Electrocatalytic activity of cobalt phosphide-modified graphite felt toward VO2+/VO2+ redox reaction

NASA Astrophysics Data System (ADS)

Ge, Zhijun; Wang, Ling; He, Zhangxing; Li, Yuehua; Jiang, Yingqiao; Meng, Wei; Dai, Lei

2018-04-01

A novel strategy for improving the electro-catalytic properties of graphite felt (GF) electrode in vanadium redox flow battery (VRFB) is designed by depositing cobalt phosphide (CoP) onto GF surface. The CoP powder is synthesized by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation. Cyclic voltammetry results confirm that the CoP-modified graphite felt (GF-CoP) electrode has excellent reversibility and electro-catalytic activity to the VO2+/VO2+ cathodic reaction compared with the pristine GF electrode. The cell using GF-CoP electrode shows apparently higher discharge capacity over that based on GF electrode. The cell using GF-CoP electrode has the capacity of 67.2 mA h at 100 mA cm-2, 32.7 mA h larger than that using GF electrode. Compared with cell using GF electrode, the voltage efficiency of the cell based on GF-CoP electrode increases by 5.9% and energy efficiency by 5.4% at a current density of 100 mA cm-2. The cell using GF-CoP electrode can reach 94.31% capacity retention after 50 cycles at a current density of 30 mA cm-2. The results show that the CoP can effectively promote the VO2+/VO2+ redox reaction, implying that metal phosphides are a new kind of potential catalytic materials for VRFB.

The electrochemical performance of graphene modified electrodes: an analytical perspective.

PubMed

Brownson, Dale A C; Foster, Christopher W; Banks, Craig E

2012-04-21

We explore the use of graphene modified electrodes towards the electroanalytical sensing of various analytes, namely dopamine hydrochloride, uric acid, acetaminophen and p-benzoquinone via cyclic voltammetry. In line with literature methodologies and to investigate the full-implications of employing graphene in this electrochemical context, we modify electrode substrates that exhibit either fast or slow electron transfer kinetics (edge- or basal- plane pyrolytic graphite electrodes respectively) with well characterised commercially available graphene that has not been chemically treated, is free from surfactants and as a result of its fabrication has an extremely low oxygen content, allowing the true electroanalytical applicability of graphene to be properly de-convoluted and determined. In comparison to the unmodified underlying electrode substrates (constructed from graphite), we find that graphene exhibits a reduced analytical performance in terms of sensitivity, linearity and observed detection limits towards each of the various analytes studied within. Owing to graphene's structural composition, low proportion of edge plane sites and consequent slow heterogeneous electron transfer rates, there appears to be no advantages, for the analytes studied here, of employing graphene in this electroanalytical context.

Surface properties and graphitization of polyacrylonitrile based fiber electrodes affecting the negative half-cell reaction in vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Langner, J.; Bruns, M.; Dixon, D.; Nefedov, A.; Wöll, Ch.; Scheiba, F.; Ehrenberg, H.; Roth, C.; Melke, J.

2016-07-01

Carbon felt electrodes for vanadium redox flow batteries are obtained by the graphitization of polyacrylonitrile based felts at different temperatures. Subsequently, the surface of the felts is modified via thermal oxidation at various temperatures. A single-cell experiment shows that the voltage efficiency is increased by this treatment. Electrode potentials measured with reference electrode setup show that this voltage efficiency increase is caused mainly by a reduction of the overpotential of the negative half-cell reaction. Consequently, this reaction is investigated further by cyclic voltammetry and the electrode activity is correlated with structural and surface chemical properties of the carbon fibers. By Raman, X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy the role of edge sites and oxygen containing functional groups (OCFs) for the electrochemical activity are elucidated. A significant activity increase is observed in correlation with these two characteristics. The amount of OCFs is correlated with structural defects (e.g. edge sites) of the carbon fibers and therefore decreases with an increasing graphitization degree. Thus, for the same thermal oxidation temperature carbon fibers graphitized at a lower temperature show higher activities than those graphitized at a higher temperature.

Electrochemical sensing and biosensing platform based on chemically reduced graphene oxide.

PubMed

Zhou, Ming; Zhai, Yueming; Dong, Shaojun

2009-07-15

In this paper, the characterization and application of a chemically reduced graphene oxide modified glassy carbon (CR-GO/GC) electrode, a novel electrode system, for the preparation of electrochemical sensing and biosensing platform are proposed. Different kinds of important inorganic and organic electroactive compounds (i.e., probe molecule (potassium ferricyanide), free bases of DNA (guanine (G), adenine (A), thymine (T), and cytosine (C)), oxidase/dehydrogenase-related molecules (hydrogen peroxide (H2O2)/beta-nicotinamide adenine dinucleotide (NADH)), neurotransmitters (dopamine (DA)), and other biological molecules (ascorbic acid (AA), uric acid (UA), and acetaminophen (APAP)) were employed to study their electrochemical responses at the CR-GO/GC electrode, which shows more favorable electron transfer kinetics than graphite modified glassy carbon (graphite/GC) and glassy carbon (GC) electrodes. The greatly enhanced electrochemical reactivity of the four free bases of DNA at the CR-GO/GC electrode compared with that at graphite/GC and GC electrodes makes the CR-GO/GC electrode a better choice for the electrochemical biosensing of four DNA bases in both the single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) at physiological pH without a prehydrolysis step. This allows us to detect a single-nucleotide polymorphism (SNP) site for short oligomers with a particular sequence at the CR-GO/GC electrode without any hybridization or labeling processes in this work, suggesting the potential applications of CR-GO in the label-free electrochemical detection of DNA hybridization or DNA damage for further research. Based on the greatly enhanced electrochemical reactivity of H2O2 and NADH at the CR-GO/GC electrode, CR-GO/GC electrode-based bioelectrodes (in connection with glucose oxidase (GOD) and alcohol dehydrogenase (ADH)) show a better analytical performance for the detection of glucose and ethanol compared with graphite/GC- or GC-based bioelectrodes. By comparing the electrochemical performance of CR-GO with that of the conventional graphite and GC, we reveal that CR-GO with the nature of a single sheet showing favorable electrochemical activity should be a kind of more robust and advanced carbon electrode material which may hold great promise for electrochemical sensors and biosensors design.

Electroanalytical detection of pindolol: comparison of unmodified and reduced graphene oxide modified screen-printed graphite electrodes.

PubMed

Cumba, Loanda R; Smith, Jamie P; Brownson, Dale A C; Iniesta, Jesús; Metters, Jonathan P; do Carmo, Devaney R; Banks, Craig E

2015-03-07

Recent work has reported the first electroanalytical detection of pindolol using reduced graphene oxide (RGO) modified glassy carbon electrodes [S. Smarzewska and W. Ciesielski, Anal. Methods, 2014, 6, 5038] where it was reported that the use of RGO provided significant improvements in the electroanalytical signal in comparison to a bare (unmodified) glassy carbon electrode. We demonstrate, for the first time, that the electroanalytical quantification of pindolol is actually possible using bare (unmodified) screen-printed graphite electrodes (SPEs). This paper addresses the electroanalytical determination of pindolol utilising RGO modified SPEs. Surprisingly, it is found that bare (unmodified) SPEs provide superior electrochemical signatures over that of RGO modified SPEs. Consequently the electroanalytical sensing of pindolol is explored at bare unmodified SPEs where a linear range between 0.1 μM-10.0 μM is found to be possible whilst offering a limit of detection (3σ) corresponding to 0.097 μM. This provides a convenient yet analytically sensitive method for sensing pindolol. The optimised electroanalytical protocol using the unmodified SPEs, which requires no pre-treatment (electrode polishing) or electrode modification step (such as with the use of RGO), was then further applied to the determination of pindolol in urine samples. This work demonstrates that the use of RGO modified SPEs have no significant benefits when compared to the bare (unmodified) alternative and that the RGO free electrode surface can provide electro-analytically useful performances.

Graphite felt modified with bismuth nanoparticles as negative electrode in a vanadium redox flow battery.

PubMed

Suárez, David J; González, Zoraida; Blanco, Clara; Granda, Marcos; Menéndez, Rosa; Santamaría, Ricardo

2014-03-01

A graphite felt decorated with bismuth nanoparticles was studied as negative electrode in a vanadium redox flow battery (VRFB). The results confirm the excellent electrochemical performance of the bismuth modified electrode in terms of the reversibility of the V(3+) /V(2+) redox reactions and its long-term cycling performance. Moreover a mechanism that explains the role that Bi nanoparticles play in the redox reactions in this negative half-cell is proposed. Bi nanoparticles favor the formation of BiHx , an intermediate that reduces V(3+) to V(2+) and, therefore, inhibits the competitive irreversible reaction of hydrogen formation (responsible for the commonly observed loss of Coulombic efficiency of VRFBs). Thus, the total charge consumed during the cathodic sweep in this electrode is used to reduce V(3+) to V(2+) , resulting in a highly reversible and efficient process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

A simple and sensitive methodology for voltammetric determination of valproic acid in human blood plasma samples using 3-aminopropyletriethoxy silane coated magnetic nanoparticles modified pencil graphite electrode.

PubMed

Zabardasti, Abedin; Afrouzi, Hossein; Talemi, Rasoul Pourtaghavi

2017-07-01

In this work, we have prepared a nano-material modified pencil graphite electrode for the sensing of valproic acid (VA) by immobilization 3-aminopropyletriethoxy silane coated magnetic nanoparticles (APTES-MNPs) on the pencil graphite surface (PGE). Electrochemical studies indicated that the APTES-MNPs efficiently increased the electron transfer kinetics between VA and the electrode and the free NH 2 groups of the APTES on the outer surface of magnetic nanoparticles can interact with carboxyl groups of VA. Based on this, we have proposed a sensitive, rapid and convenient electrochemical method for VA determination. Under the optimized conditions, the reduction peak current of VA is found to be proportional to its concentration in the range of 1.0 (±0.2) to 100.0 (±0.3) ppm with a detection limit of 0.4 (±0.1) ppm. The whole sensor fabrication process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods with using [Fe(CN) 6 ] 3-/4- as an electrochemical redox indicator. The prepared modified electrode showed several advantages such as high sensitivity, selectivity, ease of preparation and good repeatability, reproducibility and stability. The proposed method was applied to determination of valproic acid in blood plasma samples and the obtained results were satisfactory accurate. Copyright © 2017. Published by Elsevier B.V.

Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites

DOEpatents

Guadalupe, Ana R.; Guo, Yizhu

2001-05-15

A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.

Stripping voltammetry in environmental and food analysis.

PubMed

Brainina, K Z; Malakhova, N A; Stojko, N Y

2000-10-01

The review covers over 230 papers published mostly in the last 5 years. The goal of the review is to attract the attention of researchers and users to stripping voltammetry in particular, its application in environmental monitoring and analysis of foodstuffs. The sensors employed are impregnated graphite, carbon paste, thick film carbon/graphite and thin film metallic electrodes modified in-situ or beforehand. Hanging mercury drop electrodes and mercury coated glassy carbon electrodes are also mentioned. Strip and long-lived sensors for portable instruments and flow through systems are discussed as devices for future development and application of stripping voltammetry.

Outstanding electrochemical performance of a graphene-modified graphite felt for vanadium redox flow battery application

NASA Astrophysics Data System (ADS)

González, Zoraida; Flox, Cristina; Blanco, Clara; Granda, Marcos; Morante, Juan R.; Menéndez, Rosa; Santamaría, Ricardo

2017-01-01

The development of more efficient electrode materials is essential to obtain vanadium redox flow batteries (VRFBs) with enhanced energy densities and to make these electrochemical energy storage devices more competitive. A graphene-modified graphite felt synthesized from a raw graphite felt and a graphene oxide water suspension by means of electrophoretic deposition (EPD) is investigated as a suitable electrode material in the positive side of a VRFB cell by means of cyclic voltammetry, impedance spectroscopy and charge/discharge experiments. The remarkably enhanced performance of the resultant hybrid material, in terms of electrochemical activity and kinetic reversibility towards the VO2+/VO2+, and mainly the markedly high energy efficiency of the VRFB cell (c.a. 95.8% at 25 mA cm-2) can be ascribed to the exceptional morphological and chemical characteristics of this tailored material. The 3D-architecture consisting of fibers interconnected by graphene-like sheets positively contributes to the proper development of the vanadium redox reactions and so represents a significant advance in the design of effective electrode materials.

Efficient degradation of rhodamine B using modified graphite felt gas diffusion electrode by electro-Fenton process.

PubMed

Tian, Jiangnan; Olajuyin, Ayobami Matthew; Mu, Tingzhen; Yang, Maohua; Xing, Jianmin

2016-06-01

The electro-Fenton (EF) process treatment of 0.1-M (rhodamine B) RhB solution was studied with different graphite cathode materials, and graphite felt (GF) was selected as a promising material in further investigation. Then, the degradation performances of gas diffusion electrode (GDE) and graphite felt (GF) were compared, and GDE was confirmed to be more efficient in RhB removal. The operational parameters such as Fe(2+) dosage and current density were optimized, and comparison among different modified methods-polytetrafluoroethylene-carbon black (PTFE-CB), polytetrafluoroethylene-carbon nanotube (PTFE-CNT), electrodeposition-CB, and electrodeposition-CNT-showed 98.49 % RhB removal by PTFE-CB-modified cathode in 0.05 M Na2SO4 at a current density of 50 A/m(2) and an air flow rate of 1 L/min after 20 min. Meanwhile, after cathode modified by PTFE-CB, the mineralization efficiency and mineralization current efficiency performed absolutely better than the pristine one. Cyclic voltammograms, SEM images, contact angles, and BET surface area were carried out to demonstrate stronger current responses and higher hydrophilicity of GF after modified. The value of biochemical oxygen demand/chemical oxygen demand (BOD5/COD) increased from 0.049 to 0.331 after 90-min treatment, suggesting the solution was biodegradable, and the modified cathode was confirmed to be stable after ten circle runs. Finally, a proposed degradation pathway of RhB was put forward.

A novel self-powered and sensitive label-free DNA biosensor in microbial fuel cell.

PubMed

Asghary, Maryam; Raoof, Jahan Bakhsh; Rahimnejad, Mostafa; Ojani, Reza

2016-08-15

In this work, a novel self-powered, sensitive, low-cost, and label-free DNA biosensor is reported by applying a two-chambered microbial fuel cell (MFC) as a power supply. A graphite electrode and an Au nanoparticles modified graphite electrode (AuNP/graphite electrode) were used as anode and cathode in the MFC system, respectively. The active biocatalyst in the anodic chamber was a mixed culture of microorganisms. The sensing element of the biosensor was fabricated by the well-known Au-thiol binding the ssDNA probe on the surface of an AuNP/graphite cathode. Electrons produced by microorganisms were transported from the anode to the cathode through an external circuit, which could be detected by the terminal multi-meter detector. The difference between power densities of the ssDNA probe modified cathode in the absence and presence of complementary sequence served as the detection signal of the DNA hybridization with detection limit of 3.1nM. Thereafter, this biosensor was employed for diagnosis and determination of complementary sequence in a human serum sample. The hybridization specificity studies further revealed that the developed DNA biosensor could distinguish fully complementary sequences from one-base mismatched and non-complementary sequences. Copyright © 2016 Elsevier B.V. All rights reserved.

Structure-Property Relationships in Surface-Modified Ceramics. NATO advanced Science Institutes, Series E: Applied Sciences, Volume 170

DTIC Science & Technology

1989-01-01

channelling and scanning electron microscopy (SEM) of highly oriented pyrolytic graphite ( HOPG ), comparative scratch testing results and some ideas on...electrode graphite , HOPG and carbon fibers also show enhanced wear resistance followoing irradiation (6), the extent of which depends upon the initial...literature dealing with damage effects and physical property changes following neutron irradiation of graphite (single and polycrystalline ) in nuclear

Graphene-based electrochemical sensor for detection of 2,4,6-trinitrotoluene (TNT) in seawater: the comparison of single-, few-, and multilayer graphene nanoribbons and graphite microparticles.

PubMed

Goh, Madeline Shuhua; Pumera, Martin

2011-01-01

The detection of explosives in seawater is of great interest. We compared response single-, few-, and multilayer graphene nanoribbons and graphite microparticle-based electrodes toward the electrochemical reduction of 2,4,6-trinitrotoluene (TNT). We optimized parameters such as accumulation time, accumulation potential, and pH. We found that few-layer graphene exhibits about 20% enhanced signal for TNT after accumulation when compared to multilayer graphene nanoribbons. However, graphite microparticle-modified electrode provides higher sensitivity, and there was no significant difference in the performance of single-, few-, and multilayer graphene nanoribbons and graphite microparticles for the electrochemical detection of TNT. We established the limit of detection of TNT in untreated seawater at 1 μg/mL.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

PubMed Central

Yaman, Yesim Tugce; Abaci, Serdar

2016-01-01

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability. PMID:27231912

One-step preparation of nanostructured martite catalyst and graphite electrode by glow discharge plasma for heterogeneous electro-Fenton like process.

PubMed

Khataee, Alireza; Sajjadi, Saeed; Hasanzadeh, Aliyeh; Vahid, Behrouz; Joo, Sang Woo

2017-09-01

Natural Martite ore particles and graphite were modified by alternating current (AC) glow discharge plasma to form nanostructured catalyst and cathode electrode for using in the heterogeneous-electro Fenton-like (Het-EF-like) process. The performance of the plasma-treated martite (PTM) and graphite electrode (PTGE) was studied for the treatment of paraquat herbicide in a batch system. 85.78% degradation efficiency for 20 mg L -1 paraquat was achieved in the modified process under desired operational conditions (i.e. current intensity of 300 mA, catalyst amount of 1 g L -1 , pH = 6, and background electrolyte (Na 2 SO 4 ) concentration of 0.05 mol L -1 ) which was higher than the 41.03% for the unmodified one after 150 min of treatment. The ecofriendly modification of the martite particles and the graphite electrode, no chemical needed, low leached iron and milder operational pH were the main privileges of plasma utilization. Moreover, the degradation efficiency through the process was not declined after five repeated cycles at the optimized conditions, which proved the stability of the nanostructured PTM and PTGE in the long-term usage. The archived results exhibit this method is the first example of high efficient, cost-effective, and environment-friendly method for generation of nanostructured samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Modified Au nanoparticles-imprinted sol-gel, multiwall carbon nanotubes pencil graphite electrode used as a sensor for ranitidine determination.

PubMed

Rezaei, B; Lotfi-Forushani, H; Ensafi, A A

2014-04-01

A new, simple, and disposable molecularly imprinted electrochemical sensor for the determination of ranitidine was developed on pencil graphite electrode (PGE) via cyclic voltammetry (CV). The PGEs were coated with MWCNTs containing the carboxylic functional group (f-MWCNTs), imprinted with sol-gel and Au nanoparticle (AuNPs) layers (AuNP/MIP-sol-gel/f-MWCNT/PGE), respectively, to enhance the electrode's electrical transmission and sensitivity. The thin film of molecularly imprinted sol-gel polymers with specific binding sites for ranitidine was cast on modified PGE by electrochemical deposition. The AuNP/MIP-sol-gel/f-MWCNT/PGE thus developed was characterized by electrochemical impedance spectroscopy (EIS) and CV. The interaction between the imprinted sensor and the target molecule was also observed on the electrode by measuring the current response of 5.0mMK3[Fe(CN)6] solution as an electrochemical probe. The pick currents of ranitidine increased linearly with concentration in the ranges of 0.05 to 2.0μM, with a detection limit of (S/N=3) 0.02μM. Finally, the modified electrode was successfully employed to determine ranitidine in human urine samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Specific and Reversible Immobilization of Proteins Tagged to the Affinity Polypeptide C-LytA on Functionalized Graphite Electrodes

PubMed Central

Bello-Gil, Daniel; Maestro, Beatriz; Fonseca, Jennifer; Feliu, Juan M.; Climent, Víctor; Sanz, Jesús M.

2014-01-01

We have developed a general method for the specific and reversible immobilization of proteins fused to the choline-binding module C-LytA on functionalized graphite electrodes. Graphite electrode surfaces were modified by diazonium chemistry to introduce carboxylic groups that were subsequently used to anchor mixed self-assembled monolayers consisting of N,N-diethylethylenediamine groups, acting as choline analogs, and ethanolamine groups as spacers. The ability of the prepared electrodes to specifically bind C-LytA-tagged recombinant proteins was tested with a C-LytA-β-galactosidase fusion protein. The binding, activity and stability of the immobilized protein was evaluated by electrochemically monitoring the formation of an electroactive product in the enzymatic hydrolysis of the synthetic substrate 4-aminophenyl β-D-galactopyranoside. The hybrid protein was immobilized in an specific and reversible way, while retaining the catalytic activity. Moreover, these functionalized electrodes were shown to be highly stable and reusable. The method developed here can be envisaged as a general, immobilization procedure on the protein biosensor field. PMID:24498237

Specific and reversible immobilization of proteins tagged to the affinity polypeptide C-LytA on functionalized graphite electrodes.

PubMed

Bello-Gil, Daniel; Maestro, Beatriz; Fonseca, Jennifer; Feliu, Juan M; Climent, Víctor; Sanz, Jesús M

2014-01-01

We have developed a general method for the specific and reversible immobilization of proteins fused to the choline-binding module C-LytA on functionalized graphite electrodes. Graphite electrode surfaces were modified by diazonium chemistry to introduce carboxylic groups that were subsequently used to anchor mixed self-assembled monolayers consisting of N,N-diethylethylenediamine groups, acting as choline analogs, and ethanolamine groups as spacers. The ability of the prepared electrodes to specifically bind C-LytA-tagged recombinant proteins was tested with a C-LytA-β-galactosidase fusion protein. The binding, activity and stability of the immobilized protein was evaluated by electrochemically monitoring the formation of an electroactive product in the enzymatic hydrolysis of the synthetic substrate 4-aminophenyl β-D-galactopyranoside. The hybrid protein was immobilized in an specific and reversible way, while retaining the catalytic activity. Moreover, these functionalized electrodes were shown to be highly stable and reusable. The method developed here can be envisaged as a general, immobilization procedure on the protein biosensor field.

Nitrogen-Doped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries.

PubMed

Wang, Shuangyin; Zhao, Xinsheng; Cochell, Thomas; Manthiram, Arumugam

2012-08-16

Nitrogen-doped carbon nanotubes have been grown, for the first time, on graphite felt (N-CNT/GF) by a chemical vapor deposition approach and examined as an advanced electrode for vanadium redox flow batteries (VRFBs). The unique porous structure and nitrogen doping of N-CNT/GF with increased surface area enhances the battery performance significantly. The enriched porous structure of N-CNTs on graphite felt could potentially facilitate the diffusion of electrolyte, while the N-doping could significantly contribute to the enhanced electrode performance. Specifically, the N-doping (i) modifies the electronic properties of CNT and thereby alters the chemisorption characteristics of the vanadium ions, (ii) generates defect sites that are electrochemically more active, (iii) increases the oxygen species on CNT surface, which is a key factor influencing the VRFB performance, and (iv) makes the N-CNT electrochemically more accessible than the CNT.

In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

PubMed

Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

2015-09-15

Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. Copyright © 2015 Elsevier B.V. All rights reserved.

Simultaneous determination of Cd(II) and Pb(II) by differential pulse anodic stripping voltammetry based on graphite nanofibers-Nafion composite modified bismuth film electrode.

PubMed

Li, Dongyue; Jia, Jianbo; Wang, Jianguo

2010-12-15

A bismuth-film modified graphite nanofibers-Nafion glassy carbon electrode (BiF/GNFs-NA/GCE) was constructed for the simultaneous determination of trace Cd(II) and Pb(II). The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as deposition potential, deposition time, and bismuth ion concentration were optimized for the purpose of determination of trace metal ions in 0.10 M acetate buffer solution (pH 4.5). Under optimal conditions, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L(-1) for Cd(II) and 0.02 μg L(-1) for Pb(II) with a 10 min preconcentration. In addition, the BiF/GNFs-NA/GCE displayed good reproducibility and selectivity, making it suitable for the simultaneous determination of Cd(II) and Pb(II) in real sample such as river water and human blood samples. Copyright © 2010 Elsevier B.V. All rights reserved.

Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles.

PubMed

Asadian, Elham; Iraji Zad, Azam; Shahrokhian, Saeed

2016-01-01

By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable decrease in its reduction overpotential. These results can be attributed to the incredible enlargement in the microscopic surface area of the electrode due to the presence of graphene nanosheets together with strong adsorption of Aza on its surface. The effect of experimental parameters such as accumulation time, the amount of modifier suspension and pH of the supporting electrolyte were also optimized toward obtaining the maximum sensitivity. Under the optimum conditions, the calibration curve studies demonstrated that the peak current increased linearly with Aza concentrations in the range of 7 × 10(-7) to 1 × 10(-4)mol L(-1) with the detection limit of 68 nM. Further experiments revealed that the modified electrode can be successfully applied for the accurate determination of Aza in pharmaceutical preparations. Copyright © 2015 Elsevier B.V. All rights reserved.

Sputtering graphite coating to improve the elevated-temperature cycling ability of the LiMn2O4 electrode.

PubMed

Wang, Jiexi; Zhang, Qiaobao; Li, Xinhai; Wang, Zhixing; Guo, Huajun; Xu, Daguo; Zhang, Kaili

2014-08-14

To improve the cycle performance of LiMn2O4 at elevated temperature, a graphite layer is introduced to directly cover the surface of a commercial LiMn2O4-based electrode via room-temperature DC magnetron sputtering. The as-modified cathodes display improved capacity retention as compared to the bare LiMn2O4 cathode (BLMO) at 55 °C. When sputtering graphite for 30 min, the sample shows the best cycling performance at 55 °C, maintaining 96.2% capacity retention after 200 cycles. Reasons with respect to the graphite layer for improving the elevated-temperature performance of LiMn2O4 are systematically investigated via the methods of cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectrometry, scanning and transmission electron microscopy, X-ray diffraction and inductively coupled plasma-atomic emission spectrometry. The results demonstrate that the graphite coated LiMn2O4 cathode has much less increased electrode polarization and electrochemical impedance than BLMO during the elevated-temperature cycling process. Furthermore, the graphite layer is able to alleviate the severe dissolution of manganese ions into the electrolyte and mitigate the morphological and structural degradation of LiMn2O4 during cycling. A model for the electrochemical kinetics process is also suggested for explaining the roles of the graphite layer in suppressing the Mn dissolution.

Phosphomolybdic acid immobilized on graphite as an environmental photoelectrocatalyst.

PubMed

Aber, Soheil; Yaghoubi, Zeynab; Zarei, Mahmoud

2016-10-01

A new phosphomolybdic acid (PMA)/Graphite surface was prepared based on electrostatic interactions between phosphomolybdic acid and graphite surface. The PMA/Graphite was characterized by cyclic voltammetry (CV) analysis and scanning electron microscope (SEM). SEM images showed that the phosphomolybdic acid particles were well stabilized on the graphite surface and they were evidenced the size of particles (approximately 10 nm). The CV results not only showed that the modified surface has good electrochemical activity toward the removal of the dyestuff, but also exhibits long term stability. The PMA/Graphite was used as a photoanode for decolorization of Reactive Yellow 39 by photoelectrocatalytic system under UV irradiation. The effects of parameters such as the amount of phosphomolybdic acid used in preparation of PMA/Graphite surface, applied potential on anode electrode and solution pH were studied by response surface methodology. The optimum conditions were obtained as follows: dye solution pH 3, 1.5 g of immobilized PMA on graphite surface and applied potential on anode electrode 1 V. Under optimum conditions after 90 min of reaction time, the decolorization efficiency was 95%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Toxic Effect of Cadmium Assay in Contaminated Soil Earthworm Cell Using Modified Sensor

PubMed Central

Kyung, Lee; Kim, Chae Hwa; Seo, Roma; Lee, Soo Youn; Kim, Lina; Chae, Su min; Choi, Sung Wook; Kim, Ji Yoon

2015-01-01

A voltammetric toxic metal of cadmium detection was studied using a fluorine doped graphite pencil electrode (FPE) in a seawater electrolyte. In this study, square wave (SW) stripping and chronoamerometry were used for determination of Cd(II) in seawater. Affordable pencils and an auxiliary electrode were used as reference. All experiments in this study could be performed at reasonable cost by using graphite pencil. The application was performed on the tissue of contaminated soil earthworm. The results show that the method can be applicable for vegetables and in vivo fluid or medicinal diagnosis. PMID:26191388

2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction.

PubMed

Rowley-Neale, Samuel J; Brownson, Dale A C; Smith, Graham C; Sawtell, David A G; Kelly, Peter J; Banks, Craig E

2015-11-21

We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER.

Mesoscopic modeling and parameter estimation of a lithium-ion battery based on LiFePO4/graphite

NASA Astrophysics Data System (ADS)

Jokar, Ali; Désilets, Martin; Lacroix, Marcel; Zaghib, Karim

2018-03-01

A novel numerical model for simulating the behavior of lithium-ion batteries based on LiFePO4(LFP)/graphite is presented. The model is based on the modified Single Particle Model (SPM) coupled to a mesoscopic approach for the LFP electrode. The model comprises one representative spherical particle as the graphite electrode, and N LFP units as the positive electrode. All the SPM equations are retained to model the negative electrode performance. The mesoscopic model rests on non-equilibrium thermodynamic conditions and uses a non-monotonic open circuit potential for each unit. A parameter estimation study is also carried out to identify all the parameters needed for the model. The unknown parameters are the solid diffusion coefficient of the negative electrode (Ds,n), reaction-rate constant of the negative electrode (Kn), negative and positive electrode porosity (εn&εn), initial State-Of-Charge of the negative electrode (SOCn,0), initial partial composition of the LFP units (yk,0), minimum and maximum resistance of the LFP units (Rmin&Rmax), and solution resistance (Rcell). The results show that the mesoscopic model can simulate successfully the electrochemical behavior of lithium-ion batteries at low and high charge/discharge rates. The model also describes adequately the lithiation/delithiation of the LFP particles, however, it is computationally expensive compared to macro-based models.

Determination of atropine sulfate using a novel sensitive DNA-biosensor based on its interaction on a modified pencil graphite electrode.

PubMed

Ensafi, Ali A; Nasr-Esfahani, Parisa; Heydari-Bafrooei, Esmaeil; Rezaei, B

2015-01-01

A novel, selective, rapid and simple electrochemical method is developed for the determination of atropine sulfate. UV-Vis and differential pulse voltammetry are used to study the interaction of atropine sulfate with salmon sperm ds-DNA on the surface of salmon sperm ds-DNA modified-pencil graphite electrode (PGE). For this purpose, a pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs), titanium dioxide nanoparticles (TiO2NPs), and poly-dialyldimethylammonium chloride (PDDA) decorated with ds-DNA is tested for the determination of atropine sulfate. The electrochemical oxidation peak current of adenine and guanine bonded on the surface of ds-DNA/PDDA-TiO2NPs-MWCNTs/PGE is used to obtain the analytical signal. Decreases in the intensities of guanine and adenine oxidation signals after their interaction with atropine sulfate are used as indicator signals for the sensitive determination of atropine sulfate. Using ds-DNA/PDDA-TiO2NPs-MWCNTs/PGE and based on the guanine signal, linear calibration curves were obtained in the range of 0.6 to 30.0 μmol L(-1) and 30.0 to 600.0 μmol L(-1) atropine sulfate with low detection limits of 30.0 nmol L(-1). The biosensor shows a good selectivity for the determination of atropine sulfate. Finally, the applicability of the biosensor is evaluated by measuring atropine sulfate in real samples with good accuracy. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

PubMed

Yumak, Tugrul; Kuralay, Filiz; Muti, Mihrican; Sinag, Ali; Erdem, Arzum; Abaci, Serdar

2011-09-01

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1). Copyright © 2011 Elsevier B.V. All rights reserved.

Preparation of Graphene Sheets by Electrochemical Exfoliation of Graphite in Confined Space and Their Application in Transparent Conductive Films.

PubMed

Wang, Hui; Wei, Can; Zhu, Kaiyi; Zhang, Yu; Gong, Chunhong; Guo, Jianhui; Zhang, Jiwei; Yu, Laigui; Zhang, Jingwei

2017-10-04

A novel electrochemical exfoliation mode was established to prepare graphene sheets efficiently with potential applications in transparent conductive films. The graphite electrode was coated with paraffin to keep the electrochemical exfoliation in confined space in the presence of concentrated sodium hydroxide as the electrolyte, yielding ∼100% low-defect (the D band to G band intensity ratio, I D /I G = 0.26) graphene sheets. Furthermore, ozone was first detected with ozone test strips, and the effect of ozone on the exfoliation of graphite foil and the microstructure of the as-prepared graphene sheets was investigated. Findings indicate that upon applying a low voltage (3 V) on the graphite foil partially coated with paraffin wax that the coating can prevent the insufficiently intercalated graphite sheets from prematurely peeling off from the graphite electrode thereby affording few-layer (<5 layers) holey graphene sheets in a yield of as much as 60%. Besides, the ozone generated during the electrochemical exfoliation process plays a crucial role in the exfoliation of graphite, and the amount of defect in the as-prepared graphene sheets is dependent on electrolytic potential and electrode distance. Moreover, the graphene-based transparent conductive films prepared by simple modified vacuum filtration exhibit an excellent transparency and a low sheet resistance after being treated with NH 4 NO 3 and annealing (∼1.21 kΩ/□ at ∼72.4% transmittance).

A simple preparation of graphite/gelatin composite for electrochemical detection of dopamine.

PubMed

Rajkumar, Chellakannu; Thirumalraj, Balamurugan; Chen, Shen-Ming; Chen, His-An

2017-02-01

In this study, we demonstrate a simple preparation of graphite (GR) sheets assisted with gelatin (GLN) polypeptide composite was developed for sensitive detection of dopamine (DA) sensor. The GR/GLN composite was prepared by GR powder in GLN solution (5mg/mL) via sonication process. The prepared GR/GLN composite displays well dispersion ability in biopolymer matrix and characterized via scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS) studies. The GR/GLN modified electrode showed an excellent electrocatalytic activity toward the oxidation of DA, suggesting that the successful formation of GR sheets crosslinked with the functional groups of GLN polypeptide. In addition, the GR/GLN modified electrode achieved a wide linear response ranging from 0.05 to 79.5μM with a detection limit of 0.0045μM. The calculated analytical sensitivity of the sensor was 1.36±0.02μAμM -1 cm -2 . Conversely, the modified electrode demonstrates a good storage stability, reproducibility and repeatability. In addition, the sensor manifests the determination of DA in human serum and urine samples for practical applications. Copyright © 2016 Elsevier Inc. All rights reserved.

2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction

NASA Astrophysics Data System (ADS)

Rowley-Neale, Samuel J.; Brownson, Dale A. C.; Smith, Graham C.; Sawtell, David A. G.; Kelly, Peter J.; Banks, Craig E.

2015-10-01

We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER.We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05164a|ART

ZrO2-Nanoparticle-Modified Graphite Felt: Bifunctional Effects on Vanadium Flow Batteries.

PubMed

Zhou, Haipeng; Shen, Yi; Xi, Jingyu; Qiu, Xinping; Chen, Liquan

2016-06-22

To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium flow batteries (VFBs), we synthesize a series of ZrO2-modified GF (ZrO2/GF) electrodes with varying ZrO2 contents via a facile immersion-precipitation approach. It is found that the uniform immobilization of ZrO2 nanoparticles on the GF not only significantly promotes the accessibility of vanadium electrolyte, but also provides more active sites for the redox reactions, thereby resulting in better electrochemical activity and reversibility toward the VO(2+)/VO2(+) and V(2+)/V(3+) redox reactions as compared with those of GF. In particular, The ZrO2/GF composite with 0.3 wt % ZrO2 displays the best electrochemical performance with voltage and energy efficiencies of 71.9% and 67.4%, respectively, which are much higher than those of 57.3% and 53.8% as obtained from the GF electrode at 200 mA cm(-2). The cycle life tests demonstrate that the ZrO2/GF electrodes exhibit outstanding stability. The ZrO2/GF-based VFB battery shows negligible activity decay after 200 cycles.

Monolithic quasi-solid-state dye-sensitized solar cells based on graphene-modified mesoscopic carbon-counter electrodes

NASA Astrophysics Data System (ADS)

Rong, Yaoguang; Han, Hongwei

2013-01-01

A monolithic quasi-solid-state dye-sensitized solar cell (DSSC) based on graphene-modified mesoscopic carbon-counter electrode is developed. A TiO2-working electrode layer, ZrO2 spacer layer, and carbon counter electrode layer were constructed on a single conducting glass substrate by screen printing. The quasi-solid-state polymer gel electrolyte employed a polymer composite as the gelator, and effectively infiltrated the porous layers. Fabricated with normal carbon-counter electrode (NC-CE) containing graphite and carbon black, the DSSC had a power conversion efficiency (PCE) of 5.09% with the fill factor of 0.63 at 100 mW cm-2 AM1.5 illumination. When the NC-CE was modified with graphene sheets, the PCE and fill factor were enhanced to 6.27% and 0.71, respectively. This improvement indicates excellent conductivity and high electrocatalytic activity of the graphene sheets, which have been considered as a promising platinum-free electrode material for DSSCs.

ELECTROCHEMICAL DECHLORINATIONOF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

EPA Science Inventory

This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-CI BP) in aqueous environment using palladium modified granular graphite electrodes. 2-CI BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

ELECTROCHEMICAL DECHLORINATION OF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

EPA Science Inventory

This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous environment using palladium modified granular graphite electrodes. 2-Cl BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

Modified Graphene Oxide for Long Cycle Sodium-Ion Batteries

NASA Astrophysics Data System (ADS)

Shareef, Muhamed; Gunn, Harrison; Voigt, Victoria; Singh, Gurpreet

Hummer's process was modified to produce gram levels of 2-dimensional nanosheets of graphene oxide (GO) with varying degree of exfoliation and chemical functionalization. This was achieved by varying the weight ratios and reaction times of oxidizing agents used in the process. Based on Raman and Fourier transform infra red spectroscopy we show that potassium permanganate (KMnO4) is the key oxidizing agent while sodium nitrate (NaNO3) and sulfuric acid (H2SO4) play minor role during the exfoliation of graphite. Tested as working electrode in sodium-ion half-cell, the GO nanosheets produced using this optimized approach showed high rate capability and exceptionally high energy density of ~500 mAh/g for up to at least 100 cycles, which is among the highest reported for sodium/graphite electrodes. The average Coulombic efficiency was approximately 99 %. NSF Grant No. 1454151.

