pt nanoparticles (Pt-MWCNTs) of about 3nm in diameter in MWCNTs greatly increases the current sensitivity and also the signal to noise ratio. We fabricated the CNT- based glucose sensor by immobilization the bio enzyme, glucose oxidase (GoX), on the Pt-MWCNT and electrode were prepared. The sensor has been tested effectively for both the abnormal blood glucose levels- greater than 6.9 mM and less than 3.5 mM which are the prediabetic and diabetic glucose levels, respectively. The current signal obtained from the Pt-MWCNT was much higher compared to the MWCNT based sensors.

Metallofullerenes as fuel cell electrocatalysts: a theoretical investigation of adsorbates on C59Pt.

PubMed

Gabriel, Margaret A; Genovese, Luigi; Krosnicki, Guillaume; Lemaire, Olivier; Deutsch, Thierry; Franco, Alejandro A

2010-08-28

Nano-structured electrode degradation in state-of-the-art polymer electrolyte membrane fuel cells (PEMFCs) is one of the main shortcomings that limit the large-scale development and commercialization of this technology. During normal operating conditions of the fuel cell, the PEMFC lifetime tends to be limited by coarsening of the cathode's Pt-based catalyst and by corrosion of the cathode's carbon black support. Because of their chemical properties, metallofullerenes such as C(59)Pt may be more electrochemically stable than the Pt/C mixture. In this paper we investigate, by theoretical methods, the stability of oxygen reduction reaction (ORR) adsorbates on the metallofullerene C(59)Pt and evaluate its potential as a PEMFC fuel cell catalyst.

Scanning Tunneling Microscopy and Infrared Spectroscopy as Combined In- Situ Probes of Electrochemical Adlayer Structure: Cyanide on PT(111)

DTIC Science & Technology

1994-02-01

electrochemically etched in near- saturated CaC1 2 and coated with a thermosetting plastic[13]. The quasi-reference electrode was a gold wire. The Pt(lll...annealing procedure, display arrays of small (ca 3-5 nm) terrace domains, these being separated from each other by monoatomic steps running in various

Hollow optical fiber induced solar cells with optical energy storage and conversion.

PubMed

Ding, Jie; Zhao, Yuanyuan; Duan, Jialong; Duan, Yanyan; Tang, Qunwei

2017-11-09

Hollow optical fiber induced dye-sensitized solar cells are made by twisting Ti wire/N719-TiO 2 nanotube photoanodes and Ti wire/Pt (CoSe, Pt 3 Ni) counter electrodes, yielding a maximized efficiency of 0.7% and good stability. Arising from optical energy storage ability, the solar cells can generate electricity without laser illumination.

Spin injection into Pt-polymers with large spin-orbit coupling

NASA Astrophysics Data System (ADS)

Sun, Dali; McLaughlin, Ryan; Siegel, Gene; Tiwari, Ashutosh; Vardeny, Z. Valy

2014-03-01

Organic spintronics has entered a new era of devices that integrate organic light-emitting diodes (OLED) in organic spin valve (OSV) geometry (dubbed bipolar organic spin valve, or spin-OLED), for actively manipulating the device electroluminescence via the spin alignment of two ferromagnetic electrodes (Science 337, 204-209, 2012; Appl. Phys. Lett. 103, 042411, 2013). Organic semiconductors that contain heavy metal elements have been widely used as phosphorescent dopants in white-OLEDs. However such active materials are detrimental for OSV operation due to their large spin-orbit coupling (SOC) that may limit the spin diffusion length and thus spin-OLED based on organics with large SOC is a challenge. We report the successful fabrication of OSVs based on pi-conjugated polymers which contain intrachain Platinum atoms (dubbed Pt-polymers). Spin injection into the Pt-polymers is investigated by the giant magnetoresistance (GMR) effect as a function of bias voltage, temperature and polymer layer thickness. From the GMR bias voltage dependence we infer that the ``impendence mismatch'' between ferromagnetic electrodes and Pt-polymer may be suppressed due to the large SOC. Research sponsored by the NSF (Grant No. DMR-1104495) and NSF-MRSEC (DMR 1121252) at the University of Utah.

Nitrogen-doped graphdiyne as a metal-free catalyst for high-performance oxygen reduction reactions

NASA Astrophysics Data System (ADS)

Liu, Rongji; Liu, Huibiao; Li, Yuliang; Yi, Yuanping; Shang, Xinke; Zhang, Shuangshuang; Yu, Xuelian; Zhang, Suojiang; Cao, Hongbin; Zhang, Guangjin

2014-09-01

Fuel cells and metal-air batteries will only become widely available in everyday life when the expensive platinum-based electrocatalysts used for the oxygen reduction reactions are replaced by other efficient, low-cost and stable catalysts. We report here the use of nitrogen-doped graphdiyne as a metal-free electrode with a comparable electrocatalytic activity to commercial Pt/C catalysts for the oxygen reduction reaction in alkaline fuel cells. Nitrogen-doped graphdiyne has a better stability and increased tolerance to the cross-over effect than conventional Pt/C catalysts.Fuel cells and metal-air batteries will only become widely available in everyday life when the expensive platinum-based electrocatalysts used for the oxygen reduction reactions are replaced by other efficient, low-cost and stable catalysts. We report here the use of nitrogen-doped graphdiyne as a metal-free electrode with a comparable electrocatalytic activity to commercial Pt/C catalysts for the oxygen reduction reaction in alkaline fuel cells. Nitrogen-doped graphdiyne has a better stability and increased tolerance to the cross-over effect than conventional Pt/C catalysts. Electronic supplementary information (ESI) available: Detailed RDE and RRDE experiments, additional tables and figures. See DOI: 10.1039/c4nr03185g

Investigation on direct electrochemical and electrocatalytic behavior of hemoglobin on palladium-graphene modified electrode.

PubMed

Chen, Wei; Niu, Xueliang; Li, Xiaoyan; Li, Xiaobao; Li, Guangjiu; He, Bolin; Li, Qiutong; Sun, Wei

2017-11-01

Palladium-graphene (Pd-GR) nanocomposite was acted as modifier for construction of the modified electrode with direct electrochemistry of hemoglobin (Hb) realized. By using Nafion as the immobilization film, Hb was fixed tightly on Pd-GR nanocomposite modified carbon ionic liquid electrode. Electrochemical behaviors of Hb modified electrode were checked by cyclic voltammetry and a pair of redox peaks originated from direct electron transfer of Hb was appeared. The Hb modified electrode had excellent electrocatalytic activity to the reduction of trichloroacetic acid and sodium nitrite in the concentration range from 0.6 to 13.0mmol·L -1 and from 0.04 to 0.5 mmol·L -1 . Therefore Pd-GR nanocomposite was proven to be a good candidate for the fabrication of third-generation electrochemical biosensor. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation of hemoglobin-modified boron-doped diamond for acrylamide biosensors

NASA Astrophysics Data System (ADS)

Umam, K.; Saepudin, E.; Ivandini, T. A.

2017-04-01

Boron-doped diamond (BDD) electrode was modified with haemoglobin to develop electrochemical biosensors of acrylamide. Prior to modify with haemoglobin, the BDD was modified by gold nanoparticles to increase the affinity of BDD against haemoglobin. The electrochemical behaviour of the electrode in the presence of acrylamide was studied in comparison to haemoglobin-modified gold electrodes. Cyclic voltammetry indicated the optimum responses in 0.1 M sodium acetate buffer at pH 5. The responses were linear to the acrylamide concentration range of 5-50 μM with an estimated detection limit of 5.14 μM, suggesting that the electrode was promising for acrylamide biosensors.

Electrochemiluminescence of luminol at the titanate nanotubes modified glassy carbon electrode.

PubMed

Xu, Guifang; Zeng, Xiaoxue; Lu, Shuangyan; Dai, Hong; Gong, Lingshan; Lin, Yanyu; Wang, Qingping; Tong, Yuejin; Chen, Guonan

2013-01-01

A new strategy for the construction of a sensitive and stable electrochemiluminescent platform based on titanate nanotubes (TNTs) and Nafion composite modified electrode for luminol is described, TNTs contained composite modified electrodes that showed some photocatalytic activity toward luminol electrochemiluminescence emission, and thus could dramatically enhance luminol light emission. This extremely sensitive and stable platform allowed a decrease of the experiment electrochemiluminescence luminol reagent. In addition, in luminol solution at low concentrations, we compared the capabilities of a bare glassy carbon electrode with the TNT composite modified electrode for hydrogen peroxide detection. The results indicated that compared with glassy carbon electrode this platform was extraordinarily sensitive to hydrogen peroxide. Therefore, by combining with an appropriate enzymatic reaction, this platform would be a sensitive matrix for many biomolecules.

Imprinted zeolite modified carbon paste electrode as a potentiometric sensor for uric acid

NASA Astrophysics Data System (ADS)

Khasanah, Miratul; Widati, Alfa Akustia; Fitri, Sarita Aulia

2016-03-01

Imprinted zeolite modified carbon paste electrode (carbon paste-IZ) has been developed and applied to determine uric acid by potentiometry. The imprinted zeolite (IZ) was synthesized by the mole ratio of uric acid/Si of 0.0306. The modified electrode was manufactured by mass ratio of carbon, IZ and solid paraffin was 40:25:35. The modified electrode had shown the measurement range of 10-5 M to 10-2 M with Nernst factor of 28.6 mV/decade, the detection limit of 5.86 × 10-6 M and the accuracy of 95.3 - 105.0%. Response time of the electrode for uric acid 10-5 M - 10-2 M was 25 - 44 s. The developed electrode showed the high selectivity toward uric acid in the urea matrix. Life time of the carbon paste-IZ electrode was 10 weeks.