Direct electron transfer of Phanerochaete chrysosporium cellobiose dehydrogenase at platinum and palladium nanoparticles decorated carbon nanotubes modified electrodes.

PubMed

Bozorgzadeh, Somayyeh; Hamidi, Hassan; Ortiz, Roberto; Ludwig, Roland; Gorton, Lo

2015-10-07

In the present work, platinum and palladium nanoparticles (PtNPs and PdNPs) were decorated on the surface of multi-walled carbon nanotubes (MWCNTs) by a simple thermal decomposition method. The prepared nanohybrids, PtNPs-MWCNTs and PdNPs-MWCNTs, were cast on the surface of spectrographic graphite electrodes and then Phanerochaete chrysosporium cellobiose dehydrogenase (PcCDH) was adsorbed on the modified layer. Direct electron transfer between PcCDH and the nanostructured modified electrodes was studied using flow injection amperometry and cyclic voltammetry. The maximum current responses (Imax) and the apparent Michaelis-Menten constants (K) for the different PcCDH modified electrodes were calculated by fitting the data to the Michaelis-Menten equation and compared. The sensitivity towards lactose was 3.07 and 3.28 μA mM(-1) at the PcCDH/PtNPs-MWCNTs/SPGE and PcCDH/PdNPs-MWCNTs/SPGE electrodes, respectively, which were higher than those measured at the PcCDH/MWCNTs/SPGE (2.60 μA mM(-1)) and PcCDH/SPGE (0.92 μA mM(-1)). The modified electrodes were additionally tested as bioanodes for biofuel cell applications.

Photocurrent generation by direct electron transfer using photosynthetic reaction centres

NASA Astrophysics Data System (ADS)

Mahmoudzadeh, A.; Saer, R.; Jun, D.; Mirvakili, S. M.; Takshi, A.; Iranpour, B.; Ouellet, E.; Lagally, E. T.; Madden, J. D. W.; Beatty, J. T.

2011-09-01

Photosynthetic reaction centres (RCs) convert light into separated charges with nearly perfect quantum efficiency, and have been used to generate photocurrent. Previous work has shown that electron tunnelling rates between redox centres in proteins depend exponentially on the tunnelling distance. In this work the RC from Rhodobacter sphaeroides was genetically modified with the aim of achieving the shortest tunnelling distances yet demonstrated between the RC's electron-accepting P site and underlying graphite and gold electrodes, and between the electron donor Q site and graphite electrodes. Opposite charges are carried to counter electrodes using mobile mediators, as in dye-sensitised solar cells. Native RCs are bound to graphite surfaces through N-(1-pyrene)iodoacetamide. Although the linker's length is only 4 Å, the electron transfer pathway between the Q electron donor site on the RC and the electrode surface is still too large for current to be significant. A mutant version with the electron acceptor P side close to the graphite surface produced currents of 15 nA cm-2 upon illumination. Direct binding of RCs to a gold surface is shown, resulting in currents of 5 nA cm-2. In both cases the current was unaffected by mediator concentration but increased with illumination, suggesting that direct electron transfer was achieved. The engineering of an RC to achieve direct electron transfer will help with long term efforts to demonstrate RC-based photovoltaic devices.

Label-Free Electrochemical Detection of the Specific Oligonucleotide Sequence of Dengue Virus Type 1 on Pencil Graphite Electrodes

PubMed Central

Souza, Elaine; Nascimento, Gustavo; Santana, Nataly; Ferreira, Danielly; Lima, Manoel; Natividade, Edna; Martins, Danyelly; Lima-Filho, José

2011-01-01

A biosensor that relies on the adsorption immobilization of the 18-mer single-stranded nucleic acid related to dengue virus gene 1 on activated pencil graphite was developed. Hybridization between the probe and its complementary oligonucleotides (the target) was investigated by monitoring guanine oxidation by differential pulse voltammetry (DPV). The pencil graphite electrode was made of ordinary pencil lead (type 4B). The polished surface of the working electrode was activated by applying a potential of 1.8 V for 5 min. Afterward, the dengue oligonucleotides probe was immobilized on the activated electrode by applying 0.5 V to the electrode in 0.5 M acetate buffer (pH 5.0) for 5 min. The hybridization process was carried out by incubating at the annealing temperature of the oligonucleotides. A time of five minutes and concentration of 1 μM were found to be the optimal conditions for probe immobilization. The electrochemical detection of annealing between the DNA probe (TS-1P) immobilized on the modified electrode, and the target (TS-1T) was achieved. The target could be quantified in a range from 1 to 40 nM with good linearity and a detection limit of 0.92 nM. The specificity of the electrochemical biosensor was tested using non-complementary sequences of dengue virus 2 and 3. PMID:22163916

Pseudocapacitive performance of electrodeposited porous Co3O4 film on electrophoretically modified graphite electrodes with carbon nanotubes

NASA Astrophysics Data System (ADS)

Kazazi, Mahdi; Sedighi, Ali Reza; Mokhtari, Mohammad Amin

2018-05-01

A facile and efficient two-step procedure was developed for the fabrication of a high-performance and binder-free cobalt oxide-carbon nanotubes (CO/CNT) pseudocapacitive electrode. First, CNTs were deposited on the surface of a chemically activated graphite sheet by cathodic electrophoretic deposition technique from their ethanolic suspension. In the next step, a thin film of cobalt oxide was electrodeposited on the CNTs coated graphite substrate by a galvanostatic method, followed by a thermal treatment in air. The structure and morphology of the prepared cobaltite electrode with and without CNT interlayer were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and nitrogen adsorption-desorption measurement. The results indicated that Co3O4 nanoparticles were uniformly attached on the surface of CNTs, to form a porous-structured CO/CNT composite electrode with a high specific surface area of 144.9 m2 g-1. Owing to the superior electrical conductivity of CNTs, high surface area and open porous structure, and improved integrity of the electrode structure, the composite electrode delivered a high areal capacitance of 4.96F cm-2 at a current density of 2 mA cm-2, a superior rate performance (64.7% capacitance retention from 2 mA cm-2 to 50 mA cm-2), as well as excellent cycling stability (91.8% capacitance retention after 2000 cycles), which are higher than those of the pure cobaltite electrode.

Quantifying microstructural dynamics and electrochemical activity of graphite and silicon-graphite lithium ion battery anodes

NASA Astrophysics Data System (ADS)

Pietsch, Patrick; Westhoff, Daniel; Feinauer, Julian; Eller, Jens; Marone, Federica; Stampanoni, Marco; Schmidt, Volker; Wood, Vanessa

2016-09-01

Despite numerous studies presenting advances in tomographic imaging and analysis of lithium ion batteries, graphite-based anodes have received little attention. Weak X-ray attenuation of graphite and, as a result, poor contrast between graphite and the other carbon-based components in an electrode pore space renders data analysis challenging. Here we demonstrate operando tomography of weakly attenuating electrodes during electrochemical (de)lithiation. We use propagation-based phase contrast tomography to facilitate the differentiation between weakly attenuating materials and apply digital volume correlation to capture the dynamics of the electrodes during operation. After validating that we can quantify the local electrochemical activity and microstructural changes throughout graphite electrodes, we apply our technique to graphite-silicon composite electrodes. We show that microstructural changes that occur during (de)lithiation of a pure graphite electrode are of the same order of magnitude as spatial inhomogeneities within it, while strain in composite electrodes is locally pronounced and introduces significant microstructural changes.

Construction and performance evaluation of mediator-less microbial fuel cell using carbon nanotubes as an anode material.

PubMed

Roh, Sung-Hee; Kim, Sun-Il

2012-05-01

A microbial fuel cell (MFC) is a device that converts chemical energy to electrical energy using the catalytic reaction of microorganisms. We investigated the performance of mediator-less MFC with carbon nanotubes (CNTs)/graphite felt composite electrodes. The addition of CNTs to a graphite felt electrode increases the specific surface area of the electrode and enhances the charge transfer capability so as to cause considerable improvement of the electrochemical activity for the anode reaction in a MFC. The performance of the MFC using CNTs/graphite felt electrode has been compared against a plain graphite felt electrode based MFC. A CNTs/graphite felt electrode showed as high as 15% increase in the power density (252 mW/m2) compared to graphite felt electrode (214 mW/m2). The CNTs/graphite felt anode therefore offers good prospects for application in MFCs.

Reagent-less amperometric glucose biosensor based on a graphite rod electrode layer-by-layer modified with 1,10-phenanthroline-5,6-dione and glucose oxidase.

PubMed

Kausaite-Minkstimiene, Asta; Simanaityte, Ruta; Ramanaviciene, Almira; Glumbokaite, Laura; Ramanavicius, Arunas

2017-08-15

A reagent-less amperometric glucose biosensor operating in not-stirred sample solution was developed. A working electrode of the designed biosensor was based on a graphite rod (GR) electrode, which was modified with 1,10-phenanthroline-5,6-dione (PD) and glucose oxidase (GOx). The PD and the GOx were layer-by-layer adsorbed on the GR electrode surface with subsequent drying followed by chemical cross-linking of the adsorbed GOx with glutaraldehyde (GA). Optimal preparation conditions of the working electrode (GR/PD/GOx) were achieved with 12.6μg and 0.24mg loading amount of PD and GOx, respectively and 25min lasting cross-linking of the GOx with GA. A current response to glucose of the GR/PD/GOx electrode was measured at +200mV potential vs Ag/AgCl reference electrode. Maximum current response was registered when the pH of the buffer solution was 6.0. The registered current response to glucose was linear in the concentration range of 0.1-76mmolL -1 (R 2 =0.9985) and a detection limit was 0.025mmolL -1 . The GR/PD/GOx electrode demonstrated good reproducibility and repeatability with the relative standard deviation of 6.2% and 1.8% (at 4.0mmolL -1 of glucose), respectively, high anti-interference ability to uric and ascorbic acids. It was highly selective to glucose and demonstrated good accuracy in the analysis of human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation of β-cyclodextrin entrapped graphite composite for sensitive detection of dopamine.

PubMed

Palanisamy, Selvakumar; Sakthinathan, S; Chen, Shen-Ming; Thirumalraj, Balamurugan; Wu, Tsung-Han; Lou, Bih-Show; Liu, Xiaoheng

2016-01-01

A simple dopamine (DA) electrochemical sensor was developed based on a screen-printed carbon electrode (SPCE) modified with β-cyclodextrin entrapped graphite (GR/β-CD) composite for the first time. The polar hydroxyl groups on the β-CD rims interact with polar groups of edges of GR sheets resulting into the high dispersion ability of GR in β-CD solution. The GR/β-CD modified electrode exhibited a higher electrochemical response to DA with a lower oxidation potential (0.224V) than that of bare/β-CD (0.38V) and GR (0.525V) modified SPCEs, revealing an excellent electro-oxidation behavior of GR/β-CD composite toward DA. Under optimum conditions, the fabricated sensor detects the DA in the linear concentration range from 0.1 to 58.5μM with a limit of detection of 0.011μM and the sensitivity of 1.27±0.02μAμM(-1)cm(-2). The fabricated sensor also exhibits the excellent repeatability, practicality, reproducibility, storage stability along with acceptable selectivity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Monolithic quasi-solid-state dye-sensitized solar cells based on graphene modified mesoscopic carbon counter electrodes

NASA Astrophysics Data System (ADS)

Rong, Yaoguang; Li, Xiong; Liu, Guanghui; Wang, Heng; Ku, Zhiliang; Xu, Mi; Liu, Linfeng; Hu, Min; Yang, Ying; Han, Hongwei

2013-03-01

We have developed a monolithic quasi-solid-state dye-sensitized solar cell (DSSC) based on graphene modified mesoscopic carbon counter electrode (GC-CE), which offers a promising prospect for commercial applications. Based on the design of a triple layer structure, the TiO2 working electrode layer, ZrO2 spacer layer and carbon counter electrode (CE) layer are constructed on a single conducting glass substrate by screen-printing. The quasi-solid-state polymer gel electrolyte employs a polymer composite as the gelator and could effectively infiltrate into the porous layers. Fabricated with normal carbon counter electrode (NC-CE) containing graphite and carbon black, the device shows a power conversion efficiency (PCE) of 5.09% with the fill factor (FF) of 0.63 at 100 mW cm-2 AM1.5 illumination. When the NC-CE is modified with graphene sheets, the PCE and FF could be enhanced to 6.27% and 0.71, respectively. This improvement indicates excellent conductivity and high electrocatalytic activity of the graphene sheets, which have been considered as a promising platinum-free electrode material for DSSCs.

Artificially-built solid electrolyte interphase via surface-bonded vinylene carbonate derivative on graphite by molecular layer deposition

NASA Astrophysics Data System (ADS)

Chae, Seulki; Lee, Jeong Beom; Lee, Jae Gil; Lee, Tae-jin; Soon, Jiyong; Ryu, Ji Heon; Lee, Jin Seok; Oh, Seung M.

2017-12-01

Vinylene carbonate (VC) is attached in a ring-opened form on a graphite surface by molecular layer deposition (MLD) method, and its role as a solid electrolyte interphase (SEI) former is studied. When VC is added into the electrolyte solution of a graphite/LiNi0.5Mn1.5O4 (LNMO) full-cell, it is reductively decomposed to form an effective SEI on the graphite electrode. However, VC in the electrolyte solution has serious adverse effects due to its poor stability against electrochemical oxidation on the LNMO positive electrode. A excessive acid generation as a result of VC oxidation is observed, causing metal dissolution from the LNMO electrode. The dissolved metal ions are plated on the graphite electrode to destroy the SEI layer, eventually causing serious capacity fading and poor Coulombic efficiency. The VC derivative on the graphite surface also forms an effective SEI layer on the graphite negative electrode via reductive decomposition. The detrimental effects on the LNMO positive electrode, however, can be avoided because the bonded VC derivative on the graphite surface cannot move to the LNMO electrode. Consequently, the graphite/LNMO full-cell fabricated with the VC-attached graphite outperforms the cells without VC or with VC in the electrolyte, in terms of Coulombic efficiency and capacity retention.

Surfactant exfoliated 2D hexagonal Boron Nitride (2D-hBN) explored as a potential electrochemical sensor for dopamine: surfactants significantly influence sensor capabilities.

PubMed

Khan, Aamar F; Brownson, Dale A C; Foster, Christopher W; Smith, Graham C; Banks, Craig E

2017-05-21

Surfactant exfoliated 2D hexagonal Boron Nitride (2D-hBN) nanosheets are explored as a potential electrochemical sensing platform and evaluated towards the electroanalytical sensing of dopamine (DA) in the presence of the common interferents, ascorbic acid (AA) and uric acid (UA). Surfactant exfoliated 2D-hBN nanosheets (2-4 layers) fabricated using sodium cholate in aqueous media are electrically wired via a drop-casting modification process onto disposable screen-printed graphite electrodes (SPEs). We critically evaluate the performance of these 2D-hBN modified SPEs and demonstrate the effect of 'mass coverage' towards the detection of DA, AA and UA. Previous studies utilising surfactant-free (pristine) 2D-hBN modified SPEs have shown a beneficial effect towards the detection of DA, AA and UA when compared to the underlying/unmodified graphite-based electrode. We show that the fabrication route utilised to prepare 2D-hBN is a vital experimental consideration, such that the beneficial effect previously reported is considerably reduced when surfactant exfoliated 2D-hBN is utilised. We demonstrate for the first time, through implementation of control experiments in the form of surfactant modified graphite electrodes, that sodium cholate is a major contributing factor to the aforementioned detrimental behaviour. The significance here is not in the material per se, but the fundamental knowledge of the surfactant and surface coverage changing the electrochemical properties of the material under investigation. Given the wide variety of ionic and non-ionic surfactants that are utilised in the manufacture of novel 2D materials, the control experiments reported herein need to be performed in order to de-convolute the electrochemical response and effectively evaluate the 'underlying surface/surfactant/2D materials' electrocatalytic contribution.

Roll-to-Roll Laser-Printed Graphene-Graphitic Carbon Electrodes for High-Performance Supercapacitors.

PubMed

Kang, Sangmin; Lim, Kyungmi; Park, Hyeokjun; Park, Jong Bo; Park, Seong Chae; Cho, Sung-Pyo; Kang, Kisuk; Hong, Byung Hee

2018-01-10

Carbon electrodes including graphene and thin graphite films have been utilized for various energy and sensor applications, where the patterning of electrodes is essentially included. Laser scribing in a DVD writer and inkjet printing were used to pattern the graphene-like materials, but the size and speed of fabrication has been limited for practical applications. In this work, we devise a simple strategy to use conventional laser-printer toner materials as precursors for graphitic carbon electrodes. The toner was laser-printed on metal foils, followed by thermal annealing in hydrogen environment, finally resulting in the patterned thin graphitic carbon or graphene electrodes for supercapacitors. The electrochemical cells made of the graphene-graphitic carbon electrodes show remarkably higher energy and power performance compared to conventional supercapacitors. Furthermore, considering the simplicity and scalability of roll-to-roll (R2R) electrode patterning processes, the proposed method would enable cheaper and larger-scale synthesis and patterning of graphene-graphitic carbon electrodes for various energy applications in the future.

Sensitive electrochemical detection of NADH and ethanol at low potential based on pyrocatechol violet electrodeposited on single walled carbon nanotubes-modified pencil graphite electrode.

PubMed

Zhu, Jun; Wu, Xiao-Yan; Shan, Dan; Yuan, Pei-Xin; Zhang, Xue-Ji

2014-12-01

In this work, the electrodeposition of pyrocatechol violet (PCV) was initially investigated by the electrochemical surface plasmon resonance (ESPR) technique. Subsequently, PCV was used as redox-mediator and was electrodeposited on the surface of pencil graphite electrode (PGE) modified with single-wall carbon nanotubes (SWCNTs). Owing to the remarkable synergistic effect of SWCNTs and PCV, PGE/SWCNTs/PCV exhibited excellent electrocatalytic activity towards dihydronicotinamide adenine dinucleotide (NADH) oxidation at low potential (0.2V vs. SCE) with fast amperometric response (<10s), broad linear range (1.3-280 μM), good sensitivity (146.2 μA mM(-1)cm(-2)) and low detection limit (1.3 μM) at signal-to-noise ratio of 3. Thus, this PGE/SWCNTs/PCV could be further used to fabricate a sensitive and economic ethanol biosensor using alcohol dehydrogenase (ADH) via a glutaraldehyde/BSA cross-linking procedure. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparative performances of a bare graphite-polyurethane composite electrode unmodified and modified with graphene and carbon nanotubes in the electrochemical determination of escitalopram.

PubMed

Baccarin, Marina; Cervini, Priscila; Cavalheiro, Eder Tadeu Gomes

2018-02-01

A bare composite graphite-polyurethane electrode (EGPU) and two other modified with graphene (EGPU-GR) and functionalized multi-walled carbon nanotubes (EGPU-CNTs) were prepared and compared regarding their voltammetric response to escitalopran (EST). The modifiers were characterized by Raman spectroscopy and the resulting electrode materials by contact angle measurements with a hydrophilicity character in the ascending order for the composites: GPU > GPU-GR > GPU-CNTs and scanning electron microscopy (SEM). The electroactive areas of the EGPU, EGPU-GR, and EGPU-CNTs were 0.065, 0.080, and 0.092cm 2 , respectively, calculated from the chronocoulometry using K 3 [Fe(CN) 6 ] as a probe and the Cottrell equation. The cyclic voltammograms obtained for EST indicated irreversible electrochemical behavior, with an anodic peak at ca. +0.80V (νs. SCE). These measurements were carried out with the three electrodes, and comparison of the analytical responses led to the EGPU-GR electrode being selected for use in the subsequent experiments. Under optimal conditions, square wave and differential pulse voltammetry at EGPU-GR presented linear dynamic ranges between 1.5 × 10 -6 and 1.2 × 10 -5 mol L -1 , with a detection limit of 2.5 × 10 -7 molL -1 (SWV) and 1.5 × 10 -6 and 1.2 × 10 -5 molL -1 , with a detection limit of 3.2 × 10 -7 molL -1 (DPV) for EST. The proposed method was applied for the quantification of EST in synthetic urine and cerebrospinal fluid samples, offering advantages including simplicity of fabrication, no requirement for analyte preconcentration and surface renewal, fast response, and selectivity. Copyright © 2017 Elsevier B.V. All rights reserved.

76 FR 36092 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-21

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... antidumping duty order on small diameter graphite electrodes from the People's Republic of China (``PRC'') for... preliminary results of this review were published on March 7, 2011. See Small Diameter Graphite Electrodes...

Predicting ion specific capacitances of supercapacitors due to quantum ionic interactions.

PubMed

Parsons, Drew F

2014-08-01

A new theoretical framework is now available to help explain ion specific (Hofmeister) effects. All measurements in physical chemistry show ion specificity, inexplicable by classical electrostatic theories. These ignore ionic dispersion forces that change ionic adsorption. We explored ion specificity in supercapacitors using a modified Poisson-Boltzmann approach that includes ionic dispersion energies. We have applied ab initio quantum chemical methods to determine required ion sizes and ion polarisabilities. Our model represents graphite electrodes through their optical dielectric spectra. The electrolyte was 1.2 M Li salt in propylene carbonate, using the common battery anions, PF6(-), BF4(-) and ClO4(-). We also investigated the perhalate series with BrO4(-) and IO4(-). The capacitance C=dσ/dψ was calculated from the predicted electrode surface charge σ of each electrode with potential ψ between electrodes. Compared to the purely electrostatic calculation, the capacitance of a positively charged graphite electrode was enhanced by more than 15%, with PF6(-) showing >50% increase in capacitance. IO4(-) provided minimal enhancement. The enhancement is due to adsorption of both anions and cations, driven by ionic dispersion forces. The Hofmeister series in the single-electrode capacitance was PF6(-)>BF4(-)>ClO4(-)>BrO4(-)>IO4(-) . When the graphite electrode was negatively charged, the perhalates provided almost no enhancement of capacitance, while PF6(-) and BF4(-) decreased capacitance by about 15%. Due to the asymmetric impact of nonelectrostatic ion interactions, the capacitances of positive and negative electrodes are not equal. The capacitance of a supercapacitor should therefore be reported as two values rather than one, similar to the matrix of mutual capacitances used in multielectrode devices. Copyright © 2014 Elsevier Inc. All rights reserved.

An ultrasensitive electrochemiluminescent sensor based on a pencil graphite electrode modified with CdS nanorods for detection of chlorogenic acid in honeysuckle.

PubMed

Zheng, Ruijuan; Zhong, Jianhai; Zhao, Chenhao; Lang, Xiaoling; Hu, Zhibiao; Luo, Jiangshui

2017-08-01

In this paper, a novel and ultrasensitive electrochemiluminescent sensor employing a solvothermal-synthesized CdS nanorod-modified pencil graphite electrode (CdS/PGE) for the determination of chlorogenic acid (CA) is fabricated. In the first step, the PGE surface is modified using CdS nanorods. In the next step, the developed electrode is used to detect CA using a electrochemiluminescent (ECL) technique, in which potassium persulfate (K 2 S 2 O 8 ) served as a co-reactant. The possible ECL mechanism is investigated, and the influences of pH and cyclic voltammetric scanning rate on the signal response are studied. The ECL intensity decreases quantitatively in relation to the concentration of the target molecule. Under optimized conditions, the linear correlation between the quenched ECL intensity and the logarithm of CA concentration is observed in the range from 2 × 10 -9 to 8 × 10 -7  mol L -1 with a limit of detection of 1 × 10 -9  mol L -1 . This proposed method is applied to the analysis of CA in honeysuckle flower, giving recoveries of 99-107%. The experimental results demonstrate that this ECL sensor shows good stability and reproducibility. Copyright © 2016 John Wiley & Sons, Ltd.

Electrochemical detection of DNA damage induced by acrylamide and its metabolite at the graphene-ionic liquid-Nafion modified pyrolytic graphite electrode.

PubMed

Qiu, Yanyan; Qu, Xiangjin; Dong, Jing; Ai, Shiyun; Han, Ruixia

2011-06-15

A new electrochemical biosensor for directly detecting DNA damage induced by acrylamide (AA) and its metabolite was presented in this work. The graphene-ionic liquid-Nafion modified pyrolytic graphite electrode (PGE) was prepared, and then horseradish peroxidase (HRP) and natural double-stranded DNA were alternately assembled on the modified electrode by the layer-by-layer method. The PGE/graphene-ionic liquid-Nafion and the construction of the (HRP/DNA)(n) film were characterized by electrochemical impedance spectroscopy. With the guanine signal in DNA as an indicator, the damage of DNA was detected by differential pulse voltammetry after PGE/graphene-ionic liquid-Nafion/(HRP/DNA)(n) was incubated in AA solution or AA+H(2)O(2) solution at 37°C. This method provides a new model to mimic and directly detect DNA damage induced by chemical pollutants and their metabolites in vitro. The results indicated that, in the presence of H(2)O(2), HRP was activated and catalyzed the transformation of AA to glycidamide, which could form DNA adducts and induce more serious damage of DNA than AA. In order to further verify these results, UV-vis spectrophotometry was also used to investigate DNA damage induced by AA and its metabolites in solution and the similar results were obtained. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells.

PubMed

Epifanio, Monica; Inguva, Saikumar; Kitching, Michael; Mosnier, Jean-Paul; Marsili, Enrico

2015-12-01

The attachment of electrochemically active microorganisms (EAM) on an electrode is determined by both the chemistry and topography of the electrode surface. Pre-treatment of the electrode surface by atmospheric air plasma introduces hydrophilic functional groups, thereby increasing cell attachment and electroactivity in short-term experiments. In this study, we use graphite and carbon felt electrodes to grow the model EAM Shewanella loihica PV-4 at oxidative potential (0.2 V vs. Ag/AgCl). Cell attachment and electroactivity are measured through electrodynamic methods. Atmospheric air plasma pre-treatment increases cell attachment and current output at graphite electrodes by 25%, while it improves the electroactivity of the carbon felt electrodes by 450%. Air plasma pre-treatment decreased the coulombic efficiency on both carbon felt and graphite electrodes by 60% and 80%, respectively. Microbially produced flavins adsorb preferentially at the graphite electrode, and air plasma pre-treatment results in lower flavin adsorption at both graphite and carbon felt electrodes. Results show that air plasma pre-treatment is a feasible option to increase current output in bioelectrochemical systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Biosensing applications of titanium dioxide coated graphene modified disposable electrodes.

PubMed

Kuralay, Filiz; Tunç, Selma; Bozduman, Ferhat; Oksuz, Lutfi; Oksuz, Aysegul Uygun

2016-11-01

In the present work, preparation of titanium dioxide coated graphene (TiO2/graphene) and the use of this nanocomposite modified electrode for electrochemical biosensing applications were detailed. The nanocomposite was prepared with radio frequency (rf) rotating plasma method which serves homogeneous distribution of TiO2 onto graphene. TiO2/graphene was characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Then, this nanocomposite was dissolved in phosphate buffer solution (pH 7.4) and modified onto disposable pencil graphite electrode (PGE) by dip coating for the investigation of the biosensing properties of the prepared electrode. TiO2/graphene modified PGE was characterized with SEM, EDS and cyclic voltammetry (CV). The sensor properties of the obtained surface were examined for DNA and DNA-drug interaction. The detection limit was calculated as 1.25mgL(-1) (n=3) for double-stranded DNA (dsDNA). RSD% was calculated as 2.4% for three successive determinations at 5mgL(-1) dsDNA concentration. Enhanced results were obtained compared to the ones obtained with graphene and unmodified (bare) electrodes. Copyright © 2016 Elsevier B.V. All rights reserved.

Cycling behavior of NCM523/graphite lithium-ion cells in the 3–4.4 V range: Diagnostic studies of full cells and harvested electrodes

DOE PAGES

Gilbert, James A.; Bareño, Javier; Spila, Timothy; ...

2016-09-22

Energy density of full cells containing layered-oxide positive electrodes can be increased by raising the upper cutoff voltage above the current 4.2 V limit. In this article we examine aging behavior of cells, containing LiNi 0.5Co 0.2Mn 0.3O 2 (NCM523)-based positive and graphite-based negative electrodes, which underwent up to ~400 cycles in the 3-4.4 V range. Electrochemistry results from electrodes harvested from the cycled cells were obtained to identify causes of cell performance loss; these results were complemented with data from X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) measurements. Our experiments indicate that the full cell capacitymore » fade increases linearly with cycle number and results from irreversible lithium loss in the negative electrode solid electrolyte interphase (SEI) layer. The accompanying electrode potential shift reduces utilization of active material in both electrodes and causes the positive electrode to cycle at higher states-of-charge. Here, full cell impedance rise on aging arises primarily at the positive electrode and results mainly from changes at the electrode-electrolyte interface; the small growth in negative electrode impedance reflects changes in the SEI layer. Our results indicate that cell performance loss could be mitigated by modifying the electrode-electrolyte interfaces through use of appropriate electrode coatings and/or electrolyte additives.« less

Graphitization in Carbon MEMS and Carbon NEMS

NASA Astrophysics Data System (ADS)

Sharma, Swati

Carbon MEMS (CMEMS) and Carbon NEMS (CNEMS) are an emerging class of miniaturized devices. Due to the numerous advantages such as scalable manufacturing processes, inexpensive and readily available precursor polymer materials, tunable surface properties and biocompatibility, carbon has become a preferred material for a wide variety of future sensing applications. Single suspended carbon nanowires (CNWs) integrated on CMEMS structures fabricated by electrospinning of SU8 photoresist on photolithographially patterned SU8 followed by pyrolysis are utilized for understanding the graphitization process in micro and nano carbon materials. These monolithic CNW-CMEMS structures enable the fabrication of very high aspect ratio CNWs of predefined length. The CNWs thus fabricated display core---shell structures having a graphitic shell with a glassy carbon core. The electrical conductivity of these CNWs is increased by about 100% compared to glassy carbon as a result of enhanced graphitization. We explore various tunable fabrication and pyrolysis parameters to improve graphitization in the resulting CNWs. We also suggest gas-sensing application of the thus fabricated single suspended CNW-CMEMS devices by using the CNW as a nano-hotplate for local chemical vapor deposition. In this thesis we also report on results from an optimization study of SU8 photoresist derived carbon electrodes. These electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 microgL-1 were achieved. To further improve upon the electrochemical behavior of the carbon electrodes we elucidate a modified pyrolysis technique featuring an ultra-fast temperature ramp for obtaining bubbled porous carbon from lithographically patterned SU8. We conclude this dissertation by suggesting the possible future works on enhancing graphitization as well as on electrochemical applications

Biosensing of glucose in flow injection analysis system based on glucose oxidase-quantum dot modified pencil graphite electrode.

PubMed

Sağlam, Özlem; Kızılkaya, Bayram; Uysal, Hüseyin; Dilgin, Yusuf

2016-01-15

A novel amperometric glucose biosensor was proposed in flow injection analysis (FIA) system using glucose oxidase (GOD) and Quantum dot (ZnS-CdS) modified Pencil Graphite Electrode (PGE). After ZnS-CdS film was electrochemically deposited onto PGE surface, GOD was immobilized on the surface of ZnS-CdS/PGE through crosslinking with chitosan (CT). A pair of well-defined reversible redox peak of GOD was observed at GOD/CT/ZnS-CdS/PGE based on enzyme electrode by direct electron transfer between the protein and electrode. Further, obtained GOD/CT/ZnS-CdS/PGE offers a disposable, low cost, selective and sensitive electrochemical biosensing of glucose in FIA system based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. Under optimum conditions (flow rate, 1.3mL min(-1); transmission tubing length, 10cm; injection volume, 100μL; and constant applied potential, -500mV vs. Ag/AgCl), the proposed method displayed a linear response to glucose in the range of 0.01-1.0mM with detection limit of 3.0µM. The results obtained from this study would provide the basis for further development of the biosensing using PGE based FIA systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrochemical enzymatic fenitrothion sensor based on a tyrosinase/poly(2-hydroxybenzamide)-modified graphite electrode.

PubMed

Alves, Maria de Fátima; Corrêa, Ricardo Augusto Moreira de Souza; da Cruz, Filipe Soares; Franco, Diego Leoni; Ferreira, Lucas Franco

2018-07-15

This paper reports the electrosynthesis and characterisation of a polymeric film derived from 2-hydroxybenzamide over a graphite electrode and its application as an enzymatic biosensor for the determination and quantification of the pesticide fenitrothion. The material was analysed by scanning electron microscopy and its electrochemical properties characterised by cyclic voltammetry and electrochemical impedance spectroscopy. The enzyme tyrosinase was immobilised over the modified electrode by the drop and dry technique. Catechol was determined by direct reduction of biocatalytically formed o-quinone by employing the flow injection analysis technique. The analytical characteristics of the proposed sensor were optimised as follows: phosphate buffer 0.050 M at pH 6.5, flow rate 5.0 mL min -1 , sample injection volume 150 μL, catechol concentration 1.0 mM and maximum inhibition time by fenitrothion of 6 min. The biosensors showed a linear response to pesticide concentration from 0.018 to 3.60 μM. The limit of detection and limit of quantification were calculated as 4.70 nM and 15.9 nM (RSD < 2.7%), respectively. The intra- and inter-electrode RSDs were 3.35% (n = 15) and 8.70% (n = 7), respectively. In addition, water samples spiked with the pesticide showed an average recovery of 97.6% (±1.53). Copyright © 2018 Elsevier Inc. All rights reserved.

EFFECT OF SOLVENTS IN WATER ON ELECTROCATALYTIC DECHLORINATION OF 2-CL BP AT A PALLADIUM MODIFIED GRANULAR-GRAPHITE ELECTRODE

EPA Science Inventory

Remediation of soils and sediments contaminated by polychlorinated biphenyls (PCBs) usually involves use of organic solvents because PCBs have very limited solubility in water. The resulting liquids require further treatment to degrade these toxic contaminants. Catalytic and elec...

Development of Microbial and Enzymatic Fuel Cells for Bio-Inspired Power Sources

DTIC Science & Technology

2009-03-01

that of the oxidation of NADH as possible.[30] A variety of organic mediators have been studied for the anode, including phenazines ,[38] dyes,[39,40...glucose-6-phosphate dehydrogenase on the rotating graphite disc electrode modified with phenazine methosulfate. Enzyme Microb. Technol. 1993, 15 (6), 525

ELECTROLYTIC DECHLORINATION OF 2-CHLOROBIPHENYL AT A PALLADIUM MODIFIED GRANULAR-GRAPHITE-PACKED ELECTRODE

EPA Science Inventory

Polychlorinated biphenyls (PCBs) and other chlorinated aromatic compounds are distributed in soils and sediments at over 400 sites in the USA. A national need exists for both in situ and ex situ methods to destroy these persistent organic pollutants in soils and sediments at ambi...

Highly selective electrode for potentiometric analysis of methadone in biological fluids and pharmaceutical formulations.

PubMed

Ardeshiri, Moslem; Jalali, Fahimeh

2016-06-01

In order to develop a fast and simple procedure for methadone analysis in biological fluids, a graphite paste electrode (GPE) was modified with the ion-pair of methadone-phosphotungstic acid, and multiwalled carbon nanotubes (MWCNTs). Optimized composition of the electrode with respect to graphite powder:paraffin oil:MWCNTs:ion pair, was 58:30:8:4 (w/w%). The electrode showed a near-Nernstian slope of 58.9 ± 0.3 mV/decade for methadone in a wide linear range of 1.0 × 10(-8)-4.6 × 10(-3)M, with a detection limit of 1.0 × 10(-8)M. The electrode response was independent of pH in the range of 5-11, with a fast response time (~4s) at 25 °C. The sensor showed high selectivity and was successfully applied to the determination of sub-micromolar concentrations of methadone in human blood serum and urine samples, with recoveries in the range of 95-99.8%. The average recovery of methadone from tablets (5 mg/tablet) by using the proposed method was 98%. The life time of the modified electrode was more than 5 months, due to the characteristic of GPE which can be cut off and fresh electrode surface be available. A titration procedure was performed for methadone analysis by using phosphotungstic acid, as titrating agent, which showed an accurate end point and 1:1 stoichiometry for the ion-pair formed (methadone:phosphotungstic acid). The simple and rapid procedure as well as excellent detection limit and selectivity are some of the advantages of the proposed sensor for methadone. Copyright © 2016 Elsevier B.V. All rights reserved.

Catalytic behavior of a palladium doped binder free paper based cobalt electrode in electroreduction of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Zhang, Dongming; Ye, Ke; Cao, Dianxue; Yin, Jinling; Cheng, Kui; Wang, Bin; Xu, Yang; Wang, Guiling

2015-01-01

A piece of flexible and conductive A4 paper is prepared by coating a layer of graphite with a normal 8B pencil. Then, Co nano-plates and Pd are assembled by a simple electrodeposition and chemical-reduction methods on the surface of the electrified paper, respectively. The as-prepared paper substrate/graphite-Co film-Pd (PG-CoPd) electrode is characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope and X-ray diffractometer. The catalytic activity of the PG-CoPd electrode for H2O2 electroreduction is investigated by means of cyclic voltammetry and chronoamperometry. The preparation process of the PG-CoPd electrode does not use any binder and it exhibits a three dimensional (3D) nano structure, high stability and good electric conductivity. The mass of the Pd in PG-CoPd is about 0.0535 mg cm-2 and the reduction current density reaches to -4.30 A cm-2 mg-1 in 1 mol dm-3 NaOH and 1.4 mol dm-3 H2O2 at -0.5 V, which is higher than our previous reports of Au/Pd modified Co electrode.

Electrochemical Ultracapacitors Using Graphitic Nanostacks

NASA Technical Reports Server (NTRS)

Marotta, Christopher

2012-01-01

Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS surface will be added that can exhibit pseudocapacitance. This pseudocapacitance exhibits faradaic (charge transfer) properties that can further increase the overall relative and volumetric capacitance of the material. A process is also proposed to use GNF as a precursor material to fabricate GNS that will be used as EC electrodes. This results in much better electrical conductivity than activated carbon. This is advantageous for high-pulsed-power applications to reduce parasitic heating. Larger average pore size allows more complete electrolyte wetting (faster charge transfer kinetics). These properties contribute to a lowered equivalent series resistance (ESR), increased specific power, shorter charging times, and decreased parasitic heating. The high density of basal plane edges provides nucleation sites for activation (addition of hydrophilic functional groups) that facilitate electrolyte wetting, and will contribute to pseudocapacitance.