Faraday efficiency and mechanism of electrochemical surface reactions: CO2 reduction and H2 formation on Pt(111).

PubMed

Hussain, Javed; Jónsson, Hannes; Skúlason, Egill

2016-12-22

An atomic scale model of the electrical double layer is used to calculate the mechanism and rate of electrochemical reduction of CO 2 as well as H 2 formation at a Pt(111) electrode. The water layer contains solvated protons and the electrode has excess electrons at the surface. Density functional theory within the generalized gradient approximation is used to describe the electronic structure while the mechanism and activation energy of the various elementary reactions is obtained by calculating minimum energy paths using the nudged elastic band method. The applied electrical potential is deduced from the calculated work function. The optimal reaction mechanism for CO 2 reduction to either methane or methanol is found and the estimated rate compared with that of the competing reaction, H 2 formation. When the free energy of only the intermediates and reactants is taken into account, not the activation energy, Pt(111) would seem to be a good electrocatalyst for CO 2 reduction, significantly better than Cu(111). This, however, contradicts experimental findings. Detailed calculations reported here show that the activation energy for CO 2 reduction is high for both Heyrovsky and Tafel mechanisms on Pt(111) in the relevant range of applied potential. The rate-limiting step of the Heyrovsky mechanism, *COOH + H + + e - → *CO + H 2 O, is estimated to have an activation energy of 0.95 eV at -0.9 V vs. standard hydrogen electrode. Under the same conditions, the activation energy for H 2 formation is estimated to be only 0.5 eV. This explains why attempts to reduce CO 2 using platinum electrodes have produced only H 2 . A comparison is made with analogous results for Cu(111) [J. Hussain et al., Procedia Comput. Sci., 2015, 51, 1865] where a reaction mechanism with low activation energy for CO 2 electroreduction to methane was identified. The difference between the two electrocatalysts is discussed.

Structural and electrochemical characterization of carbon supported Pt-Pr catalysts for direct ethanol fuel cells prepared using a modified formic acid method in a CO atmosphere.

PubMed

Corradini, Patricia Gon; Antolini, Ermete; Perez, Joelma

2013-07-28

Pt-Pr/C electrocatalysts were prepared using a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation was compared to Pt/C. No appreciable alloy formation was detected by XRD analysis. By TEM measurements it was found that Pt particle size increases with an increasing Pr content in the catalysts and with decreasing metal precursor addition time. XPS measurements indicated Pt segregation on the catalyst surface and the presence of Pr2O3 and PrO2 oxides. The addition of Pr increased the electro-catalytic activity of Pt for both CO and CH3CH2OH oxidation. The enhanced activity of Pt-Pr/C catalysts was ascribed to both an electronic effect, caused by the presence of Pr2O3, and the bi-functional mechanism, caused by the presence of PrO2.

Development of amperometric lysine biosensors based on Au nanoparticles/multiwalled carbon nanotubes/polymers modified Au electrodes.

PubMed

Chauhan, Nidhi; Singh, Anamika; Narang, Jagriti; Dahiya, Swati; Pundir, C S

2012-11-07

The construction of two amperometric l-lysine biosensors is described in this study. The construction comprises the covalent immobilization of lysine oxidase (LOx) onto nanocomposite composed of gold nanoparticles (AuNPs) and carboxylated multiwalled carbon nanotubes (c-MWCNT), decorated on (i) polyaniline (PANI) and (ii) poly 1,2 diaminobenzene (DAB), electrodeposited on Au electrodes. The biosensors were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and electrochemical impedance spectroscopy (EIS) studies. The optimum response (current) was observed within 2 s at pH 7.0 and 25 °C for LOx/AuNPs/c-MWCNT/PANI/Au, and 4 s at pH 7.0 and 30 °C for LOx/AuNPs/c-MWCNT/DAB/Au electrodes. There was a linear relationship between current and lysine concentration ranging from 5.0 to 600 μM for LOx/AuNPs/c-MWCNT/PANI/Au with a detection limit of 5.0 μM, and 20 to 600 μM for the LOx/AuNPs/c-MWCNT/DAB/Au electrode with a detection limit of 20 μM. The PANI modified electrode was in good agreement with the standard HPLC method, with a better correlation (r = 0.992) compared to the DAB modified electrode (r = 0.986). These observations revealed that the PANI modified Au electrode was better than the DAB modified electrode, and hence it was employed for the determination of lysine in milk, pharmaceutical tablets and sera. The PANI modified electrode showed a half life of 120 days, compared to that of 90 days for the DAB modified electrode, after their 100 uses, when stored at 4 °C.

A hybrid nanostructure of platinum-nanoparticles/graphitic-nanofibers as a three-dimensional counter electrode in dye-sensitized solar cells.

PubMed

Hsieh, Chien-Kuo; Tsai, Ming-Chi; Su, Ching-Yuan; Wei, Sung-Yen; Yen, Ming-Yu; Ma, Chen-Chi M; Chen, Fu-Rong; Tsai, Chuen-Horng

2011-11-07

We directly synthesized a platinum-nanoparticles/graphitic-nanofibers (PtNPs/GNFs) hybrid nanostructure on FTO glass. We applied this structure as a three-dimensional counter electrode in dye-sensitized solar cells (DSSCs), and investigated the cells' photoconversion performance. This journal is © The Royal Society of Chemistry 2011

Polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Gottesfeld, S.

The recent increase in attention to polymer electrolyte fuel cells (PEFC's) is the result of significant technical advances in this technology and the initiation of some projects for the demonstration of complete PEFC-based power system in a bus or in a passenger car. A PEFC powered vehicle has the potential for zero emission, high energy conversion efficiency and extended range compared to present day battery powered EV's. This paper describes recent achievements in R&D on PEFC's. The major thrust areas have been: (1) demonstration of membrane/electrode assemblies with stable high performance in life tests lasting 4000 hours, employing ultra-low Pt loadings corresponding to only 1/2 oz of Pt for the complete power source of a passenger car; (2) effective remedies for the high sensitivity of the Pt electrocatalyst to impurities in the fuel feed stream; and (3) comprehensive evaluation of the physicochemical properties of membrane and electrodes in the PEFC, clarifying the water management issues and enabling effective codes and diagnostics for this fuel cell.

Colloidal Au and Au-alloy catalysts for direct borohydride fuel cells: Electrocatalysis and fuel cell performance

NASA Astrophysics Data System (ADS)

Atwan, Mohammed H.; Macdonald, Charles L. B.; Northwood, Derek O.; Gyenge, Elod L.

Supported colloidal Au and Au-alloys (Au-Pt and Au-Pd, 1:1 atomic ratio) on Vulcan XC-72 (with 20 wt% metal load) were prepared by the Bönneman method. The electrocatalytic activity of the colloidal metals with respect to borohydride electro-oxidation for fuel cell applications was investigated by voltammetry on static and rotating electrodes, chronoamperometry, chronopotentiometry and fuel cell experiments. The fundamental electrochemical techniques showed that alloying Au, a metal that leads to the maximum eight-electron oxidation of BH 4 -, with Pd or Pt, well-known catalysts of dehydrogenation reactions, improved the electrode kinetics of BH 4 - oxidation. Fuel cell experiments corroborated the kinetic studies. Using 5 mg cm -2 colloidal metal load on the anode, it was found that Au-Pt was the most active catalyst giving a cell voltage of 0.47 V at 100 mA cm -2 and 333 K, while under identical conditions the cell voltage using colloidal Au was 0.17 V.

Laser synthesized super-hydrophobic conducting carbon with broccoli-type morphology as a counter-electrode for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Gokhale, Rohan; Agarkar, Shruti; Debgupta, Joyashish; Shinde, Deodatta; Lefez, Benoit; Banerjee, Abhik; Jog, Jyoti; More, Mahendra; Hannoyer, Beatrice; Ogale, Satishchandra

2012-10-01

A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode.A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode. Electronic supplementary information (ESI) available: Materials and equipment details, solar cell fabrication protocol, electrolyte spreading time measurement details, XPS spectra, electronic study, film adhesion test detailed analysis and field emission results. See DOI: 10.1039/c2nr32082g

Nitrogen-doped graphene anchored with mixed growth patterns of CuPt alloy nanoparticles as a highly efficient and durable electrocatalyst for the oxygen reduction reaction in an alkaline medium.

PubMed

Illathvalappil, Rajith; Dhavale, Vishal M; Bhange, Siddheshwar N; Kurungot, Sreekumar

2017-07-06

A highly active and durable CuPt alloy catalyst with trigonal bipyramidal and truncated cube-type mixed morphologies, anchored on the nitrogen-doped graphene (NGr) surface (CuPt-TBTC/NGr), was prepared by a simple and fast method. The obtained CuPt alloy showed improved oxygen reduction reaction (ORR) activity, with a 30 mV positive shift in the half-wave potential value, as compared to the state-of-the-art Pt/C catalyst in a 0.1 M KOH solution. The CuPt alloy with the trigonal bipyramidal morphology possesses porous type inter-connected sides, which help to achieve improved mass transport of oxygen during the ORR. The exposure of the (111) plane of the CuPt alloy further improved the catalytic activity towards the dioxygen reduction in alkaline media. The ORR activity of the NGr-supported CuPt alloy was found to be dependent on the reaction time, and improved activity was obtained on the material derived at a reaction time of 90 min (CuPt-TBTC/NGr-90). The material synthesized at a lower or higher reaction time than 90 min resulted in a partially formed trigonal bipyramidal morphology with more truncated cubes or agglomerated trigonal bipyramidal and truncated cubes with closed type structures, respectively. Along with the high intrinsic ORR activity, CuPt-TBTC/NGr-90 displayed excellent electrochemical stability. Even after repeated 1000 potential cycling in a window ranging from 0.10 to 1.0 V (vs. RHE), the system clearly outperformed the state-of-the-art Pt/C catalyst with 15 and 60 mV positive shifts in the onset and half-wave potentials, respectively. CuPt-TBTC/NGr-90 also exhibited 2.1 times higher mass activity and 2.2 times higher specific activity, compared to Pt/C at 0.90 V (vs. RHE). Finally, a zinc-air battery fabricated with the alloy catalyst as the air electrode displayed a peak power density of 300 mW cm -2 , which is much higher than the peak power density of 253 mW cm -2 obtained for the state-of-the-art Pt/C catalyst as the air electrode.

Controlling Shape and Plasmon Resonance of Pt-Etched Au@Ag Nanorods.

PubMed

Ye, Rongkai; Zhang, Yanping; Chen, Yuyu; Tang, Liangfeng; Wang, Qiong; Wang, Qianyu; Li, Bishan; Zhou, Xuan; Liu, Jianyu; Hu, Jianqiang

2018-05-22

Pt-based catalysts with novel structure have attracted great attention due to their outstanding performance. In this work, H 2 PtCl 6 was used as both precursor and etching agent to realize the shape-controlled synthesis of Pt-modified Au@Ag nanorods (NRs). During the synthesis, the as-prepared Ag shell played a crucial role in both protecting the Au NRs from being etched away by PtCl 6 2- and leading to an unusual growth mode of Pt component. The site-specified etching and/or growth depended on the concentration of H 2 PtCl 6 , where high-yield core-shell structure or dumbbell-like structure could be obtained. The shape-controlled synthesis also led to a tunable longitudinal surface plasmon resonance from ca. 649 to 900 nm. Meanwhile, the core-shell Pt-modified Au@Ag NRs showed approximately 4-fold enhancement in catalytic reduction reaction of p-nitrophenol than that of the Au NRs, suggesting the great potential for photocatalytic reaction.

Application of three-dimensional reduced graphene oxide-gold composite modified electrode for direct electrochemistry and electrocatalysis of myoglobin.

PubMed

Shi, Fan; Xi, Jingwen; Hou, Fei; Han, Lin; Li, Guangjiu; Gong, Shixing; Chen, Chanxing; Sun, Wei

2016-01-01

In this paper a three-dimensional (3D) reduced graphene oxide (RGO) and gold (Au) composite was synthesized by electrodeposition and used for the electrode modification with carbon ionic liquid electrode (CILE) as the substrate electrode. Myoglobin (Mb) was further immobilized on the surface of 3D RGO-Au/CILE to obtain an electrochemical sensing platform. Direct electrochemistry of Mb on the modified electrode was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the modified electrode. The results can be ascribed to the presence of highly conductive 3D RGO-Au composite on the electrode surface that accelerate the electron transfer rate between the electroactive center of Mb and the electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.2 to 36.0 mmol/L with the detection limit of 0.06 mmol/L (3σ). Copyright © 2015 Elsevier B.V. All rights reserved.

Molecular dynamics simulations of the formation of 1D spin-valves from stretched Au-Co and Pt-Co nanowires

NASA Astrophysics Data System (ADS)

Cortes-Huerto, R.; Sondon, T.; Saúl, A.

2014-11-01

We have performed molecular dynamics (MD) simulations of stretched Aux-Co1 - x and Ptx-Co1 - x nanowires to investigate the formation of bimetallic monoatomic wires between two electrodes. We have considered nanowires with two concentrations x = 0.2 and 0.8, aspect ratio of 13, a cross section of 1 nm2 and a wide range of temperatures (from 10 to 400 K). For the MD simulations we have used a semi-empirical interatomic potential based on the second moment approximation (SMA) of the density of states to the tight-binding Hamiltonian. For Au-Co alloys, Au atoms tends to migrate towards the narrowed region to form almost pure Au wires. In the PtCo case the formed chains usually consist of Pt enriched alternating structures. The most striking result is probably the Au0.2-Co0.8 alloy where pure monoatomic Au chains form between two Co electrodes constituting a potential 1D spin valve. Despite the known ease with which the 5d metals (Pt, Ir, and Au) form monoatomic chains (MACS), our results show that in the presence of Co (x = 0.2), the percentage of chain formation is higher than in the Pt and Au rich cases (x = 0.8).

Synthesis of ZnO nanorods and their application in the construction of a nanostructure-based electrochemical sensor for determination of levodopa in the presence of carbidopa.

PubMed

Molaakbari, Elahe; Mostafavi, Ali; Beitollahi, Hadi; Alizadeh, Reza

2014-09-07

A novel carbon paste electrode modified with ZnO nanorods and 5-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4'-AAZCPE) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for the electrocatalytic oxidation of levodopa, is described. The electrode was employed to study the electrocatalytic oxidation of levodopa, using cyclic voltammetry (CV), chronoamperometry (CHA), and square-wave voltammetry (SWV) as diagnostic techniques. It has been found that the oxidation of levodopa at the surface of the modified electrode occurs at a potential of about 370 mV less positive than that of an unmodified carbon paste electrode. The SWV results exhibit a linear dynamic range from 1.0 × 10(-7) M to 7.0 × 10(-5) M and a detection limit of 3.5 × 10(-8) M for levodopa. In addition, this modified electrode was used for the simultaneous determination of levodopa and carbidopa. Finally, the modified electrode was used for the determination of levodopa and carbidopa in some real samples.

Electrochemical investigation of the voltammetric determination of hydrochlorothiazide using a nickel hydroxide modified nickel electrode.

PubMed

Machini, Wesley B S; David-Parra, Diego N; Teixeira, Marcos F S

2015-12-01

The preparation and electrochemical characterization of a nickel hydroxide modified nickel electrode as well as its behavior as electrocatalyst toward the oxidation of hydrochlorothiazide (HCTZ) were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of HCTZ were explored using cyclic voltammetry. The voltammetric response of the modified electrode in the detection of HCTZ is based on the electrochemical oxidation of the Ni(II)/Ni(III) and a chemical redox process. The analytical parameters for the electrooxidation of HCTZ by the nickel hydroxide modified nickel electrode were obtained in NaOH solution, in which the linear voltammetric response was in the concentration range from 1.39×10(-5) to 1.67×10(-4)mol L(-1) with a limit of detection of 7.92×10(-6)mol L(-1) and a sensitivity of 0.138 μA Lmmol(-1). Tafel analysis was used to elucidate the kinetics and mechanism of HCTZ oxidation by the modified electrode. Copyright © 2015 Elsevier B.V. All rights reserved.

One-Step Electrochemical Fabrication of Reduced Graphene Oxide/Gold Nanoparticles Nanocomposite-Modified Electrode for Simultaneous Detection of Dopamine, Ascorbic Acid, and Uric Acid

PubMed Central

Lee, Chang-Seuk; Yu, Su Hwan; Kim, Tae Hyun

2017-01-01

Here, we introduce the preparation of the hybrid nanocomposite-modified electrode consisting of reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) using the one-step electrochemical method, allowing for the simultaneous and individual detection of dopamine (DA), ascorbic acid (AA), and uric acid (UA). RGO/AuNPs nanocomposite was formed on a glassy carbon electrode by the co-reduction of GO and Au3+ using the potentiodynamic method. The RGO/AuNPs nanocomposite-modified electrode was produced by subjecting a mixed solution of GO and Au3+ to cyclic sweeping from −1.5 V to 0.8 V (vs. Ag/AgCl) at a scan rate 10 mV/s for 3 cycles. The modified electrode was characterized by scanning electron microscopy, Raman spectroscopy, contact angle measurement, electrochemical impedance spectroscopy, and cyclic voltammetry. Voltammetry results confirm that the RGO/AuNPs nanocomposite-modified electrode has high catalytic activity and good resolution for the detection of DA, AA, and UA. The RGO/AuNPs nanocomposite-modified electrode exhibits stable amperometric responses for DA, AA, and UA, respectively, and its detection limits were estimated to be 0.14, 9.5, and 25 μM. The modified electrode shows high selectivity towards the determination of DA, AA, or UA in the presence of potentially active bioelements. In addition, the resulting sensor exhibits many advantages such as fast amperometric response, excellent operational stability, and appropriate practicality. PMID:29301209

Comparison of iridium- and ruthenium-based, Pt-surface-enriched, nanosize catalysts for the oxygen-reduction reaction

NASA Astrophysics Data System (ADS)

Kaplan, D.; Goor, M.; Alon, M.; Tsizin, S.; Burstein, L.; Rosenberg, Y.; Popov, I.; Peled, E.

2016-02-01

Pt-surface-enriched nanosize catalysts (Pt-SENS catalysts) with ruthenium and iridium cores, supported on XC72, were synthesized and characterized. The structure and composition of the catalysts are determined by Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Scanning Transmission Electron Microscopy (STEM) and X-Ray Diffraction (XRD). Electrochemical characterization tests, including oxygen-reduction-catalysis activity and durability studies of catalysts are performed with the use of cyclic-voltammetry and rotating-disk-electrode (RDE) techniques at room temperature. The ORR activity of the homemade catalysts is also compared to ORR activity of commercial 50%Pt/C catalyst. It is determined that the Ir-based catalyst (Pt/Ir/XC72) shows higher ORR activity in terms of A g-1 of Pt (at 0.85 V vs. RHE) than the Ru-based catalyst (Pt/Ru/XC72) and the commercial 50%Pt/C. The Ru-based catalyst shows similar ORR activity in terms of A g-1 of Pt, to that of the commercial 50%Pt/C, but with much lower durability.