High efficiency of CO2-activated graphite felt as electrode for vanadium redox flow battery application

NASA Astrophysics Data System (ADS)

Chang, Yu-Chung; Chen, Jian-Yu; Kabtamu, Daniel Manaye; Lin, Guan-Yi; Hsu, Ning-Yih; Chou, Yi-Sin; Wei, Hwa-Jou; Wang, Chen-Hao

2017-10-01

A simple method for preparing CO2-activated graphite felt as an electrode in a vanadium redox flow battery (VRFB) was employed by the direct treatment in a CO2 atmosphere at a high temperature for a short period. The CO2-activated graphite felt demonstrates excellent electrochemical activity and reversibility. The VRFB using the CO2-activated graphite felts in the electrodes has coulombic, voltage, and energy efficiencies of 94.52%, 88.97%, and 84.15%, respectively, which is much higher than VRFBs using the electrodes of untreated graphite felt and N2-activated graphite felt. The efficiency enhancement was attributed to the higher number of oxygen-containing functional groups on the graphite felt that are formed during the CO2-activation, leading to improving the electrochemical behaviour of the resultant VRFB.

Construction of ferrocene modified conducting polymer based amperometric urea biosensor.

PubMed

Dervisevic, Muamer; Dervisevic, Esma; Senel, Mehmet; Cevik, Emre; Yildiz, Huseyin Bekir; Camurlu, Pınar

2017-07-01

Herein, an electrochemical urea sensing bio-electrode is reported that has been constructed by firstly electropolymerizing 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline monomer (SNS-Aniline) on Pencil Graphite Electrode (PGE), then modifying the polymer coated electrode surface with di-amino-Ferrocene (DAFc) as the mediator, and lastly Urease enzyme through glutaraldehyde crosslinking. The effect of pH, temperature, polymer thickness, and applied potential on the electrode current response was investigated besides performing storage and operational stability experiments with the interference studies. The resulting urea biosensor's amperometric response was linear in the range of 0.1-8.5mM with the sensitivity of 0.54μA/mM, detection limit of 12μM, and short response time of 2s. The designed bio-electrode was tested with real human blood and urine samples where it showed excellent analytical performance with insignificant interference. Copyright © 2017 Elsevier Inc. All rights reserved.

Using gold nanostars modified pencil graphite electrode as a novel substrate for design a sensitive and selective Dopamine aptasensor.

PubMed

Talemi, Rasoul Pourtaghavi; Mousavi, Seyed Mehdi; Afruzi, Hossein

2017-04-01

For the first time, gold nanostars (GNS) were applied for electrostatic and covalent immobilizing a thiol modified Dopamine aptamer on the pencil graphite electrode and signal amplification. Dopamine aptamer was immobilized on the gold nanostars through electrostatic interaction between negatively charged phosphate groups of aptamer and positively charged gold nanostars and AuS well known covalent interaction. In the presence of Dopamine in the test solution, the charge transfer resistance (R CT ) on the electrode surface increased with the increase of the Dopamine concentration due to specific interaction between Dopamine aptamer and Dopamine molecules, which made a barrier for electrons and inhibited the electron-transfer. So, the proposed approach showed a high sensitivity and a wide linearity to Dopamine in the range from 1.0 (±0.1) to 100.0 (±0.3) ngL -1 (ppt) with detection and quantification limits of 0.29 (±0.10) and 0.90 (±0.08) ngL -1 (ppt), respectively. Finally, the sensor was successfully used for determination of Dopamine in biological (human blood plasma and urine) samples. The results open up the path for manufacturing cost effective aptasensors for other biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical properties and electrocatalytic activity of conducting polymer/copper nanoparticles supported on reduced graphene oxide composite

NASA Astrophysics Data System (ADS)

Ehsani, Ali; Jaleh, Babak; Nasrollahzadeh, Mahmoud

2014-07-01

Reduced graphene oxide (rGO) was used to support Cu nanoparticles. As electro-active electrodes for supercapacitors composites of reduced graphene oxide/Cu nanoparticles (rGO/CuNPs) and polytyramine (PT) with good uniformity are prepared by electropolymerization. Composite of rGO/CuNPs-PT was synthesized by cyclic voltammetry (CV) methods and electrochemical properties of film were investigated by using electrochemical techniques. The results show that, the rGO/CuNPs-PT/G has better capacitance performance. This is mainly because of the really large surface area and the better electronic and ionic conductivity of rGO/CuNPs-PT/G, which lead to greater double-layer capacitance and faradic pseudo capacitance. Modified graphite electrodes (rGO/CuNPs-PT/G) were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) were employed. In comparison with a Cu-PT/G (Graphite), rGO/CuNPs-PT/G modified electrode shows a significantly higher response for methanol oxidation. A mechanism based on the electro-chemical generation of Cu(III) active sites and their subsequent consumptions by methanol have been discussed.

Enhanced performance of graphite anode materials by AlF3 coating for lithium-ion batteries

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

Ding, Fei; Xu, Wu; Choi, Daiwon

2012-04-27

In order to form the stable surface film and to further enhance the long-term cycling stability of the graphite anodes of lithium-ion batteries, the surface of graphite powders has been modified by AlF3 coating through chemical precipitation method. The AlF3-coated graphite shows no evident changes in the bulk structure and a thin AlF3-coating layer of about 2 nm thick is found to uniformly cover the graphite particles with 2 wt% AlF3 content. However, it delivers a higher initial discharge capacity and largely improved rate performances compared to the pristine graphite. Remarkably, AlF3 coated graphite demonstrated a much better cycle life.more » After 300 cycles, AlF3 coated graphite and uncoated graphite show capacity retention of 92% and 81%, respectively. XPS measurement shows that a more conductive solid electrode interface (SEI) layer was formed on AlF3 coated graphite as compared to uncoated graphite. SEM monograph also reveals that the AlF3-coated graphite particles have a much more stable surface morphology after long-term cycling. Therefore, the improved electrochemical performance of AlF3 coated graphite can be attributed to a more stable and conductive SEI formed on coated graphite anode during cycling process.« less

Design, fabrication and performance of small, graphite electrode, multistage depressed collectors with 200-W, CW, 8- to 18-GHz traveling-wave tubes

NASA Technical Reports Server (NTRS)

Ebihara, Ben T.; Ramins, Peter

1987-01-01

Small multistage depressed collectors (MDC's) which used pyrolytic graphite, ion-beam-textured pyrolytic graphite, and isotropic graphite electrodes were designed, fabricated, and evaluated in conjuntion with 200-W, continuous wave (CW), 8- to 18-GHz traveling-wave tubes (TWT's). The design, construction, and performance of the MDC's are described. The bakeout performance of the collectors, in terms of gas evolution, was indistinguishable from that of typical production tubes with copper collectors. However, preliminary results indicate that some additional radiofrequency (RF) and dc beam processing time (and/or longer or higher temperature bakeouts) may be needed beyond that of typical copper electrode collectors. This is particularly true for pyrolytic graphite electrodes and for TWT's without appendage ion pumps. Extended testing indicated good long-term stability of the textured pyrolytic graphite and isotropic graphite electrode surfaces. The isotropic graphite in particular showed considerable promise as an MDC electrode material because of its high purity, low cost, simple construction, potential for very compact overall size, and relatively low secondary electron emission yield characteristics in the as-machined state. However, considerably more testing experience is required before definitive conclusions on its suitability for electronic countermeasure systems and space TWT's can be made.

Biosensor based on ds-DNA decorated chitosan modified multiwall carbon nanotubes for voltammetric biodetection of herbicide amitrole.

PubMed

Ensafi, Ali A; Amini, Maryam; Rezaei, Behzad

2013-09-01

The interaction of amitrole and salmon sperm ds-DNA was studied using UV-vis and differential pulse voltammetry (DPV) at both bare and DNA-modified electrodes. Amitrole showed an oxidation peak at 0.445 V at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV-vis spectra showed that the absorption intensity of the ds-DNA at 260 nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs-CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025-2.4 ng mL(-1) amitrole with a detection limit of 0.017 ng mL(-1). The sensor showed a good selectivity and precision for the determination of amitrole. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity. Copyright © 2013 Elsevier B.V. All rights reserved.

Development of a simple, low cost chronoamperometric assay for fructose based on a commercial graphite-nanoparticle modified screen-printed carbon electrode.

PubMed

Nicholas, Phil; Pittson, Robin; Hart, John P

2018-02-15

This paper describes the development of a simple, low cost chronoamperometric assay, for the measurement of fructose, using a graphite-nanoparticle modified screen-printed electrode (SPCE-G-COOH). Cyclic voltammetry showed that the response of the SPCE-G-COOH enhanced the sensitivity and precision, towards the enzymatically generated ferrocyanide species, over a plain SPCE; therefore the former was employed in subsequent studies. Calibration studies were carried out using chronoamperometry with a 40µl mixture containing fructose, mediator and FDH, deposited onto the SPCE-G-COOH. The response was linear from 0.1mM to 1.0mM. A commercial fruit juice sample was analysed using the developed assay and the fructose concentration was calculated to be 477mM with a precision of 3.03% (n=5). Following fortification (477mM fructose) the mean recovery was found to be 97.12% with a coefficient of variation of 6.42% (n=5); consequently, the method holds promise for the analysis of commercial fruit juices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrochemical monitoring of biointeraction by graphene-based material modified pencil graphite electrode.

PubMed

Eksin, Ece; Zor, Erhan; Erdem, Arzum; Bingol, Haluk

2017-06-15

Recently, the low-cost effective biosensing systems based on advanced nanomaterials have received a key attention for development of novel assays for rapid and sequence-specific nucleic acid detection. The electrochemical biosensor based on reduced graphene oxide (rGO) modified disposable pencil graphite electrodes (PGEs) were developed herein for electrochemical monitoring of DNA, and also for monitoring of biointeraction occurred between anticancer drug, Daunorubicin (DNR), and DNA. First, rGO was synthesized chemically and characterized by using UV-Vis, TGA, FT-IR, Raman Spectroscopy and SEM techniques. Then, the quantity of rGO assembling onto the surface of PGE by passive adsorption was optimized. The electrochemical behavior of rGO-PGEs was examined by cyclic voltammetry (CV). rGO-PGEs were then utilized for electrochemical monitoring of surface-confined interaction between DNR and DNA using differential pulse voltammetry (DPV) technique. Additionally, voltammetric results were complemented with electrochemical impedance spectroscopy (EIS) technique. Electrochemical monitoring of DNR and DNA was resulted with satisfying detection limits 0.55µM and 2.71µg/mL, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Marcus-Hush-Chidsey theory of electron transfer to and from species bound at a non-uniform electrode surface: Theory and experiment

NASA Astrophysics Data System (ADS)

Henstridge, Martin C.; Batchelor-McAuley, Christopher; Gusmão, Rui; Compton, Richard G.

2011-11-01

Two simple models of electrode surface inhomogeneity based on Marcus-Hush theory are considered; a distribution in formal potentials and a distribution in electron tunnelling distances. Cyclic voltammetry simulated using these models is compared with that simulated using Marcus-Hush theory for a flat, uniform and homogeneous electrode surface, with the two models of surface inhomogeneity yielding broadened peaks with decreased peak-currents. An edge-plane pyrolytic graphite electrode is covalently modified with ferrocene via 'click' chemistry and the resulting voltammetry compared with each of the three previously considered models. The distribution of formal potentials is seen to fit the experimental data most closely.

Design and development of high efficiency 140W space TWT with graphite collector

NASA Astrophysics Data System (ADS)

Srivastava, V.; Purohit, G.; Sharma, R. K.; Sharma, S. M.; Bera, A.; Bhaskar, P. V.; Singh, R. R.; Prasad, K.; Kiran, V.

2008-05-01

4-stage graphite collector assembly has been designed and developed for a 140W Ku-band space TWT to achieve the collector efficiency more than 80%. The UHV compatible, high density, copper impregnated POCO graphite (DFP-1C) was used to fabricate the four collector electrodes of the 4-stage depressed collector. Copper impregnated graphite material is used for the collector electrodes because of its low secondary electron emission coefficient, high thermal and electrical conductivities, easy machining and brazing, low thermal expansion coefficient and low weight. The graphite material was characterized for the UHV compatibility. The collector electrodes were precisely fabricated by careful machining, and technology was developed for brazing of graphite electrodes with high voltage alumina insulators. Complete TWT with four-stage graphite collector was developed and 140W output power at gain more than 55 dB was achieved. The TWT was pumped from both the gun and the collector ends.

Study of Copper and Purine-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry

PubMed Central

Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek

2008-01-01

Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes. PMID:27879715

Effects of Propylene Carbonate Content in CsPF6-Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries

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

Zheng, Jianming; Yan, Pengfei; Cao, Ruiguo

2016-02-10

Cesium salt has been demonstrated as an efficient electrolyte additive in suppressing the lithium (Li) dendrite formation and directing the formation of an ultrathin and stable solid electrolyte interphase (SEI) even in propylene carbonate (PC)-ethylene carbonate (EC)-based electrolytes. Here, we further investigate the effect of PC content in the presence of CsPF6 additive (0.05 M) on the performances of graphite electrode in Li||graphite half cells and in graphite||LiNi0.80Co0.15Al0.05O2 (NCA) full cells. It is found that the performance of graphite electrode is also affected by PC content even though CsPF6 additive is present in the electrolytes. An optimal PC content ofmore » 20% by weight in the solvent mixtures is identified. The enhanced electrochemical performance of graphite electrode is attributed to the synergistic effects of the Cs+ additive and the PC solvent. The formation of a robust, ultrathin and compact SEI layer containing lithium-enriched species on the graphite electrode, directed by Cs+, effectively suppresses the PC co-intercalation and thus prevents the graphite exfoliation. This SEI layer is only permeable for de-solvated Li+ ions and allows fast Li+ ion transport through it, which therefore largely alleviates the Li dendrite formation on graphite electrode during lithiation even at high current densities. The presence of low-melting-point PC solvent also enables the sustainable operation of the graphite||NCA full cells under a wide spectrum of temperatures. The fundamental findings of this work shed light on the importance of manipulating/maintaining the electrode/electrolyte interphasial stability in a variety of energy storage devices.« less

Construction of titanium dioxide nanorod/graphite microfiber hybrid electrodes for a high performance electrochemical glucose biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Yu, Xin; Guo, Weibo; Qiu, Jichuan; Mou, Xiaoning; Li, Aixue; Liu, Hong

2016-04-01

The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring.The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01360k

Electrode systems for in situ vitrification

DOEpatents

Buelt, James L.; Carter, John G.; Eschbach, Eugene A.; FitzPatrick, Vincent F.; Koehmstedt, Paul L.; Morgan, William C.; Oma, Kenton H.; Timmerman, Craig L.

1990-01-01

An electrode comprising a molybdenum rod is received within a conductive collar formed of graphite. The molybdenum rod and the graphite collar may be physically joined at the bottom. A pair of such electrodes are placed in soil containing buried waste material and an electric current is passed therebetween for vitrifying the soil. The graphite collar enhances the thermal conductivity of the combination, bringing heat to the surface, and preventing formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is suitably filled with a conductive ceramic powder that sinters upon the molybdenum rod, protecting the same from oxidation as graphite material is consumed, or a metal powder which liquefies at operating temperatures. The center of the molybdenum rod, used with a collar of separately, can be hollow and filled with a powdered metal, such as copper, which liquefies at operating temperatures. Connection to electrodes can be provided below ground level to avoid open circuit due to electrode deterioration, or sacrificial electrodes may be employed when operation is started. Outboard electrodes cna be utilized to square up a vitrified area.

Composite electrochemical biosensors: a comparison of three different electrode matrices for the construction of amperometric tyrosinase biosensors.

PubMed

Serra, B; Jiménez, S; Mena, M L; Reviejo, A J; Pingarrón, J M

2002-03-01

A comparison of the behaviour of three different rigid composite matrices for the construction of amperometric tyrosinase biosensors, which are widely used for the detection of phenolic compounds, is reported. The composite electrode matrices were, graphite-Teflon; reticulated vitreous carbon (RVC)-epoxy resin; and graphite-ethylene/propylene/diene (EPD) terpolymer. After optimization of the experimental conditions, different aspects regarding the stability of the three composite tyrosinase electrode designs were considered and compared. A better reproducibility of the amperometric responses was found with the graphite-EPD electrodes, whereas a longer useful lifetime was observed for the graphite-Teflon electrodes. The kinetic parameters of the tyrosinase reaction were calculated for eight different phenolic compounds, as well as their corresponding calibration plots. The general trend in sensitivity was graphite-EPD>graphite-Teflon>RVC-epoxy resin. A correlation between sensitivity and the catalytic efficiency of the enzyme reaction for each phenolic substrate was found. Furthermore, differences in the sensitivity order for the phenolic compounds were observed among the three biocomposite electrodes, which suggests that the nature of the electrode matrix influences the interactions in the tyrosinase catalytic cycle.

75 FR 64250 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-19

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit for the Preliminary Results of the... review of the antidumping duty order on small diameter graphite electrodes from the People's Republic of...

Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium.

PubMed

Guo, Xiaolei; Wan, Jiafeng; Yu, Xiujuan; Lin, Yuhui

2016-12-01

In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO 2 -TiO 2 /Nano-G) composite was synthesized by a sol-gel method and SnO 2 -TiO 2 /Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N 2 adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO 2 -TiO 2 /Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO 2 , SnO 2 and Nano-G were composited successfully, and TiO 2 and SnO 2 particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO 2 modified anode was higher than that of TiO 2 /Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO 2 -TiO 2 /Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO 2 -TiO 2 /Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO 2 -TiO 2 /Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO 2 -TiO 2 /Nano-G electrode. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of Propylene Carbonate Content in CsPF 6 -Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries

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

Zheng, Jianming; Yan, Pengfei; Cao, Ruiguo

2016-02-15

The effects Of propylene carbonate (PC) content in CsPF6-containing electrolytes on the performances of graphite electrode in lithium half cells and in graphite parallel to LiNi0.80Co0.15Al0.05O2 (NCA) full cells are investigated. It is found that the performance of graphite electrode is significantly-affected by PC content in the CsPF6-containing electrolytes. An optimal PC content of 20% by weight in the solvent mixtures is identified. The enhanced electrochemical performance of graphite electrode can be attributed to the synergistic effects of the PC solvent and the Cs+ additive. The synergistic effects of Cs+ additive and appropriate amount of PC enable the formation ofmore » a robust, ultrathin, and compact solid electrolyte interphase (SEI) layer on the surface of graphite electrode, which is only permeable for desolvated Li+ ions and allows fast Li+ ion transport through it. Therefore, this SEI layer effectively suppresses the PC cointercalation and largely alleviates the Li dendrite formation on graphite electrode during lithiation even at relatively high current densities. The presence of low-melting-point PC solvent improves the sustainable operation of graphite parallel to NCA full cells under a wide temperature range. The fundamental findings also shed light On the importance of manipulating/maintaining the electrode/electrolyte interphasial stability in various energy-storage devices.« less

A new strategy for the modification of a carbon paste electrode with carrageenan hydrogel for a sensitive and selective determination of arsenic in natural waters.

PubMed

Núñez, Claudia; Arancibia, Verónica; Triviño, Juan José

2018-09-01

An adsorptive stripping voltammetric method for the determination of As(III) and As total in water samples using a carrageenan modified carbon paste electrode is presented for the first time (CAR-CPE). The modified electrode was prepared in different ways: by adding CAR in solid form or as a hydrogel together with graphite and paraffin, as well as adsorbing CAR by applying a potential on an unmodified carbon paste electrode. The best results were obtained when CAR was incorporated as hydrogel (HCAR-CPE). The selection of the ratio amounts for electrode preparation was carried out applying a multivariate experimental design. Variables like amount of graphite (U 1 ), HCAR (U 2 ) and paraffin (U 3 ) were optimized using a (2 K +2K+C) model. The results showed that the amount of HCAR was the most significant factor, and the adequate U 1 :U 2 :U 3 ratio to prepare the electrode was: 493 mg of graphite, 214 μL of paraffin and 134 μL of carrageenan as gel. The optimum parameters for the determination of As(III) were pH = 3.25 (0.01 mol L -1 H 3 PO 4 /H 2 PO 4 - solution); E acc = -0.50 V and t acc = 30 s. The electrode presents good linear behavior concentration range from 0.50 to 6.70 μg L -1 , with a limit of detection of 0.22 μg L -1 . The relative standard deviation was 5.0% at the 1.5 μg L -1 As(III) level (n = 16). The method was validated by quantifying As(III) in spiked tap water from laboratory (RE: 3.0%), and it was applied for the determination of As total in water samples from the Loa River (North of Chile) prior reduction of As(V) with Na 2 S 2 O 3 solution, obtaining 814.00 ± 0.03 μg L -1 . The results of the proposed method were compared with those obtained by adsorptive stripping voltammetry with HMDE and by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) techniques. Copyright © 2018 Elsevier B.V. All rights reserved.

78 FR 56864 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-16

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... (Department) determines that imports from the People's Republic of China (PRC) of graphite electrodes... Act of 1930, as amended (the Act).\\1\\ \\1\\ See Antidumping Duty Order: Small Diameter Graphite...

Graphite nanoplatelets/multiwalled carbon nanotubes hybrid nanostructure for electrochemical capacitor.

PubMed

Mishra, Ashish Kumar; Ramaprabhu, S

2012-08-01

Recently, the focus on carbon based nanostructures for various applications has been due to their novel properties such as high electrical conductivity, high mechanical strength and high surface area. In the present work, we have investigated the charge storage capacity of modified graphite nanoplatelets and hybrid structure of graphite nanoplatelets-multiwalled carbon nanotubes (MWNTs). These MWNTs can be used as spacers to reduce the possibility of restacking of graphite nanoplatelets and hence increases the surface area of the hybrid carbon nanostructure thereby high degree of metal oxide decoration is achieved over the hybrid structure. MWNTs were prepared by catalytic chemical vapor deposition technique and further purified with air oxidation and acid treatment. Graphite was treated with conc. nitric acid and sulphuric acid in the volumetric ratio of 1:3 for 3 days and these modified graphite nanoplatelets were further stirred with MWNTs in equal weight ratio to form hybrid nanostructure. Further, ruthenium oxide (RuO2) nanoparticles were decorated on this hybrid structure using chemical route followed by calcination. RuO2 decorated hybrid carbon nanostructure was characterized by using X-ray diffraction, Electron microscopy and Raman spectroscopy. The performance of the hybrid structure based nanocomposite as electrochemical capacitor electrodes was analyzed by studing its capacitive and charge-discharge behaviours using cyclic voltammetry and chronopotentiometry techniques and the results have been discussed.

Electrochemical lithiation performance and characterization of silicon-graphite composites with lithium, sodium, potassium, and ammonium polyacrylate binders.

PubMed

Han, Zhen-Ji; Yamagiwa, Kiyofumi; Yabuuchi, Naoaki; Son, Jin-Young; Cui, Yi-Tao; Oji, Hiroshi; Kogure, Akinori; Harada, Takahiro; Ishikawa, Sumihisa; Aoki, Yasuhito; Komaba, Shinichi

2015-02-07

Poly(acrylic acid) (PAH), which is a water soluble polycarboxylic acid, is neutralized by adding different amounts of LiOH, NaOH, KOH, and ammonia (NH4OH) aqueous solutions to fix neutralization degrees. The differently neutralized polyacid, alkali and ammonium polyacrylates are examined as polymeric binders for the preparation of Si-graphite composite electrodes as negative electrodes for Li-ion batteries. The electrode performance of the Si-graphite composite depends on the alkali chemicals and neutralization degree. It is found that 80% NaOH-neutralized polyacrylate binder (a pH value of the resultant aqueous solution is ca. 6.7) is the most efficient binder to enhance the electrochemical lithiation and de-lithiation performance of the Si-graphite composite electrode compared to that of conventional PVdF and the other binders used in this study. The optimum polyacrylate binder highly improves the dispersion of active material in the composite electrode. The binder also provides the strong adhesion, suitable porosity, and hardness for the composite electrode with 10% (m/m) binder content, resulting in better electrochemical reversibility. From these results, the factors of alkali-neutralized polyacrylate binders affecting the electrode performance of Si-graphite composite electrodes are discussed.

Critical evaluation of the stability of highly concentrated LiTFSI - Acetonitrile electrolytes vs. graphite, lithium metal and LiFePO4 electrodes

NASA Astrophysics Data System (ADS)

Nilsson, Viktor; Younesi, Reza; Brandell, Daniel; Edström, Kristina; Johansson, Patrik

2018-04-01

Highly concentrated LiTFSI - acetonitrile electrolytes have recently been shown to stabilize graphite electrodes in lithium-ion batteries (LIBs) much better than comparable more dilute systems. Here we revisit this system in order to optimise the salt concentration vs. both graphite and lithium metal electrodes with respect to electrochemical stability. However, we observe an instability regardless of concentration, making lithium metal unsuitable as a counter electrode, and this also affects evaluation of e.g. graphite electrodes. While the highly concentrated electrolytes have much improved electrochemical stabilities, their reductive decomposition below ca. 1.2 V vs. Li+/Li° still makes them less practical vs. graphite electrodes, and the oxidative reaction with Al at ca. 4.1 V vs. Li+/Li° makes them problematic for high voltage LIB cells. The former originates in an insufficiently stable solid electrolyte interphase (SEI) dissolving and continuously reforming - causing self-discharge, as observed by paused galvanostatic cycling, while the latter is likely caused by aluminium current collector corrosion. Yet, we show that medium voltage LiFePO4 positive electrodes can successfully be used as counter and reference electrodes.

77 FR 6060 - Small Diameter Graphite Electrodes from the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-07

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... Department) initiated an administrative review of the antidumping duty order on small diameter graphite... preliminary results of this review by 95 days until February 3, 2012. See Small Diameter Graphite Electrodes...

76 FR 67411 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-01

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... diameter graphite electrodes from the People's Republic of China (PRC) for the period February 1, 2010... Graphite, Co. The preliminary results of the review are currently due no later than October 31, 2011...

Covalently functionalized single-walled carbon nanotubes and graphene composite electrodes for pseudocapacitor application

NASA Astrophysics Data System (ADS)

Le Barny, Pierre; Servet, Bernard; Campidelli, Stéphane; Bondavalli, Paolo; Galindo, Christophe

2013-09-01

The use of carbon-based materials in electrochemical double-layer supercapacitors (EDLC) is currently being the focus of much research. Even though activated carbon (AC) is the state of the art electrode material, AC suffers from some drawbacks including its limited electrical conductivity, the need for a binder to ensure the expected electrode cohesion and its limited accessibility of its pores to solvated ions of the electrolyte. Owing to their unique physical properties, carbon nanotubes (CNTs) or graphene could overcome these drawbacks. It has been demonstrated that high specific capacitance could be obtained when the carbon accessible surface area of the electrode was finely tailored by using graphene combined with other carbonaceous nanoparticles such as CNTs12.In this work, to further increase the specific capacitance of the electrode, we have covalently grafted onto the surface of single-walled carbon nanotubes (SWCNTs), exfoliated graphite or graphene oxide (GO), anthraquinone (AQ) derivatives which are electrochemically active materials. The modified SWCNTs and graphene-like materials have been characterized by Raman spectroscopy, X-ray photoemission and cyclic voltammetry . Then suspensions based on mixtures of modified SWCNTs and modified graphene-like materials have been prepared and transformed into electrodes either by spray coating or by filtration. These electrodes have been characterized by SEM and by cyclic voltammetry in 0.1M H2S04 electrolyte.

Electrochemical label-free and sensitive nanobiosensing of DNA hybridization by graphene oxide modified pencil graphite electrode.

PubMed

Ahour, F; Shamsi, A

2017-09-01

Based on the strong interaction between single-stranded DNA (ss-DNA) and graphene material, we have constructed a novel label-free electrochemical biosensor for rapid and facile detection of short sequences ss-DNA molecules related to hepatitis C virus 1a using graphene oxide modified pencil graphite electrode. The sensing mechanism is based on the superior adsorption of single-stranded DNA to GO over double stranded DNA (ds-DNA). The intrinsic guanine oxidation signal measured by differential pulse voltammetry (DPV) has been used for duplex DNA formation detection. The probe ss-DNA adsorbs onto the surface of GO via the π- π* stacking interactions leading to a strong background guanine oxidation signal. In the presence of complementary target, formation of helix which has weak binding ability to GO induced ds-DNA to release from the electrode surface and significant variation in differential pulse voltammetric response of guanine bases. The results indicated that the oxidation peak current was proportional to the concentration of complementary strand in the range of 0.1 nM-0.5 μM with a detection limit of 4.3 × 10 -11  M. The simple fabricated electrochemical biosensor has high sensitivity, good selectivity, and could be applied as a new platform for a range of target molecules in future. Copyright © 2017 Elsevier Inc. All rights reserved.

Spontaneous modification of carbon surface with neutral red from its diazonium salts for bioelectrochemical systems.

PubMed

Guo, Kun; Chen, Xin; Freguia, Stefano; Donose, Bogdan C

2013-09-15

This study introduces a novel and simple method to covalently graft neutral red (NR) onto carbon surfaces based on spontaneous reduction of in situ generated NR diazonium salts. Immobilization of neutral red on carbon surface was achieved by immersing carbon electrodes in NR-NaNO2-HCl solution. The functionalized electrodes were characterized by cyclic voltammetry (CV), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Results demonstrated that NR attached in this way retains high electrochemical activity and proved that NR was covalently bound to the carbon surface via the pathway of reduction of aryl diazonium salts. The NR-modified electrodes showed a good stability when stored in PBS solution in the dark. The current output of an acetate-oxidising microbial bioanode made of NR-modified graphite felts were 3.63±0.36 times higher than the unmodified electrodes, which indicates that covalently bound NR can act as electron transfer mediator to facilitate electron transfer from bacteria to electrodes. Copyright © 2013 Elsevier B.V. All rights reserved.

PALLADIUM-FACILITATED ELECTROLYTIC DECHLORINATION OF 2-CHLOROBIPHENYL USING A GRANULAR-GRAPHITE ELECTRODE.

EPA Science Inventory

Palladium-assisted electrocatalytic dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous solutions was conducted in a membrane-separated electrochemical reactor with granular-graphite packed electrodes. The dechlorination took place at a granular-graphite cathode while Pd was ...

Electrochemical and impedance investigation of the effect of lithium malonate on the performance of natural graphite electrodes in lithium-ion batteries

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

Sun, Xiao-Guang; Dai, Sheng

2010-01-01

Lithium malonate (LM) was coated on the surface of a natural graphite (NG) electrode, which was then tested as the negative electrode in the electrolytes of 0.9 M LiPF6/EC-PC-DMC (1/1/3, by weight) and 1.0 M LiBF4/EC-PC-DMC (1/1/3, by weight) under a current density of 0.075 mA cm-2. LM was also used as an additive to the electrolyte of 1.0 M LiPF6/EC-DMC-DEC (1/1/1, by volume) and tested on a bare graphite electrode. It was found that both the surface coating and the additive approach were effective in improving first charge discharge capacity and coulomb efficiency. Electrochemical impedance spectra showed that themore » decreased interfacial impedance was coupled with improved coulomb efficiency of the cells using coated graphite electrodes. Cyclic voltammograms (CVs) on fresh bare and coated natural graphite electrodes confirmed that all the improvement in the half-cell performance was due to the suppression of the solvent decomposition through the surface modification with LM. The CV data also showed that the carbonate electrolyte with LM as the additive was not stable against oxidation, which resulted in lower capacity of the full cell with commercial graphite and LiCoO2 electrodes.« less

Electrochemical response of carbon paste electrode modified with mixture of titanium dioxide/zirconium dioxide in the detection of heavy metals: lead and cadmium.

PubMed

Nguyen, Phuong Khanh Quoc; Lunsford, Suzanne K

2012-11-15

A novel carbon modified electrode was developed by incorporating titanium dioxide/zirconium dioxide into the graphite carbon paste electrode to detect heavy metals-cadmium and lead. In this work, the development of the novel titanium dioxide/zirconium dioxide modified carbon paste electrode was studied to determine the optimum synthesis conditions related to the temperature, heating duration, amount and ratio of titanium dioxide/zirconium dioxide, and amount of surfactant, to create the most reproducible results. Using cyclic voltammetric (CV) analysis, this study has proven that the novel titanium dioxide/zirconium dioxide can be utilized to detect heavy metals-lead and cadmium, at relatively low concentrations (7.6×10(-6) M and 1.1×10(-5) M for Pb and Cd, respectively) at optimum pH value (pH=3). From analyzing CV data the optimal electrodes surface area was estimated to be 0.028 (±0.003) cm(2). Also, under the specific experimental conditions, electron transfer coefficients were estimated to be 0.44 and 0.33 along with the heterogeneous electron transfer rate constants of 5.64×10(-3) and 2.42×10(-3) (cm/s) for Pb and Cd, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Influence of solvent species on the charge-discharge characteristics of a natural graphite electrode

NASA Astrophysics Data System (ADS)

Fujimoto, Masahisa; Shoji, Yoshihiro; Kida, Yoshinori; Ohshita, Ryuji; Nohma, Toshiyuki; Nishio, Koji

The charge-discharge characteristics of a natural graphite electrode are examined in a mixed solvent composed of ethylene carbonate (EC) and propylene carbonate (PC). The characteristics are influenced largely by the solvent species. Natural graphite electrode displays good charge-discharge characteristics in an electrolyte containing EC with a high volume fraction. In an electrolyte containing PC, however, the electrode cannot be charged and the solvent is decomposed. X-ray photoelectron spectroscopy is used to obtain information about the surface of natural graphite. A thin LiF layer, the decomposition product of lithium hexafluorophosphate (LiPF 6), is formed on the surface of the natural graphite charged to 0.5 V (vs. Li/Li +) in an electrolyte containing a high volume fraction of EC. On the other hand, LiF and a carbonate compound are formed in the bulk and on the surface of natural graphite when the volume fraction of PC is high. These results suggest that the thin LiF layer, which is produced at a potential higher than 0.5 V (vs. Li/Li +) on the surface of natural graphite, enables the lithium ions to intercalate into the natural graphite without further decomposition of the electrolyte.

Poly(dimethylsiloxane) cross-linked carbon paste electrodes for microfluidic electrochemical sensing.

PubMed

Sameenoi, Yupaporn; Mensack, Meghan M; Boonsong, Kanokporn; Ewing, Rebecca; Dungchai, Wijitar; Chailapakul, Orawan; Cropek, Donald M; Henry, Charles S

2011-08-07

Recently, the development of electrochemical biosensors as part of microfluidic devices has garnered a great deal of attention because of the small instrument size and portability afforded by the integration of electrochemistry in microfluidic systems. Electrode fabrication, however, has proven to be a major obstacle in the field. Here, an alternative method to create integrated, low cost, robust, patternable carbon paste electrodes (CPEs) for microfluidic devices is presented. The new CPEs are composed of graphite powder and a binder consisting of a mixture of poly(dimethylsiloxane) (PDMS) and mineral oil. The electrodes are made by filling channels molded in previously cross-linked PDMS using a method analogous to screen printing. The optimal binder composition was investigated to obtain electrodes that were physically robust and performed well electrochemically. After studying the basic electrochemistry, the PDMS-oil CPEs were modified with multi-walled carbon nanotubes (MWCNT) and cobalt phthalocyanine (CoPC) for the detection of catecholamines and thiols, respectively, to demonstrate the ease of electrode chemical modification. Significant improvement of analyte signal detection was observed from both types of modified CPEs. A nearly 2-fold improvement in the electrochemical signal for 100 μM dithiothreitol (DTT) was observed when using a CoPC modified electrode (4.0 ± 0.2 nA (n = 3) versus 2.5 ± 0.2 nA (n = 3)). The improvement in signal was even more pronounced when looking at catecholamines, namely dopamine, using MWCNT modified CPEs. In this case, an order of magnitude improvement in limit of detection was observed for dopamine when using the MWCNT modified CPEs (50 nM versus 500 nM). CoPC modified CPEs were successfully used to detect thiols in red blood cell lysate while MWCNT modified CPEs were used to monitor temporal changes in catecholamine release from PC12 cells following stimulation with potassium.

Graphite fiber brush anodes for increased power production in air-cathode microbial fuel cells.

PubMed

Logan, Bruce; Cheng, Shaoan; Watson, Valerie; Estadt, Garett

2007-05-01

To efficiently generate electricity using bacteria in microbial fuel cells (MFCs), highly conductive noncorrosive materials are needed that have a high specific surface area (surface area per volume) and an open structure to avoid biofouling. Graphite brush anodes, consisting of graphite fibers wound around a conductive, but noncorrosive metal core, were examined for power production in cube (C-MFC) and bottle (B-MFC) air-cathode MFCs. Power production in C-MFCs containing brush electrodes at 9600 m2/m3 reactor volume reached a maximum power density of 2400 mW/m2 (normalized to the cathode projected surface area), or 73 W/m3 based on liquid volume, with a maximum Coulombic efficiency (CE) of 60%. This power density, normalized by cathode projected area, is the highest value yet achieved by an air-cathode system. The increased power resulted from a reduction in internal resistance from 31 to 8 Q. Brush electrodes (4200 m2/m3) were also tested in B-MFCs, consisting of a laboratory media bottle modified to have a single side arm with a cathode clamped to its end. B-MFCs inoculated with wastewater produced up to 1430 mW/m2 (2.3 W/m3, CE = 23%) with brush electrodes, versus 600 mW/m2 with a plain carbon paper electrode. These findings show that brush anodes that have high surface areas and a porous structure can produce high power densities, and therefore have qualities that make them ideal for scaling up MFC systems.

An amperometric bienzymatic cholesterol biosensor based on functionalized graphene modified electrode and its electrocatalytic activity towards total cholesterol determination.

PubMed

Manjunatha, Revanasiddappa; Shivappa Suresh, Gurukar; Melo, Jose Savio; D'Souza, Stanislaus F; Venkatesha, Thimmappa Venkatarangaiah

2012-09-15

Cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been covalently immobilized onto functionalized graphene (FG) modified graphite electrode. Enzymes modified electrodes were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). FG accelerates the electron transfer from electrode surface to the immobilized ChOx, achieving the direct electrochemistry of ChOx. A well defined redox peak was observed, corresponding to the direct electron transfer of the FAD/FADH(2) of ChOx. The electron transfer coefficient (α) and electron transfer rate constant (K(s)) were calculated and their values are found to be 0.31 and 0.78 s(-1), respectively. For the free cholesterol determination, ChOx-FG/Gr electrode exhibits a sensitive response from 50 to 350 μM (R=-0.9972) with a detection limit of 5 μM. For total cholesterol determination, co-immobilization of ChEt and ChOx on modified electrode, i.e. (ChEt/ChOx)-FG/Gr electrode showed linear range from 50 to 300 μM (R=-0.9982) with a detection limit of 15 μM. Some common interferents like glucose, ascorbic acid and uric acid did not cause any interference, due to the use of a low operating potential. The FG/Gr electrode exhibits good electrocatalytic activity towards hydrogen peroxide (H(2)O(2)). A wide linear response to H(2)O(2) ranging from 0.5 to 7 mM (R=-0.9967) with a sensitivity of 443.25 μA mM(-1) cm(-2) has been obtained. Copyright © 2012 Elsevier B.V. All rights reserved.