Characterization of the Ternary Compound Pd5Pt3Ni2 for PEMFC Cathode Electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarvis, Karalee; Zhao, J; Allard Jr, Lawrence Frederick

2010-01-01

Research on proton exchange membrane fuel cells (PEMFC) has increased over the last decade due to an increasing demand for alternative energy solutions. Most PEMFCs use Pt on carbon support as electrocatalysts for oxygen reduction reactions (ORR) [1]. Due to the high cost of Pt, there is a strong drive to develop less expensive catalysts that meet or exceed the performance of Pt. Binary and ternary Pt alloys with less expensive metals are a possible route [1]. In this work, a ternary alloy with composition Pd5Pt3Ni2 was studied as a potential cathode material. Preliminary results showed similar catalytic performance tomore » pure Pt in single-cell tests. However, to enhance its performance, it is necessary to understand how this ternary catalyst behaves during fuel cell operation. Various electron microscopy techniques were used to characterize the ternary Pd5Pt3Ni2 catalysts within the membrane-electrode assembly (MEA) both before and after fuel cell operation.« less

Efficient inverted polymer solar cells based on conjugated polyelectrolyte and zinc oxide modified ITO electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Tao; Zhu, Xiaoguang; Tu, Guoli, E-mail: tgl@hust.edu.cn

Efficient inverted polymer solar cells (PSCs) were constructed by utilizing a conjugated polyelectrolyte PF{sub EO}SO{sub 3}Na and zinc oxide to modify the indium tin oxide (ITO) electrode. The ITO electrode modified by PF{sub EO}SO{sub 3}Na and zinc oxide possesses high transparency, increased electron mobility, smoothened surface, and lower work function. PTB7:PC{sub 71}BM inverted PSCs containing the modified ITO electrode achieved a high power conversion efficiency (PCE) of 8.49%, exceeding that of the control device containing a ZnO modified ITO electrode (7.48%). Especially, PCE-10:PC{sub 71}BM inverted polymer solar cells achieved a high PCE up to 9.4%. These results demonstrate a usefulmore » approach to improve the performance of inverted polymer solar cells.« less

Amplified cathodic electrochemiluminescence of luminol based on Pd and Pt nanoparticles and glucose oxidase decorated graphene as trace label for ultrasensitive detection of protein.

PubMed

Cao, Yaling; Yuan, Ruo; Chai, Yaqin; Liu, Huijing; Liao, Yuhong; Zhuo, Ying

2013-09-15

An ultrasensitive electrochemiluminescence (ECL) immunosensor was constructed for ultrasensitive detection of carcinoembryonic antigen (CEA) based on an amplified cathodic ECL of luminol at low potential. Firstly, Au nanoparticles (AuNPs) were electrodeposited onto single walled carbon nanotube-graphene composites (CNTs-Gra) coated glass carbon electrode (GCE) with enhanced surface area and good biocompatibility to capture primary antibody (Ab1) and then bind the antigen analytes. Secondly, Pd and Pt nanoparticles (Pd&PtNPs) decorated reduced graphene oxide (Pd&PtNPs@rGO) and glucose oxidase (GOD) labeled secondary antibody (Pd&PtNPs@ rGO-GOD-Ab2) could be captured onto the electrode surface by a sandwich immunoassay protocol to generate amplified cathodic ECL signals of luminol in the presence of glucose. The Pd&PtNPs@rGO composites and loaded GOD promoted luminol cathodic ECL response by efficiently catalyzing glucose to in-situ produce amount of hydrogen peroxide (H2O2) working as a coreactant of luminol. Then in turn Pd&PtNPs catalyzed H2O2 to generate various reactive oxygen species (ROSs), which accelerated the cathodic ECL reaction of luminol, enhanced the cathodic ECL intensity of luminol and improved the sensitivity of the immunosensor. The as-proposed ECL immunosensor exhibited sensitive response on the detection of CEA ranging from 0.0001 ng mL(-1) to 160 ng mL(-1) with a detection limit of 0.03 pg mL(-1) (S/N=3). Moreover, the stability, specificity, lifetime and reproducibility tests demonstrated the feasibility of the developed immunoassay, which can be further extended to the detection of other disease biomarkers. Copyright © 2013 Elsevier B.V. All rights reserved.

Use of Hydrogen Chemisorption and Ethylene Hydrogenation as Predictors for Aqueous Phase Reforming of Lactose over Ni@Pt and Co@Pt Bimetallic Overlayer Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Qinghua; Skoglund, Michael D.; Zhang, Chen

Overlayer Pt on Ni (Ni@Pt) or Co (Co@Pt) were synthesized and tested for H2 generation from APR of lactose. H2 chemisorption descriptor showed that Ni@Pt and Co@Pt overlayer catalysts had reduced H2 adsorption strength compared to a Pt only catalyst, which agree with computational predictions. The overlayer catalysts also demonstrated lower activity for ethylene hydrogenation than the Pt only catalyst, which likely resulted from decreased H2 binding strength decreasing the surface coverage of H2. XAS results showed that overlayer catalysts exhibited higher white line intensity than the Pt catalyst, which indicates a negative d-band shift for the Pt overlayer, furthermore » providing evidence for overlayer formation. Lactose APR studies showed that lactose can be used as feedstock to produce H2 and CO under desirable reaction conditions. The Pt active sites of Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. The results suggest that overlayer formation using directed deposition technique could modify the behavior of the surface metal and ultimately modify the APR activity.« less

Fabrication Method for Laboratory-Scale High-Performance Membrane Electrode Assemblies for Fuel Cells.

PubMed

Sassin, Megan B; Garsany, Yannick; Gould, Benjamin D; Swider-Lyons, Karen E

2017-01-03

Custom catalyst-coated membranes (CCMs) and membrane electrode assemblies (MEAs) are necessary for the evaluation of advanced electrocatalysts, gas diffusion media (GDM), ionomers, polymer electrolyte membranes (PEMs), and electrode structures designed for use in next-generation fuel cells, electrolyzers, or flow batteries. This Feature provides a reliable and reproducible fabrication protocol for laboratory scale (10 cm 2 ) fuel cells based on ultrasonic spray deposition of a standard Pt/carbon electrocatalyst directly onto a perfluorosulfonic acid PEM.

Application of N-doped graphene modified carbon ionic liquid electrode for direct electrochemistry of hemoglobin.

PubMed

Sun, Wei; Dong, Lifeng; Deng, Ying; Yu, Jianhua; Wang, Wencheng; Zhu, Qianqian

2014-06-01

Nitrogen-doped graphene (NG) was synthesized and used for the investigation on direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode as the substrate electrode. Due to specific characteristics of NG such as excellent electrocatalytic property and large surface area, direct electron transfer of Hb was realized with enhanced electrochemical responses appearing. Electrochemical behaviors of Hb on the NG modified electrode were carefully investigated with the electrochemical parameters calculated. The Hb modified electrode exhibited excellent electrocatalytic reduction activity toward different substrates, such as trichloroacetic acid and H2O2, with wider dynamic range and lower detection limit. These findings show that NG can be used for the preparation of chemically modified electrodes with improved performance and has potential applications in electrochemical sensing. Copyright © 2014 Elsevier B.V. All rights reserved.

Pristine multi-walled carbon nanotubes/SDS modified carbon paste electrode as an amperometric sensor for epinephrine.

PubMed

Thomas, Tony; Mascarenhas, Ronald J; D' Souza, Ozma J; Detriche, Simon; Mekhalif, Zineb; Martis, Praveen

2014-07-01

An amperometric sensor for the determination of epinephrine (EP) was fabricated by modifying the carbon paste electrode (CPE) with pristine multi-walled carbon nanotubes (pMWCNTs) using bulk modification followed by drop casting of sodium dodecyl sulfate (SDS) onto the surface for its optimal potential application. The modified electrode showed an excellent electrocatalytic activity towards EP by decreasing the overpotential and greatly enhancing the current sensitivity. FE-SEM images confirmed the dispersion of pMWCNTs in the CPE matrix. EDX analysis ensured the surface coverage of SDS. A comparative study of pMWCNTs with those of oxidized MWCNTs (MWCNTsOX) modified electrodes reveals that the former is the best base material for the construction of the sensor with advantages of lower oxidation overpotential and the least background current. The performance of the modified electrode was impressive in terms of the least charge transfer resistance (Rct), highest values for diffusion coefficient (DEP) and standard heterogeneous electron transfer rate constant (k°). Analytical characterization of the modified electrode exhibited two linear dynamic ranges from 1.0×10(-7) to 1.0×10(-6)M and 1.0×10(-6) to 1.0×10(-4)M with a detection limit of (4.5±0.18)×10(-8)M. A 100-fold excess of serotonin, acetaminophen, folic acid, uric acid, tryptophan, tyrosine and cysteine, 10-fold excess of ascorbic acid and twofold excess of dopamine do not interfere in the quantification of EP at this electrode. The analytical applications of the modified electrode were demonstrated by determining EP in spiked blood serum and adrenaline tartrate injection. The modified electrode involves a simple fabrication procedure, minimum usage of the modifier, quick response, excellent stability, reproducibility and anti-fouling effects. Copyright © 2014 Elsevier B.V. All rights reserved.