Effective degradation of rhodamine B by electro-Fenton process, using ferromagnetic nanoparticles loaded on modified graphite felt electrode as reusable catalyst: in neutral pH condition and without external aeration.

PubMed

Tian, Jiangnan; Zhao, Jixiang; Olajuyin, Ayobami Matthew; Sharshar, Moustafa Mohamed; Mu, Tingzhen; Yang, Maohua; Xing, Jianmin

2016-08-01

Polytetrafluoroethylene/ferromagnetic nanoparticle/carbon black (PTFE/MNP/CB)-modified graphite felt (GF) was successfully applied as cathode for the mineralization of rhodamine B (RhB) in electro-Fenton (EF) process. The modified cathode showed high decolorization efficiency for RhB solution even in neutral pH condition and without external aeration, achieving nearly complete decolorization and 89.52 % total organic carbon (TOC) removal after 270-min oxidation with the MNP load 1.2 g at 50 A/m(2). Moreover, the operational parameters (current density, MNP load, initial pH, and airflow rate) were optimized. After that, adsorption isotherm was also conducted to compare the absorption quantity of CB and carbon nanotube (CNT). Then, the surface morphologies of MNPs were characterized by transmission electron microscope (TEM), energy-dispersive X-ray detector (EDX), and Fourier transform infrared spectroscopy (FTIR); and the modified cathode was characterized by SEM and contact angle. Finally, the stability and reusability of modified cathode were tested. Result uncovered that the PTFE/MNP/CB-modified cathode has the potential for industrial application and the solution after treatment was easily biodegradable.

Porous carbon derived from disposable shaddock peel as an excellent catalyst toward VO2+/VO2+ couple for vanadium redox battery

NASA Astrophysics Data System (ADS)

Liu, J.; Wang, Z. A.; Wu, X. W.; Yuan, X. H.; Hu, J. P.; Zhou, Q. M.; Liu, Z. H.; Wu, Y. P.

2015-12-01

Functional porous carbon (PC) derived from bio-friendly shaddock peel has been firstly explored as catalyst for vanadium redox flow battery (VRB). The prepared PC is micro-mesoporous with high BET surface area of 882.7 m2 g-1, has some surface oxygen-containing functional groups, and is doped with N and P heteroatoms. These three factors greatly favor the electrochemical reactions of VO2+/VO2+ on the PC modified glass carbon (PC-GC). Compared with the naked GC and graphite modified GC, the PC-GC presents a lower peak separation (66 mV), higher anodic current density (17.1 mA cm-2) and cathodic current density (15.0 mA cm-2). The VRB using PC modified graphite felt (GF) as positive electrode demonstrates an enhanced voltage efficiency of 82.7% at the current density of 60 mA cm-2, and a better rate performance than that from the virginal GF.

Ordered mesoporous carbon modified carbon ionic liquid electrode for the electrochemical detection of double-stranded DNA.

PubMed

Zhu, Zhihong; Li, Xia; Zeng, Yan; Sun, Wei

2010-06-15

In this paper the direct electrochemistry of double-stranded DNA (dsDNA) was investigated on ordered mesoporous carbon (OMC) modified carbon ionic liquid electrode (CILE). CILE was prepared by mixing graphite powder with 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM]EtOSO(3)) and liquid paraffin. A stable OMC film was formed on the surface of CILE with the help of Nafion to get a modified electrode denoted as Nafion-OMC/CILE. Due to the specific characteristics of OMC and IL present on the electrode surface, the fabricated electrode showed good electrochemical performances to different electroactive molecules. The electrochemical responses of dsDNA were carefully investigated on this electrode with two irreversible oxidation peak appeared at +1.250 V and +0.921 V (vs. SCE), which was corresponding to the oxidation of adenine and guanine residues in dsDNA structure. The electrochemical behaviors of dsDNA were carefully investigated on the Nafion-OMC/CILE. Experimental results indicated that the electron transfer rate was promoted with the increase of the oxidation peak current and the decrease of the oxidation peak potential, which was due to the electrocatalytic ability of OMC on the electrode surface. Under the optimal conditions the oxidation peak current increased with dsDNA concentration in the range of 10.0-600.0 microg mL(-1) by differential pulse voltammetry (DPV) with the detection limit of 1.2 microg mL(-1) (3sigma). Copyright 2010 Elsevier B.V. All rights reserved.

Electro-catalytic degradation of sulfisoxazole by using graphene anode.

PubMed

Wang, Yanyan; Liu, Shuan; Li, Ruiping; Huang, Yingping; Chen, Chuncheng

2016-05-01

Graphite and graphene electrodes were prepared by using pure graphite as precursor. The electrode materials were characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) measurements. The electro-catalytic activity for degradation of sulfisoxazole (SIZ) was investigated by using prepared graphene or graphite anode. The results showed that the degradation of SIZ was much more rapid on the graphene than that on the graphite electrode. Moreover, the graphene electrode exhibited good stability and recyclability. The analysis on the intermediate products and the measurement of active species during the SIZ degradation demonstrated that indirect oxidation is the dominant mechanism, involving the electro-catalytic generation of OH and O2(-) as the main active oxygen species. This study implies that graphene is a promising potential electrode material for long-term application to electro-catalytic degradation of organic pollutants. Copyright © 2015. Published by Elsevier B.V.

Exploring the electrochemical performance of graphitic paste electrodes: graphene vs. graphite.

PubMed

Figueiredo-Filho, Luiz C S; Brownson, Dale A C; Gómez-Mingot, Maria; Iniesta, Jesús; Fatibello-Filho, Orlando; Banks, Craig E

2013-11-07

We report the fabrication, characterisation (SEM, TEM, XPS and Raman spectroscopy) and electrochemical implementation of a graphene paste electrode. The paste electrodes utilised are constructed by simply mixing graphene with mineral oil (which acts as a binder) prior to loading the resultant paste into a piston-driven polymeric-tubing electrode-shell, where this electrode configuration allows for rapid renewal of the electrode surface. The fabricated paste electrode is electrochemically characterised using both inner-sphere and outer-sphere redox probes, namely potassium ferrocyanide(ii), hexaammine-ruthenium(iii) chloride and hexachloroiridate(iii), in addition to the biologically relevant and electroactive analytes, l-ascorbic acid (AA) and uric acid (UA). Comparisons are made with a graphite paste alternative and the benefits of graphene implementation as a paste electrode within electrochemistry are explored, as well as the characterisation of their electroanalytical performances. We reveal no observable differences in the electrochemical performance and thus suggest that there are no advantages of using graphene over graphite in the fabrication of paste electrodes. Such work is highly important and informative for those working in the field of electroanalysis where electrochemistry can provide portable, rapid, reliable and accurate sensing protocols (bringing the laboratory into the field), with particular relevance to those searching for new electrode materials.

Conductive polymer binder for nano-silicon/graphite composite electrode in lithium-ion batteries towards a practical application

DOE PAGES

Zhao, Hui; Du, Allen; Ling, Min; ...

2016-05-10

The state-of-the-art graphite anode containing a small portion of silicon represents a promising way of applying high-capacity alloy anode in the next generation high energy density lithium-ion batteries. The conductive polymeric binders developed for Si anodes proved to be an effective binder for this graphite/nanoSi composite electrode. Without any acetylene black conductive additives in the electrode, a high areal capacity of above 2.5 mAh/cm 2 is achieved during long-term cycling over 100 cycles. Finally, this conductive polymer-enabled graphite/nanoSi composite electrode exhibits high specific capacity and high 1 st cycle efficiency, which is a significant progress toward commercial application of Simore » anodes.« less

Cold cap subsidence for in situ vitrification and electrodes therefor

DOEpatents

Buelt, James L.; Carter, John G.; Eschbach, Eugene A.; FitzPatrick, Vincent F.; Koehmstedt, Paul L.; Morgan, William C.; Oma, Kenton H.; Timmerman, Craig L.

1992-01-01

An electrode for use in in situ vitrification of soil comprises a molybdenum rod received within a conductive sleeve or collar formed of graphite. Electrodes of this type are placed on either side of a region containing buried waste material and an electric current is passed therebetween for vitrifying the soil between the electrodes. The graphite collar enhances the thermal conductivity of the electrode, bringing heat to the surface, and preventing the formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is filled with a conductive ceramic powder of a type that sinters upon the molybdenum rod, protecting the same from oxidation as the graphite material is consumed, or a metal powder which liquifies at operating temperatures. The molybdenum rod in the former case may be coated with an oxidation protectant, e.g. of molybdenum disilicide. As insulative blanket is suitably placed on the surface of the soil during processing to promote subsidence by allowing off-gassing and reducing surface heat loss. In other embodiments, connection to vitrification electrodes is provided below ground level to avoid loss of connection due to electrodes deterioration, or a sacrificial electrode may be employed when operation is started. Outboard electrodes can be utilized to square up the vitrified area. Further, the center of the molybdenum rod can be made hollow and filled with a powdered metal, such as copper, which liquifies at operating temperatures. In one embodiment, the molybdenum rod and the graphite collar are physically joined at the bottom.

Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor.

PubMed

Heydari, Hamid; Gholivand, Mohammad B; Abdolmaleki, Abbas

2016-09-01

In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. Copyright © 2016. Published by Elsevier B.V.

Non-destructive control of graphite electrodes with use of current displacement effect

NASA Astrophysics Data System (ADS)

Myatezh, A. V.; Malozyomov, B. V.; Smirnov, M. A.

2017-10-01

The work is devoted to methods of nondestructive diagnostics and their use for solving the problem of diagnosing various defects in solid surface of graphite electrodes used in steelmaking furnaces. Various non-destructive control methods of materials are analyzed. In the article, methods of eddy-current defectoscopy of graphite electrodes are considered. Rationalization of the sensitivity increase of the method and localization of damage is described. Imitating modeling of electromagnetic processes was executed; results were made and conclusions were drawn.

Pencil graphite leads as simple amperometric sensors for microchip electrophoresis.

PubMed

Natiele Tiago da Silva, Eiva; Marques Petroni, Jacqueline; Gabriel Lucca, Bruno; Souza Ferreira, Valdir

2017-11-01

In this work we demonstrate, for the first time, the use of inexpensive commercial pencil graphite leads as simple amperometric sensors for microchip electrophoresis. A PDMS support containing one channel was fabricated through soft lithography and sanded pencil graphite leads were inserted into this channel to be used as working electrodes. The electrochemical and morphological characterization of the sensor was carried out. The graphite electrode was coupled to PDMS microchips in end-channel configuration and electrophoretic experiments were performed using nitrite and ascorbate as probe analytes. The analytes were successfully separated and detected in well-defined peaks with satisfactory resolution using the microfluidic platform proposed. The repeatability of the pencil graphite electrode was satisfactory (RSD values of 1.6% for nitrite and 12.3% for ascorbate, regarding the peak currents) and its lifetime was estimated to be ca. 700 electrophoretic runs over a cost of ca. $ 0.05 per electrode. The limits of detection achieved with this system were 2.8 μM for nitrite and 5.7 μM for ascorbate. For proof of principle, the pencil graphite electrode was employed for the real analysis of well water samples and nitrite was successfully quantified at levels below its maximum contaminant level established in Brazil and US. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pencil graphite electrodes for improved electrochemical detection of oleuropein by the combination of Natural Deep Eutectic Solvents and graphene oxide.

PubMed

Gomez, Federico J V; Spisso, Adrian; Fernanda Silva, María

2017-11-01

A novel methodology is presented for the enhanced electrochemical detection of oleuropein in complex plant matrices by Graphene Oxide Pencil Grahite Electrode (GOPGE) in combination with a buffer modified with a Natural Deep Eutectic Solvent, containing 10% (v/v) of Lactic acid, Glucose and H 2 O (LGH). The electrochemical behavior of oleuropein in the modified-working buffer was examined using differential pulse voltammetry. The combination of both modifications, NADES modified buffer and nanomaterial modified electrode, LGH-GOPGE, resulted on a signal enhancement of 5.3 times higher than the bare electrode with unmodified buffer. A calibration curve of oleuropein was performed between 0.10 to 37 μM and a good linearity was obtained with a correlation coefficient of 0.989. Detection and quantification limits of the method were obtained as 30 and 102 nM, respectively. In addition, precision studies indicated that the voltammetric method was sufficiently repeatable, %RSD 0.01 and 3.16 (n = 5) for potential and intensity, respectively. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract prepared by ultrasound-assisted extraction. The results obtained with the proposed electrochemical sensor were compared with Capillary Zone Electrophoresis analysis with satisfactory results. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium nanoparticle-modified screen-printed graphite electrodes for the determination of hydrogen peroxide in tea extracts in the presence of oxygen.

PubMed

Gatselou, Vasiliki A; Giokas, Dimothenis L; Vlessidis, Athanasios G; Prodromidis, Mamas I

2015-03-01

In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on polyethyleneimine (PEI)-supported rhodium nanoparticles (Rh-NP) over graphite screen-printed electrodes (SPEs) for the determination of hydrogen peroxide in the presence of oxygen. Rh-NP, electrostatically stabilized by citrate anions, were immobilized over graphite SPEs, through coulombic attraction on a thin film of positively charged PEI. The functionalized sensors, polarized at 0.0 V vs. Ag/AgCl/3 M KCl, exhibited a linear response to H2O2 over the concentration range from 5 to 600 μmol L(-1) H2O2 in the presence of oxygen. The 3σ limit of detection was 2 μmol L(-1) H2O2, while the reproducibility of the method at the concentration level of 10 μmol L(-1) H2O2 (n=10) and between different sensors (n=4) was lower than 3 and 5%, respectively. Most importantly, the sensors showed an excellent working and storage stability at ambient conditions and they were successfully applied to the determination of H2O2 produced by autooxidation of polylphenols in tea extracts with ageing. Recovery rates ranged between 97 and 104% suggesting that the as-prepared electrodes can be used for the development of small-scale, low-cost chemical sensors for use in on-site applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Determination of vanadium(V) by direct automatic potentiometric titration with EDTA using a chemically modified electrode as a potentiometric sensor.

PubMed

Quintar, S E; Santagata, J P; Cortinez, V A

2005-10-15

A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure. The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste. Automatic potentiometric titration curves were obtained for V(V) within 5 x 10(-5) to 2 x 10(-3)M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prosthesis.

Efficient detection of hazardous catechol and hydroquinone with MOF-rGO modified carbon paste electrode.

PubMed

Wang, Hailong; Hu, Quanqin; Meng, Yuan; Jin, Zier; Fang, Zilin; Fu, Qinrui; Gao, Wenhua; Xu, Liang; Song, Yibing; Lu, Fushen

2018-02-19

Reduced graphite oxide (rGO) was incorporated into a metal organic framework (MOF) MIL-101(Cr) for the modification of carbon paste electrode. Taking advantages of the large surface area of MOF and the electrical conductivity of rGO, the resulted electrodes exhibited high sensitivity and reliability in the simultaneous electrochemical identification and quantification of catechol (CC) and hydroquinone (HQ). Specifically, in the mixture solution of catechol and hydroquinone (constant concentration of an analyte), the linear response ranges for catechol and hydroquinone were 10-1400 μM and 4-1000 μM, and detection limits were 4 μM and 0.66 μM (S/N = 3) for individual catechol and hydroquinone, respectively. Therefore, the relatively easy fabrication of modified CPE and its fascinating reliability towards HQ and CC detection may simulate more research interest in the applications of MIL-101(Cr)-rGO composites for electrochemical sensors. Copyright © 2018 Elsevier B.V. All rights reserved.

Glucose sensing on graphite screen-printed electrode modified by sparking of copper nickel alloys.

PubMed

Riman, Daniel; Spyrou, Konstantinos; Karantzalis, Alexandros E; Hrbac, Jan; Prodromidis, Mamas I

2017-04-01

Electric spark discharge was employed as a green, fast and extremely facile method to modify disposable graphite screen-printed electrodes (SPEs) with copper, nickel and mixed copper/nickel nanoparticles (NPs) in order to be used as nonenzymatic glucose sensors. Direct SPEs-to-metal (copper, nickel or copper/nickel alloys with 25/75, 50/50 and 75/25wt% compositions) sparking at 1.2kV was conducted in the absence of any solutions under ambient conditions. Morphological characterization of the sparked surfaces was performed by scanning electron microscopy, while the chemical composition of the sparked NPs was evaluated with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The performance of the various sparked SPEs towards the electro oxidation of glucose in alkaline media and the critical role of hydroxyl ions were evaluated with cyclic voltammetry and kinetic studies. Results indicated a mixed charge transfer- and hyroxyl ion transport-limited process. Best performing sensors fabricated by Cu/Ni 50/50wt% alloy showed linear response over the concentration range 2-400μM glucose and they were successfully applied to the amperometric determination of glucose in blood. The detection limit (S/N 3) and the relative standard deviation of the method were 0.6µM and <6% (n=5, 2µM glucose), respectively. Newly devised sparked Cu/Ni graphite SPEs enable glucose sensing with distinct advantages over existing glucose chemical sensors in terms of cost, fabrication simplicity, disposability, and adaptation of green methods in sensor's development. Copyright © 2017 Elsevier B.V. All rights reserved.

Direct synthesis of platelet graphitic-nanofibres as a highly porous counter-electrode in dye-sensitized solar cells.

PubMed

Hsieh, Chien-Kuo; Tsai, Ming-Chi; Yen, Ming-Yu; Su, Ching-Yuan; Chen, Kuei-Fu; Ma, Chen-Chi M; Chen, Fu-Rong; Tsai, Chuen-Horng

2012-03-28

We synthesized platelet graphitic-nanofibres (GNFs) directly onto FTO glass and applied this forest of platelet GNFs as a highly porous structural counter-electrode in dye-sensitized solar cells (DSSCs). We investigated the electrochemical properties of counter-electrodes made from the highly porous structural GNFs and the photoconversion performance of the cells made with these electrodes.

Preparation of genosensor for detection of specific DNA sequence of the hepatitis B virus

NASA Astrophysics Data System (ADS)

Honorato Castro, Ana C.; França, Erick G.; de Paula, Lucas F.; Soares, Marcia M. C. N.; Goulart, Luiz R.; Madurro, João M.; Brito-Madurro, Ana G.

2014-09-01

An electrochemical genosensor was constructed for detection of specific DNA sequence of the hepatitis B virus, based on graphite electrodes modified with poly(4-aminophenol) and incorporating a specific oligonucleotide probe. The modified electrode containing the probe was evaluated by differential pulse voltammetry, before and after incubation with the complementary oligonucleotide target. Detection was performed by monitoring oxidizable DNA bases (direct detection) or using ethidium bromide as indicator of the hybridization process (indirect detection). The device showed a detection limit for the oligonucleotide target of 2.61 nmol L-1. Indirect detection using ethidium bromide was promising in discriminating mismatches, which is a very desirable attribute for detection of disease-related point mutations. In addition, it was possible to observe differences between hybridized and non-hybridized surfaces by atomic force microscopy.

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.

Degradation Mechanisms of Electrochemically Cycled Graphite Anodes in Lithium-ion Cells

NASA Astrophysics Data System (ADS)

Bhattacharya, Sandeep

This research is aimed at developing advanced characterization methods for studying the surface and subsurface damage in Li-ion battery anodes made of polycrystalline graphite and identifying the degradation mechanisms that cause loss of electrochemical capacity. Understanding microstructural aspects of the graphite electrode degradation mechanisms during charging and discharging of Li-ion batteries is of key importance in order to design durable anodes with high capacity. An in-situ system was constructed using an electrochemical cell with an observation window, a large depth-of-field digital microscope and a micro-Raman spectrometer. It was revealed that electrode damage by removal of the surface graphite fragments of 5-10 mum size is the most intense during the first cycle that led to a drastic capacity drop. Once a solid electrolyte interphase (SEI) layer covered the electrode surface, the rate of graphite particle loss decreased. Yet, a gradual loss of capacity continued by the formation of interlayer cracks adjacent to SEI/graphite interfaces. Deposition of co-intercalation compounds, LiC6, Li2CO3 and Li2O, near the crack tips caused partial closure of propagating graphite cracks during cycling and reduced the crack growth rate. Bridging of crack faces by delaminated graphite layers also retarded crack propagation. The microstructure of the SEI layer, formed by electrochemical reduction of the ethylene carbonate based electrolyte, consisted of ˜5-20 nm sized crystalline domains (containing Li2CO3, Li2O 2 and nano-sized graphite fragments) dispersed in an amorphous matrix. During the SEI formation, two regimes of Li-ion diffusion were identified at the electrode/electrolyte interface depending on the applied voltage scan rate (dV/dt). A low Li-ion diffusion coefficient ( DLi+) at dV/dt < 0.05 mVs-1 produced a tubular SEI that uniformly covered the graphite surface and prevented damage at 25°C. At 60°C, a high D Li+ formed a Li2CO3-enriched SEI and ensued a 28% increase in the battery capacity at 25°C. On correlating the microscopic information to the electrochemical performance, novel Li2CO3-coated electrodes were fabricated that were durable. The SEI formed on pre-treated electrodes reduced the strain in the graphite lattice from 0.4% (for uncoated electrodes) to 0.1%, facilitated Li-ion diffusion and hence improved the capacity retention of Li-ion batteries during long-term cycling.

Purification process of natural graphite as anode for Li-ion batteries: chemical versus thermal

NASA Astrophysics Data System (ADS)

Zaghib, K.; Song, X.; Guerfi, A.; Rioux, R.; Kinoshita, K.

The intercalation of Li ions in natural graphite that was purified by chemical and thermal processes was investigated. A new chemical process was developed that involved a mixed aqueous solution containing 30% H 2SO 4 and 30% NH xF y heated to 90 °C. The results of this process are compared to those obtained by heating the natural graphite from 1500 to 2400 °C in an inert environment (thermal process). The first-cycle coulombic efficiency of the purified natural graphite obtained by the chemical process is 91 and 84% after the thermal process at 2400 °C. Grinding the natural graphite before or after purification had no significant effect on electrochemical performance at low currents. However, grinding to a very small particle size before purification permitted optimization of the size distribution of the particles, which gives rise to a more homogenous electrode. The impurities in the graphite play a role as microabrasion agents during grinding which enhances its hardness and improves its mechanical properties. Grinding also modifies the particle morphology from a 2- to a 3-D structure (similar in shape to a potato). This potato-shaped natural graphite shows high reversible capacity at high current densities (about 90% at 1 C rate). Our analysis suggests that thermal processing is considerably more expensive than the chemical process to obtain purified natural graphite.

Graphene/graphite paste electrode incorporated with molecularly imprinted polymer nanoparticles as a novel sensor for differential pulse voltammetry determination of fluoxetine.

PubMed

Alizadeh, Taher; Azizi, Sorour

2016-07-15

Molecularly imprinted polymer (MIP) nanoparticles including highly selective recognition sites for fluoxetine were synthesized, utilizing precipitation polymerization. Methacrylic acid and vinyl benzene were used as functional monomers. Ethylene glycol dimethacrylate was used as cross-linker agent. The obtained polymeric nanoparticles were incorporated with carbon paste electrode (CPE) in order to construct a fluoxetine selective sensor. The response of the MIP-CP electrode to fluoxetine was remarkably higher than the electrode, modified with the non-imprinted polymer, indicating the excellent efficiency of the MIP sites for target molecule recognition. It was found that the addition of a little amount of graphene, synthesized via modified hummer's method, to the MIP-CP resulted in considerable enhancement in the sensitivity of the electrode to fluoxetine. Also, the style of electrode components mixing, before carbon paste preparation, was demonstrated to be influential factor in the electrode response. Some parameters, affecting sensor response, were optimized and then a calibration curve was plotted. A dynamic linear range of 6×10(-9)-1.0×10(-7)molL(-1) was obtained. The detection limit of the sensor was calculated equal to 2.8×10(-9)molL(-1) (3Sb/m). This sensor was used successfully for fluoxetine determination in the spiked plasma samples as well as fluoxetine capsules. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of pulse ON and OFF time and electrode types on the material removal rate and tool wear rate of the Ti-6Al-4V Alloy using EDM machining with reverse polarity

NASA Astrophysics Data System (ADS)

Praveen, L.; Geeta Krishna, P.; Venugopal, L.; Prasad, N. E. C.

2018-03-01

Electrical Discharge Machining (EDM) is an unconventional metal removal process that is extensively used for removing the difficult-to-machine metal such as Ti alloys, super alloys and metal matrix composites. This paper investigates the effects of pulse (ON/OFF) time on EDM machining characteristics of Ti-6Al-4V alloy using copper and graphite as electrodes in reverse polarity condition. Full factorial design method was used to design the experiments. Two variables (Pulse On and OFF) with three levels are considered. The output variables are the tool wear rate and the material removal rate. The important findings from the present work are: (1) the material removal rate (MRR) increases gradually with an increase of the Pulse ON time whereas the change is insignificant with an increase of the Pulse OFF time, (2) Between copper and graphite electrodes, the copper electrode is proved to be good in terms of MRR, (3) a combination of high pulse ON time and OFF time is desirable for high MRR rate in the Cu electrode whereas for the graphite electrode, a combination of high pulse ON time and low pulse OFF time is desirable for high MRR rate, (4) the tool wear rate (TWR) reduces with the Pulse On or OFF time, the rate of TWR is uniform for the graphite electrode in contrast to abrupt decrease from 25 to 50 μs (pulse ON time) in the copper electrode, (5) In order to keep the TWR as minimum possible, it is desirable to have a combination of high pulse ON time and OFF time for both the copper and the graphite electrode.

Amperometric glucose biosensor with remarkable acid stability based on glucose oxidase entrapped in colloidal gold-modified carbon ionic liquid electrode.

PubMed

Liu, Xiaoying; Zeng, Xiandong; Mai, Nannan; Liu, Yong; Kong, Bo; Li, Yonghong; Wei, Wanzhi; Luo, Shenglian

2010-08-15

A colloidal gold-modified carbon ionic liquid electrode was constructed by mixing colloidal gold-modified graphite powder with a solid room temperature ionic liquid n-octyl-pyridinium hexafluorophosphate (OPPF(6)). Glucose oxidase (GOD) was entrapped in this composite matrix and maintained its bioactivity well and displayed excellent stability. The effect conditions of pH, applied potential and GOD loading were examined. Especially, the glucose oxidase entrapped in this carbon ionic liquid electrode fully retained its activity upon stressing in strongly acidic conditions (pH 2.0) for over one hour. The proposed biosensor responds to glucose linearly over concentration range of 5.0x10(-6) to 1.2x10(-3) and 2.6x10(-3) to 1.3x10(-2) M, and the detection limit is 3.5x10(-6) M. The response time of the biosensor is fast (within 10s), and the life time is over two months. The effects of electroactive interferents, such as ascorbic acid, uric acid, can be significantly reduced by a Nafion film casting on the surface of resulting biosensor. Copyright 2010 Elsevier B.V. All rights reserved.

Alternate electrode materials for the SP100 reactor

NASA Astrophysics Data System (ADS)

Randich, E.

1992-05-01

This work was performed in response to a request by the Astro-Space Division of the General Electric Co. to develop alternate electrodes materials for the electrodes of the PD2 modules to be used in the SP100 thermoelectric power conversion system. Initially, the project consisted of four tasks: (1) development of a ZrB2 (C) CVD coating on SiMo substrates; (2) development of a ZrB2 (C) CVD coating on SiGe substrates; (3) development of CVI W for porous graphite electrodes; and (4) technology transfer of pertinent developed processes. The project evolved initially into developing only ZrB2 coatings on SiGe and graphite substrates, and later into developing ZrB2 coatings only on graphite substrates. Several sizes of graphite and pyrolytic carbon-coated graphite substrates were coated with ZrB2 during the project. For budgetary reasons, the project was terminated after half the allotted time had passed. Apart from the production of coated specimens for evaluation, the major accomplishment of the project was the development of the CVD processing to produce the desired coatings.

Simulating Supercapacitors: Can We Model Electrodes As Constant Charge Surfaces?

PubMed

Merlet, Céline; Péan, Clarisse; Rotenberg, Benjamin; Madden, Paul A; Simon, Patrice; Salanne, Mathieu

2013-01-17

Supercapacitors based on an ionic liquid electrolyte and graphite or nanoporous carbon electrodes are simulated using molecular dynamics. We compare a simplified electrode model in which a constant, uniform charge is assigned to each carbon atom with a realistic model in which a constant potential is applied between the electrodes (the carbon charges are allowed to fluctuate). We show that the simulations performed with the simplified model do not provide a correct description of the properties of the system. First, the structure of the adsorbed electrolyte is partly modified. Second, dramatic differences are observed for the dynamics of the system during transient regimes. In particular, upon application of a constant applied potential difference, the increase in the temperature, due to the Joule effect, associated with the creation of an electric current across the cell follows Ohm's law, while unphysically high temperatures are rapidly observed when constant charges are assigned to each carbon atom.

CuC1 thermochemical cycle for hydrogen production

DOEpatents

Fan, Qinbai [Chicago, IL; Liu, Renxuan [Chicago, IL

2012-01-03

An electrochemical cell for producing copper having a dense graphite anode electrode and a dense graphite cathode electrode disposed in a CuCl solution. An anion exchange membrane made of poly(ethylene vinyl alcohol) and polyethylenimine cross-linked with a cross-linking agent selected from the group consisting of acetone, formaldehyde, glyoxal, glutaraldehyde, and mixtures thereof is disposed between the two electrodes.

Lithium-ion capacitors using carbide-derived carbon as the positive electrode - A comparison of cells with graphite and Li4Ti5O12 as the negative electrode

NASA Astrophysics Data System (ADS)

Rauhala, Taina; Leis, Jaan; Kallio, Tanja; Vuorilehto, Kai

2016-11-01

The use of carbide-derived carbon (CDC) as the positive electrode material for lithium-ion capacitors (LICs) is investigated. CDC based LIC cells are studied utilizing two different negative electrode materials: graphite and lithium titanate Li4Ti5O12 (LTO). The graphite electrodes are prelithiated before assembling the LICs, and LTO containing cells are studied with and without prelithiation. The rate capability and cycle life stability during 1000 cycles are evaluated by galvanostatic cycling at current densities of 0.4-4 mA cm-2. The CDC shows a specific capacitance of 120 F g-1 in the organic lithium-containing electrolyte, and the LICs demonstrate a good stability over 1000 charge-discharge cycles. The choice of the negative electrode is found to have an effect on the utilization of the CDC positive electrode during cycling and on the specific energy of the device. The graphite/CDC cell delivers a maximum specific discharge energy of 90 Wh kg-1 based on the total mass of active material in the cell. Both the prelithiated and non-prelithiated LTO/CDC cells show a specific energy of around 30 Wh kg-1.

Method for fabricating carbon/lithium-ion electrode for rechargeable lithium cell

NASA Technical Reports Server (NTRS)

Attia, Alan I. (Inventor); Halpert, Gerald (Inventor); Huang, Chen-Kuo (Inventor); Surampudi, Subbarao (Inventor)

1995-01-01

The method includes steps for forming a carbon electrode composed of graphitic carbon particles adhered by an ethylene propylene diene monomer binder. An effective binder composition is disclosed for achieving a carbon electrode capable of subsequent intercalation by lithium ions. The method also includes steps for reacting the carbon electrode with lithium ions to incorporate lithium ions into graphitic carbon particles of the electrode. An electrical current is repeatedly applied to the carbon electrode to initially cause a surface reaction between the lithium ions and to the carbon and subsequently cause intercalation of the lithium ions into crystalline layers of the graphitic carbon particles. With repeated application of the electrical current, intercalation is achieved to near a theoretical maximum. Two differing multi-stage intercalation processes are disclosed. In the first, a fixed current is reapplied. In the second, a high current is initially applied, followed by a single subsequent lower current stage. Resulting carbon/lithium-ion electrodes are well suited for use as an anode in a reversible, ambient temperature, lithium cell.

Method for electrostatic deposition of graphene on a substrate

NASA Technical Reports Server (NTRS)

Sumanasekera, Gamini (Inventor); Sidorov, Anton N. (Inventor); Ouseph, P. John (Inventor); Yazdanpanah, Mehdi M. (Inventor); Cohn, Robert W. (Inventor); Jalilian, Romaneh (Inventor)

2010-01-01

A method for electrostatic deposition of graphene on a substrate comprises the steps of securing a graphite sample to a first electrode; electrically connecting the first electrode to a positive terminal of a power source; electrically connecting a second electrode to a ground terminal of the power source; placing the substrate over the second electrode; and using the power source to apply a voltage, such that graphene is removed from the graphite sample and deposited on the substrate.

Electrochemical behaviour of vanadium(V)/vanadium(IV) redox couple at graphite electrodes

NASA Astrophysics Data System (ADS)

Zhong, S.; Skyllas-Kazacos, M.

The electrochemical behaviour of the V(V)/V(IV) couple has been studied at a graphite disc electrode in sulfuric acid using both cyclic and rotating-disc voltammetry. The results from the latter technique have revealed that the cathodic and anodic characteristics of this redox couple are quite different. The diffusion coefficient for V(IV), 2.14×10-6 cm2 s-1, is independent of the vanadium concentration. For V(IV) oxidation, the electrode kinetic parameters i0 and α have values of 2.47×10-4 A cm-2 and 0.71, respectively. The exchange current density, i0, for the V(V)/V(IV) reaction has been obtained at both graphite felt and reticulated vitreous carbon electrodes.

Development of a novel and cost-effective redox sensor for voltammetric determination of pantoprazole sodium during pharmacokinetic studies

PubMed Central

Khashaba, Pakinaz Y.; Ali, Hassan Refat H.

2017-01-01

A pencil graphite electrode modified with poly (bromocresol green (BCG)) was prepared by electro-polymerization process for the determination of pantoprazole sodium. The surface morphology and structure of poly (BCG) film were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The determination of pantoprazole sodium in Britton–Robinson buffer (pH 7.0) was carried out by square wave adsorptive stripping voltammetric technique. Under optimum conditions, the linear response of the peak with concentration of the cited drug was in the range of 6.6–360 × 10−8 M with limit of detection of 2.2 × 10−8 M. Moreover, the poly (BCG)-modified electrode has been successfully applied to determine pantoprazole sodium in tablets, vials and during pharmacokinetic studies. PMID:28878983

IDENTIFICATION OF CHLOROMETHANE FROMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

EPA Science Inventory

The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

IDENTIFICATION OF CHLOROMETHANE FORMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

EPA Science Inventory

The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead

PubMed Central

Vu, Dai Long; Žabčíková, Simona; Ertek, Bensu; Dilgin, Yusuf

2015-01-01

Summary In this paper, a pencil graphite electrode was pretreated using chronoamperometry technique in phosphate buffer solution (pH=7.0) for sensitive determination of quercetin. Oxidation of quercetin was investigated using pretreated pencil graphite electrode and anodic stripping differential pulse voltammetry. Under optimal conditions, the anodic current of quercetin exhibited linear response to its concentration in the range from 0.001 to 1.5 µmol/L with the limit of detection of 0.3·10–3 µmol/L. The proposed method was successfully applied for the determination of quercetin in cranberry and blackcurrant juices with recovery rate from 93.2 to 94.7%. Solid-phase extraction was found to be necessary prior to voltammetric determination of quercetin in fruit juice samples using pretreated pencil graphite electrode. PMID:27904372

Density impact on performance of composite Si/graphite electrodes

DOE PAGES

Dufek, Eric J.; Picker, Michael; Petkovic, Lucia M.

2016-01-27

The ability of alkali-substituted binders for composite Si and graphite negative electrodes to minimize capacity fade for lithium ion batteries is investigated. Polymer films and electrodes are described and characterized by FTIR following immersion in electrolyte (1:2 EC:DMC) for 24 h. FTIR analysis following electrode formation displayed similar alkali-ion dependent shifts in peak location suggesting that changes in the vibrational structure of the binder are maintained after electrode formation. The Si and graphite composite electrodes prepared using the alkali-substituted polyacrylates were also exposed to electrochemical cycling and it has been found that the performance of the Na-substituted binder is superiormore » to a comparable density K-substituted system. However, in comparing performance across many different electrode densities attention needs to be placed on making comparisons at similar densities, as low density electrodes tend to exhibit lower capacity fade over cycling. This is highlighted by a 6% difference between a low density K-substituted electrode and a high density Na-substituted sample. As a result, this low variance between the two systems makes it difficult to quickly make a direct evaluation of binder performance unless electrode density is tightly controlled.« less

The Unusual Colour of Copper Deposited on a Graphite Electrode in an Aqueous Solution of CuSO[subscript 4

ERIC Educational Resources Information Center

Petrusevski, Vladimir M.; Stojanovska, Marina

2010-01-01

The colour of the copper layer deposited on a graphite electrode during electrolysis of an aqueous solution of copper(II) sulfate looks whitish-grey when inspected in situ. Taking the electrode out of the solution reveals the familiar orange-red colour of deposited copper. The explanation is found in terms of the almost ideal complementary colours…

77 FR 33405 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-06

...The Department of Commerce (``Department'') preliminarily determines that certain small diameter graphite electrodes (``SDGE'') are being exported from the United Kingdom (``U.K.'') to the United States by UK Carbon and Graphite Co., Ltd. (``UKCG'') in circumvention of the antidumping duty order on SDGE from the People's Republic of China (``PRC''),\\1\\ as provided in section 781(b) of the Tariff Act of 1930, as amended (``the Act''). ---------------------------------------------------------------------------

Comparison of reduction products from graphite oxide and graphene oxide for anode applications in lithium-ion batteries and sodium-ion batteries.

PubMed

Sun, Yige; Tang, Jie; Zhang, Kun; Yuan, Jinshi; Li, Jing; Zhu, Da-Ming; Ozawa, Kiyoshi; Qin, Lu-Chang

2017-02-16

Hydrazine-reduced graphite oxide and graphene oxide were synthesized to compare their performances as anode materials in lithium-ion batteries and sodium-ion batteries. Reduced graphite oxide inherits the layer structure of graphite, with an average spacing between neighboring layers (d-spacing) of 0.374 nm; this exceeds the d-spacing of graphite (0.335 nm). The larger d-spacing provides wider channels for transporting lithium ions and sodium ions in the material. We showed that reduced graphite oxide as an anode in lithium-ion batteries can reach a specific capacity of 917 mA h g -1 , which is about three times of 372 mA h g -1 , the value expected for the LiC 6 structures on the electrode. This increase is consistent with the wider d-spacing, which enhances lithium intercalation and de-intercalation on the electrodes. The electrochemical performance of the lithium-ion batteries and sodium-ion batteries with reduced graphite oxide anodes show a noticeable improvement compared to those with reduced graphene oxide anodes. This improvement indicates that reduced graphite oxide, with larger interlayer spacing, has fewer defects and is thus more stable. In summary, we found that reduced graphite oxide may be a more favorable form of graphene for the fabrication of electrodes for lithium-ion and sodium-ion batteries and other energy storage devices.

Thermally Regenerative Battery with Intercalatable Electrodes and Selective Heating Means

NASA Technical Reports Server (NTRS)

Sharma, Pramod K. (Inventor); Narayanan, Sekharipuram R. (Inventor); Hickey, Gregory S. (Inventor)

2000-01-01

The battery contains at least one electrode such as graphite that intercalates a first species from the electrolyte disposed in a first compartment such as bromine to form a thermally decomposable complex during discharge. The other electrode can also be graphite which supplies another species such as lithium to the electrolyte in a second electrode compartment. The thermally decomposable complex is stable at room temperature but decomposes at elevated temperatures such as 50 C. to 150 C. The electrode compartments are separated by a selective ion permeable membrane that is impermeable to the first species. Charging is effected by selectively heating the first electrode.

Microstructure of room temperature ionic liquids at stepped graphite electrodes

DOE PAGES

Feng, Guang; Li, Song; Zhao, Wei; ...

2015-07-14

Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two-dimensional microstructure of ionmore » layers exhibits different patterns and alignments of counter-ion/co-ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL-electrode interfaces in supercapacitors.« less

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

NASA Astrophysics Data System (ADS)

Lin, Na; Jia, Zhe; Wang, Zhihui; Zhao, Hui; Ai, Guo; Song, Xiangyun; Bai, Ying; Battaglia, Vincent; Sun, Chengdong; Qiao, Juan; Wu, Kai; Liu, Gao

2017-10-01

The structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystalline graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.

Potassium-Based Dual Ion Battery with Dual-Graphite Electrode.

PubMed

Fan, Ling; Liu, Qian; Chen, Suhua; Lin, Kairui; Xu, Zhi; Lu, Bingan

2017-08-01

A potassium ion battery has potential applications for large scale electric energy storage systems due to the abundance and low cost of potassium resources. Dual graphite batteries, with graphite as both anode and cathode, eliminate the use of transition metal compounds and greatly lower the overall cost. Herein, combining the merits of the potassium ion battery and dual graphite battery, a potassium-based dual ion battery with dual-graphite electrode is developed. It delivers a reversible capacity of 62 mA h g -1 and medium discharge voltage of ≈3.96 V. The intercalation/deintercalation mechanism of K + and PF 6 - into/from graphite is proposed and discussed in detail, with various characterizations to support. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphite-silicone rubber composite electrode: Preparation and possibilities of analytical application.

PubMed

de Oliveira, Aline Carlos; dos Santos, Sidney Xavier; Cavalheiro, Eder Tadeu Gomes

2008-01-15

Composite electrodes were prepared using graphite powder and silicone rubber in different compositions. The use of such hydrophopic materials interned to diminish the swallowing observed in other cases when the electrodes are used in aqueous solutions for a long time. The composite was characterized for the response reproducibility, ohmic resistance, thermal behavior and active area. The voltammetric response in relation to analytes with known voltammetric behavior was also evaluated, always in comparison with the glassy carbon. The 70% (graphite, w/w) composite electrode was used in the quantitative determination of hydroquinone (HQ) in a DPV procedure in which a detection limit of 5.1x10(-8)molL(-1) was observed. HQ was determined in a photographic developer sample with errors lower then 1% in relation to the label value.

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

DOE PAGES

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.; ...

2018-02-09

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

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

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Lithium loss in the solid electrolyte interphase: Lithium quantification of aged lithium ion battery graphite electrodes by means of laser ablation inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Schwieters, Timo; Evertz, Marco; Mense, Maximilian; Winter, Martin; Nowak, Sascha

2017-07-01

In this work we present a new method using LA-ICP-MS to quantitatively determine the lithium content in aged graphite electrodes of a lithium ion battery (LIB) by performing total depth profiling. Matrix matched solid external standards are prepared using a solid doping approach to avoid elemental fractionation effects during the measurement. The results are compared and matched to the established ICP-OES technique for bulk quantification after performing a microwave assisted acid digestion. The method is applied to aged graphite electrodes in order to determine the lithium immobilization (= "Li loss") in the solid electrolyte interphase after the first cycle of formation. For this, different samples including a reference sample are created to obtain varying thicknesses of the SEI covering the electrode particles. By applying defined charging voltages, an initial lithiation process is performed to obtain specific graphite intercalation compounds (GICs, with target stoichiometries of LiC30, LiC18, LiC12 and LiC6). Afterwards, the graphite electrode is completely discharged to obtain samples without mobile, thus active lithium in its lattice. Taking the amount of lithium into account which originates from the residues of the LiPF6 (dissolved in the carbon components containing electrolyte), it is possible to subtract the amount of lithium in the SEI.

Capacitive behavior of highly-oxidized graphite

NASA Astrophysics Data System (ADS)

Ciszewski, Mateusz; Mianowski, Andrzej

2014-09-01

Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

Vertical distribution of overpotentials and irreversible charge losses in lithium ion battery electrodes.

PubMed

Klink, Stefan; Schuhmann, Wolfgang; La Mantia, Fabio

2014-08-01

Porous lithium ion battery electrodes are characterized using a vertical distribution of cross-currents. In an appropriate simplification, this distribution can be described by a transmission line model (TLM) consisting of infinitely thin electrode layers. To investigate the vertical distribution of currents, overpotentials, and irreversible charge losses in a porous graphite electrode in situ, a multi-layered working electrode (MWE) was developed as the experimental analogue of a TLM. In this MWE, each layer is in ionic contact but electrically insulated from the other layers by a porous separator. It was found that the negative graphite electrodes get lithiated and delithiated stage-by-stage and layer-by-layer. Several mass-transport- as well as non-mass-transport-limited processes could be identified. Local current densities can reach double the average, especially on the outermost layer at the beginning of each intercalation stage. Furthermore, graphite particles close to the counter electrode act as "electrochemical sieve" reducing the impurities present in the electrolyte such as water. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel integration system of magnetically immobilized cells and a pair of graphite plate-stainless iron mesh electrodes for the bioremediation of coking wastewater.

PubMed

Jiang, Bei; Tan, Liang; Ning, Shuxiang; Shi, Shengnan

2016-09-01

Magnetically immobilized cells of Comamonas sp. JB coupling with electrode reaction was developed to enhance the treatment efficiency of coking wastewater containing phenol, carbazole (CA), dibenzofuran (DBF), and dibenzothiophene (DBT). The pair of graphite plate-stainless iron mesh electrodes was chosen as the most suitable electrodes. Magnetically immobilized cells coupling with graphite plate-stainless iron mesh electrodes (coupling system) exhibited high degradation activity for all the compounds, which were significantly higher than the sum by single magnetically immobilized cells and electrode reaction at the optimal voltage. Recycling experiments demonstrated that the degradation activity of coupling system increased gradually during eight recycles, indicating that there was a coupling effect between the biodegradation and electrode reaction. Phenol hydroxylase and qPCR assays confirmed that appropriate electrical stimulation could improve phenol hydroxylase activity and promote cells growth. Toxicity assessment suggested the treatment of the coking wastewater by coupling system led to less toxicity than untreated wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electrochemical biosensor based on glucose oxidase encapsulated within enzymatically synthesized poly(1,10-phenanthroline-5,6-dione).

PubMed

Ciftci, Hakan; Oztekin, Yasemin; Tamer, Ugur; Ramanaviciene, Almira; Ramanavicius, Arunas

2014-11-01

This study is focused on the investigation of electrocatalytic effect of glucose oxidase (GOx) immobilized on the graphite rod (GR) electrode. The enzyme modified electrode was prepared by encapsulation of immobilized GOx within enzymatically formed poly(1,10-phenanthroline-5,6-dione) (pPD) film. The electrochemical responses of such enzymatic electrode (pPD/GOx/GR) vs. different glucose concentrations were examined chronoamperometrically in acetate-phosphate buffer solution (A-PBS), pH 6.0, under aerobic or anaerobic conditions. Amperometric signals of the pPD/GOx/GR electrode exhibited well-defined hyperbolic dependence upon glucose concentration. Amperometric signals at 100mM of glucose were 41.17 and 32.27 μA under aerobic and anaerobic conditions, respectively. Amperometric signals of the pPD/GOx/GR electrode decreased by 6% within seven days. The pPD/GOx/GR electrode showed excellent selectivity in the presence of dopamine and uric acid. Furthermore it had a good reproducibility and repeatability with standard deviation of 9.4% and 8.0%, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

EPA Science Inventory

Electrochemical dechlorination of TCE ws conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was comple...

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

EPA Science Inventory

Electrochemical dechlorination of TCE was conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was compl...

A "Sticky" Mucin-Inspired DNA-Polysaccharide Binder for Silicon and Silicon-Graphite Blended Anodes in Lithium-Ion Batteries.

PubMed

Kim, Sunjin; Jeong, You Kyeong; Wang, Younseon; Lee, Haeshin; Choi, Jang Wook

2018-05-14

New binder concepts have lately demonstrated improvements in the cycle life of high-capacity silicon anodes. Those binder designs adopt adhesive functional groups to enhance affinity with silicon particles and 3D network conformation to secure electrode integrity. However, homogeneous distribution of silicon particles in the presence of a substantial volumetric content of carbonaceous components (i.e., conductive agent, graphite, etc.) is still difficult to achieve while the binder maintains its desired 3D network. Inspired by mucin, the amphiphilic macromolecular lubricant, secreted on the hydrophobic surface of gastrointestine to interface aqueous serous fluid, here, a renatured DNA-alginate amphiphilic binder for silicon and silicon-graphite blended electrodes is reported. Mimicking mucin's structure comprised of a hydrophobic protein backbone and hydrophilic oligosaccharide branches, the renatured DNA-alginate binder offers amphiphilicity from both components, along with a 3D fractal network structure. The DNA-alginate binder facilitates homogeneous distribution of electrode components in the electrode as well as its enhanced adhesion onto a current collector, leading to improved cyclability in both silicon and silicon-graphite blended electrodes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Defining the origins of electron transfer at screen-printed graphene-like and graphite electrodes: MoO2 nanowire fabrication on edge plane sites reveals electrochemical insights.

PubMed

Rowley-Neale, Samuel J; Brownson, Dale A C; Banks, Craig E

2016-08-18

Molybdenum (di)oxide (MoO2) nanowires are fabricated onto graphene-like and graphite screen-printed electrodes (SPEs) for the first time, revealing crucial insights into the electrochemical properties of carbon/graphitic based materials. Distinctive patterns observed in the electrochemical process of nanowire decoration show that electron transfer occurs predominantly on edge plane sites when utilising SPEs fabricated/comprised of graphitic materials. Nanowire fabrication along the edge plane sites (and on edge plane like-sites/defects) of graphene/graphite is confirmed with Cyclic Voltammetry, Scanning Electron Microscopy (SEM) and Raman Spectroscopy. Comparison of the heterogeneous electron transfer (HET) rate constants (k°) at unmodified and nanowire coated SPEs show a reduction in the electrochemical reactivity of SPEs when the edge plane sites are effectively blocked/coated with MoO2. Throughout the process, the basal plane sites of the graphene/graphite electrodes remain relatively uncovered; except when the available edge plane sites have been utilised, in which case MoO2 deposition grows from the edge sites covering the entire surface of the electrode. This work clearly illustrates the distinct electron transfer properties of edge and basal plane sites on graphitic materials, indicating favourable electrochemical reactivity at the edge planes in contrast to limited reactivity at the basal plane sites. In addition to providing fundamental insights into the electron transfer properties of graphite and graphene-like SPEs, the reported simple, scalable, and cost effective formation of unique and intriguing MoO2 nanowires realised herein is of significant interest for use in both academic and commercial applications.

Graphite anode surface modification with controlled reduction of specific aryl diazonium salts for improved microbial fuel cells power output.

PubMed

Picot, Matthieu; Lapinsonnière, Laure; Rothballer, Michael; Barrière, Frédéric

2011-10-15

Graphite electrodes were modified with reduction of aryl diazonium salts and implemented as anodes in microbial fuel cells. First, reduction of 4-aminophenyl diazonium is considered using increased coulombic charge density from 16.5 to 200 mC/cm(2). This procedure introduced aryl amine functionalities at the surface which are neutral at neutral pH. These electrodes were implemented as anodes in "H" type microbial fuel cells inoculated with waste water, acetate as the substrate and using ferricyanide reduction at the cathode and a 1000 Ω external resistance. When the microbial anode had developed, the performances of the microbial fuel cells were measured under acetate saturation conditions and compared with those of control microbial fuel cells having an unmodified graphite anode. We found that the maximum power density of microbial fuel cell first increased as a function of the extent of modification, reaching an optimum after which it decreased for higher degree of surface modification, becoming even less performing than the control microbial fuel cell. Then, the effect of the introduction of charged groups at the surface was investigated at a low degree of surface modification. It was found that negatively charged groups at the surface (carboxylate) decreased microbial fuel cell power output while the introduction of positively charged groups doubled the power output. Scanning electron microscopy revealed that the microbial anode modified with positively charged groups was covered by a dense and homogeneous biofilm. Fluorescence in situ hybridization analyses showed that this biofilm consisted to a large extent of bacteria from the known electroactive Geobacter genus. In summary, the extent of modification of the anode was found to be critical for the microbial fuel cell performance. The nature of the chemical group introduced at the electrode surface was also found to significantly affect the performance of the microbial fuel cells. The method used for modification is easy to control and can be optimized and implemented for many carbon materials currently used in microbial fuel cells and other bioelectrochemical systems. Copyright © 2011 Elsevier B.V. All rights reserved.

Pyrolytic graphite collector development program

NASA Technical Reports Server (NTRS)

Wilkins, W. J.

1982-01-01

Pyrolytic graphite promises to have significant advantages as a material for multistage depressed collector electrodes. Among these advantages are lighter weight, improved mechanical stiffness under shock and vibration, reduced secondary electron back-streaming for higher efficiency, and reduced outgassing at higher operating temperatures. The essential properties of pyrolytic graphite and the necessary design criteria are discussed. This includes the study of suitable electrode geometries and methods of attachment to other metal and ceramic collector components consistent with typical electrical, thermal, and mechanical requirements.

Mechanical Degradation of Graphite/PVDF Composite Electrodes: A Model-Experimental Study

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

Takahashi, Kenji; Higa, Kenneth; Mair, Sunil

2015-12-11

Mechanical failure modes of a graphite/polyvinylidene difluoride (PVDF) composite electrode for lithium-ion batteries were investigated by combining realistic stress-stain tests and mathematical model predictions. Samples of PVDF mixed with conductive additive were prepared in a similar way to graphite electrodes and tested while submerged in electrolyte solution. Young's modulus and tensile strength values of wet samples were found to be approximately one-fifth and one-half of those measured for dry samples. Simulations of graphite particles surrounded by binder layers given the measured material property values suggest that the particles are unlikely to experience mechanical damage during cycling, but that the fatemore » of the surrounding composite of PVDF and conductive additive depends completely upon the conditions under which its mechanical properties were obtained. Simulations using realistic property values produced results that were consistent with earlier experimental observations.« less

Auger Electrons as Probes for Composite Micro- and Nano- structured Materials: Application to Solid Electrolyte Interphases in Graphite and Silicon-Graphite Electrodes

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

Kalaga, Kaushik; Shkrob, Ilya A.; Haasch, Richard T.

In this study, Auger electron spectroscopy (AES) combined with ion sputtering profilometry, Xray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) have been used in a complementary fashion to examine chemical and microstructural changes in graphite (Gr) and silicon/graphite (Si/Gr) blends contained in the negative electrodes of lithium-ion cells. We demonstrate how AES can be used to characterize morphology of the solid-electrolyte interphase (SEI) deposits in such heterogeneous media, complementing well-established methods, such as XPS and SEM. In this way we demonstrate that the SEI does not consist of uniformly thick layers on the graphite and silicon; the thickness ofmore » the SEI layers in cycle-life aged electrodes follows an exponential distribution with a mean of ca. 13 nm for the graphite and ca. 20-25 nm for the silicon nanoparticles (with a crystalline core of 50-70 nm in diameter). Furthermore, a “sticky-sphere” model, in which Si nanoparticles are covered with a layer of polymer binder (that is replaced by the SEI during cycling) of variable thickness is introduced to account for the features observed.« less

Auger Electrons as Probes for Composite Micro- and Nano- structured Materials: Application to Solid Electrolyte Interphases in Graphite and Silicon-Graphite Electrodes

DOE PAGES

Kalaga, Kaushik; Shkrob, Ilya A.; Haasch, Richard T.; ...

2017-10-05

In this study, Auger electron spectroscopy (AES) combined with ion sputtering profilometry, Xray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) have been used in a complementary fashion to examine chemical and microstructural changes in graphite (Gr) and silicon/graphite (Si/Gr) blends contained in the negative electrodes of lithium-ion cells. We demonstrate how AES can be used to characterize morphology of the solid-electrolyte interphase (SEI) deposits in such heterogeneous media, complementing well-established methods, such as XPS and SEM. In this way we demonstrate that the SEI does not consist of uniformly thick layers on the graphite and silicon; the thickness ofmore » the SEI layers in cycle-life aged electrodes follows an exponential distribution with a mean of ca. 13 nm for the graphite and ca. 20-25 nm for the silicon nanoparticles (with a crystalline core of 50-70 nm in diameter). Furthermore, a “sticky-sphere” model, in which Si nanoparticles are covered with a layer of polymer binder (that is replaced by the SEI during cycling) of variable thickness is introduced to account for the features observed.« less

75 FR 76026 - United States v. Graftech International Ltd., Et al.; Proposed Final Judgment and Competitive...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-07

... and other inputs to form cylinders that are shot through with electricity and baked to produce... electricity into the furnace, heating the furnace and melting scrap steel. 11. Graphite electrodes oxidize and... consumption of graphite electrodes. 12. Petroleum needle coke, relative to other varieties of coke, is...

Development of Nitrogen Sensor for Determination of PN(2) in Body Tissues.

DTIC Science & Technology

1982-07-01

3) The progress of the reduction reaction (1) was followed by voltammetry. A single anodic potential sweep , starting from the open circuit...Graphite Electrode The progressive attachment of [Ru(NH3 ) 5 H2 0] +2 to PVP-coated graphite electrodes was observed by cyclic voltametry as an

Electrocatalytic Dechlorination Of A PCB Congener At A Palladized Granular Graphite-Packed Electrode: Reaction Equilibrium And Mechanism

EPA Science Inventory

Our previous study on the electrocatalytic dechlorination of 2-chlorobiphenyl at a Pd-loaded granular graphite-packed electrode demonstrated that the process did not follow the first order kinetics. The rate constant varied with the applied potential at the beginning, but later b...

Dose measurement in heterogeneous phantoms with an extrapolation chamber

NASA Astrophysics Data System (ADS)

Deblois, Francois

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water(TM) and bone-equivalent material was used for determining absolute dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x-rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The air gaps used were between 2 and 3 mm and the sensitive air volume of the extrapolation chamber was remotely controlled through the motion of the motorized piston with a precision of +/-0.0025 mm. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain dose data for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC from 0.7 to ˜2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water(TM) PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). The collecting electrode material in comparison with the polarizing electrode material has a larger effect on the electrode correction factor; the thickness of thin electrodes, on the other hand, has a negligible effect on dose determination. The uncalibrated hybrid PEEC is an accurate and absolute device for measuring the dose directly in bone material in conjunction with appropriate correction factors determined with Monte Carlo techniques.

On-line/on-site analysis of heavy metals in water and soils by laser induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Meng, Deshuo; Zhao, Nanjing; Wang, Yuanyuan; Ma, Mingjun; Fang, Li; Gu, Yanhong; Jia, Yao; Liu, Jianguo

2017-11-01

The enrichment method of heavy metal in water with graphite and aluminum electrode was studied, and combined with plasma restraint device for improving the sensitivity of detection and reducing the limit of detection (LOD) of elements. For aluminum electrode enrichment, the LODs of Cd, Pb and Ni can be as low as several ppb. For graphite enrichment, the measurement time can be less than 3 min. The results showed that the graphite enrichment and aluminum electrode enrichment method can effectively improve the LIBS detection ability. The graphite enrichment method combined with plasma spatial confinement is more suitable for on-line monitoring of industrial waste water, the aluminum electrode enrichment method can be used for trace heavy metal detection in water. A LIBS method and device for soil heavy metals analysis was also developed, and a mobile LIBS system was tested in outfield. The measurement results deduced from LIBS and ICP-MS had a good consistency. The results provided an important application support for rapid and on-site monitoring of heavy metals in soil. (Left: the mobile LIBS system for analysis of heavy metals in soils. Top right: the spatial confinement device. Bottom right: automatic graphite enrichment device for on0line analysis of heavy metals in water).

Bulk-modified modified screen-printing carbon electrodes with both lactate oxidase (LOD) and horseradish peroxide (HRP) for the determination of L-lactate in flow injection analysis mode.

PubMed

Ghamouss, Fouad; Ledru, Sophie; Ruillé, Nadine; Lantier, Françoise; Boujtita, Mohammed

2006-06-16

A screen-printed carbon electrode modified with both HRP and LOD (SPCE-HRP/LOD) has been developed for the determination of L-lactate concentration in real samples. The resulting SPCE-HRP/LOD was prepared in a one-step procedure, and was then optimised as an amperometric biosensor operating at [0, -100]mV versus Ag/AgCl for L-lactate determination in flow injection mode. A significant improvement in the reproducibility (coefficient variation of about 10%) of the preparation of the biosensors was obtained when graphite powder was modified with LOD in the presence of HRP previously oxidised by periodate ion (IO4-). Optimisation studies were performed by examining the effects of LOD loading, periodation step and rate of the binder on analytical performances of SPCE-HRP/LOD. The sensitivity of the optimised SPCE-HRP/LOD to L-lactate was 0.84 nAL micromol(-1) in a detection range between 10 and 180 microMol. The possibility of using the developed biosensor to determine L-lactate concentrations in various dairy products was also evaluated.

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

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

Lin, Na; Jia, Zhe; Wang, Zhihui

Here in this paper, the structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystallinemore » graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.« less

Understanding the crack formation of graphite particles in cycled commercial lithium-ion batteries by focused ion beam - scanning electron microscopy

DOE PAGES

Lin, Na; Jia, Zhe; Wang, Zhihui; ...

2017-10-01

Here in this paper, the structure degradation of commercial Lithium-ion battery (LIB) graphite anodes with different cycling numbers and charge rates was investigated by focused ion beam (FIB) and scanning electron microscopy (SEM). The cross-section image of graphite anode by FIB milling shows that cracks, resulted in the volume expansion of graphite electrode during long-term cycling, were formed in parallel with the current collector. The crack occurs in the bulk of graphite particles near the lithium insertion surface, which might derive from the stress induced during lithiation and de-lithiation cycles. Subsequently, crack takes place along grain boundaries of the polycrystallinemore » graphite, but only in the direction parallel with the current collector. Furthermore, fast charge graphite electrodes are more prone to form cracks since the tensile strength of graphite is more likely to be surpassed at higher charge rates. Therefore, for LIBs long-term or high charge rate applications, the tensile strength of graphite anode should be taken into account.« less

Measurement of absorbed dose with a bone-equivalent extrapolation chamber.

PubMed

DeBlois, François; Abdel-Rahman, Wamied; Seuntjens, Jan P; Podgorsak, Ervin B

2002-03-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to approximately 2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams.

Electrochemical cell and negative electrode therefor

DOEpatents

Kaun, Thomas D.

1982-01-01

A secondary electrochemical cell with the positive and negative electrodes separated by a molten salt electrolyte with the negative electrode comprising a particulate mixture of lithium-aluminum alloy and electrolyte and an additive selected from graphitized carbon, Raney iron or mixtures thereof. The lithium-aluminum alloy is present in the range of from about 45 to about 80 percent by volume of the negative electrode, and the electrolyte is present in an amount not less than about 10 percent by volume of the negative electrode. The additive of graphitized carbon is present in the range of from about 1 to about 10 percent by volume of the negative electrode, and the Raney iron additive is present in the range of from about 3 to about 10 percent by volume of the negative electrode.

Surface amplification of pencil graphite electrode with polypyrrole and reduced graphene oxide for fabrication of a guanine/adenine DNA based electrochemical biosensors for determination of didanosine anticancer drug

NASA Astrophysics Data System (ADS)

Karimi-Maleh, Hassan; Bananezhad, Asma; Ganjali, Mohammad R.; Norouzi, Parviz; Sadrnia, Abdolhossein

2018-05-01

Didanosine is nucleoside analog reverse transcriptase inhibitors with many side effects such as nausea and vomiting, stomach pain, tingling, burning and numbness and determination of this drug is very important in biological samples. This paper presents a DNA biosensor for determination of didanosine (DDI) in pharmaceutical samples. A pencil graphite electrode modified with conductive materials such as polypyrrole (PPy) and reduced graphene oxide (rGO) (PGE/PPy/rGO) was used for this goal. The double-stranded DNA was successfully immobilized on PGE/PPy/rGO. The PGE/PPy/rGO was characterized by microscopic and electrochemical methods. Then, the interaction of DDI with DNA was identified by decreases in the oxidation currents of guanine and adenine by differential pulse voltammetric (DPV) method. The dynamic range of DDI identified in the range of 0.02-50.0 μM and this electrode provided a low limit of detection (LOD = 8.0 nM) for DDI. The PGE/PPy/rGO loaded with ds-DNA was utilized for the measurement of DDI in real samples and obtained data were compared with HPLC method. The statistical tests such as F-test and t-test were used for confirming ability of PGE/PPy/rGO loaded with ds-DNA for analysis of DDI in real samples.

A Mini-Electrochemical System with Integrated Micropipet Tip and Pencil Graphite Electrode for Measuring Cytotoxicity.

PubMed

Wu, Dong-Mei; Guo, Xiao-Ling; Wang, Qian; Li, Jin-Lian; Cui, Ji-Wen; Zhou, Shi; Hao, Su-E

2017-01-01

A novel mini-electrochemical system has been developed for evaluating cytotoxicity of anticancer drugs based on trace cell samples. The mini-electrochemical system was integrated by using pencil graphite modified with threonine as working electrode, an Ag/AgCl reference electrode and a micropipet tip as electrochemical cell. The mini-electrochemical system dramatically reduces sample volumes from 500 μL in a traditional electrochemical system to 10 μL, and exhibits excellent electrocatalytic activity toward oxidation of purine from MCF-7 cells due to increased sensitivity provided by threonine. Moreover, the relationship between peak current and the cell concentration in the range from 3.0 × l0 3 to 7.0 × l0 6 cells/mL was studied, and a nonlinear exponential relationship between them was established over a wide concentration range. In evaluating the effect of anticancer drugs on cell viability, the results of drug cytotoxicity test based on cyclophosphamide were in close agreement with classical 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assays. The proposed device is so simple, cheap, and easy to operate that it could be applied to single-use applications. The mini-electrochemical system proved to be a useful tool and can be applied to electrochemical studies of cancer cells as well as other biological samples such as proteins and DNA.

Electrodes for sealed secondary batteries

NASA Technical Reports Server (NTRS)

Boies, D. B.; Child, F. T.

1972-01-01

Self-supporting membrane electrode structures, in which active ingredients and graphite are incorporated in a polymeric matrix, improve performance of electrodes in miniature, sealed, alkaline storage batteries.

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

Small, Leo J.; Brumbach, Michael T.; Clem, Paul G.

A new multi-step, solution-phase method for the spontaneous deposition of tungsten from a room temperature ethereal solution is reported. This immersion process relies on the deposition of a sacrificial zinc coating which is galvanically displaced by the ether-mediated reduction of oxophilic WCl 6. Subsequent thermal treatment renders a crystalline, metallic tungsten film. The chemical evolution of the surface and formation of a complex intermediate tungsten species is characterized by X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Efficient metallic tungsten deposition is first characterized on a graphite substrate and then demonstrated on a functional carbon foam electrode. The resulting electrochemicalmore » performance of the modified electrode is interrogated with the canonical aqueous ferricyanide system. A tungsten-coated carbon foam electrode showed that both electrode resistance and overall electrochemical cell resistance were reduced by 50%, resulting in a concomitant decrease in redox peak separation from 1.902 V to 0.783 V. Furthermore, this process promises voltage efficiency gains in electrodes for energy storage technologies and demonstrates the viability of a new route to tungsten coating for technologies and industries where high conductivity and chemical stability are paramount.« less

Electrochemical Behavior of Sulfur in Aqueous Alkaline Solutions

NASA Astrophysics Data System (ADS)

Mamyrbekova, Aigul; Mamitova, A. D.; Mamyrbekova, Aizhan

2018-03-01

The kinetics and mechanism of the electrode oxidation-reduction of sulfur on an electrically conductive sulfur-graphite electrode in an alkaline solution was studied by the potentiodynamic method. To examine the mechanism of electrode processes occurring during AC polarization on a sulfur-graphite electrode, the cyclic polarization in both directions and anodic polarization curves were recorded. The kinetic parameters: charge transfer coefficients (α), diffusion coefficients ( D), heterogeneous rate constants of electrode process ( k s), and effective activation energies of the process ( E a) were calculated from the results of polarization measurements. An analysis of the results and calculated kinetic parameters of electrode processes showed that discharge ionization of sulfur in alkaline solutions occurs as a sequence of two stages and is a quasireversible process.

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

Doped graphene supercapacitors.

PubMed

Kumar, Nanjundan Ashok; Baek, Jong-Beom

2015-12-11

Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

Doped graphene supercapacitors

NASA Astrophysics Data System (ADS)

Ashok Kumar, Nanjundan; Baek, Jong-Beom

2015-12-01

Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

From Rome to Como: 20 years of active research on carbon-based electrodes for lithium batteries at INP-Grenoble

NASA Astrophysics Data System (ADS)

Yazami, Rachid

This paper reviews the main areas of research performed at different Laboratories of the Institut National Polytechnique de Grenoble (INPG) over the past 20 years, specifically on cabonaceous materials for electrode applications in lithium batteries. The most significant event was the discovery in the early 1980s of reversible lithium intercalation into graphite in polymer electrolytes, which led to the use of this material in today's lithium-ion batteries. Important work was also carried out on positive electrode for primary and secondary batteries, especially graphite oxide and graphite fluoride. Most of these results were presented at the 10 IMLB series Symposia, which started in Rome in 1982 and were back to Como, Italy, in 2000.

3D-printed conductive static mixers enable all-vanadium redox flow battery using slurry electrodes

NASA Astrophysics Data System (ADS)

Percin, Korcan; Rommerskirchen, Alexandra; Sengpiel, Robert; Gendel, Youri; Wessling, Matthias

2018-03-01

State-of-the-art all-vanadium redox flow batteries employ porous carbonaceous materials as electrodes. The battery cells possess non-scalable fixed electrodes inserted into a cell stack. In contrast, a conductive particle network dispersed in the electrolyte, known as slurry electrode, may be beneficial for a scalable redox flow battery. In this work, slurry electrodes are successfully introduced to an all-vanadium redox flow battery. Activated carbon and graphite powder particles are dispersed up to 20 wt% in the vanadium electrolyte and charge-discharge behavior is inspected via polarization studies. Graphite powder slurry is superior over activated carbon with a polarization behavior closer to the standard graphite felt electrodes. 3D-printed conductive static mixers introduced to the slurry channel improve the charge transfer via intensified slurry mixing and increased surface area. Consequently, a significant increase in the coulombic efficiency up to 95% and energy efficiency up to 65% is obtained. Our results show that slurry electrodes supported by conductive static mixers can be competitive to state-of-the-art electrodes yielding an additional degree of freedom in battery design. Research into carbon properties (particle size, internal surface area, pore size distribution) tailored to the electrolyte system and optimization of the mixer geometry may yield even better battery properties.

Structure and Performance of Epoxy Resin Cladded Graphite Used as Anode

NASA Astrophysics Data System (ADS)

Zhou, Zhentao; Li, Haijun

This paper is concerning to prepare modified natural graphite which is low-cost and advanced materials used as lithium ion battery anode using the way of cladding natural graphite with epoxy resin. The results shows that the specific capacity and circular performance of the modified natural graphite, which is prepared in the range of 600°C and 1000°C, have been apparently improved compare with the not-modified natural graphite. The first reversible capacity of the modified natural graphite is 338mAh/g and maintain more than 330mAh/g after 20 charge/discharge circles.

A comparative study of graphite electrodes using the co-intercalation phenomenon for rechargeable Li, Na and K batteries.

PubMed

Kim, Haegyeom; Yoon, Gabin; Lim, Kyungmi; Kang, Kisuk

2016-10-18

Here, we demonstrate that graphite can serve as a versatile electrode for various rechargeable battery types by reversibly accommodating solvated alkali ions (such as K, Na, and Li) through co-intercalation in its galleries. The co-intercalation of alkali ions is observed to occur via staging reactions. Notably, their insertion behaviors, including their specific capacity, are remarkably similar regardless of the alkali ion species despite the different solubility limits of K, Na, and Li ions in graphite. Nevertheless, the insertion potentials of the solvated alkali ions differ from each other and are observed to be correlated with the interlayer distance in the intercalated graphite gallery.

Environmentally-friendly oxygen-free roasting/wet magnetic separation technology for in situ recycling cobalt, lithium carbonate and graphite from spent LiCoO2/graphite lithium batteries.

PubMed

Li, Jia; Wang, Guangxu; Xu, Zhenming

2016-01-25

The definite aim of the present paper is to present some novel methods that use oxygen-free roasting and wet magnetic separation to in situ recycle of cobalt, Lithium Carbonate and Graphite from mixed electrode materials. The in situ recycling means to change waste into resources by its own components, which is an idea of "waste+waste→resources." After mechanical scraping the mixed electrode materials enrich powders of LiCoO2 and graphite. The possible reaction between LiCoO2 and graphite was obtained by thermodynamic analysis. The feasibility of the reaction at high temperature was studied with the simultaneous thermogravimetry analysis under standard atmospheric pressure. Then the oxygen-free roasting/wet magnetic separation method was used to transfer the low added value mixed electrode materials to high added value products. The results indicated that, through the serious technologies of oxygen-free roasting and wet magnetic separation, mixture materials consist with LiCoO2 and graphite powders are transferred to the individual products of cobalt, Lithium Carbonate and Graphite. Because there is not any chemical solution added in the process, the cost of treating secondary pollution can be saved. This study provides a theoretical basis for industrial-scale recycling resources from spent LIBs. Copyright © 2015 Elsevier B.V. All rights reserved.

Simultaneous voltammetric determination of prednisone and prednisolone in human body fluids.

PubMed

Goyal, Rajendra N; Bishnoi, Sunita

2009-08-15

A sensitive, rapid and reliable electrochemical method based on voltammetry at single wall carbon nanotube (SWNT) modified edge plane pyrolytic graphite electrode (EPPGE) is proposed for the simultaneous determination of prednisolone and prednisone in human body fluids and pharmaceutical preparations. The electrochemical response of both the drugs was evaluated by osteryoung square wave voltammetry (OSWV) in phosphate buffer medium of pH 7.2. The modified electrode exhibited good electrocatalytic properties towards prednisone and prednisolone reduction with a peak potential of approximately -1230 and approximately -1332 mV respectively. The concentration versus peak current plots were linear for both the analytes in the range 0.01-100 microM and the detection limit (3 sigma/slope) observed for prednisone and prednisolone were 0.45 x 10(-8), 0.90 x 10(-8)M, respectively. The results of the quantitative estimation of prednisone and prednisolone in biological fluids were also compared with HPLC and the results were in good agreement.

Graphene nanosheets and polyacrylic acid grafted silicon composite anode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Assresahegn, Birhanu Desalegn; Ossonon, Benjamin Diby; Bélanger, Daniel

2018-07-01

A silicon/graphene composite anode for lithium-ion batteries was fabricated with a high loading of Si by combining surface-modified silicon with graphene. The Si nanopowder was modified by a binder-like organic moeity (1-(bromoethyl) benzene and polyacrylic acid) grafted on the surface of hydrogenated silicon by diazonium chemistry and surface initiated atom transfer radical polymerization. The graphene was produced by electrochemical exfoliation of natural graphite. The optimum composite electrode prepared without a binder, with silicon loading as high as 85 wt% and a mass loading of 1.1 ± 0.1 mg cm-2 yielded a discharge capacity of 1020 mAh per gram of electrode mass (or 1200 mAh per gram of Si) after 586 charge/discharge cycles at a rate of 3.4 A g-1. It showed first cycle Coulombic efficiency of more than 90% in the absence of electrolyte additives at a current rate of 0.05 A g-1.

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.

An improved amperometric L-lactate biosensor based on covalent immobilization of microbial lactate oxidase onto carboxylated multiwalled carbon nanotubes/copper nanoparticles/polyaniline modified pencil graphite electrode.

PubMed

Dagar, Kusum; Pundir, C S

2017-01-01

An improved amperometric l-lactate biosensor was constructed based on covalent immobilization of lactate oxidase (LOx) from Pediococcus species onto carboxylated multiwalled carbon nanotubes (cMWCNT)/copper nanoparticles (CuNPs)/polyaniline (PANI) hybrid film electrodeposited on the surface of a pencil graphite electrode (PGE). The enzyme electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS), while CuNPs synthesized by chemical reduction method, were characterized by transmission electron microscopy (TEM), UV spectrascopy and X-ray diffraction (XRD). The biosensor showed maximum response within 5s at pH 8.0 in 0.05M sodium phosphate buffer and 37°C, when operated at 20mVs -1 . The biosensor had a detection limit of 0.25μM with a wide working range between 1μM-2500μM. The biosensor was employed for measurement of l-lactic acid level in plasma of apparently healthy and diseased persons. Analytical recovery of added lactic acid in plasma was 95.5%. Within- and between-batch coefficients of variations were 6.24% and 4.19% respectively. There was a good correlation (R 2 =0.97) between plasma lactate values as measured by standard enzymatic spectrophotometric method and the present biosensor. The working enzyme electrode was used 180 times over a period of 140 days, when stored at 4°C. Copyright © 2016. Published by Elsevier Inc.