Properties of dielectric dead layers for SrTiO3 thin films on Pt electrodes

NASA Astrophysics Data System (ADS)

Finstrom, Nicholas H.; Cagnon, Joel; Stemmer, Susanne

2007-02-01

Dielectric measurements as a function of temperature were used to characterize the properties of the dielectric dead layers in parallel-plate capacitors with differently textured SrTiO3 thin films and Pt electrodes. The apparent thickness dependence of the permittivity was described with low-permittivity passive (dead) layers at the interfaces connected in series with the bulk of the SrTiO3 film. Interfacial capacitance densities changed with the film microstructure and were weakly temperature dependent. Estimates of the dielectric dead layer thickness and permittivity were limited by the film surface roughness (˜5nm ). The consequences for the possible origins of dielectric dead layers that have been proposed in the literature are discussed.

Chemically modified graphite for electrochemical cells

DOEpatents

Greinke, Ronald Alfred; Lewis, Irwin Charles

1998-01-01

This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (i) the electrode, (ii) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (iii) a counterelectrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes.

Facile Fabrication of Platinum-Cobalt Alloy Nanoparticles with Enhanced Electrocatalytic Activity for a Methanol Oxidation Reaction

NASA Astrophysics Data System (ADS)

Huang, Huihong; Hu, Xiulan; Zhang, Jianbo; Su, Nan; Cheng, Jiexu

2017-03-01

Decreasing the cost associated with platinum-based catalysts along with improving their catalytic properties is a major challenge for commercial direct methanol fuel cells. In this work, a simple and facile strategy was developed for the more efficient preparation of multi-walled carbon nanotube (MWCNT) -supported Pt/CoPt composite nanoparticles (NPs) via solution plasma sputtering with subsequent thermal annealing. Quite different from general wet synthesis methods, Pt/CoPt composite NPs were directly derived from metal wire electrodes without any additions. The obtained Pt/CoPt/MWCNTs composite catalysts exhibited tremendous improvement in the electro-oxidation of methanol in acidic media with mass activities of 1719 mA mg-1Pt. This value is much higher than that of previous reports of Pt-Co alloy and commercial Pt/C (3.16 times) because of the many active sites and clean surface of the catalysts. The catalysts showed good stability due to the special synergistic effects of the CoPt alloy. Pt/CoPt/MWCNTs can be used as a promising catalyst for direct methanol fuel cells. In addition, this solution plasma sputtering-assisted synthesis method introduces a general and feasible route for the synthesis of binary alloys.

Facile Fabrication of Platinum-Cobalt Alloy Nanoparticles with Enhanced Electrocatalytic Activity for a Methanol Oxidation Reaction.

PubMed

Huang, Huihong; Hu, Xiulan; Zhang, Jianbo; Su, Nan; Cheng, JieXu

2017-03-30

Decreasing the cost associated with platinum-based catalysts along with improving their catalytic properties is a major challenge for commercial direct methanol fuel cells. In this work, a simple and facile strategy was developed for the more efficient preparation of multi-walled carbon nanotube (MWCNT) -supported Pt/CoPt composite nanoparticles (NPs) via solution plasma sputtering with subsequent thermal annealing. Quite different from general wet synthesis methods, Pt/CoPt composite NPs were directly derived from metal wire electrodes without any additions. The obtained Pt/CoPt/MWCNTs composite catalysts exhibited tremendous improvement in the electro-oxidation of methanol in acidic media with mass activities of 1719 mA mg -1 Pt . This value is much higher than that of previous reports of Pt-Co alloy and commercial Pt/C (3.16 times) because of the many active sites and clean surface of the catalysts. The catalysts showed good stability due to the special synergistic effects of the CoPt alloy. Pt/CoPt/MWCNTs can be used as a promising catalyst for direct methanol fuel cells. In addition, this solution plasma sputtering-assisted synthesis method introduces a general and feasible route for the synthesis of binary alloys.

Highly Sensitive Electrochemical Biosensor for Evaluation of Oxidative Stress Based on the Nanointerface of Graphene Nanocomposites Blended with Gold, Fe3O4, and Platinum Nanoparticles.

PubMed

Wang, Le; Zhang, Yuanyuan; Cheng, Chuansheng; Liu, Xiaoli; Jiang, Hui; Wang, Xuemei

2015-08-26

High levels of H2O2 pertain to high oxidative stress and are associated with cancer, autoimmune, and neurodegenerative disease, and other related diseases. In this study, a sensitive H2O2 biosensor for evaluation of oxidative stress was fabricated on the basis of the reduced graphene oxide (RGO) nanocomposites decorated with Au, Fe3O4, and Pt nanoparticles (RGO/AuFe3O4/Pt) modified glassy carbon electrode (GCE) and used to detect the released H2O2 from cancer cells and assess the oxidative stress elicited from H2O2 in living cells. Electrochemical behavior of RGO/AuFe3O4/Pt nanocomposites exhibits excellent catalytic activity toward the relevant reduction with high selection and sensitivity, low overpotential of 0 V, low detection limit of ∼0.1 μM, large linear range from 0.5 μM to 11.5 mM, and outstanding reproducibility. The as-prepared biosensor was applied in the measurement of efflux of H2O2 from living cells including healthy normal cells and tumor cells under the external stimulation. The results display that this new nanocomposites-based biosensor is a promising candidate of nonenzymatic H2O2 sensor which has the possibility of application in clinical diagnostics to assess oxidative stress of different kinds of living cells.

Electrochemistry of Metal Surfaces

DTIC Science & Technology

1990-06-30

i) 3-pyridine carboxylic acid ( nicotinic acid, NA) binds to Pt surfaces through both the nitrogen atom and an oxygen atom of the carboxylate group...formed from aqueous electrolytes at Pt(1l1) electrode surfaces have been compared with the IR and Raman spectra of the unadsorbed compounds in order...vibrational absorptivities between EELS spectra of adsorbed species and IR and Raman spectra of the corresponding unadsorbed compounds (146). Of

Fabrication and characteristics of thin disc piezoelectric transformers based on piezoelectric buzzers with gap circles.

PubMed

Chang, Kuo-Tsai; Lee, Chun-Wei

2008-04-01

This paper investigates design, fabrication and test of thin disc piezoelectric transformers (PTs) based on piezoelectric buzzers with gap circles at different diameters of the gap circles. The performance test is focused on characteristics of voltage gains, including maximum voltage gains and maximum-gain frequencies, for each piezoelectric transformer under different load conditions. Both a piezoelectric buzzer and a gap circle on a silver electrode of the buzzer are needed to build any type of the PTs. Here, the gap circle is used to form a ring-shaped input electrode and a circle-shaped output electrode for each piezoelectric transformer. To do so, both structure and connection of a PT are first expressed. Then, operating principle of a PT and its related vibration mode observed by a carbon-power imaging technique are described. Moreover, an experimental setup for characterizing each piezoelectric transformer is constructed. Finally, effects of diameters of the gap circles on characteristics of voltage gains at different load resistances are discussed.

Three-dimensional nitrogen doped holey reduced graphene oxide framework as metal-free counter electrodes for high performance dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Yu, Mei; Zhang, Jindan; Li, Songmei; Meng, Yanbing; Liu, Jianhua

2016-03-01

Three-dimensional nitrogen doped holey reduced graphene oxide framework (NHGF) with hierarchical porosity structure was developed as high-performance metal-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). With plenty of exposed active sites, efficient electron and ion transport pathways as well as a high surface hydrophilicity, NHGF-CE exhibits good electrocatalytic performances for I- /I3- redox couple and a low charge transfer resistance (Rct). The Rct of NHGF-CE is 1.46 Ω cm2, which is much lower than that of Pt-CE (4.02 Ω cm2). The DSSC with NHGF-CE reaches a power conversion efficiency of 5.56% and a fill factor of 65.5%, while those of the DSSC with Pt-CE are only 5.45% and 62.3%, respectively. The achievement of the highly efficient 3D structure presents a potential way to fabricate low-cost and metal-free counter electrodes with excellent performance.

Highly Stretchable and Conductive Silver Nanoparticle Embedded Graphene Flake Electrode Prepared by In situ Dual Reduction Reaction.

PubMed

Yoon, Yeoheung; Samanta, Khokan; Lee, Hanleem; Lee, Keunsik; Tiwari, Anand P; Lee, JiHun; Yang, Junghee; Lee, Hyoyoung

2015-09-18

The emergence of stretchable devices that combine with conductive properties offers new exciting opportunities for wearable applications. Here, a novel, convenient and inexpensive solution process was demonstrated to prepare in situ silver (Ag) or platinum (Pt) nanoparticles (NPs)-embedded rGO hybrid materials using formic acid duality in the presence of AgNO3 or H2PtCl6 at low temperature. The reduction duality of the formic acid can convert graphene oxide (GO) to rGO and simultaneously deposit the positively charged metal ion to metal NP on rGO while the formic acid itself is converted to a CO2 evolving gas that is eco-friendly. The AgNP-embedded rGO hybrid electrode on an elastomeric substrate exhibited superior stretchable properties including a maximum conductivity of 3012 S cm(-1) (at 0 % strain) and 322.8 S cm(-1) (at 35 % strain). Its fabrication process using a printing method is scalable. Surprisingly, the electrode can survive even in continuous stretching cycles.

High efficiency organic-electrolyte DSSC based on hydrothermally deposited titanium carbide-carbon counter electrodes

NASA Astrophysics Data System (ADS)

Towannang, Madsakorn; Kumlangwan, Pantiwa; Maiaugree, Wasan; Ratchaphonsaenwong, Kunthaya; Harnchana, Viyada; Jarenboon, Wirat; Pimanpang, Samuk; Amornkitbamrung, Vittaya

2015-07-01

Pt-free TiC based electrodes were hydrothermally deposited onto FTO/glass substrates and used as dye-sensitized solar cell (DSSC) counter electrodes. A promising efficiency of 3.07% was obtained from the annealed hydrothermal TiC DSSCs based on a disulfide/thiolate electrolyte. A pronounced improvement in performance of 3.59% was achieved by compositing TiC with carbon, compared to that of a Pt DSSC, 3.84%. TEM analysis detected that the TiC particle surfaces were coated by thin carbon layer (7 nm). The SAED pattern and Raman spectrum of TiC-carbon films suggested that the carbon layer was composed of amorphous and graphite carbon. The formation of graphite on the TiC nanoparticles plays a crucial role in enhancing the film's reduction current to 10.12 mA/cm2 and in reducing the film impedance to 237.63 Ω, resulting in a high efficiency of the TiC-carbon DSSC. [Figure not available: see fulltext.

Effect of ordered mesoporous carbon contact layer on the sensing performance of sputtered RuO2 thin film pH sensor.

PubMed

Lonsdale, W; Maurya, D K; Wajrak, M; Alameh, K

2017-03-01

The effect of contact layer on the pH sensing performance of a sputtered RuO 2 thin film pH sensor is investigated. The response of pH sensors employing RuO 2 thin film electrodes on screen-printed Pt, carbon and ordered mesoporous carbon (OMC) contact layers are measured over a pH range from 4 to 10. Working electrodes with OMC contact layer are found to have Nernstian pH sensitivity (-58.4mV/pH), low short-term drift rate (5.0mV/h), low hysteresis values (1.13mV) and fast reaction times (30s), after only 1h of conditioning. A pH sensor constructed with OMC carbon contact layer displays improved sensing performance compared to Pt and carbon-based counterparts, making this electrode more attractive for applications requiring highly-accurate pH sensing with reduced conditioning time. Copyright © 2016 Elsevier B.V. All rights reserved.

Pd0@Polyoxometalate Nanostructures as Green Electrocatalysts: Illustrative Example of Hydrogen Production

PubMed Central

Biboum, Rosa N.; Keita, Bineta; Franger, Sylvain; Njiki, Charles P. Nanseu; Zhang, Guangjin; Zhang, Jie; Liu, Tianbo; Mbomekalle, Israel-Martyr; Nadjo, Louis

2010-01-01

Green-chemistry type procedures were used to synthesize Pd0 nanostructures encapsulated by a vanadium-substituted Wells-Dawson-type polyoxometalate (Pd0@POM). The cyclic voltammogram run with the Pd0@POM-modified glassy carbon electrode shows well-defined waves, associated with Pd0 nanostructures and the VV/VIV redox couple. The Pd0@POM-modified electrode displayed remarkably reproducible cyclic voltammetry patterns. The hydrogen evolution reaction (HER) was selected as an illustrative example to test the electrocatalytic behavior of the electrode. The kinetic parameters of the HER show the high efficiency of the Pd0@POM-modified electrode. This is the first example of electrochemical characterization of a modified electrode based on a vanado-tungstic POM and Pd0 nanostructures.

Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

NASA Astrophysics Data System (ADS)

Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

2016-09-01

The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

High-durability catalytic electrode composed of Pt nanoparticle-supported carbon nanowalls synthesized by radical-injection plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Imai, Shun; Kondo, Hiroki; Cho, Hyungjun; Kano, Hiroyuki; Ishikawa, Kenji; Sekine, Makoto; Hiramatsu, Mineo; Ito, Masafumi; Hori, Masaru

2017-10-01

For polymer electrolyte fuel cell applications, carbon nanowalls (CNWs) were synthesized by radical-injection plasma-enhanced chemical vapor deposition, and a high density of Pt nanoparticles (>1012 cm-2) was supported on the CNWs using a supercritical fluid deposition system. The high potential cycle tests were applied and the electrochemical surface area of the Pt nanoparticle-supported CNWs did not change significantly, even after 20 000 high potential cycles. According to transmission electron microscopy observations, the mean diameter of Pt changed slightly after the cycle tests, while the crystallinity of the CNWs evaluated using Raman spectroscopy showed almost no change.

From bio-mineralisation to fuel cells: biomanufacture of Pt and Pd nanocrystals for fuel cell electrode catalyst.

PubMed

Yong, P; Paterson-Beedle, M; Mikheenko, I P; Macaskie, L E

2007-04-01

Biosynthesis of nano-scale platinum and palladium was achieved via enzymatically-mediated deposition of metal ions from solution. The bio-accumulated Pt(0) and Pd(0) crystals were dried, applied onto carbon paper and tested as anodes in a polymer electrolyte membrane (PEM) fuel cell for power production. Up to 100% and 81% of the maximum power generation was achieved by the bio-Pt and bio-Pd catalysts, respectively, compared to commercial fuel cell grade Pt catalyst. Hence, biomineralisation could pave the way for economical production of fuel cell catalysts since previous studies have shown that precious metals can be biorecovered from wastes into catalytically active bionanomaterials.

Pt skin coated hollow Ag-Pt bimetallic nanoparticles with high catalytic activity for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Fu, Tao; Huang, Jianxing; Lai, Shaobo; Zhang, Size; Fang, Jun; Zhao, Jinbao

2017-10-01

The catalytic activity and stability of electrocatalyst is critical for the commercialization of fuel cells, and recent reports reveal the great potential of the hollow structures with Pt skin coat for developing high-powered electrocatalysts due to their highly efficient utilization of the Pt atoms. Here, we provide a novel strategy to prepare the Pt skin coated hollow Ag-Pt structure (Ag-Pt@Pt) of ∼8 nm size at room temperature. As loaded on the graphene, the Ag-Pt@Pt exhibits a remarkable mass activity of 0.864 A/mgPt (at 0.9 V, vs. reversible hydrogen electrode (RHE)) towards oxygen reduction reaction (ORR), which is 5.30 times of the commercial Pt/C catalyst, and the Ag-Pt@Pt also shows a better stability during the ORR catalytic process. The mechanism of this significant enhancement can be attributed to the higher Pt utilization and the unique Pt on Ag-Pt surface structure, which is confirmed by the density functional theory (DFT) calculations and other characterization methods. In conclusion, this original work offers a low-cost and environment-friendly method to prepare a high active electrocatalyst with cheaper price, and this work also discloses the correlation between surface structures and ORR catalytic activity for the hollow structures with Pt skin coat, which can be instructive for designing novel advanced electrocatalysts for fuel cells.

Using sewage sludge pyrolytic gas to modify titanium alloy to obtain high-performance anodes in bio-electrochemical systems

NASA Astrophysics Data System (ADS)

Gu, Yuan; Ying, Kang; Shen, Dongsheng; Huang, Lijie; Ying, Xianbin; Huang, Haoqian; Cheng, Kun; Chen, Jiazheng; Zhou, Yuyang; Chen, Ting; Feng, Huajun

2017-12-01

Titanium is under consideration as a potential stable bio-anode because of its high conductivity, suitable mechanical properties, and electrochemical inertness in the operating potential window of bio-electrochemical systems; however, its application is limited by its poor electron-transfer capacity with electroactive bacteria and weak ability to form biofilms on its hydrophobic surface. This study reports an effective and low-cost way to convert a hydrophobic titanium alloy surface into a hydrophilic surface that can be used as a bio-electrode with higher electron-transfer rates. Pyrolytic gas of sewage sludge is used to modify the titanium alloy. The current generation, anodic biofilm formation surface, and hydrophobicity are systematically investigated by comparing bare electrodes with three modified electrodes. Maximum current density (15.80 A/m2), achieved using a modified electrode, is 316-fold higher than that of the bare titanium alloy electrode (0.05 A/m2) and that achieved by titanium alloy electrodes modified by other methods (12.70 A/m2). The pyrolytic gas-modified titanium alloy electrode can be used as a high-performance and scalable bio-anode for bio-electrochemical systems because of its high electron-transfer rates, hydrophilic nature, and ability to achieve high current density.

The development of a multichannel electrode array for retinal prostheses.

PubMed

Terasawa, Yasuo; Tashiro, Hiroyuki; Uehara, Akihiro; Saitoh, Tohru; Ozawa, Motoki; Tokuda, Takashi; Ohta, Jun

2006-01-01

The development of a multielectrode array is the key issue for retinal prostheses. We developed a 10 x 10 platinum electrode array that consists of an 8-microm polyimide layer sandwiched between 5-microm polymonochloro-para-xylylene (parylene-C) layers. Each electrode was formed as a 30-microm-high bump by Pt/Au double-layer electroplating. We estimated the charge delivery capability (CDC) of the electrode by measuring the CDCs of two-channel electrode arrays. The dimensions of each electrode of the two-channel array were the same as those of each electrode formed on the 10 x 10 array. The results suggest that for cathodic-first (CF) pulses, 80% of electrodes surpassed our development target of 318 microC/cm2, which corresponds to the charge density of pulses of 500 micros duration and 200 microA amplitude for a 200-microm-diameter planar electrode.

Pt-Free Counter Electrodes with Carbon Black and 3D Network Epoxy Polymer Composites

NASA Astrophysics Data System (ADS)

Kang, Gyeongho; Choi, Jongmin; Park, Taiho

2016-03-01

Carbon black (CB) and a 3D network epoxy polymer composite, representing dual functions for conductive corrosion protective layer (CCPL) and catalytic layer (CL) by the control of CB weight ratio against polymer is developed. Our strategy provides a proper approach which applies high catalytic ability and chemical stability of CB in corrosive triiodide/iodide (I3-/I-) redox electrolyte system. The CB and a 3D network epoxy polymer composite coated on the stainless steel (SS) electrode to alternate counter electrodes in dye sensitized solar cells (DSSCs). A two-step spray pyrolysis process is used to apply a solution containing epoxy monomers and a polyfunctional amine hardener with 6 wt% CB to a SS substrate, which forms a CCPL. Subsequently, an 86 wt% CB is applied to form a CL. The excellent catalytic properties and corrosion protective properties of the CB and 3D network epoxy polymer composites produce efficient counter electrodes that can replace fluorine-doped tin oxide (FTO) with CCPL/SS and Pt/FTO with CL/CCPL/SS in DSSCs. This approach provides a promising approach to the development of efficient, stable, and cheap solar cells, paving the way for large-scale commercialization.