Electrode material comprising graphene-composite materials in a graphite network

DOEpatents

Kung, Harold H.; Lee, Jung K.

2014-07-15

A durable electrode material suitable for use in Li ion batteries is provided. The material is comprised of a continuous network of graphite regions integrated with, and in good electrical contact with a composite comprising graphene sheets and an electrically active material, such as silicon, wherein the electrically active material is dispersed between, and supported by, the graphene sheets.

Electrode material comprising graphene-composite materials in a graphite network

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

Kung, Harold H.; Lee, Jung K.

A durable electrode material suitable for use in Li ion batteries is provided. The material is comprised of a continuous network of graphite regions integrated with, and in good electrical contact with a composite comprising graphene sheets and an electrically active material, such as silicon, wherein the electrically active material is dispersed between, and supported by, the graphene sheets.

The effect of temperature deposited on the performance of ZnO-CNT-graphite for supercapacitors

NASA Astrophysics Data System (ADS)

Darari, Alfin; Hakim, Istajib S.; Priyono; Subagio, Agus; Pardoyo; Subhan, Achmad

2017-07-01

Carbon nanotubes (CNTs), graphite are now widely studied as the electrodes of supercapacitor, owing to their high conductivity, large surface area, chemical stability, etc. A lot of research has been focused on Carbon/metal oxide nanocomposite electrode for Electrode supercapacitor because it will increase the total capacitance. In this research, ZnO nanoparticles were deposited onto substrate CNT:Graphite in different temperatures such as 300°, 350°, and 400°C. The characterization of the crystal size using X-Ray Diffraction (XRD) patterns showed ZnO material peak was detected a ZnO crystallite. The size of ZnO crystallite in 300°, 350°, and 400°C consecutively is 101.1; 103.4; and 116.7 nm. The test results are Electrochemical impedance spectrometry (EIS) high electrical conductivity values obtained on the composition of ZnO-CNT-graphite with a temperature of 350°C 4.6 (S/m); and (2) the highest value of capacitance in 300°C is 1.23 F/g.

Microwave-assisted preparation of carbon nanofiber-functionalized graphite felts as electrodes for polymer-based redox-flow batteries

NASA Astrophysics Data System (ADS)

Schwenke, A. M.; Janoschka, T.; Stolze, C.; Martin, N.; Hoeppener, S.; Schubert, U. S.

2016-12-01

A simple and fast microwave-assisted protocol to functionalize commercially available graphite felts (GFs) with carbon nanofibers (CNFs) for the application as electrode materials in redox-flow batteries (RFB) is demonstrated. As catalyst for the CNF synthesis nickel acetate is applied and ethanol serves as the carbon source. By the in-situ growth of CNFs, the active surface of the electrodes is increased by a factor of 50, which is determined by the electrochemical double layer capacities of the obtained materials. Furthermore, the morphology of the CNF-coating is investigated by scanning electron microscopy. Subsequently, the functionalized electrodes are applied in a polymer-based redox-flow battery (pRFB) using a TEMPO- and a viologen polymer as active materials. Due to the increased surface area as compared to an untreated graphite felt electrode, the current rating is improved by about 45% at 80 mA cm-2 and, furthermore, a decrease in overpotentials is observed. Thus, using this microwave-assisted synthesis approach, CNF-functionalized composite electrodes are prepared with a very simple protocol suitable for real life applications and an improvement of the overall performance of the polymer-based redox-flow battery is demonstrated.

USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

EPA Science Inventory

Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

Adsorption behavior of bisphenol A on CTAB-modified graphite

NASA Astrophysics Data System (ADS)

Wang, Li-Cong; Ni, Xin-jiong; Cao, Yu-Hua; Cao, Guang-qun

2018-01-01

In this work, the adsorption behavior of BPA on CTAB-modified graphite was investigated thoroughly to develop a novel absorbent material. Atomic force microscopy revealed that conical admicelles formed on the surface of graphite. The surface area of graphite decreased significantly from 1.46 to 0.95 m2 g-1, which confirmed the formation of the larger size admicelle instead of the original smaller particle on the surface. CTAB concentration and incubation time affected the progress of admicelle formation on the surface of graphite. Adsolubilization is key in BPA adsorption by CTAB-modified graphite. An extraordinary cation-π electron interaction between CTAB and BPA, revealed by a red-shift in the ultraviolet spectrum, as well as a hydrophobic interaction contribute substantially to BPA adsolubilization. The equilibrium adsorption capacity of the modified graphite for BPA was 125.01 mg g-1. The adsorption kinetic curves of BPA on modified graphite were shown to follow a pseudosecond-order rate. The adsorption process was observed to be both spontaneous and exothermic complied with the Freundlich model.

Flower-like Copper Cobaltite Nanosheets on Graphite Paper as High-Performance Supercapacitor Electrodes and Enzymeless Glucose Sensors.

PubMed

Liu, Shude; Hui, K S; Hui, K N

2016-02-10

Flower-like copper cobaltite (CuCo2O4) nanosheets anchored on graphite paper have been synthesized using a facile hydrothermal method followed by a postannealing treatment. Supercapacitor electrodes employing CuCo2O4 nanosheets exhibit an enhanced capacitance of 1131 F g(-1) at a current density of 1 A g(-1) compared with previously reported supercapacitor electrodes. The CuCo2O4 electrode delivers a specific capacitance of up to 409 F g(-1) at a current density of as high as 50 A g(-1), and a good long-term cycling stability, with 79.7% of its specific capacitance retained after 5000 cycles at 10 A g(-1). Furthermore, the as-prepared CuCo2O4 nanosheets on graphite paper can be fabricated as electrodes and used as enzymeless glucose sensors, which exhibit good sensitivity (3.625 μA μM(-1) cm(-2)) and an extraordinary linear response ranging up to 320 μM with a low detection limit (5 μM).

Layered oxide, graphite and silicon-graphite electrodes for Lithium-ion cells: Effect of electrolyte composition and cycling windows

DOE PAGES

Klett, Matilda; Gilbert, James A.; Pupek, Krzysztof Z.; ...

2016-10-14

The electrochemical performance of cells with a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2 (NCM523) positive electrode and a blended silicon-graphite (Si-Gr) negative electrode are investigated using various electrolyte compositions and voltage cycling windows. Voltage profiles of the blended Si-Gr electrode show a superposition of graphite potential plateaus on a sloped Si profile with a large potential hysteresis. The effect of this hysteresis is seen in the cell impedance versus voltage data, which are distinctly different for the charge and discharge cycles. We confirm that the addition of compounds, such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to themore » baseline 1.2 M LiPF 6 in ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7 w/w) electrolyte, improves cell capacity retention with higher retention seen at higher additive contents. We show that reducing the lower cutoff voltage (LCV) of full cells to 2.5 V increases the Si-Gr electrode potential to 1.12 V vs. Li/Li +; this relatively-high delithiation potential correlates with the lower capacity retention displayed by the cell. Hence, we show that raising the upper cutoff voltage (UCV) can increase cell energy density without significantly altering capacity retention over 100 charge discharge cycles.« less

Layered oxide, graphite and silicon-graphite electrodes for Lithium-ion cells: Effect of electrolyte composition and cycling windows

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

Klett, Matilda; Gilbert, James A.; Pupek, Krzysztof Z.

The electrochemical performance of cells with a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2 (NCM523) positive electrode and a blended silicon-graphite (Si-Gr) negative electrode are investigated using various electrolyte compositions and voltage cycling windows. Voltage profiles of the blended Si-Gr electrode show a superposition of graphite potential plateaus on a sloped Si profile with a large potential hysteresis. The effect of this hysteresis is seen in the cell impedance versus voltage data, which are distinctly different for the charge and discharge cycles. We confirm that the addition of compounds, such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to themore » baseline 1.2 M LiPF 6 in ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7 w/w) electrolyte, improves cell capacity retention with higher retention seen at higher additive contents. We show that reducing the lower cutoff voltage (LCV) of full cells to 2.5 V increases the Si-Gr electrode potential to 1.12 V vs. Li/Li +; this relatively-high delithiation potential correlates with the lower capacity retention displayed by the cell. Hence, we show that raising the upper cutoff voltage (UCV) can increase cell energy density without significantly altering capacity retention over 100 charge discharge cycles.« less

Facile Synthesis of Pre-Doping Lithium-Ion Into Nitrogen-Doped Graphite Negative Electrode for Lithium-Ion Capacitor.

PubMed

Lee, Seul-Yi; Kim, Ji-Il; Rhee, Kyong Yop; Park, Soo-Jin

2015-09-01

Nitrogen-doped graphite, prepared via the thermal decomposition of melamine into a carbon matrix for use as the negative electrode in lithium-ion capacitors (LICs), was evaluated by electrochemical measurements. Furthermore, in order to study the performance of pre-doped lithium components as a function of nitrogen-doped material, the pre-doped lithium graphite was allowed to react with a lithium salt solution. The results showed that the nitrogen functional groups in the graphite largely influenced the pre-doped lithium components, thereby contributing to the discharge capacity and cycling performance. We confirmed that the large initial irreversible capacity could be significantly decreased by using pre-doped lithium components obtained through the nitrogen-doping method.

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.

Research notes : evaluation of the performance of reference electrodes embedded in reinforced concrete.

DOT National Transportation Integrated Search

1995-07-01

The objectives of this work were to examine placement strategies for reference electrodes and to evaluate the suitability of graphite reference electrodes as imbedded reference electrodes in reinforced concrete structures that are cathodically protec...

The staging mechanism of AlCl4 intercalation in a graphite electrode for an aluminium-ion battery.

PubMed

Bhauriyal, Preeti; Mahata, Arup; Pathak, Biswarup

2017-03-15

Identifying a suitable electrode material with desirable electrochemical properties remains a primary challenge for rechargeable Al-ion batteries. Recently an ultrafast rechargeable Al-ion battery was reported with high charge/discharge rate, (relatively) high discharge voltage and high capacity that uses a graphite-based cathode. Using calculations from first-principles, we have investigated the staging mechanism of AlCl 4 intercalation into bulk graphite and evaluated the stability, specific capacity and voltage profile of AlCl 4 intercalated compounds. Ab initio molecular dynamics is performed to investigate the thermal stability of AlCl 4 intercalated graphite structures. Our voltage profiles show that the first AlCl 4 intercalation step could be a more sluggish step than the successive intercalation steps. However, the diffusion of AlCl 4 is very fast in the expanded graphite host layers with a diffusion barrier of ∼0.01 eV, which justifies the ultrafast charging rate of a graphite based Al-ion battery. And such an AlCl 4 intercalated battery provides an average voltage of 2.01-2.3 V with a maximum specific capacity of 69.62 mA h g -1 , which is excellent for anion intercalated batteries. Our density of states and Bader charge analysis shows that the AlCl 4 intercalation into the bulk graphite is a charging process. Hence, we believe that our present study will be helpful in understanding the staging mechanism of AlCl 4 intercalation into graphite-like layered electrodes for Al-ion batteries, thus encouraging further experimental work.

Electrode behavior RE-visited: Monitoring potential windows, capacity loss, and impedance changes in Li 1.03 (Ni 0.5Co 0.2Mn 0.3) 0.97O 2/silicon-graphite full cells

DOE PAGES

Klett, Matilda; Gilbert, James A.; Trask, Stephen E.; ...

2016-03-04

Here, the capacity and power performance of lithium-ion battery cells evolve over time. The mechanisms leading to these changes can often be identified through knowledge of electrode potentials, which contain information about electrochemical processes at the electrode-electrolyte interfaces. In this study we monitor electrode potentials within full cells containing a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2–based (NCM523) positive electrode, a silicon-graphite negative electrode, and an LiPF6-bearing electrolyte, with and without fluoroethylene carbonate (FEC) or vinylene carbonate (VC) additives. The electrode potentials are monitored with a Li-metal reference electrode (RE) positioned besides the electrode stack; changes in these potentials aremore » used to examine electrode state-of-charge (SOC) shifts, material utilization, and loss of electrochemically active material. Electrode impedances are obtained with a Li xSn RE located within the stack; the data display the effect of cell voltage and electrode SOC changes on the measured values after formation cycling and after aging. Our measurements confirm the beneficial effect of FEC and VC electrolyte additives in reducing full cell capacity loss and impedance rise after cycling in a 3.0–4.2 V range. Comparisons with data from a full cell containing a graphite-based negative highlight the consequences of including silicon in the electrode. Our observations on electrode potentials, capacity, and impedance changes on cycling are crucial to designing long-lasting, silicon-bearing, lithium-ion cells.« less

Direct laser writing of micro-supercapacitors on hydrated graphite oxide films.

PubMed

Gao, Wei; Singh, Neelam; Song, Li; Liu, Zheng; Reddy, Arava Leela Mohana; Ci, Lijie; Vajtai, Robert; Zhang, Qing; Wei, Bingqing; Ajayan, Pulickel M

2011-07-31

Microscale supercapacitors provide an important complement to batteries in a variety of applications, including portable electronics. Although they can be manufactured using a number of printing and lithography techniques, continued improvements in cost, scalability and form factor are required to realize their full potential. Here, we demonstrate the scalable fabrication of a new type of all-carbon, monolithic supercapacitor by laser reduction and patterning of graphite oxide films. We pattern both in-plane and conventional electrodes consisting of reduced graphite oxide with micrometre resolution, between which graphite oxide serves as a solid electrolyte. The substantial amounts of trapped water in the graphite oxide makes it simultaneously a good ionic conductor and an electrical insulator, allowing it to serve as both an electrolyte and an electrode separator with ion transport characteristics similar to that observed for Nafion membranes. The resulting micro-supercapacitor devices show good cyclic stability, and energy storage capacities comparable to existing thin-film supercapacitors.

Direct laser writing of micro-supercapacitors on hydrated graphite oxide films

NASA Astrophysics Data System (ADS)

Gao, Wei; Singh, Neelam; Song, Li; Liu, Zheng; Reddy, Arava Leela Mohana; Ci, Lijie; Vajtai, Robert; Zhang, Qing; Wei, Bingqing; Ajayan, Pulickel M.

2011-08-01

Microscale supercapacitors provide an important complement to batteries in a variety of applications, including portable electronics. Although they can be manufactured using a number of printing and lithography techniques, continued improvements in cost, scalability and form factor are required to realize their full potential. Here, we demonstrate the scalable fabrication of a new type of all-carbon, monolithic supercapacitor by laser reduction and patterning of graphite oxide films. We pattern both in-plane and conventional electrodes consisting of reduced graphite oxide with micrometre resolution, between which graphite oxide serves as a solid electrolyte. The substantial amounts of trapped water in the graphite oxide makes it simultaneously a good ionic conductor and an electrical insulator, allowing it to serve as both an electrolyte and an electrode separator with ion transport characteristics similar to that observed for Nafion membranes. The resulting micro-supercapacitor devices show good cyclic stability, and energy storage capacities comparable to existing thin-film supercapacitors.

Highly catalytic and stabilized titanium nitride nanowire array-decorated graphite felt electrodes for all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Wei, L.; Zhao, T. S.; Zeng, L.; Zeng, Y. K.; Jiang, H. R.

2017-02-01

In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm-2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.

Nickel-Tin Electrode Materials for Nonaqueous Li-Ion Cells

NASA Technical Reports Server (NTRS)

Ehrlich, Grant M.; Durand, Christopher

2005-01-01

Experimental materials made from mixtures of nickel and tin powders have shown promise for use as the negative electrodes of rechargeable lithium-ion electrochemical power cells. During charging (or discharging) of a lithium-ion cell, lithium ions are absorbed into (or desorbed from, respectively) the negative electrode, typically through an intercalation or alloying process. The negative electrodes (for this purpose, designated as anodes) in state-of-the-art Li-ion cells are made of graphite, in which intercalation occurs. Alternatively, the anodes can be made from metals, in which alloying can occur. For reasons having to do with the electrochemical potential of intercalated lithium, metallic anode materials (especially materials containing tin) are regarded as safer than graphite ones; in addition, such metallic anode materials have been investigated in the hope of obtaining reversible charge/discharge capacities greater than those of graphite anodes. However, until now, each of the tin-containing metallic anode formulations tested has been found to be inadequate in some respect.

A glassy carbon electrode modified with poly(2,4-dinitrophenylhydrazine) for simultaneous detection of dihydroxybenzene isomers.

PubMed

Lopa, Nasrin Siraj; Rahman, Md Mahbubur; Jang, Hohyoun; Sutradhar, Sabuj Chandra; Ahmed, Faiz; Ryu, Taewook; Kim, Whangi

2017-12-06

2,4-Dinitrophenylhydrazine (DNPH) was electropolymerized on the surface of an anodized glassy carbon electrode by cyclic voltammetry. The anodized electrode has a highly electroactive surface due to the creation of chemically functionalized graphitic nanoparticles, and this facilitates the formation of poly-DNPH via radical polymerization. Poly-DNPH displays excellent redox activity due to the presence of nitro groups on its backbone. These catalyze the electro-oxidation of hydroquinone (HQ) and catechol (CT). The peak-to-peak separation is around 109 mV, while a bare GCE cannot resolve the peaks (located at 165 and 274 mV vs. Ag/AgCl). Sensitivity is also enhanced to ∼1.20 and 1.19 μA·cm -2 ·μM -1 , respectively. The sensor has a linear response that covers the 20-250 μM concentration range for both HQ and CT, with 0.75 and 0.76 μM detection limits, respectively, at simultaneous detection. Commonly present species do not interfere. Graphical abstract A novel conducting poly(2,4-dinitrophenylhydrazine)-modified anodized glassy carbon electrode (pDNPH/AGCE) was developed by electrochemical method. The electro-catalytic activity of pDNPH/AGCE sensor was investigated for the selective and simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CT), which revealed high sensitivities and low detection limits with excellent stability.

Biopolymer-modified graphite oxide nanocomposite films based on benzalkonium chloride-heparin intercalated in graphite oxide

NASA Astrophysics Data System (ADS)

Meng, Na; Zhang, Shuang-Quan; Zhou, Ning-Lin; Shen, Jian

2010-05-01

Heparin is a potent anticoagulant agent that interacts strongly with antithrombin III to prevent the formation of fibrin clots. In the present work, poly(dimethylsiloxane)(PDMS)/graphite oxide-benzalkonium chloride-heparin (PDMS/modified graphite oxide) nanocomposite films were obtained by the solution intercalation technique as a possible drug delivery system. The heparin-benzalkonium chloride (BAC-HEP) was intercalated into graphite oxide (GO) layers to form GO-BAC-HEP (modified graphite oxide). Nanocomposite films were characterized by XRD, SEM, TEM, ATR-FTIR and TGA. The modified graphite oxide was observed to be homogeneously dispersed throughout the PDMS matrix. The effect of modified graphite oxide on the mechanical properties of the nanocomposite film was investigated. When the modified graphite oxide content was lower than 0.2 wt%, the nanocomposites showed excellent mechanical properties. Furthermore, nanocomposite films become delivery systems that release heparin slowly to make the nanocomposite films blood compatible. The in vitro studies included hemocompatibility testing for effects on platelet adhesion, platelet activation, plasma recalcification profiles, and hemolysis. Results from these studies showed that the anticoagulation properties of PDMS/GO-BCA-HEP nanocomposite films were greatly superior to those for no treated PDMS. Cell culture assay indicated that PDMS/GO-BCA-HEP nanocomposite films showed enhanced cell adhesion.

Gold nanoparticles coated polystyrene/reduced graphite oxide microspheres with improved dispersibility and electrical conductivity for dopamine detection.

PubMed

Qian, Tao; Yu, Chenfei; Wu, Shishan; Shen, Jian

2013-12-01

Gold nanoparticles coated polystyrene/reduced graphite oxide (AuNPs@PS/RGO) microspheres have been successfully prepared via a facile process, and the decorative gold nanoparticles could prevent the aggregation of RGO by electrostatic repulsive interaction, and lead to high dispersibility of the composite. The prepared composite has a highly increased conductivity of 129Sm(-1) due to the unique electrical properties of citrate reduced gold nanoparticles. Being employed as an electrochemical sensor for detection of dopamine, the modified electrode exhibits remarkable sensitivity (3.44μA/μM) and lower detection limit (5nM), with linear response in a range of 0.05-20μM. Moreover, valid response to dopamine obtained in present work also indicates the prospective performances of AuNPs@PS/RGO microspheres to other biological molecules, such as nucleic acids, proteins and enzymes. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrochemical modification of a pyrolytic graphite sheet for improved negative electrode performance in the vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Kabir, Humayun; Gyan, Isaiah O.; Francis Cheng, I.

2017-02-01

The vanadium redox flow battery is a promising technology for buffering renewable energies. It is recognized that negative electrode is the limitation in this device where there are problems of slow heterogeneous electron transfer (HET) of V3+/2+ and parasitic H2 evolution. Any methods aimed at addressing one of these barriers must assess the effects on the other. We examine electrochemical enhancement of a common commercially available material. Treatment of Panasonic pyrolytic graphite sheets is through oxidation at 2.1 V vs. Ag/AgCl for 1 min in 1 M H2SO4. This increases the standard HET rate for V3+/2+ from 3.2 × 10-7 to 1 × 10-3 cm/s, one of the highest in literature and shifts voltammetric reductive peak potential from -1.0 V to -0.65 V in 50 mM V3+ in 1 M H2SO4. Infrared analysis of the surfaces indicates formation of Csbnd OH, Cdbnd O, and Csbnd O functionalities. These groups catalyze HET with V3+/2+ as hypothesized by Skyllas-Kasacos. Also of significance is that electrode modification decreases the fraction of the current directed towards H2 evolution. This proportion decreases by two orders of a magnitude from 12% to 0.1% as measured at the respective voltammetric peak potentials of -1.0 V (pristine) and -0.65 V (modified).

Graphite Based Electrode for ECG Monitoring: Evaluation under Freshwater and Saltwater Conditions.

PubMed

Thap, Tharoeun; Yoon, Kwon-Ha; Lee, Jinseok

2016-04-15

We proposed new electrodes that are applicable for electrocardiogram (ECG) monitoring under freshwater- and saltwater-immersion conditions. Our proposed electrodes are made of graphite pencil lead (GPL), a general-purpose writing pencil. We have fabricated two types of electrode: a pencil lead solid type (PLS) electrode and a pencil lead powder type (PLP) electrode. In order to assess the qualities of the PLS and PLP electrodes, we compared their performance with that of a commercial Ag/AgCl electrode, under a total of seven different conditions: dry, freshwater immersion with/without movement, post-freshwater wet condition, saltwater immersion with/without movement, and post-saltwater wet condition. In both dry and post-freshwater wet conditions, all ECG-recorded PQRST waves were clearly discernible, with all types of electrodes, Ag/AgCl, PLS, and PLP. On the other hand, under the freshwater- and saltwater-immersion conditions with/without movement, as well as post-saltwater wet conditions, we found that the proposed PLS and PLP electrodes provided better ECG waveform quality, with significant statistical differences compared with the quality provided by Ag/AgCl electrodes.

Diagnosis of EGFR exon21 L858R point mutation as lung cancer biomarker by electrochemical DNA biosensor based on reduced graphene oxide /functionalized ordered mesoporous carbon/Ni-oxytetracycline metallopolymer nanoparticles modified pencil graphite electrode.

PubMed

Shoja, Yalda; Kermanpur, Ahmad; Karimzadeh, Fathallah

2018-08-15

In this present work we made a novel, fast, selective and sensitive electrochemical genobiosensor to detection of EGFR exon 21 point mutation based on two step electropolymerization of Ni(II)-oxytetracycline conducting metallopolymer nanoparticles (Ni-OTC NPs) on the surface of pencil graphite electrode (PGE) which was modified by reduced graphene oxide/carboxyl functionalized ordered mesoporous carbon (rGO/f-OMC) nanocomposite. ssDNA capture probe with amine groups at the5' end which applied as recognition element was immobilized on the rGO/f-OMC/PGE surface via the strong amide bond. Ni-OTC metallopolymer NPs were electropolymerized to rGO/ssDNA-OMC/PGE surface and then hybridization fallows through the peak current change in differential pulse voltammetry (DPV) using Ni-OTC NPs as a redox label. The biosensor was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), FT-IR spectroscopy, energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry and Nitrogen adsorption-desorption analysis. The Ni-OTC current response verified only the complementary sequence indicating a significant reduction current signal in comparison to single point mismatched and non-complementary and sequences. Under optimal conditions, the prepared biosensor showed long-term stability (21 days) with a wide linear range from 0.1 µM to 3 µM with high sensitivity (0.0188 mA/µM) and low detection limit (120 nM). Copyright © 2018 Elsevier B.V. All rights reserved.

Deposition of tungsten metal by an immersion process

DOE PAGES

Small, Leo J.; Brumbach, Michael T.; Clem, Paul G.; ...

2017-03-23

A new multi-step, solution-phase method for the spontaneous deposition of tungsten from a room temperature ethereal solution is reported. This immersion process relies on the deposition of a sacrificial zinc coating which is galvanically displaced by the ether-mediated reduction of oxophilic WCl 6. Subsequent thermal treatment renders a crystalline, metallic tungsten film. The chemical evolution of the surface and formation of a complex intermediate tungsten species is characterized by X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Efficient metallic tungsten deposition is first characterized on a graphite substrate and then demonstrated on a functional carbon foam electrode. The resulting electrochemicalmore » performance of the modified electrode is interrogated with the canonical aqueous ferricyanide system. A tungsten-coated carbon foam electrode showed that both electrode resistance and overall electrochemical cell resistance were reduced by 50%, resulting in a concomitant decrease in redox peak separation from 1.902 V to 0.783 V. Furthermore, this process promises voltage efficiency gains in electrodes for energy storage technologies and demonstrates the viability of a new route to tungsten coating for technologies and industries where high conductivity and chemical stability are paramount.« less

Reduced graphite oxide in supercapacitor electrodes.

PubMed

Lobato, Belén; Vretenár, Viliam; Kotrusz, Peter; Hulman, Martin; Centeno, Teresa A

2015-05-15

The current energy needs have put the focus on highly efficient energy storage systems such as supercapacitors. At present, much attention focuses on graphene-like materials as promising supercapacitor electrodes. Here we show that reduced graphite oxide offers a very interesting potential. Materials obtained by oxidation of natural graphite and subsequent sonication and reduction by hydrazine achieve specific capacitances as high as 170 F/g in H2SO4 and 84F/g in (C2H5)4NBF4/acetonitrile. Although the particle size of the raw graphite has no significant effect on the physico-chemical characteristics of the reduced materials, that exfoliated from smaller particles (<75 μm) result more advantageous for the release of the stored electrical energy. This effect is particularly evident in the aqueous electrolyte. Graphene-like materials may suffer from a drop in their specific surface area upon fabrication of electrodes with features of the existing commercial devices. This should be taken into account for a reliable interpretation of their performance in supercapacitors. Copyright © 2015 Elsevier Inc. All rights reserved.

Graphite oxide/β-Ni(OH)2 composites for application in supercapacitors

NASA Astrophysics Data System (ADS)

Singh, Arvinder; Chandra, Amreesh

2013-06-01

Graphite oxide/β-Ni(OH)2 composites have been investigated as electrode material in supercapacitors. Phase formation of electrode material is investigated using diffraction measurements. Particle shape-size studies show deposition of β-Ni(OH)2 nanoparticles on graphite oxide (GO) sheets. Electrochemical performance of GO/β-Ni(OH)2 composite in supercapacitors is discussed based on the analysis of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge studies. Excellent energy density of ˜53 Wh/kg in 1M Na2SO4 aqueous electrolyte is reported at power density of ˜1364W/kg. The significance of results is discussed in the paper.

Electron reflection and secondary emission characteristics of sputter-textured pyrolytic graphite surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Curren, A. N.; Sovey, J. S.

1981-01-01

Low secondary and reflected primary electron emission from the collector electrode surfaces is important for optimum collector efficiency and hence for high overall efficiency of microwave amplifier tubes used in communication satellites and in military systems. Ion sputter texturing of the surface effectively suppresses electron emission from pyrolytic graphite, which is a promising collector electrode material. Secondary and reflected primary electron emission characteristics of sputter textured pyrolytic graphite surfaces with microstructures of various sizes and densities are presented. The microstructure with the lowest electron emission levels, less than those of soot, consists of a dense array of tall, thin spires.

New method for binder and carbon black detection at nanometer scale in carbon electrodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Pfaffmann, Lukas; Jaiser, Stefan; Müller, Marcus; Scharfer, Philip; Schabel, Wilhelm; Bauer, Werner; Scheiba, Frieder; Ehrenberg, Helmut

2017-09-01

In the current work, graphite electrodes comprising PVDF binder and carbon black are subjected to characterization. An energy selective backscatter detector is used to localize carbon black and fluorine of PVDF. Therefore, it is necessary to distinguish between graphite, amorphous carbon and fluorine rich regions. Typically, an angular selective backscatter detector is employed to obtain an image providing the material contrast of the sample. Suitable materials for that detector are e.g. alloys to observe intermetallic phases, semiconductor for ;channeling contrast;, or imaging SiO2 and Au nanoparticles in biological cells. However, this detector cannot be used to distinguish between light elements with low atomic numbers, such as C to P. In addition, the contrast of fluorine rich regions and graphite is poor in normal in-lens images due to the low difference of the atomic mass between C and F. The aim of this study is to enhance the contrast of fluorine rich regions to graphite to carbon black. Therefore, the energy selective backscatter detector is used and its advantages and setup is described. Finally this technique is applied to investigate 400 μm thick cross-sections of graphite electrodes dried at different temperatures and obtain the carbon black distribution.

Redox hydrogel based bienzyme electrode for L-glutamate monitoring.

PubMed

Belay, A; Collins, A; Ruzgas, T; Kissinger, P T; Gorton, L; Csöregi, E

1999-02-01

Amperometric bienzyme electrodes based on coupled L-glutamate oxidase (GlOx) and horseradish peroxidase (HRP) were constructed for the direct monitoring of L-glutamate in a flow injection (FI)-system. The bienzyme electrodes were constructed by coating solid graphite rods with a premixed solution containing GlOx and HRP crosslinked with a redox polymer formed of poly(1-vinylimidazole) complexed with (osmium (4-4'-dimethylbpy)2 Cl)II/III. Poly(ethylene glycol) diglycidyl ether (PEGDGE) was used as the crosslinker and the modified electrodes were inserted as the working electrode in a conventional three electrode flow through amperometric cell operated at -0.05 V versus Ag¿AgCl (0.1 M KCl). The bienzyme electrode was optimized with regard to wire composition, Os-loading of the wires, enzyme ratios, coating procedure, flow rate, effect of poly(ethyleneimine) addition, etc. The optimized electrodes were characterized by a sensitivity of 88.36 +/- 0.14 microA mM(-1) cm(-2), a detection limit of 0.3 microM (calculated as three times the signal-to-noise ratio), a response time of less than 10 s and responded linearly between 0.3 and 250 microM (linear regression coefficient = 0.999) with an operational stability of only 3% sensitivity loss during 8 h of continuous FI operation at a sample throughput of 30 injections h(-1).

Final Report: Novel ALD-Coated Nanoparticle Anodes for Enhanced Performance Lithium-Ion Batteries

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

Groner, Markus

2009-04-16

The Phase I effort is described in detail in the Phase I report given below. The key accomplishments of the Phase I project were (1) the demonstration of high stability LiCoO2 cathodes using ALD-coated LiCoO2 particles, as well as on ALD-coated LiCoO2 electrodes and (2) the demonstration of high stability of graphite anodes using ALD-coated graphite electrodes.

Preparation, Characterization and Utilization of Electrodes Coated with Polymeric Networks Formed by Gamma Radiation Crosslinking.

DTIC Science & Technology

1987-04-01

polymers such as poly[ diallyl dimethyl ammonium chloride] , poly [vinylbenzyl trimethyl ammonium chloride], poly[styrene sulfonic acid , sodium salt] and...poly[acrylic acid ], which would ordinarily dissolve from the electrode surface in aqueous solution unless crosslinked into a network, and several...Irradiation on a Water-Soluble Polymer: DDAC 8 E. Electrochemistry of DDAC Networks on Platinum and Graphite 10 F. Poly [acrylic acid ] Films on Graphite

A new ring-shaped graphite monitor ionization chamber

NASA Astrophysics Data System (ADS)

Yoshizumi, M. T.; Caldas, L. V. E.

2010-07-01

A ring-shaped monitor ionization chamber was developed at the Instituto de Pesquisas Energéticas e Nucleares. This ionization chamber presents an entrance window of aluminized polyester foil. The guard ring and collecting electrode are made of graphite coated Lucite plates. The main difference between this new ionization chamber and commercial monitor chambers is its ring-shaped design. The new monitor chamber has a central hole, allowing the passage of the direct radiation beam without attenuation; only the penumbra radiation is measured by the sensitive volume. This kind of ionization chamber design has already been tested, but using aluminium electrodes. By changing the electrode material from aluminium to a graphite coating, an improvement in the chamber response stability was expected. The pre-operational tests, as saturation curve, recombination loss and polarity effect showed satisfactory results. The repeatability and the long-term stability tests were also evaluated, showing good agreement with international recommendations.

Nanoscale electrochemical patterning reveals the active sites for catechol oxidation at graphite surfaces.

PubMed

Patel, Anisha N; McKelvey, Kim; Unwin, Patrick R

2012-12-19

Graphite-based electrodes (graphite, graphene, and nanotubes) are used widely in electrochemistry, and there is a long-standing view that graphite step edges are needed to catalyze many reactions, with the basal surface considered to be inert. In the present work, this model was tested directly for the first time using scanning electrochemical cell microscopy reactive patterning and shown to be incorrect. For the electro-oxidation of dopamine as a model process, the reaction rate was measured at high spatial resolution across a surface of highly oriented pyrolytic graphite. Oxidation products left behind in a pattern defined by the scanned electrochemical cell served as surface-site markers, allowing the electrochemical activity to be correlated directly with the graphite structure on the nanoscale. This process produced tens of thousands of electrochemical measurements at different locations across the basal surface, unambiguously revealing it to be highly electrochemically active, with step edges providing no enhanced activity. This new model of graphite electrodes has significant implications for the design of carbon-based biosensors, and the results are additionally important for understanding electrochemical processes on related sp(2)-hybridized materials such as pristine graphene and nanotubes.

Understanding the anisotropic strain effects on lithium diffusion in graphite anodes: A first-principles study

NASA Astrophysics Data System (ADS)

Ji, Xiang; Wang, Yang; Zhang, Junqian

2018-06-01

The lithium diffusion in graphite anode, which is the most widely used commercial electrode material today, affects the charge/discharge performance of lithium-ion batteries. In this study, the anisotropic strain effects on lithium diffusion in graphite anodes are systematically investigated using first-principles calculations based on density functional theory (DFT) with van der Waals corrections. It is found that the effects of external applied strains along various directions of LixC6 (i.e., perpendicular or parallel to the basal planes of the graphite host) on lithium diffusivity are different. Along the direction perpendicular to the graphite planes, the tensile strain facilitates in-plane Li diffusion by reducing the energy barrier, and the compressive strain hinders in-plane Li diffusion by raising the energy barrier. In contrast, the in-plane biaxial tensile strain (parallel to the graphite planes) hinders in-plane Li diffusion, and the in-plane biaxial compressive strain facilitates in-plane Li diffusion. Furthermore, both in-plane and transverse shear strains slightly influence Li diffusion in graphite anodes. A discussion is presented to explain the anisotropic strain dependence of lithium diffusion. This research provides data for the continuum modelling of the electrodes in the lithium-ion batteries.

Lithium insertion in graphite from ternary ionic liquid-lithium salt electrolytes: II. Evaluation of specific capacity and cycling efficiency and stability at room temperature

NASA Astrophysics Data System (ADS)

Lux, Simon F.; Schmuck, Martin; Appetecchi, Giovanni B.; Passerini, Stefano; Winter, Martin; Balducci, Andrea

In this paper we report the results about the use of ternary room temperature ionic liquid-lithium salt mixtures as electrolytes for lithium-ion battery systems. Mixtures of N-methyl- N-propyl pyrrolidinium bis(fluorosulfonyl) imide, PYR 13FSI, and N-butyl- N-methylpyrrolidinium bis(trifluoromethansulfonyl) imide, PYR 14TFSI, with lithium hexafluorophosphate, LiPF 6 and lithium bis(trifluoromethansulfonyl) imide, LiTFSI, containing 5 wt.% of vinylene carbonate (VC) as additive, have been used in combination with a commercial graphite, KS6 TIMCAL. The performance of the graphite electrodes has been considered in term of specific capacity, cycling efficiency and cycling stability. The results clearly show the advantage of the use of ternary mixtures on the performance of the graphite electrode.

Charge and discharge characteristics of lithium-ion graphite electrodes in solid-state cells

NASA Astrophysics Data System (ADS)

Lemont, S.; Billaud, D.

Lithium ions have been electrochemically intercalated into graphite in solid-state cells operating with solid polymer electrolytes based on poly(ethylene oxide) (PEO) complexed with lithium perchlorate (LiClO 4). The working composite electrode is composed of active-divided natural graphite associated with P(EO) 8-LiClO 4 acting as a binder and a Li + ionic conductor. Intercalation and de-intercalation of Li + were performed using galvanostatic or voltammetry techniques. The curves obtained in our solid-state cells were compared with those performed in liquid ethylene carbonate-LiClO 4 electrolyte. It is shown that in solid-state cells, side reactions occur both in the reduction and in the oxidation processes which leads to some uncertainty in the determination of the maximum reversible capacity of the graphite material.

Fabrication of gallium hexacyanoferrate modified carbon ionic liquid paste electrode for sensitive determination of hydrogen peroxide and glucose.