Electrocatalytic oxidation of 2-mercaptoethanol using modified glassy carbon electrode by MWCNT in combination with unsymmetrical manganese (II) Schiff base complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohebbi, Sajjad, E-mail: smohebbi@uok.ac.ir; Eslami, Saadat

2015-06-15

Highlights: • High electocatalytic efficiency and stability of modified hybrid electrode GC/MWCNTs/MnSaloph. • Direct reflection of catalytic activity of manganese complexes on electrocatalytic oxidation of 2-ME. • Decreasing overpotential and increasing catalytic peak current toward oxidation of 2-ME. • Deposition of range of novel substituted N{sub 2}O{sub 2} Saloph complexes of manganese(II) on GCE/MWCNT. • Enhancement of electrocatalytic oxidation activity upon electron donating substitutions on the Saloph. - Abstract: The performance of modified hybrid glassy carbon electrode with composite of carbon nanotubes and manganese complexes for the electrocatalytic oxidation of 2-mercaptoethanol is developed. GC electrode was modified using MWCNT andmore » new N{sub 2}O{sub 2} unsymmetrical tetradentate Schiff base complexes of manganese namely Manganese Saloph complexes 1-5, with general formula Mn[(5-x-4-y-Sal)(5-x′-4-y′-Sal) Ph], where x, x′ = H, Br, NO{sub 2} and y, y′ = H, MeO. Direct immobilization of CNT on the surface of GCE is performed by abrasive immobilization, and then modified by manganese(II) complexes via direct deposition method. These novel modified electrodes clearly demonstrate the necessity of modifying bare carbon electrodes to endow them with the desired behavior and were identified by HRTEM. Also complexes were characterized by elemental analyses, MS, UV–vis and IR spectroscopy. Modified hybrid GC/MWCNT/MnSaloph electrode exhibits strong and stable electrocatalytic activity towards the electrooxidation of 2-mercaptoethanol molecules in comparison with bare glassy carbon electrode with advantages of very low over potential and high catalytic current. Such ability promotes the thiol’s electron transfer reaction. Also, electron withdrawing substituent on the Saloph was enhanced electrocatalytic oxidation activity.« less

Interface architecture determined electrocatalytic activity of Pt on vertically oriented TiO(2) nanotubes.

PubMed

Rettew, Robert E; Allam, Nageh K; Alamgir, Faisal M

2011-02-01

The surface atomic structure and chemical state of Pt is consequential in a variety of surface-intensive devices. Herein we present the direct interrelationship between the growth scheme of Pt films, the resulting atomic and electronic structure of Pt species, and the consequent activity for methanol electro-oxidation in Pt/TiO(2) nanotube hybrid electrodes. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements were performed to relate the observed electrocatalytic activity to the oxidation state and the atomic structure of the deposited Pt species. The atomic structure as well as the oxidation state of the deposited Pt was found to depend on the pretreatment of the TiO(2) nanotube surfaces with electrodeposited Cu. Pt growth through Cu replacement increases Pt dispersion, and a separation of surface Pt atoms beyond a threshold distance from the TiO(2) substrate renders them metallic, rather than cationic. The increased dispersion and the metallic character of Pt results in strongly enhanced electrocatalytic activity toward methanol oxidation. This study points to a general phenomenon whereby the growth scheme and the substrate-to-surface-Pt distance dictates the chemical state of the surface Pt atoms, and thereby, the performance of Pt-based surface-intensive devices.

EFFECTS OF TiOx INTERLAYER ON RESISTANCE SWITCHING OF Pt/TiOx/ZnO/n+-Si STRUCTURES

NASA Astrophysics Data System (ADS)

Li, Hongxia; Lv, Xiaojun; Xi, Junhua; Wu, Xin; Mao, Qinan; Liu, Qingmin; Ji, Zhenguo

2014-08-01

In this paper, we fabricated Pt/TiOx/ZnO/n+-Si structures by inserting TiOx interlayer between Pt top electrode (TE) and ZnO thin film for non-volatile resistive random access memory (ReRAM) applications. Effects of TiOx interlayer with different thickness on the resistance switching of Pt/TiOx/ZnO/n+-Si structures were investigated. Conduction behaviors in high and low resistance state (HRS and LRS) fit well with the trap-controlled space-charge-limited conduction (SCLC) and Ohmic behavior, respectively. Variations of set and reset voltages and HRS and LRS resistances of Pt/TiOx/ZnO/n+-Si structures were investigated as a function of TiOx thickness. Switching cycling tests were attempted to evaluate the endurance reliability of Pt/TiOx/ZnO/n+-Si structures. Additionally, the switching mechanism was analyzed by the filament model.

Electrocatalytic response of poly(cobalt tetraaminophthalocyanine)/multi-walled carbon nanotubes-Nafion modified electrode toward sulfadiazine in urine*

PubMed Central

Hong, Xiao-ping; Zhu, Yan; Zhang, Yan-zhen

2012-01-01

A highly sensitive amperometric sulfadiazine sensor fabricated by electrochemical deposition of poly(cobalt tetraaminophthalocyanine) (poly(CoIITAPc)) on the surface of a multi-walled carbon nanotubes-Nafion (MWCNTs-Nafion) modified electrode is described. This electrode showed a very attractive performance by combining the advantages of CoIITAPc, MWCNTs, and Nafion. Compared with the bare glassy carbon electrode (GCE) and the MWCNTs-Nafion modified electrode, the electrocatalytic activity of poly(CoIITAPc)-coated MWCNTs-Nafion GCE generated greatly improved electrochemical detections toward sulfadiazine including low oxidation potential, high current responses, and good anti-fouling performance. The oxidation peak currents of sulfadiazine obtained on the new modified electrode increased linearly while increasing the concentration of sulfadiazine from 0.5 to 43.5 μmol/L with the detection limit of 0.17 μmol/L. PMID:22661213

Correlation of the impedance and effective electrode area of doped PEDOT modified electrodes for brain-machine interfaces.

PubMed

Harris, Alexander R; Molino, Paul J; Kapsa, Robert M I; Clark, Graeme M; Paolini, Antonio G; Wallace, Gordon G

2015-05-07

Electrode impedance is used to assess the thermal noise and signal-to-noise ratio for brain-machine interfaces. An intermediate frequency of 1 kHz is typically measured, although other frequencies may be better predictors of device performance. PEDOT-PSS, PEDOT-DBSA and PEDOT-pTs conducting polymer modified electrodes have reduced impedance at 1 kHz compared to bare metal electrodes, but have no correlation with the effective electrode area. Analytical solutions to impedance indicate that all low-intermediate frequencies can be used to compare the electrode area at a series RC circuit, typical of an ideal metal electrode in a conductive solution. More complex equivalent circuits can be used for the modified electrodes, with a simplified Randles circuit applied to PEDOT-PSS and PEDOT-pTs and a Randles circuit including a Warburg impedance element for PEDOT-DBSA at 0 V. The impedance and phase angle at low frequencies using both equivalent circuit models is dependent on the electrode area. Low frequencies may therefore provide better predictions of the thermal noise and signal-to-noise ratio at modified electrodes. The coefficient of variation of the PEDOT-pTs impedance at low frequencies was lower than the other conducting polymers, consistent with linear and steady-state electroactive area measurements. There are poor correlations between the impedance and the charge density as they are not ideal metal electrodes.

Sulfur-doped porous reduced graphene oxide hollow nanosphere frameworks as metal-free electrocatalysts for oxygen reduction reaction and as supercapacitor electrode materials.

PubMed

Chen, Xi'an; Chen, Xiaohua; Xu, Xin; Yang, Zhi; Liu, Zheng; Zhang, Lijie; Xu, Xiangju; Chen, Ying; Huang, Shaoming

2014-11-21

Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and much better methanol tolerance and durability, and to be a supercapacitor electrode material with a high specific capacitance of 343 F g(-1), good rate capability and excellent cycling stability in aqueous electrolytes. The impressive performance for ORR and supercapacitors is believed to be due to the synergistic effect caused by sulfur-doping enhancing the electrochemical activity and 3D porous hollow nanosphere framework structures facilitating ion diffusion and electronic transfer.

Voltammetric enzyme sensor for urea using mercaptohydroquinone-modified gold electrode as the base transducer.

PubMed

Mizutani, F; Yabuki, S; Sato, Y

1997-01-01

A voltammetric urea-sensing electrode was prepared by combining a lipid-attached urease layer with a 2,5-dihydroxythiophenol-modified gold electrode. A self-assembled monolayer of dihydroxythiophenol was prepared on the gold surface by soaking the electrode into an ethanolic solution containing the modifier. A layer of the lipid-attached enzyme and that of acetyl cellulose overcoat were successively made on the dihydroxythiophenol-modified electrode by applying a dip-coating procedure. The addition of urea in a test solution (10 mM phosphate buffer, pH 7.0) brought about an increase of pH near the urease layer. The pH shift accompanied a negative shift of the anodic peak, which corresponded to the electro-oxidation of dihydroxyphenol moiety to form quinone, on the linear sweep voltammograms for the urease/dihydroxythiophenol electrode. The concentration of urea (0.2-5 mM) could be determined by measuring the electrode current at -0.05 V versus Ag/AgCl from the voltammogram. The electrode was applied to the determination of urea in human urine; the measurement of electrode current at such a low potential provided the urea determination without any electrochemical interference from L-ascorbic acid and uric acid.