PubMed

Haghighi, Behzad; Khosravi, Mehdi; Barati, Ali

2014-07-01

Gallium hexacyanoferrate (GaHCFe) and graphite powder were homogeneously dispersed into n-dodecylpyridinium hexafluorophosphate and paraffin to fabricate GaHCFe modified carbon ionic liquid paste electrode (CILPE). Mixture experimental design was employed to optimize the fabrication of GaHCFe modified CILPE (GaHCFe-CILPE). A pair of well-defined redox peaks due to the redox reaction of GaHCFe through one-electron process was observed for the fabricated electrode. The fabricated GaHCFe-CILPE exhibited good electrocatalytic activity towards reduction and oxidation of H2O2. The observed sensitivities for the electrocatalytic oxidation and reduction of H2O2 at the operating potentials of +0.8 and -0.2V were about 13.8 and 18.3 mA M(-1), respectively. The detection limit (S/N=3) for H2O2 was about 1 μM. Additionally, glucose oxidase (GOx) was immobilized on GaHCFe-CILPE using two methodology, entrapment into Nafion matrix and cross-linking with glutaraldehyde and bovine serum albumin, in order to fabricate glucose biosensor. Linear dynamic rage, sensitivity and detection limit for glucose obtained by the biosensor fabricated using cross-linking methodology were 0.1-6mM, 0.87 mA M(-1) and 30 μM, respectively and better than those obtained (0.2-6mM, 0.12 mA M(-1) and 50 μM) for the biosensor fabricated using entrapment methodology. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of fluoride intercalation/de-intercalation processes on graphite electrodes in aqueous and aqueous methanolic HF media

NASA Astrophysics Data System (ADS)

Noel, M.; Santhanam, R.; Francisca Flora, M.

The solvent can play a major role in the intercalation/de-intercalation process and the stability of graphite substrates towards this process. This fact is established in the present work that involves fluoride intercalation/de-intercatlation on graphite electrodes in aqueous and aqueous methanolic HF solutions where the HF concentration is varied between 1.0 and 18.0 M. In addition to cyclic voltammetry and potentiostatic polarization, open-circuit potential decay measurements, scanning electron microscopy and X-ray diffraction measurements have been employed. In general, addition of methanol and increasing concentration of HF raise the overall intercalation/de-intercalation efficiency. Methanol is adsorbed preferentially on the graphite lattice and, hence, suppresses both oxygen evolution and the formation of passive graphite oxides. In 15.0 M HF, the optimum methanol concentration is 5 vol.%. This suggests that, in addition to the adsorption effect, there is some weakening of the structured water molecules that facilitates the solvated fluoride ions for efficient intercalation.

Fast and Sensitive Detection of Pb2+ in Foods Using Disposable Screen-Printed Electrode Modified by Reduced Graphene Oxide

PubMed Central

Jian, Jin-Ming; Liu, Yan-Yan; Zhang, Ye-Lei; Guo, Xi-Shan; Cai, Qiang

2013-01-01

In this study, reduced graphene oxide (rGO) was electrochemically deposited on the surface of screen-printed carbon electrodes (SPCE) to prepare a disposable sensor for fast detection of Pb2+ in foods. The SEM images showed that the rGO was homogeneously deposited onto the electrode surface with a wrinkled nanostructure, which provided 2D bridges for electron transport and a larger active area for Pb2+ adsorption. Results showed that rGO modification enhanced the activity of the electrode surface, and significantly improved the electrochemical properties of SPCE. The rGO modified SPCE (rGO-SPCE) was applied to detect Pb2+ in standard aqueous solution, showing a sharp stripping peak and a relatively constant peak potential in square wave anodic stripping voltammetry (SWASV). The linear range for Pb2+ detection was 5∼200 ppb (R2 = 0.9923) with a low detection limit of 1 ppb (S/N = 3). The interference of Cd2+ and Cu2+ at low concentrations was effectively avoided. Finally, the rGO-SPCE was used for determination of lead in real tap water, juice, preserved eggs and tea samples. Compared with results from graphite furnace atomic absorption spectroscopy (GFAAS), the results based on rGO-SPCE were both accurate and reliable, suggesting that the disposable sensor has great potential in application for fast, sensitive and low-cost detection of Pb2+ in foods. PMID:24077322

Electrode Induced Removal and Recovery of Uranium (VI) from Acidic Subsurfaces

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

Gregory, Kelvin

2013-08-12

The overarching objective of this research is to provide an improved understanding of how aqueous geochemical conditions impact the removal of U and Tc from groundwater and how engineering design may be utilized to optimize removal of these radionuclides. Experiments were designed to address the unique conditions in Area 3 of ORNL while also providing broader insight into the geochemical effectors of the removal rates and extent for U and Tc. The specific tasks of this work were to: 1) quantify the impact of common aqueous geochemical and operational conditions on the rate and extent of U removal and recoverymore » from water, 2) investigate the removal of Tc with polarized graphite electrode, and determine the influence of geochemical and operational conditions on Tc removal and recovery, 3) determine whether U and Tc may be treated simultaneous from Area 3 groundwater, and examine the bench-scale performance of electrode-based treatment, and 4) determine the capacity of graphite electrodes for U(VI) removal and develop a mathematical, kinetic model for the removal of U(VI) from aqueous solution. Overall the body of work suggests that an electrode-based approach for the remediation of acidic subsurface environments, such as those observed in Area 3 of ORNL may be successful for the removal for both U(VI) and Tc. Carbonaceous (graphite) electrode materials are likely to be the least costly means to maximize removal rates and efficiency by maximizing the electrode surface area.« less

Capacity Fade and Its Mitigation in Li-Ion Cells with Silicon-Graphite Electrodes

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

Bareno, Javier; Shkrob, Ilya A.; Gilbert, James A.

Silicon-graphite (Si-Gr) electrodes typically contain lithiated carboxylates as polymer binders that are introduced through aqueous processing. Li-ion cells with such electrodes show significantly faster capacity fade than cells with graphite (Gr) electrodes. Here we examine the causes for capacity loss in Si-Gr cells containing LiPF 6-based electrolytes. The presence of SiO xF y in the Si-Gr electrode, fluorophosphate species in the electrolyte, and silica on the positive electrode indicates the crucial role of the hydrolytic cycle. In particular, HF acid that is generated through LiPF 6 hydrolysis corrodes Si particles. As it reacts, the released water re-enters the cycle. Wemore » trace the moisture initiating this detrimental cycle to the hydration water in the lithiated binders that cannot be fully removed by thermal treatment. The rate of HF corrosion can be reduced through the use of electrolyte additives. For the fluoroethylene carbonate (FEC) additive, the improved performance arises from changes to the solid electrolyte interphase (SEI) that serves as a barrier against HF attack. Here, we propose that the greater extent of polymer cross-linking, that gives FEC-derived SEI elastomer properties, slows down HF percolation through this SEI membrane and inhibits the formation of deep cracks through which HF can access and degrade the Si surface.« less

Capacity Fade and Its Mitigation in Li-Ion Cells with Silicon-Graphite Electrodes

DOE PAGES

Bareno, Javier; Shkrob, Ilya A.; Gilbert, James A.; ...

2017-09-06

Silicon-graphite (Si-Gr) electrodes typically contain lithiated carboxylates as polymer binders that are introduced through aqueous processing. Li-ion cells with such electrodes show significantly faster capacity fade than cells with graphite (Gr) electrodes. Here we examine the causes for capacity loss in Si-Gr cells containing LiPF 6-based electrolytes. The presence of SiO xF y in the Si-Gr electrode, fluorophosphate species in the electrolyte, and silica on the positive electrode indicates the crucial role of the hydrolytic cycle. In particular, HF acid that is generated through LiPF 6 hydrolysis corrodes Si particles. As it reacts, the released water re-enters the cycle. Wemore » trace the moisture initiating this detrimental cycle to the hydration water in the lithiated binders that cannot be fully removed by thermal treatment. The rate of HF corrosion can be reduced through the use of electrolyte additives. For the fluoroethylene carbonate (FEC) additive, the improved performance arises from changes to the solid electrolyte interphase (SEI) that serves as a barrier against HF attack. Here, we propose that the greater extent of polymer cross-linking, that gives FEC-derived SEI elastomer properties, slows down HF percolation through this SEI membrane and inhibits the formation of deep cracks through which HF can access and degrade the Si surface.« less

Green synthesis of nitrogen-doped graphitic carbon sheets with use of Prunus persica for supercapacitor applications

NASA Astrophysics Data System (ADS)

Atchudan, Raji; Edison, Thomas Nesakumar Jebakumar Immanuel; Perumal, Suguna; Lee, Yong Rok

2017-01-01

Nitrogen-doped graphitic carbon sheets (N-GCSs) were prepared from the extract of unripe Prunus persica fruit by a direct hydrothermal method. The synthesized N-GCSs were examined by high resolution transmission electron microscopy (HRTEM), nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy. HRTEM showed that the synthesized carbon sheets were graphitic with lattice fringes and an inter-layer distance of 0.36 nm. Doping with the nitrogen moiety present over the synthesized GCSs was confirmed by XPS, FT-IR spectroscopy, and energy dispersive X-ray spectroscopy elemental mapping. The fruit extract associated with hydrothermal-carbonization method is economical and eco-friendly with a single step process. The resulting carbon sheets could be modified and are promising candidates for nano-electronic applications, including supercapacitors. The synthesized N-GCSs-2 provided a high specific capacitance of 176 F g-1 at a current density of 0.1 A g-1. This electrode material has excellent cyclic stability, even after 2000 cycles of charge-discharge at a current density of 0.5 A g-1.

Alkaline electrochemical advanced oxidation process for chromium oxidation at graphitized multi-walled carbon nanotubes.

PubMed

Xue, Yudong; Zheng, Shili; Sun, Zhi; Zhang, Yi; Jin, Wei

2017-09-01

Alkaline electrochemical advanced oxidation processes for chromium oxidation and Cr-contaminated waste disposal were reported in this study. The highly graphitized multi-walled carbon nanotubes g-MWCNTs modified electrode was prepared for the in-situ electrochemical generation of HO 2 - . RRDE test results illustrated that g-MWCNTs exhibited much higher two-electron oxygen reduction activity than other nanocarbon materials with peak current density of 1.24 mA cm -2 , %HO 2 - of 77.0% and onset potential of -0.15 V (vs. Hg/HgO). It was originated from the highly graphitized structure and good electrical conductivity as illustrated from the Raman, XRD and EIS characterizations, respectively. Large amount of reactive oxygen species (HO 2 - and ·OH) were in-situ electro-generated from the two-electron oxygen reduction and chromium-induced alkaline electro-Fenton-like reaction. The oxidation of Cr(III) was efficiently achieved within 90 min and the conversion ratio maintained more than 95% of the original value after stability test, offering an efficient and green approach for the utilization of Cr-containing wastes. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Danial, Wan Hazman, E-mail: hazmandanial@gmail.com; Majid, Zaiton Abdul, E-mail: zaiton@kimia.fs.utm.my; Aziz, Madzlan

The present work reports the synthesis and characterization of graphene via electrochemical exfoliation of graphite rod using two-electrode system assisted by Sodium Dodecyl Sulphate (SDS) as a surfactant. The electrochemical process was carried out with sequence of intercalation of SDS onto the graphite anode followed by exfoliation of the SDS-intercalated graphite electrode when the anode was treated as cathode. The effect of intercalation potential from 5 V to 9 V and concentration of the SDS surfactant of 0.1 M and 0.01 M were investigated. UV-vis Spectroscopic analysis indicated an increase in the graphene production with higher intercalation potential. Transmission Electron Microscopy (TEM)more » analysis showed a well-ordered hexagonal lattice of graphene image and indicated an angle of 60° between two zigzag directions within the honeycomb crystal lattice. Raman spectroscopy analysis shows the graphitic information effects after the exfoliation process.« less

Room temperature stable single molecule rectifiers with graphite electrodes

NASA Astrophysics Data System (ADS)

Rungger, Ivan; Kaliginedi, V.; Droghetti, A.; Ozawa, H.; Kuzume, A.; Haga, M.; Broekmann, P.; Rudnev, A. V.

In this combined theoretical and experimental study we present new molecular electronics device characteristics of unprecedented stability at room temperature by using electrodes based on highly oriented pyrolytic graphite with covalently attached molecules. To this aim, we explore the effect of the anchoring group chemistry on the charge transport properties of graphite/molecule contacts by means of the scanning tunneling microscopy break-junction technique and ab initio simulations. The theoretical approach to evaluate the conductance is based on density functional theory calculations combined with the non-equilibrium Greens function technique, as implemented in the Smeagol electron transport code. We also demonstrate a strong bias dependence and rectification of the single molecule conductance induced by the anchoring chemistry in combination with the very low density of states of graphite around the Fermi energy. We show that the direction of tunneling current rectification can be tuned by anchoring group chemistry.

In Situ Activation of Nitrogen-Doped Graphene Anchored on Graphite Foam for a High-Capacity Anode.

PubMed

Ji, Junyi; Liu, Jilei; Lai, Linfei; Zhao, Xin; Zhen, Yongda; Lin, Jianyi; Zhu, Yanwu; Ji, Hengxing; Zhang, Li Li; Ruoff, Rodney S

2015-08-25

We report the fabrication of a three-dimensional free-standing nitrogen-doped porous graphene/graphite foam by in situ activation of nitrogen-doped graphene on highly conductive graphite foam (GF). After in situ activation, intimate "sheet contact" was observed between the graphene sheets and the GF. The sheet contact produced by in situ activation is found to be superior to the "point contact" obtained by the traditional drop-casting method and facilitates electron transfer. Due to the intimate contact as well as the use of an ultralight GF current collector, the composite electrode delivers a gravimetric capacity of 642 mAh g(-1) and a volumetric capacity of 602 mAh cm(-3) with respect to the whole electrode mass and volume (including the active materials and the GF current collector). When normalized based on the mass of the active material, the composite electrode delivers a high specific capacity of up to 1687 mAh g(-1), which is superior to that of most graphene-based electrodes. Also, after ∼90 s charging, the anode delivers a capacity of about 100 mAh g(-1) (with respect to the total mass of the electrode), indicating its potential use in high-rate lithium-ion batteries.

Influence of various Activated Carbon based Electrode Materials in the Performance of Super Capacitor

NASA Astrophysics Data System (ADS)

Ajay, K. M.; Dinesh, M. N.

2018-02-01

Various activated carbon based electrode materials with different surface areas was prepared on stainless steel based refillable super capacitor model using spin coating. Bio Synthesized Activated Carbon (BSAC), Activated Carbon (AC) and Graphite powder are chosen as electrode materials in this paper. Electrode materials prepared using binder solution which is 6% by wt. polyvinylidene difluoride, 94% by wt. dimethyl fluoride. 3M concentrated KOH solution is used as aqueous electrolyte with PVDF thin film as separator. It is tested for electrochemical characterizations and material characterizations. It is observed that the Specific capacitance of Graphite, Biosynthesized active carbon and Commercially available activated carbon are 16.1F g-1, 53.4F g-1 and 107.6F g-1 respectively at 5mV s-1 scan rate.

Structure and Li+ ion transport in a mixed carbonate/LiPF6 electrolyte near graphite electrode surfaces: a molecular dynamics study.

PubMed

Boyer, Mathew J; Vilčiauskas, Linas; Hwang, Gyeong S

2016-10-12

Electrolyte and electrode materials used in lithium-ion batteries have been studied separately to a great extent, however the structural and dynamical properties of the electrolyte-electrode interface still remain largely unexplored despite its critical role in governing battery performance. Using molecular dynamics simulations, we examine the structural reorganization of solvent molecules (cyclic ethylene carbonate : linear dimethyl carbonate 1 : 1 molar ratio doped with 1 M LiPF 6 ) in the vicinity of graphite electrodes with varying surface charge densities (σ). The interfacial structure is found to be sensitive to the molecular geometry and polarity of each solvent molecule as well as the surface structure and charge distribution of the negative electrode. We also evaluated the potential difference across the electrolyte-electrode interface, which exhibits a nearly linear variation with respect to σ up until the onset of Li + ion accumulation onto the graphite edges from the electrolyte. In addition, well-tempered metadynamics simulations are employed to predict the free-energy barriers to Li + ion transport through the relatively dense interfacial layer, along with analysis of the Li + solvation sheath structure. Quantitative analysis of the molecular arrangements at the electrolyte-electrode interface will help better understand and describe electrolyte decomposition, especially in the early stages of solid-electrolyte-interphase (SEI) formation. Moreover, the computational framework presented in this work offers a means to explore the effects of solvent composition, electrode surface modification, and operating temperature on the interfacial structure and properties, which may further assist in efforts to engineer the electrolyte-electrode interface leading to a SEI layer that optimizes battery performance.

78 FR 22843 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-17

...The Department of Commerce (``Department'') preliminarily determines that imports from the People's Republic of China (``PRC'') of certain graphite electrodes, produced and/or exported by Sinosteel Jilin Carbon Co., Ltd. and Jilin Carbon Import & Export Company (collectively, ``Jilin Carbon''), with an actual or nominal diameter of 17 inches, and otherwise meeting the description of in-scope merchandise, constitutes merchandise altered in form or appearance in such minor respects that it should be included within the scope of the Order.\\1\\ ---------------------------------------------------------------------------

Battery Electrode Materials with High Cycle Lifetimes

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

Prof. Brent Fultz

2001-06-29

In an effort to understand the capacity fade of nickel-metal hydride (Ni-MH) batteries, we performed a systematic study of the effects of solute additions on the cycle life of metal hydride electrodes. We also performed a series of measurements on hydrogen absorption capacities of novel carbon and graphite-based materials including graphite nanofibers and single-walled carbon nanotubes. Towards the end of this project we turned our attention to work on Li-ion cells with a focus on anode materials.

Fabrication of an Inexpensive Ion-Selective Electrode.

ERIC Educational Resources Information Center

Palanivel, A.; Riyazuddin, P.

1984-01-01

The preparation and performance of a graphite (silver/copper sulfide) electrode is described. This rod, extracted from a used dry cell, is an acceptable substitute for ion-selective electrodes after it has been cleaned by abrasion followed by an overnight treatment with hydrochloric acid. (JN)

Theoretical Considerations for Improving the Pulse Power of a Battery through the Addition of a Second Electrochemically Active Material

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

Knehr, K. W.; West, Alan C.

Here, porous electrode theory is used to conduct case studies for when the addition of a second electrochemically active material can improve the pulse-power performance of an electrode. Case studies are conducted for the positive electrode of a sodium metal-halide battery and the graphite negative electrode of a lithium “rocking chair” battery. The replacement of a fraction of the nickel chloride capacity with iron chloride in a sodium metal-halide electrode and the replacement of a fraction of the graphite capacity with carbon black in a lithium-ion negative electrode were both predicted to increase the maximum pulse power by up tomore » 40%. In general, whether or not a second electrochemically active material increases the pulse power depends on the relative importance of ohmic-to-charge transfer resistances within the porous structure, the capacity fraction of the second electrochemically active material, and the kinetic and thermodynamic parameters of the two active materials.« less

Theoretical Considerations for Improving the Pulse Power of a Battery through the Addition of a Second Electrochemically Active Material

DOE PAGES

Knehr, K. W.; West, Alan C.

2016-05-26

Here, porous electrode theory is used to conduct case studies for when the addition of a second electrochemically active material can improve the pulse-power performance of an electrode. Case studies are conducted for the positive electrode of a sodium metal-halide battery and the graphite negative electrode of a lithium “rocking chair” battery. The replacement of a fraction of the nickel chloride capacity with iron chloride in a sodium metal-halide electrode and the replacement of a fraction of the graphite capacity with carbon black in a lithium-ion negative electrode were both predicted to increase the maximum pulse power by up tomore » 40%. In general, whether or not a second electrochemically active material increases the pulse power depends on the relative importance of ohmic-to-charge transfer resistances within the porous structure, the capacity fraction of the second electrochemically active material, and the kinetic and thermodynamic parameters of the two active materials.« less

Graphitic carbon nitride nanosheet electrode-based high-performance ionic actuator

PubMed Central

Wu, Guan; Hu, Ying; Liu, Yang; Zhao, Jingjing; Chen, Xueli; Whoehling, Vincent; Plesse, Cédric; Nguyen, Giao T. M.; Vidal, Frédéric; Chen, Wei

2015-01-01

Ionic actuators have attracted attention due to their remarkably large strain under low-voltage stimulation. Because actuation performance is mainly dominated by the electrochemical and electromechanical processes of the electrode layer, the electrode material and structure are crucial. Here, we report a graphitic carbon nitride nanosheet electrode-based ionic actuator that displays high electrochemical activity and electromechanical conversion abilities, including large specific capacitance (259.4 F g−1) with ionic liquid as the electrolyte, fast actuation response (0.5±0.03% in 300 ms), large electromechanical strain (0.93±0.03%) and high actuation stability (100,000 cycles) under 3 V. The key to the high performance lies in the hierarchical pore structure with dominant size <2 nm, optimal pyridinic nitrogen active sites (6.78%) and effective conductivity (382 S m−1) of the electrode. Our study represents an important step towards artificial muscle technology in which heteroatom modulation in electrodes plays an important role in promoting electrochemical actuation performance. PMID:26028354

NASA redox storage system development project

NASA Technical Reports Server (NTRS)

1983-01-01

The operating temperature was raised from 25 C to 65 C, which enhanced the kinetics of the chromium electrode charging reactions. The design of the auxiliary electrochemical cell, which is used to keep both reactants at the same state of charge, was modified, leading to better and more stable performance. Preliminary testing has shown that the four tank mode of operation improves energy efficiency as much as 5 percentage points over the conventional two tank mode. Another variation in operating mode, the use of mixed reactants, potentially offers several very attractive advantages. Preliminary reactant cost studies lend further weight to the feasibility of the mixed reactant concept. Electrode studies show that reproducibility of performance is very dependent on the pyrolysis temperature at which the carbon/graphite felt substrate is formed. Membrane development work continued to concentrate on cost reduction and the enhancement of resistivity and selectivity.

Electrochemical studies on polysorbate-20 (Tween 20)-entrapped haemoglobin and its application in a hydrogen peroxide biosensor.

PubMed

Ma, Xiang; Chen, Ting; Liu, Lifang; Li, Genxi

2005-06-01

Haemoglobin (Hb) was entrapped in polysorbate 20 and then modified on a pyrolytic graphite electrode. Electrochemical studies revealed that a pair of stable and well-defined redox peaks attributed to the direct redox reaction of Hb could be observed in a phosphate buffer solution (pH 6.0). The anodic and cathodic peaks were located at -236 and -316 mV (versus a saturated calomel reference electrode) separately. The formal potential, E0', was linearly varied with pH in the range from 3.0 to 10.0 with a slope of -48.0 mV.pH-1. Moreover, the protein was capable of catalysing the reduction of H2O2. Accordingly, an unmediated biosensor for H2O2 was prepared with a linear range from 8.0x10(-7) to 1.0x10(-3) M. This biosensor exhibited good stability, sensitivity and reproducibility.

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

PubMed

Raj, C Justin; Kim, Byung Chul; Cho, Won-Je; Lee, Won-gil; Jung, Sang-Don; Kim, Yong Hee; Park, Sang Yeop; Yu, Kook Hyun

2015-06-24

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

Nanoporous Ni(OH)2 thin film on 3D Ultrathin-graphite foam for asymmetric supercapacitor.

PubMed

Ji, Junyi; Zhang, Li Li; Ji, Hengxing; Li, Yang; Zhao, Xin; Bai, Xin; Fan, Xiaobin; Zhang, Fengbao; Ruoff, Rodney S

2013-07-23

Nanoporous nickel hydroxide (Ni(OH)2) thin film was grown on the surface of ultrathin-graphite foam (UGF) via a hydrothermal reaction. The resulting free-standing Ni(OH)2/UGF composite was used as the electrode in a supercapacitor without the need for addition of either binder or metal-based current collector. The highly conductive 3D UGF network facilitates electron transport and the porous Ni(OH)2 thin film structure shortens ion diffusion paths and facilitates the rapid migration of electrolyte ions. An asymmetric supercapacitor was also made and studied with Ni(OH)2/UGF as the positive electrode and activated microwave exfoliated graphite oxide ('a-MEGO') as the negative electrode. The highest power density of the fully packaged asymmetric cell (44.0 kW/kg) was much higher (2-27 times higher), while the energy density was comparable to or higher, than high-end commercially available supercapacitors. This asymmetric supercapacitor had a capacitance retention of 63.2% after 10,000 cycles.

Influence of Inner Transducer Properties on EMF Response and Stability of Solid-Contact Anion Selective Membrane Electrodes Based on Metalloporphyrin Ionophores

PubMed Central

Górski, Łukasz; Matusevich, Alexey; Pietrzak, Mariusz; Wang, Lin; Meyerhoff, Mark E.; Malinowska, Elżbieta

2010-01-01

The performance of solid-contact/coated wire type electrodes with plasticized PVC membranes containing metalloporphyrins as anion selective ionophores is reported. The membranes are deposited on transducers based on graphite pastes and graphite rods. The hydrophobicity of the underlying conductive transducer surface is found to be a key factor that influences the formation of an aqueous layer beneath the polymer film. Elimination of this ill-defined water layer greatly improves the electrochemical properties of the ion-sensors, such as EMF stability and life-time. Only highly lipophilic electrode substrates, namely graphite paste with mineral oil, were shown to prevent the formation of aqueous layer underneath the ion-sensing membrane. The possibility of employing Co(III)-tetraphenylporphyrin both as NO2− selective ionophore and as electron/ion conducting species to ensure ion-to-electron translation was also discussed based on the results of preliminary experiments. PMID:20357903

Molecular dynamics simulation studies of ionic liquid electrolytes for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Hu, Zongzhi

Molecular Dynamics (MD) simulation has been performed on various Electric Double Layer Capacitors (EDLCs) systems with different Room Temperature Ionic Liquids (RTILs) as well as different structures and materials of electrodes using a computationally efficient, low cost, united atom (UA)/explicit atom (EA) force filed. MD simulation studies on two 1-butyl-3-methylimidazolium (BMIM) based RTILs, i.e., [BMIM][BF4] and [BMIM][PF6], have been conducted on both atomic flat and corrugated graphite as well as (001) and (011) gold electrode surfaces to understand the correlations between the Electric Double Layer (EDL) structure and their corresponding differential capacitance (DC). Our MD simulations have strong agreement with some experimental data. The structures of electrodes also have a strong effect on the capacitance of EDLCs. MD simulations have been conducted on RTILs of N-methyl-N- propylpyrrolidinium [pyr13] and bis(fluorosulfonyl)imide (FSI) as well as [BMIM][PF6] on both curvature electrodes (fullerenes, nanotube, nanowire) and atomic flat electrode surfaces. It turns out that the nanowire electrode systems have the largest capacitance, following by fullerene systems. Nanotube electrode systems have the smallest capacitance, but they are still larger than that of atomically flat electrode system. Also, RTILs with slightly different chemical structure such as [Cnmim], n = 2, 4, 6, and 8, FSI and bis(trifluoromethylsulfonyl)imide (TFSI), have been examined by MD simulation on both flat and nonflat graphite electrode surfaces to study the effect of cation and anion's chemical structures on EDL structure and DC. With prismatic (nonflat) graphite electrodes, a transition from a bell-shape to a camel-shape DC dependence on electrode potential was observed with increase of the cation alkyl tail length for FSI systems. In contrast, the [Cnmim][TFSI] ionic liquids generated only a camel-shape DC on the rough surface regardless of the length of alkyl tail.

Tunable Oxygen Functional Groups as Electrocatalysts on Graphite Felt Surfaces for All-Vanadium Flow Batteries.

PubMed

Estevez, Luis; Reed, David; Nie, Zimin; Schwarz, Ashleigh M; Nandasiri, Manjula I; Kizewski, James P; Wang, Wei; Thomsen, Edwin; Liu, Jun; Zhang, Ji-Guang; Sprenkle, Vincent; Li, Bin

2016-06-22

A dual oxidative approach using O2 plasma followed by treatment with H2 O2 to impart oxygen functional groups onto the surface of a graphite felt electrode. When used as electrodes for an all-vanadium redox flow battery (VRB) system, the energy efficiency of the cell is enhanced by 8.2 % at a current density of 150 mA cm(-2) compared with one oxidized by thermal treatment in air. More importantly, by varying the oxidative techniques, the amount and type of oxygen groups was tailored and their effects were elucidated. It was found that O-C=O groups improve the cells performance whereas the C-O and C=O groups degrade it. The reason for the increased performance was found to be a reduction in the cell overpotential after functionalization of the graphite felt electrode. This work reveals a route for functionalizing carbon electrodes to improve the performance of VRB cells. This approach can lower the cost of VRB cells and pave the way for more commercially viable stationary energy storage systems that can be used for intermittent renewable energy storage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lithium dendrite and solid electrolyte interphase investigation using OsO4

NASA Astrophysics Data System (ADS)

Zier, Martin; Scheiba, Frieder; Oswald, Steffen; Thomas, Jürgen; Goers, Dietrich; Scherer, Torsten; Klose, Markus; Ehrenberg, Helmut; Eckert, Jürgen

2014-11-01

Osmium tetroxide (OsO4) staining, commonly used to enhance scattering contrast in electron microscopy of biologic tissue and polymer blends, has been adopted for studies of graphite anodes in lithium-ion batteries. OsO4 shows a coordinated reaction with components of the solid electrolyte interphase (SEI) and lithium dendrites, thereby increasing material contrast for scanning electron microscopy investigations. Utilizing the high affinity of lithium metal to react with osmium tetroxide it was possible to localize even small lithium deposits on graphite electrodes. In spite of their reaction with the OsO4 fume, the lithium dendrite morphology remains almost untouched by the staining procedure, offering information on the dendrite growth process. Correlating the quantity of osmium detected with the amount of residual ("dead") lithium of a discharged electrode, it was possible to obtain a practical measure for lithium plating and stripping efficiencies. EDX mappings allowed for a localization of electrochemically stripped lithium dendrites by their residual stained SEI shells. Cross sections, prepared by focused ion beam (FIB) of cycled graphite electrodes treated with OsO4, revealed important information about deposition and distribution of metallic lithium and the electrolyte reduction layer across the electrode.

Enhancing biodegradation and energy generation via roughened surface graphite electrode in microbial desalination cell.

PubMed

Ebrahimi, Atieh; Yousefi Kebria, Daryoush; Najafpour Darzi, Ghasem

2017-09-01

The microbial desalination cell (MDC) is known as a newly developed technology for water and wastewater treatment. In this study, desalination rate, organic matter removal and energy production in the reactors with and without desalination function were compared. Herein, a new design of plain graphite called roughened surface graphite (RSG) was used as the anode electrode in both microbial fuel cell (MFC) and MDC reactors for the first time. Among the three type of anode electrodes investigated in this study, RSG electrode produced the highest power density and salt removal rate of 10.81 W/m 3 and 77.6%, respectively. Such a power density was 2.33 times higher than the MFC reactor due to the junction potential effect. In addition, adding the desalination function to the MFC reactor enhanced columbic efficiency from 21.8 to 31.4%. These results provided a proof-of-concept that the use of MDC instead of MFC would improve wastewater treatment efficiency and power generation, with an added benefit of water desalination. Furthermore, RSG can successfully be employed in an MDC or MFC, enhancing the bio-electricity generation and salt removal.

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.

INFLUENCES OF PH AND CURRENT ON ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE AT A GRANULAR-GRAPHITE PACKED ELECTRODE

EPA Science Inventory

Electrolytic dechlorination using a granular-graphite packed cathode is an alternative method for the remediation of chlorinated organic compounds. Its effectiveness under various conditions needs experimental investigation. Dechlorination of trichloroethylene (TCE) was conducted...

Fabrication of a transparent conducting electrode based on graphene/silver nanowires via layer-by-layer method for organic photovoltaic devices.

PubMed

Tugba Camic, B; Oytun, Faruk; Hasan Aslan, M; Jeong Shin, Hee; Choi, Hyosung; Basarir, Fevzihan

2017-11-01

A solution-processed transparent conducting electrode was fabricated via layer-by-layer (LBL) deposition of graphene oxide (GO) and silver nanowires (Ag NWs). First, graphite was oxidized with a modified Hummer's method to obtain negatively-charged GO sheets, and Ag NWs were functionalized with cysteamine hydrochloride to acquire positively-charged silver nanowires. Oppositely-charged GO and Ag NWs were then sequentially coated on a 3-aminopropyltriethoxysilane modified glass substrate via LBL deposition, which provided highly controllable thin films in terms of optical transmittance and sheet resistance. Next, the reduction of GO sheets was performed to improve the electrical conductivity of the multilayer films. The resulting GO/Ag NWs multilayer was characterized by a UV-Vis spectrometer, field emission scanning electron microscope (FE-SEM), optical microscope (OM) and sheet resistance using a four-point probe method. The best result was achieved with a 2-bilayer film, resulting in a sheet resistance of 6.5Ω sq -1 with an optical transmittance of 78.2% at 550nm, which values are comparable to those of commercial ITO electrodes. The device based on a 2-bilayer hybrid film exhibited the highest device efficiency of 1.30% among the devices with different number of graphene/Ag NW LBL depositions. Copyright © 2017 Elsevier Inc. All rights reserved.

DNA polymorphism sensitive impedimetric detection on gold-nanoislands modified electrodes.

PubMed

Bonanni, Alessandra; Pividori, Maria Isabel; del Valle, Manel

2015-05-01

Nanocomposite materials are being increasingly used in biosensing applications as they can significantly improve biosensor performance. Here we report the use of a novel impedimetric genosensor based on gold nanoparticles graphite-epoxy nanocomposite (nanoAu-GEC) for the detection of triple base mutation deletion in a cystic-fibrosis (CF) related human DNA sequence. The developed platform consists of chemisorbing gold nano-islands surrounded by rigid, non-chemisorbing, and conducting graphite-epoxy composite. The ratio of the gold nanoparticles in the composite was carefully optimized by electrochemical and microscopy studies. Such platform allows the very fast and stable thiol immobilization of DNA probes on the gold islands, thus minimizing the steric and electrostatic repulsion among the DNA probes and improving the detection of DNA polymorphism down to 2.25fmol by using electrochemical impedance spectroscopy. These findings are very important in order to develop new and renewable platforms to be used in point-of-care devices for the detection of biomolecules. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermal treatment effects on charge storage performance of graphene-based materials for supercapacitors.

PubMed

Zhang, Hongxin; Bhat, Vinay V; Gallego, Nidia C; Contescu, Cristian I

2012-06-27

Graphene materials were synthesized by reduction of exfoliated graphite oxide and then thermally treated in nitrogen to improve the surface area and their electrochemical performance as electrical double-layer capacitor electrodes. The structural and surface properties of the prepared reduced graphite oxide (RGO) were investigated using atomic force microscopy, scanning electron microscopy, Raman spectra, X-ray diffraction pattern analysis, and nitrogen adsorption/desorption studies. RGO forms a continuous network of crumpled sheets, which consist of large amounts of few-layer and single-layer graphenes. Electrochemical studies were conducted by cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge measurements. The modified RGO materials showed enhanced electrochemical performance, with maximum specific capacitance of 96 F/g, energy density of 12.8 Wh/kg, and power density of 160 kW/kg. These results demonstrate that thermal treatment of RGO at selected conditions is a convenient and efficient method for improving its specific capacitance, energy, and power density.

Graphene oxide electrochemistry: the electrochemistry of graphene oxide modified electrodes reveals coverage dependent beneficial electrocatalysis

PubMed Central

Smith, Graham C.

2017-01-01

The modification of electrode surfaces is widely implemented in order to try and improve electron transfer kinetics and surface interactions, most recently using graphene related materials. Currently, the use of ‘as is’ graphene oxide (GO) has been largely overlooked, with the vast majority of researchers choosing to reduce GO to graphene or use it as part of a composite electrode. In this paper, ‘as is’ GO is explored and electrochemically characterized using a range of electrochemical redox probes, namely potassium ferrocyanide(II), N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), dopamine hydrochloride and epinephrine. Furthermore, the electroanalytical efficacy of GO is explored towards the sensing of dopamine hydrochloride and epinephrine via cyclic voltammetry. The electrochemical response of GO is benchmarked against pristine graphene and edge plane-/basal plane pyrolytic graphite (EPPG and BPPG respectively) alternatives, where the GO shows an enhanced electrochemical/electroanalytical response. When using GO as an electrode material, the electrochemical response of the analytes studied herein deviate from that expected and exhibit altered electrochemical responses. The oxygenated species encompassing GO strongly influence and dominate the observed voltammetry, which is crucially coverage dependent. GO electrocatalysis is observed, which is attributed to the presence of beneficial oxygenated species dictating the response in specific cases, demonstrating potential for advantageous electroanalysis to be realized. Note however, that crucial coverage based regions are observed at GO modified electrodes, owing to the synergy of edge plane sites and oxygenated species. We report the true beneficial electrochemistry of GO, which has enormous potential to be beneficially used in various electrochemical applications ‘as is’ rather than be simply used as a precursor to making graphene and is truly a fascinating member of the graphene family. PMID:29291099

Integration of a Graphite/PMMA CompositeElectrode into a Poly(methyl methacrylate) (PMMA) Substrate for Electrochemical Detection in Microchips

PubMed Central

Regel, Anne; Lunte, Susan

2013-01-01

Traditional fabrication methods for polymer microchips, the bonding of two substrates together to form the microchip, can make the integration of carbon electrodes difficult. We have developed a simple and inexpensive method to integrate graphite/PMMA composite electrodes (GPCEs) into a PMMA substrate. These substrates can be bonded to other PMMA layers using a solvent-assisted thermal bonding method. The optimal composition of the GPCEs for electrochemical detection was determined using cyclic voltammetry with dopamine as a test analyte. Using the optimized GPCEs in an all-PMMA flow cell with flow injection analysis, it was possible to detect 50 nM dopamine under the best conditions. These electrodes were also evaluated for the detection of dopamine and catechol following separation by microchip electrophoresis (ME). PMID:23670816

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...

Secondary electron emission characteristics of ion-textured copper and high-purity isotropic graphite surfaces

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1984-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion textured oxygen free high conductivity copper and untreated and ion textured high purity isotropic graphite surfaces are presented for a range of primary electron beam energies and beam impingement angles. This investigation was conducted to provide information that would improve the efficiency of multistage depressed collectors (MDC's) for microwave amplifier traveling wave tubes in space communications and aircraft applications. For high efficiency, MDC electrode surfaces must have low secondary electron emission characteristics. Although copper is a commonly used material for MDC electrodes, it exhibits relatively high levels of secondary electron emission if its surface is not treated for emission control. Recent studies demonstrated that high purity isotropic graphite is a promising material for MDC electrodes, particularly with ion textured surfaces. The materials were tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the ion textured surfaces were compared with each other and with those of untreated surfaces of the same materials. Both the untreated and ion textured graphite surfaces and the ion treated copper surface exhibited sharply reduced secondary electron emission characteristics relative to those of untreated copper. The ion treated graphite surface yielded the lowest emission levels.

Synthesis and characterization of a material derived from 4-mercaptobenzoic acid: A novel platform for oligonucleotide immobilization.