Durability of De-Alloyed Platinum-Nickel Cathode Catalyst in Low Platinum Loading Membrane-Electrode Assemblies Subjected to Accelerated Stress Tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahluwalia, R. K.; Wang, X.; Peng, J. -K.

Here, the durability of de-alloyed platinum-nickel catalysts supported on high-surface area carbon (d-PtNi/C) in optimized electrodes and membrane electrode assemblies (MEAs) under an accelerated stress test (AST) protocol is investigated with the objective of developing a quantitative understanding of the degradation mechanisms and their relationship to the electrode structure, pre-conditioning, and operating conditions. It is found that the cell degradation can be mitigated by controlling the voltage cycle, acid washing the MEA to remove Ni contaminants that enter the electrode and membrane during fabrication, and monitoring the operating conditions. For example, the electrochemical surface area (ECSA) loss is <25% aftermore » 30,000 triangle cycles with 0.925 V upper potential limit if the MEA is acid washed and extensive diagnostics are avoided. The parameters that exacerbate the cell degradation also accelerate the rate at which Ni leaches out from the catalyst. A mechanistic model is presented for the degradation in performance of d-PtNi/C electrodes. The model correlates a) the degradation in ORR mass and specific activities with ECSA and Ni losses, b) the decrease in limiting current density ( iL), which is inversely proportional to the O 2 mass transport resistance, with the degradation in catalyst roughness factor, and c) the increase in mass transfer overpotentials with the reduced current density, i/iL .« less

Durability of De-Alloyed Platinum-Nickel Cathode Catalyst in Low Platinum Loading Membrane-Electrode Assemblies Subjected to Accelerated Stress Tests

DOE PAGES

Ahluwalia, R. K.; Wang, X.; Peng, J. -K.; ...

2018-04-25

Here, the durability of de-alloyed platinum-nickel catalysts supported on high-surface area carbon (d-PtNi/C) in optimized electrodes and membrane electrode assemblies (MEAs) under an accelerated stress test (AST) protocol is investigated with the objective of developing a quantitative understanding of the degradation mechanisms and their relationship to the electrode structure, pre-conditioning, and operating conditions. It is found that the cell degradation can be mitigated by controlling the voltage cycle, acid washing the MEA to remove Ni contaminants that enter the electrode and membrane during fabrication, and monitoring the operating conditions. For example, the electrochemical surface area (ECSA) loss is <25% aftermore » 30,000 triangle cycles with 0.925 V upper potential limit if the MEA is acid washed and extensive diagnostics are avoided. The parameters that exacerbate the cell degradation also accelerate the rate at which Ni leaches out from the catalyst. A mechanistic model is presented for the degradation in performance of d-PtNi/C electrodes. The model correlates a) the degradation in ORR mass and specific activities with ECSA and Ni losses, b) the decrease in limiting current density ( iL), which is inversely proportional to the O 2 mass transport resistance, with the degradation in catalyst roughness factor, and c) the increase in mass transfer overpotentials with the reduced current density, i/iL .« less

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor.

PubMed

Chekin, Fereshteh; Gorton, Lo; Tapsobea, Issa

2015-01-01

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (≈100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (≈60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 ± 0.09 μM) followed by MWCNT-SPCE (0.48 ± 0.07 μM) and SPCE (0.98 ± 0.2 μM). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 ± 3.6 nM, dopamine of 640.2 ± 9.2 nM, octopamine of 3341 ± 15 nM, pyrogallol of 50.10 ± 2.9 nM and 3,4-dihydroxy-L-phenylalanine of 980.7 ± 8.7 nM using 50 μM H2O2 in the flow carrier.

Application of a palladium hexacyanoferrate film-modified aluminum electrode to electrocatalytic oxidation of hydrazine.

PubMed

Razmi, Habib; Azadbakht, Azadeh; Sadr, Moayad Hossaini

2005-11-01

A palladium hexacyanoferrate (PdHCF) film as an electrocatalytic material was obtained at an aluminum (Al) electrode by a simple electroless dipping method. The modified Al electrode demonstrated a well-behaved redox couple due to the redox reaction of the PdHCF film. The PdHCF film showed an excellent electrocatalytic activity toward the oxidation of hydrazine. The electrocatalytic oxidation of hydrazine was studied by cyclic voltammetry and rotating disk electrode voltammetry techniques. A calibration graph obtained for the hydrazine consisted of two segments (localized at concentration ranges 0.39-10 and 20-75 mM). The rate constant k and transfer coefficient alpha for the catalytic reaction and the diffusion coefficient of hydrazine in the solution D, were found to be 3.11 x 10(3) M(-1) s(-1), 0.52 and 8.03 x 10(-6) cm2 s(-1) respectively. The modified electrode was used to amperometric determination of hydrazine in photographic developer. The interference of ascorbic acid and thiosulfate were investigated and greatly reduced using a thin film of Nafion on the modified electrode. The modified electrode indicated reproducible behavior and a high level of stability during electrochemical experiments, making it particularly suitable for analytical purposes.

Highly sensitive and selective detection of dopamine based on hollow gold nanoparticles-graphene nanocomposite modified electrode.

PubMed

Zhu, Wencai; Chen, Ting; Ma, Xuemei; Ma, Houyi; Chen, Shenhao

2013-11-01

Highly dispersed hollow gold-graphene (HAu-G) nanocomposites were synthesized by a two-step method. The immobilization of hollow gold nanoparticles (HAu NPs) onto the surface of graphene sheets was achieved by mixing an aqueous solution of HAu NPs with a poly(N-vinylpyrrolidone)-functionalized graphene dispersion at room temperature. A glassy carbon electrode (GCE) was modified with the nanocomposites, and the as-prepared modified electrode displayed high electrocatalytic activity and extraordinary electronic transport properties. Amperometric detection of dopamine (DA) performed with the HAu-G modified electrode exhibits a good linearity between 0.08 and 600 μM with a low detection limit of 0.05 μM (S/N=3) and also possesses good reproducibility and operational stability. The interference of ascorbic acid (AA) and uric acid (UA) can be excluded when using differential pulse voltammetric technique. In addition, this type of modified electrode can also be applied to the determination of DA content in dopamine hydrochloride injection. It is obvious that the HAu-G modified electrode provides a new way to detect dopamine sensitively and selectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Development of electrochemical sensor for the determination of palladium ions (Pd2+) using flexible screen printed un-modified carbon electrode.

PubMed

Velmurugan, Murugan; Thirumalraj, Balamurugan; Chen, Shen-Ming; Al-Hemaid, Fahad M A; Ajmal Ali, M; Elshikh, Mohamed S

2017-01-01

To date, the development of different modified electrodes have received much attention in electrochemistry. The modified electrodes have some drawbacks such as high cost, difficult to handle and not eco friendly. Hence, we report an electrochemical sensor for the determination of palladium ions (Pd 2+ ) using an un-modified screen printed carbon electrode has been developed for the first time, which are characterized and studied via scanning electron microscope and cyclic voltammetry. Prior to determination of Pd 2+ ions, the operational conditions of un-modified SPCE was optimized using cyclic voltammetry and showed excellent electro-analytical behavior towards the determination of Pd 2+ ions. Electrochemical determination of Pd 2+ ions reveal that the un-modified electrode showed lower detection limit of 1.32μM with a linear ranging from 3 to 133.35μM towards the Pd 2+ ions concentration via differential pulse voltammetry. The developed sensor also applied to the successfully determination of trace level Pd 2+ ions in spiked water samples. In addition, the advantage of this type of electrode is simple, disposable and cost effective in electrochemical sensors. Copyright © 2016 Elsevier Inc. All rights reserved.

Using “Tender” x-ray ambient pressure x-Ray photoelectron spectroscopy as a direct probe of solid-liquid interface

DOE PAGES

Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua; ...

2015-05-07

We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquidmore » and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt²⁺ and Pt⁴⁺ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.« less

Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

PubMed Central

Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

2017-01-01

Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region. PMID:28079056

The Nucleation Rate of Single O2 Nanobubbles at Pt Nanoelectrodes.

PubMed

Soto, Álvaro Moreno; German, Sean R; Ren, Hang; van der Meer, Devaraj; Lohse, Detlef; Edwards, Martin A; White, Henry S

2018-06-13

Nanobubble nucleation is a problem that affects efficiency in electrocatalytic reactions since those bubbles can block the surface of the catalytic sites. In this article, we focus on the nucleation rate of O 2 nanobubbles resulting from the electrooxidation of H 2 O 2 at Pt disk nanoelectrodes. Bubbles form almost instantaneously when a critical peak current, i nb p , is applied, but for lower currents, bubble nucleation is a stochastic process in which the nucleation (induction) time, t ind , dramatically decreases as the applied current approaches i nb p , a consequence of the local supersaturation level, ζ, increasing at high currents. Here, by applying different currents below i nb p , nanobubbles take some time to nucleate and block the surface of the Pt electrode at which the reaction occurs, providing a means to measure the stochastic t ind . We study in detail the different conditions in which nanobubbles appear, concluding that the electrode surface needs to be preconditioned to achieve reproducible results. We also measure the activation energy for bubble nucleation, E a , which varies in the range from (6 to 30) kT, and assuming a spherically cap-shaped nanobubble nucleus, we determine the footprint diameter L = 8-15 nm, the contact angle to the electrode surface θ = 135-155°, and the number of O 2 molecules contained in the nucleus (50 to 900 molecules).