PubMed

Alves, Rafael da Fonseca; da Silva, Amanda Gonçalves; Ferreira, Lucas Franco; Franco, Diego Leoni

2017-04-01

This paper reports the electrochemical modification of pencil carbon graphite electrodes with a polymeric material derived from 4-mercaptobenzoic acid. Acidic solutions (pH 0 and 5.02) yielded an insulating polymeric film with anionic permselective properties. Scanning Electron Microscopy (SEM) analysis showed a complete coverage of the carbon graphite electrodes with a laminar-like polymeric structure. Different characterization studies indicate that the carboxyl group remained unchanged since the absorbance peak and oxidation potential did not change with the increase in pH at the pK a accounting for the carboxyl/carboxylate redox transition. The functionalized matrix was activated using carbodiimide, succinimide and an amine-modified oligonucleotide. The immobilization and hybridization processes were successfully verified using the redox electroactive indicator methylene blue, where better electrochemical signals were obtained when compared with the traditional self-assembled monolayer system. The selectivity of the system was verified using a noncomplementary target where no significant difference in electric current was observed when compared to the system containing only the probe. The method showed a good linear correlation coefficient (r 2 =0.9915), low limit of detection (1.17nmolL -1 ), and an acceptable precision (RSD=2.75%). The proposed method is suitable for further studies using different sequences of oligonucleotides. Copyright © 2016 Elsevier B.V. All rights reserved.

Ferrocene functionalized graphene based electrode for the electro-Fenton oxidation of ciprofloxacin.

PubMed

Divyapriya, Govindaraj; Nambi, Indumathi; Senthilnathan, Jaganathan

2018-05-26

Ferrocene functionalized graphene based graphite felt electrode was firstly investigated for heterogeneous electro-Fenton oxidation of ciprofloxacin in neutral pH condition. Electrochemical reduction of Ferrocene functionalized graphene oxide (Fc-ErGO) was performed by cyclic voltammetry technique. At neutral pH condition, Fc-ErGO electrode (0.035 min ─1 ) exhibited ∼3 times and ∼9 times higher removal rates in comparison with plane ErGO (0.010 min ─1 ) and plane graphite felt (0.004 min ─1 ) electrodes respectively. The effect of pH and applied potential were studied for the degradation of ciprofloxacin in Fc-ErGO based electrode. Higher removal rate was observed at acidic pH (0.222 min ─1 ), whereas alkaline pH showed lower removal efficiency (0.014 min ─1 ). > 99% removal of ciprofloxacin was achieved with in 15 min and 120 min of reactions period at pH 3.0 and pH 7.0, respectively. H 2 O 2 generation was found to be high in plane ErGO electrode system in all of the pH conditions. Owing to the high redox ability of ferrocene, Fc-ErGO electrode generated high concentration of OH radicals (426 μM pH 3.0; 247 μM pH 7.0; 210 μM pH 9.0) than ErGO and plane graphite felt electrodes; The electrode reusability study was performed to understand the electrode stability. There was no significant change in removal efficiency even after the 5th cycle of reusability study at both acidic and neutral conditions. The possible mechanism of oxidation in Fc-ErGO based electro-Fenton process was also proposed based on the continuous monitoring of H 2 O 2 and OH radicals generated in the system. Copyright © 2018. Published by Elsevier Ltd.

Formation of Reversible Solid Electrolyte Interface on Graphite Surface from Concentrated Electrolytes

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

Lu, Dongping; Tao, Jinhui; Yan, Pengfei

2017-02-10

Interfacial phenomena have always been key determinants for the performance of energy storage technologies. The solid electrolyte interfacial (SEI) layer, pervasive on the surfaces of battery electrodes for numerous chemical couples, directly affects the ion transport, charge transfer and lifespan of the entire energy system. Almost all SEI layers, however, are unstable resulting in the continuous consumption of the electrolyte. Typically, this leads to the accumulation of degradation products on/restructuring of the electrode surface and thus increased cell impedance, which largely limits the long-term operation of the electrochemical reactions. Herein, a completely new SEI formation mechanism has been discovered, inmore » which the electrolyte components reversibly self-assemble into a protective surface coating on a graphite electrode upon changing the potential. In contrast to the established wisdom regarding the necessity of employing the solvent ethylene carbonate (EC) to form a protective SEI layer on graphite, a wide range of EC-free electrolytes are demonstrated for the reversible intercalation/deintercalation of Li+ cations within a graphite lattice, thereby providing tremendous flexibility in electrolyte tailoring for battery couples. This novel finding is broadly applicable and provides guidance for how to control interfacial reactions through the relationship between ion aggregation and solvent decomposition at polarized interfaces.« less

Electrochemical Sensor Based on Rh(III) Ion-Imprinted Polymer as a New Modifying Agent for Rhodium Determination.

PubMed

Bai, Huiping; Xiong, Caiyun; Wang, Chunqiong; Liu, Peng; Dong, Su; Cao, Qiue

2018-05-01

A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.

Amine oxidase-based biosensors for spermine and spermidine determination.

PubMed

Boffi, Alberto; Favero, Gabriele; Federico, Rodolfo; Macone, Alberto; Antiochia, Riccarda; Tortolini, Cristina; Sanzó, Gabriella; Mazzei, Franco

2015-02-01

The present work describes the development and optimization of electrochemical biosensors for specific determination of the biogenic polyamine spermine (Spm) and spermidine (Spmd) whose assessment represents a novel important analytical tool in food analysis and human diagnostics. These biosensors have been prepared using novel engineered enzymes: polyamine oxidase (PAO) endowed with selectivity towards Spm and Spmd and spermine oxidase (SMO) characterized by strict specificity towards Spm. The current design entails biosensors in which the enzymes were entrapped in poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ), a photocrosslinkable gel, onto an electrode surface. Screen-printed electrodes (SPEs) were used as electrochemical transducers for enzymatically produced hydrogen peroxide, operating at different potential vs Ag/AgCl according to the material of the working electrode (WE): +700 mV for graphite (GP) or -100 mV for Prussian blue (PB)-modified SPE, respectively. Biosensor performances were evaluated by means of flow injection amperometric (FIA) measurements. The modified electrodes showed good sensitivity, long-term stability and reproducibility. Under optimal conditions, the PAO biosensor showed a linear range 0.003-0.3 mM for Spm and 0.01-0.4 mM for Spmd, while with the SMO biosensor, a linear range of 0.004-0.5 mM for Spm has been obtained. The main kinetic parameters apparent Michaelis constant (K M), turnover number (K cat) and steady-state current (I max) were determined. The proposed device was then applied to the determination of biogenic amines in blood samples. The results obtained were in good agreement with those obtained with the GC-MS reference method.

Stacked graphene nanofibers for electrochemical oxidation of DNA bases.

PubMed

Ambrosi, Adriano; Pumera, Martin

2010-08-21

In this article, we show that stacked graphene nanofibers (SGNFs) demonstrate superior electrochemical performance for oxidation of DNA bases over carbon nanotubes (CNTs). This is due to an exceptionally high number of accessible graphene sheet edges on the surface of the nanofibers when compared to carbon nanotubes, as shown by transmission electron microscopy and Raman spectroscopy. The oxidation signals of adenine, guanine, cytosine, and thymine exhibit two to four times higher currents than on CNT-based electrodes. SGNFs also exhibit higher sensitivity than do edge-plane pyrolytic graphite, glassy carbon, or graphite microparticle-based electrodes. We also demonstrate that influenza A(H1N1)-related strands can be sensitively oxidized on SGNF-based electrodes, which could therefore be applied to label-free DNA analysis.

EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE

EPA Science Inventory

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE.

EPA Science Inventory

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

Catalytic Graphitization for Preparation of Porous Carbon Material Derived from Bamboo Precursor and Performance as Electrode of Electrical Double-Layer Capacitor

NASA Astrophysics Data System (ADS)

Tsubota, Toshiki; Maguchi, Yuta; Kamimura, Sunao; Ohno, Teruhisa; Yasuoka, Takehiro; Nishida, Haruo

2015-12-01

The combination of addition of Fe (as a catalyst for graphitization) and CO2 activation (a kind of gaseous activation) was applied to prepare a porous carbon material from bamboo powder (a waste product of superheated steam treatment). Regardless of the heat treatment temperature, many macropores were successfully formed after the heating process by removal of Fe compounds. A turbostratic carbon structure was generated in the Fe-added sample heated at 850°C. It was confirmed that the added Fe acted as a template for pore formation. Moreover, it was confirmed that the added Fe acted as a catalyst for graphitization. The resulting electrochemical performance as the electrode of an electrical double-layer capacitor, as demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge testing, could be explained based on the graphitization and activation effects. Addition of Fe could affect the electrical properties of carbon material derived from bamboo.

Electron transfer kinetics on natural crystals of MoS2 and graphite.

PubMed

Velický, Matěj; Bissett, Mark A; Toth, Peter S; Patten, Hollie V; Worrall, Stephen D; Rodgers, Andrew N J; Hill, Ernie W; Kinloch, Ian A; Novoselov, Konstantin S; Georgiou, Thanasis; Britnell, Liam; Dryfe, Robert A W

2015-07-21

Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.

Sensitive detection of cyclophosphamide using DNA-modified carbon paste, pencil graphite and hanging mercury drop electrodes.

PubMed

Palaska, P; Aritzoglou, E; Girousi, S

2007-05-15

The interaction of cyclophosphamide (CP) with calf thymus double-stranded DNA (dsDNA) and thermally denatured single-stranded DNA (ssDNA) immobilized at the carbon paste (CPE) and pencil graphite electrodes (PGE), was studied electrochemically based on oxidation signals of guanine and adenine using differential pulse voltammetry (DPV). As a result of the interaction of CP with DNA, the voltammetric signals of guanine and adenine increased in the case of dsDNA while a slight increase was observed in ssDNA. The effect of experimental parameters such as the interaction time between CP and DNA forms and the concentration of CP, were studied using DPV with CPE and PGE. Additionally, reproducibility and detection limits were determined using both electrodes. A comparison of the analytical performance between CPE and PGE was done. Our results showed that these two different DNA biosensors could be used for the sensitive, rapid and cost effective detection of CP itself as well as of CP-DNA interaction. Furthermore, the interaction of CP with dsDNA and ssDNA was studied in solution and at the electrode surface by means of alternating current voltammetry (ACV) in 0.3M NaCl and 50mM sodium phosphate buffer (pH 8.5) supporting electrolyte, using a hanging mercury drop electrode (HMDE) as working electrode. The conclusions of this study were mainly based on tensammetric peaks I (at -1.183V) and II (-1.419V) of DNA. This study involved the interaction of CP with surface-confined and solution phase DNA where experimental parameters, such as the concentration of CP and the interaction time, were studied. By increasing the concentration of CP, an increase of peak II was observed in both ds and ssDNA, while an increase of peak I was observed only in the case of dsDNA. An overall conclusion of the study using HMDE was that the interaction of CP with surface-confined DNA significantly differed from that with solution phase DNA. The increase of peaks I and II was lower in the case of interaction of CP with surface-confined DNA, probably due to steric positioning of DNA at the electrode surface.

Nitrogen-doped diamond electrode shows high performance for electrochemical reduction of nitrobenzene.

PubMed

Zhang, Qing; Liu, Yanming; Chen, Shuo; Quan, Xie; Yu, Hongtao

2014-01-30

Effective electrode materials are critical to electrochemical reduction, which is a promising method to pre-treat anti-oxidative and bio-refractory wastewater. Herein, nitrogen-doped diamond (NDD) electrodes that possess superior electrocatalytic properties for reduction were fabricated by microwave-plasma-enhanced chemical vapor deposition technology. Nitrobenzene (NB) was chosen as the probe compound to investigate the material's electro-reduction activity. The effects of potential, electrolyte concentration and pH on NB reduction and aniline (AN) formation efficiencies were studied. NDD exhibited high electrocatalytic activity and selectivity for reduction of NB to AN. The NB removal efficiency and AN formation efficiency were 96.5% and 88.4% under optimal conditions, respectively; these values were 1.13 and 3.38 times higher than those of graphite electrodes. Coulombic efficiencies for NB removal and AN formation were 27.7% and 26.1%, respectively; these values were 4.70 and 16.6 times higher than those of graphite electrodes under identical conditions. LC-MS analysis revealed that the dominant reduction pathway on the NDD electrode was NB to phenylhydroxylamine (PHA) to AN. Copyright © 2013 Elsevier B.V. All rights reserved.

Bismuth nanoparticle decorating graphite felt as a high-performance electrode for an all-vanadium redox flow battery.

PubMed

Li, Bin; Gu, Meng; Nie, Zimin; Shao, Yuyan; Luo, Qingtao; Wei, Xiaoliang; Li, Xiaolin; Xiao, Jie; Wang, Chongmin; Sprenkle, Vincent; Wang, Wei

2013-03-13

Employing electrolytes containing Bi(3+), bismuth nanoparticles are synchronously electrodeposited onto the surface of a graphite felt electrode during operation of an all-vanadium redox flow battery (VRFB). The influence of the Bi nanoparticles on the electrochemical performance of the VRFB is thoroughly investigated. It is confirmed that Bi is only present at the negative electrode and facilitates the redox reaction between V(II) and V(III). However, the Bi nanoparticles significantly improve the electrochemical performance of VRFB cells by enhancing the kinetics of the sluggish V(II)/V(III) redox reaction, especially under high power operation. The energy efficiency is increased by 11% at high current density (150 mA·cm(-2)) owing to faster charge transfer as compared with one without Bi. The results suggest that using Bi nanoparticles in place of noble metals offers great promise as high-performance electrodes for VRFB application.

Evaluation of exposure to polycyclic aromatic hydrocarbons in a coke production and a graphite electrode manufacturing plant: assessment of urinary excretion of 1-hydroxypyrene as a biological indicator of exposure.

PubMed Central

Buchet, J P; Gennart, J P; Mercado-Calderon, F; Delavignette, J P; Cupers, L; Lauwerys, R

1992-01-01

OBJECTIVES--Characterisation of the airborne concentration of 13 polycyclic aromatic hydrocarbons (PAHs) at various workplaces in a graphite electrode and a coke production plant. Validation of the urinary excretion of 1-hydroxypyrene (hydroxypyrene) as a biological marker of exposure to PAH. DESIGN--Cross sectional study of workers exposed to PAHs (106 in the graphite electrode producing plant and 16 in the coke works). METHODS--Personal air sampling during at least six hours per workshift using a glass fibre filter and a Chromosorb 102 solid sorbent tube and analysis of PAHs by high performance liquid chromatography (HPLC) and spectrofluorometric detection (SFD). Collection of spot urine samples before and after the shift and analysis of 1-hydroxypyrene by HPLC and SFD. RESULTS--The workers most exposed to PAHs were those occupied at the topside area of the coke oven plant and those working in the blending and impregnation areas of the graphite electrode producing plant (mean airborne concentration of total PAHs: 199 and 223 micrograms/m3 respectively). Except for naphthalene and perylene, the relative proportion of the different PAHs did not differ between the plants. Pyrene concentration in air was highly correlated with the total airborne PAH concentration (r = 0.83, p < 0.0001) and the correlation coefficients between hydroxypyrene concentration in postshift urine samples and pyrene or total PAHs in air were 0.67 (p < 0.0001) and 0.72 (p < 0.0001) respectively. Excretion of hydroxypyrene doubled when the exposure to pyrene in air increased 10-fold. The half life for the urinary excretion of hydroxypyrene was around 18 hours (95% confidence interval 16.1-19.8). Smoking habits only explained 2.3% of the variance in hydroxypyrene excretion compared with 45% for the pyrene concentration in air. CONCLUSION--The determination of the urinary excretion of hydroxypyrene in postshift urine samples can be used as a suitable biomarker to assess individual exposure to PAHs in coke ovens and in graphite electrode manufacturing plants. PMID:1463676

A Highly Efficient and Facile Approach for Fabricating Graphite Nanoplatelets

NASA Astrophysics Data System (ADS)

Van Thanh, Dang; Van Thien, Nguyen; Thang, Bui Hung; Van Chuc, Nguyen; Hong, Nguyen Manh; Trang, Bui Thi; Lam, Tran Dai; Huyen, Dang Thi Thu; Hong, Phan Ngoc; Minh, Phan Ngoc

2016-05-01

In this study, we report a highly efficient, convenient, and cost-effective technique for producing graphite nanoplatelets (GNPs) from plasma-expanded graphite oxides (PEGOs) obtained directly from low-cost, recycled graphite electrodes of used batteries, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy confirmed the successful preparation of GNPs. Scanning electron microscopy revealed that the GNPs have lateral width from several hundreds of nanometers to 1.5 μm with an approximate thickness of 20-50 nm. These GNPs can serve as a precursor for the preparation of GNPs-based nanocomposite.

Thermally exfoliated graphite oxide

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

2011-01-01

A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine.

PubMed

Zöllig, Hanspeter; Fritzsche, Cristina; Morgenroth, Eberhard; Udert, Kai M

2015-02-01

Electrolysis can be a viable technology for ammonia removal from source-separated urine. Compared to biological nitrogen removal, electrolysis is more robust and is highly amenable to automation, which makes it especially attractive for on-site reactors. In electrolytic wastewater treatment, ammonia is usually removed by indirect oxidation through active chlorine which is produced in-situ at elevated anode potentials. However, the evolution of chlorine can lead to the formation of chlorate, perchlorate, chlorinated organic by-products and chloramines that are toxic. This study focuses on using direct ammonia oxidation on graphite at low anode potentials in order to overcome the formation of toxic by-products. With the aid of cyclic voltammetry, we demonstrated that graphite is active for direct ammonia oxidation without concomitant chlorine formation if the anode potential is between 1.1 and 1.6 V vs. SHE (standard hydrogen electrode). A comparison of potentiostatic bulk electrolysis experiments in synthetic stored urine with and without chloride confirmed that ammonia was removed exclusively by continuous direct oxidation. Direct oxidation required high pH values (pH > 9) because free ammonia was the actual reactant. In real stored urine (pH = 9.0), an ammonia removal rate of 2.9 ± 0.3 gN·m(-2)·d(-1) was achieved and the specific energy demand was 42 Wh·gN(-1) at an anode potential of 1.31 V vs. SHE. The measurements of chlorate and perchlorate as well as selected chlorinated organic by-products confirmed that no chlorinated by-products were formed in real urine. Electrode corrosion through graphite exfoliation was prevented and the surface was not poisoned by intermediate oxidation products. We conclude that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: The formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material. Copyright © 2014 Elsevier Ltd. All rights reserved.

Glucose biosensor based on functionalized ZnO nanowire/graphite films dispersed on a Pt electrode

NASA Astrophysics Data System (ADS)

Gallay, P.; Tosi, E.; Madrid, R.; Tirado, M.; Comedi, D.

2016-10-01

We present a glucose biosensor based on ZnO nanowire self-sustained films grown on compacted graphite flakes by the vapor transport method. Nanowire/graphite films were fragmented in water, filtered to form a colloidal suspension, subsequently functionalized with glucose oxidase and finally transferred to a metal electrode (Pt). The obtained devices were evaluated using scanning electron microscopy, energy-dispersive x-ray spectroscopy, cyclic voltammetry and chronoamperometry. The electrochemical responses of the devices were determined in buffer solutions with successive glucose aggregates using a tripolar electrode system. The nanostructured biosensors showed excellent analytical performance, with linear response to glucose concentrations, high sensitivity of up to ≈17 μA cm-2 mM-1 in the 0.03-1.52 mM glucose concentration range, relatively low Michaelis-Menten constant, excellent reproducibility and a fast response. The detection limits are more than an order of magnitude lower than those achievable in commercial biosensors for glucose control, which is promising for the development of glucose monitoring methods that do not require blood extraction from potentially diabetic patients. The strong detection enhancements provided by the functionalized nanostructures are much larger than the electrode surface-area increase and are discussed in terms of the physical and chemical mechanisms involved in the detection and transduction processes.

Anodic Stripping Voltammetry with Pencil Graphite Electrode for Determination of Chromium (III)

NASA Astrophysics Data System (ADS)

Wyantuti, S.; Hafidza, R. A.; Ishmayana, S.; Hartati, Y. W.

2017-02-01

Chromium is required as micronutrient that has roles in insulin metabolism and blood glucose level regulation. Chromium (III) deficiency can cause hyperglycemia and glycosuria. However, a high amount of chromium in body can cause allergic reaction, organ damage, and even death because of its toxicity. Chromium is commonly used in steel industries. Simultaneously with the development of industry, the waste disposal that can endanger environment also increased. Therefore, a sensitive and specific analysis method for chromium detection is required. Stripping voltammetry is one of the voltammetric methods that is commonly used for heavy metal analysis due to the very low limit of detection (sub ppb). The present study was conducted to develop an analysis method for chromium (III) determination using pencil graphite electrode. Quantitative determination was performed for chromium (III) which measured at -0.8 to +1.0 V with deposition time for 60 s and 50 mV/s scan rate. Stripping voltammetric analysis of chromium (III) using pencil graphite electrode gave linear range at 12.5 to 75 ppm with limit of detection of 0.31 ppm.

HOPG/ZnO/HOPG pressure sensor

NASA Astrophysics Data System (ADS)

Jahangiri, Mojtaba; Yousefiazari, Ehsan; Ghalamboran, Milad

2017-12-01

Pressure sensor is one of the most commonly used sensors in the research laboratories and industries. These are generally categorized in three different classes of absolute pressure sensors, gauge pressure sensors, and differential pressure sensors. In this paper, we fabricate and assess the pressure sensitivity of the current vs. voltage diagrams in a graphite/ZnO/graphite structure. Zinc oxide layers are deposited on highly oriented pyrolytic graphite (HOPG) substrates by sputtering a zinc target under oxygen plasma. The top electrode is also a slice of HOPG which is placed on the ZnO layer and connected to the outside electronic circuits. By recording the I-V characteristics of the device under different forces applied to the top HOPG electrode, the pressure sensitivity is demonstrated; at the optimum biasing voltage, the device current changes 10 times upon changing the pressure level on the top electrode by 20 times. Repeatability and reproducibility of the observed effect is studied on the same and different samples. All the materials used for the fabrication of this pressure sensor are biocompatible, the fabricated device is anticipated to find potential applications in biomedical engineering.

Removal of metals from aqueous solution and sea water by functionalized graphite nanoplatelets based electrodes.

PubMed

Mishra, Ashish Kumar; Ramaprabhu, S

2011-01-15

In the present wok, we have demonstrated the simultaneous removal of sodium and arsenic (pentavalent and trivalent) from aqueous solution using functionalized graphite nanoplatelets (f-GNP) based electrodes. In addition, these electrodes based water filter was used for multiple metals removal from sea water. Graphite nanoplatelets (GNP) were prepared by acid intercalation and thermal exfoliation. Functionalization of GNP was done by further acid treatment. Material was characterized by different characterization techniques. Performance of supercapacitor based water filter was analyzed for the removal of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water, using cyclic voltametry (CV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic (both trivalent and pentavalent). Maximum adsorption capacities of 27, 29 and 32 mg/g for arsenate, arsenite and sodium were achieved in addition to good removal efficiency for sodium, magnesium, calcium and potassium from sea water. Copyright © 2010 Elsevier B.V. All rights reserved.

Performance and Surface Integrity of Ti6Al4V After Sinking EDM with Special Graphite Electrodes

NASA Astrophysics Data System (ADS)

Amorim, Fred L.; Stedile, Leandro J.; Torres, Ricardo D.; Soares, Paulo C.; Henning Laurindo, Carlos A.

2014-04-01

Titanium and its alloys have high chemical reactivity with most of the cutting tools. This makes it difficult to work with these alloys using conventional machining processes. Electrical discharge machining (EDM) emerges as an alternative technique to machining these materials. In this work, it is investigated the performance of three special grades of graphite as electrodes when ED-Machining Ti6Al4V samples under three different regimes. The main influences of electrical parameters are discussed for the samples material removal rate, volumetric relative wear and surface roughness. The samples surfaces were evaluated using SEM images, microhardness measurements, and x-ray diffraction. It was found that the best results for samples material removal rate, surface roughness, and volumetric relative wear were obtained for the graphite electrode with 10-μm particle size and negative polarity. For all samples machined by EDM and characterized by x-ray (XRD), it was identified the presence of titanium carbides. For the finish EDM regimes, the recast layer presents an increased amount of titanium carbides compared to semi-finish and rough regimes.

Excimer laser assisted very fast exfoliation and reduction of graphite oxide at room temperature under air ambient for Supercapacitors electrode

NASA Astrophysics Data System (ADS)

Malek Hosseini, S. M. B.; Baizaee, S. M.; Naderi, Hamid Reza; Dare Kordi, Ali

2018-01-01

Excimer laser was used for reduction and exfoliation of graphite oxide (GO) at room temperature under air ambient. The prepared excimer laser reduced graphite oxide (XLRGO) is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption (BET method), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption techniques for surface, structural functional groups and band gap analysis. Electrochemical properties are investigated using cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS) and continues cyclic voltammetry (CCV) in 0.5 M Na2SO4 as electrolyte. Electrochemical investigations revealed that XLRGO electrode has enhanced supercapacitive performance including specific capacitance of 299 F/g at a scan rate of 2 mV/s. Furthermore, CCV measurement showed that XLRGO electrode kept 97.8% of its initial capacitance/capacity after 4000 cycles. The obtained results from electrochemical investigations confirm that the reduction of GO by using an excimer laser produces high-quality graphene for supercapacitor applications without the need for additional operations.

The application of exfoliated graphite electrode in the electrochemical degradation of p-nitrophenol in water.

PubMed

Ntsendwana, Bulelwa; Peleyeju, Moses G; Arotiba, Omotayo A

2016-01-01

We report the application of exfoliated graphite (EG) as an electrode material in the electrochemical degradation of p-nitrophenol in water. Bulk electrolysis (degradation) of p-nitrophenol was carried out at a potential of 2.0 V (vs. Ag/AgCl) in the presence of 0.1 M Na2SO4 supporting electrolyte, while UV-Vis spectrophotometry was used to monitor the degradation efficiency. An initial p-nitrophenol load concentration of 0.2 mM for 3 h electrolysis time was studied under the optimized conditions of pH 7, and 10 mAcm(-2) current density. The electro-degradation reaction displayed a pseudo-first-order kinetic behavior with a rate constant (k(r)) of 11×10(-3) min(-1). The removal efficiency was found to be 91.5%. Chromatography coupled with time of flight mass spectrometry revealed p-benzoquinone as a major intermediate product. These results demonstrate the potential and viability of electrochemical technology as an alternative approach to water treatment using a low cost graphite electrode.

Electrochemical disinfection of simulated ballast water on PbO2/graphite felt electrode.

PubMed

Chen, Shuiping; Hu, Weidong; Hong, Jianxun; Sandoe, Steve

2016-04-15

A novel PbO2/graphite felt electrode was constructed by electrochemical deposition of PbO2 on graphite felt and characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) analysis. The prepared electrode is a viable technology for inactivation of Escherichia coli, Enterococcus faecalis, and Artemia salina as indicator organisms in simulated ballast water treatment, which meets the International Maritime Organization (IMO) Regulation D-2. The effects of contact time and current density on inactivation were investigated. An increase in current density generally had a beneficial effect on the inactivation of the three species. E.faecalis and A.salina were more resistant to electrochemical disinfection than E. coli. The complete disinfection of E.coli was achieved in <8min at an applied current density of 253A/m(2). Complete inactivation of E. faecalis and A.salina was achieved at the same current density after 60 and 40min of contact time, respectively. A. salina inactivation follows first-order kinetics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Performance evaluation of thermally treated graphite felt electrodes for vanadium redox flow battery and their four-point single cell characterization

NASA Astrophysics Data System (ADS)

Mazúr, P.; Mrlík, J.; Beneš, J.; Pocedič, J.; Vrána, J.; Dundálek, J.; Kosek, J.

2018-03-01

In our contribution we study the electrocatalytic effect of oxygen functionalization of thermally treated graphite felt on kinetics of electrode reactions of vanadium redox flow battery. Chemical and morphological changes of the felts are analysed by standard physico-chemical characterization techniques. A complex method four-point method is developed and employed for characterization of the felts in a laboratory single-cell. The method is based on electrochemical impedance spectroscopy and load curves measurements of positive and negative half-cells using platinum wire pseudo-reference electrodes. The distribution of ohmic and faradaic losses within a single-cell is evaluated for both symmetric and asymmetric electrode set-up with respect to the treatment conditions. Positive effect of oxygen functionalization is observed only for negative electrode, whereas kinetics of positive electrode reaction is almost unaffected by the treatment. This is in a contradiction to the results of typically employed cyclovoltammetric characterization which indicate that both electrodes are enhanced by the treatment to a similar extent. The developed four-point characterization method can be further used e.g., for the component screening and in-situ durability studies on single-cell scale redox flow batteries of various chemistries.

3D-Graphene supports for palladium nanoparticles: Effect of micro/macropores on oxygen electroreduction in Anion Exchange Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

Kabir, Sadia; Serov, Alexey; Atanassov, Plamen

2018-01-01

Hierarchically structured 3D-Graphene nanosheets as supports for palladium nanoparticles (Pd/3D-GNS) were fabricated using the Sacrificial Support Method. The pore size distribution of the 3D-GNS supports were tuned by utilizing smaller and larger sized sacrificial silica templates, EH5 and L90. Using a combination of Scanning Electron Microscopy (SEM), N2 sorption and Rotating Ring Disc Electrode (RRDE) technique, it was demonstrated that the EH5 and L90 modified 3D-GNS supports had higher percentage of micro- (<2 nm) and macropores (>50 nm), respectively. The templated pores also played a role in enhancing the oxygen reduction reaction (ORR) as well as membrane electrode assembly (MEA) performance of the Pd nanoparticles in comparison to non-porous 2D-GNS supports. Particularly, incorporation of micropores increased peroxide generation at higher potentials whereas presence of macropores increased both limiting current densities and reduce peroxide yields. Integration of the Pd/GNS nanocomposites into a H2/O2 fed Anion Exchange Membrane Fuel Cell (AEMFC) operating at 60 °C also demonstrated the effect of modified porosity on concentration polarization or transport losses at high current densities. This strategy for the tunable synthesis of hierarchically 3D porous graphitized supports offers a platform for developing morphologically modified nanomaterials for energy conversion.

Morphological changes of porphine films on graphite by perchloric and phosphoric electrolytes. An electrochemical-AFM study

NASA Astrophysics Data System (ADS)

Yivlialin, Rossella; Penconi, Marta; Bussetti, Gianlorenzo; Biroli, Alessio Orbelli; Finazzi, Marco; Duò, Lamberto; Bossi, Alberto

2018-06-01

Organic molecules have been proposed as promising candidates for electrode protection in acidic electrolytes. The use of tetraphenyl-porphines (H2TPP) as graphite surface-protecting agents in sulphuric acid (H2SO4) is one of the newest. With the aim of unveiling the mechanism of such a protective effect, in this paper we test the stability of a H2TPP thin film immersed in perchloric and phosphoric acid solutions that differently interact with porphyrins. The protective role of H2TPP is tested in the electrochemical potential range where the pristine graphite undergoes an oxidation process that erodes the surface and eventually exfoliate the stratified crystal. The electrochemical analysis is performed in a three-electrode cell, while the surface morphology is monitored ex-situ and in-situ by atomic force microscopy. Electrospray mass analysis is also employed to investigate the presence of H2TPP fragments in the solution. We find that the organic film is not stable in perchloric solution, while it is stable and avoids graphite surface corrosion in phosphoric acid solution. These results provide a rationale for the role played by free-base porphines in graphite protection.

Degradation of lithium ion batteries employing graphite negatives and nickel-cobalt-manganese oxide + spinel manganese oxide positives: Part 2, chemical-mechanical degradation model

NASA Astrophysics Data System (ADS)

Purewal, Justin; Wang, John; Graetz, Jason; Soukiazian, Souren; Tataria, Harshad; Verbrugge, Mark W.

2014-12-01

Capacity fade is reported for 1.5 Ah Li-ion batteries containing a mixture of Li-Ni-Co-Mn oxide (NCM) + Li-Mn oxide spinel (LMO) as positive electrode material and a graphite negative electrode. The batteries were cycled at a wide range of temperatures (10 °C-46 °C) and discharge currents (0.5C-6.5C). The measured capacity losses were fit to a simple physics-based model which calculates lithium inventory loss from two related mechanisms: (1) mechanical degradation at the graphite anode particle surface caused by diffusion-induced stresses (DIS) and (2) chemical degradation caused by lithium loss to continued growth of the solid-electrolyte interphase (SEI). These two mechanisms are coupled because lithium is consumed through SEI formation on newly exposed crack surfaces. The growth of crack surface area is modeled as a fatigue phenomenon due to the cyclic stresses generated by repeated lithium insertion and de-insertion of graphite particles. This coupled chemical-mechanical degradation model is consistent with the observed capacity loss features for the NCM + LMO/graphite cells.

PREPARATION AND CHARACTERIZATION OF MOLECULARLY IMPRINTED ELECTROPOLYMERIZED CARBON ELECTRODES

EPA Science Inventory

Molecularly imprinted polymers (MIP) selective for fluorescein, rhodamine or 2,4-dichlorophenoxyacetic acid (2,4-D) were electropolymerized onto graphite electrodes using an aqueous solution equimolar in resorsinol/ortho-phenylenediamine and in the presence of the template mole...

Electrochemical cell

DOEpatents

Kaun, Thomas D.

1984-01-01

An improved secondary electrochemical cell is disclosed having a negative electrode of lithium aluminum, a positive electrode of iron sulfide, a molten electrolyte of lithium chloride and potassium chloride, and the combination that the fully charged theoretical capacity of the negative electrode is in the range of 0.5-1.0 that of the positive electrode. The cell thus is negative electrode limiting during discharge cycling. Preferably, the negative electrode contains therein, in the approximate range of 1-10 volume % of the electrode, an additive from the materials of graphitized carbon, aluminum-iron alloy, and/or magnesium oxide.

Electrochemical cell

DOEpatents

Kaun, T.D.

An improved secondary electrochemical cell is disclosed having a negative electrode of lithium aluminum, a positive electrode of iron sulfide, a molten electrolyte of lithium chloride and potassium chloride, and the combination that the fully charged theoretical capacity of the negative electrode is in the range of 0.5 to 1.0 that of the positive electrode. The cell thus is negative electrode limiting during discharge cycling. Preferably, the negative electrode contains therein, in the approximate range of 1 to 10 volume % of the electrode, an additive from the materials of graphitized carbon, aluminum-iron alloy, and/or magnesium oxide.

76 FR 56397 - Small Diameter Graphite Electrodes from the People's Republic of China: Final Results of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-13

... value (``SV'') information: SGL Carbon LLC and Superior Graphite Co. (``Petitioners''); Fushun Jinly Petrochemical Carbon Co., Ltd. (``Fushun Jinly''); and Beijing Fangda Carbon Tech Co., Ltd. (``Beijing Fangda''), Chengdu Rongguang Carbon Co., Ltd. (``Rongguang''), Fangda Carbon New Material Co., Ltd. (``Fangda Carbon...

ELECTROCHEMICAL DEGRADATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES: IDENTIFICATION AND QUALIFICATION OF DECHLORINATION PRODUCTS

EPA Science Inventory

TCE was successfully dechlorinated in aqueous solution using granular graphite as the cathode in a mixed electrochemical reactor. In experiments with an initial TCE concentration of less than 100 mg/l, TCE was reduced approximately by 75% in the reactor under an applied cell volt...

Ion sputter textured graphite electrode plates

NASA Technical Reports Server (NTRS)

Curren, A. N.; Forman, R.; Sovey, J. S.; Wintucky, E. G. (Inventor)

1983-01-01

A specially textured surface of pyrolytic graphite exhibits extremely low yields of secondary electrons and reduced numbers of reflected primary electrons after impingement of high energy primary electrons. Electrode plates of this material are used in multistage depressed collectors. An ion flux having an energy between 500 iV and 1000 iV and a current density between 1.0 mA/sq cm and 6.0 mA/sq cm produces surface roughening or texturing which is in the form of needles or spires. Such textured surfaces are especially useful as anode collector plates in high tube devices.

76 FR 12325 - Small Diameter Graphite Electrodes From the People's Republic of China: Preliminary Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-07

... Group). 26 Haimen Shuguang Carbon Industry Co., Ltd. 27 Handan Hanbo Material Co., Ltd. 28 Hebei Long Great Wall Electrode Co., Ltd. (aka Chang Cheng Chang Electrode Co., Ltd. and Laishui Long Great Wall... Inner Mongolia Xinghe County Hongyuan Electrical Carbon Factory. 35 Jiang Long Carbon. 36 Jiangsu Yafei...

Amperometric Enzyme Electrodes

DTIC Science & Technology

1989-12-01

form of carbon (glascy carbon , graphite, reticulated vitreous carbon , carbon paste, fiber or foil). Carbon is favored for enzyme immoblization...the surface for covalent bonding. The most frequently used electrode material, glassy carbon , often displays complex behavior. Although attempts have...Mixed Carbon Paste Electrode with an Immobilized Layer of D-Gluconate Dehydrogenase from Bacteral Membranes," Agric. Biol. Chelm., 51 (1987), 747-754

Simultaneous/Selective Detection of Dopamine and Ascorbic Acid at Synthetic Zeolite-Modified/Graphite-Epoxy Composite Macro/Quasi-Microelectrodes

PubMed Central

Ilinoiu, Elida Cristina; Manea, Florica; Serra, Pier Andrea; Pode, Rodica

2013-01-01

The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications. PMID:23736851

Simultaneous/selective detection of dopamine and ascorbic acid at synthetic zeolite-modified/graphite-epoxy composite macro/quasi-microelectrodes.

PubMed

Ilinoiu, Elida Cristina; Manea, Florica; Serra, Pier Andrea; Pode, Rodica

2013-06-03

The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications.

Rate capability improvement of Co-Ni double hydroxides integrated in cathodically partially exfoliated graphite

NASA Astrophysics Data System (ADS)

Cai, Xiang; Song, Yu; Sun, Zhen; Guo, Di; Liu, Xiao-Xia

2017-10-01

In-situ growing of energy storage materials on graphene-based substrates/current collectors with low defect is a good way to boost electron transport and so enhance rate capability for the obtained electrode. Herein, high-quality graphene-like nanopetals are partially exfoliated from graphite foil (GF) through a facile and fast cathodic process. Three-dimensional porous structure is established for the afforded cathodically-exfoliated graphite foil (CEG), with many graphene-like nanopetals vertically anchoring on the graphite substrate. A hierarchical structure is constructed by the following electrochemical growth of Co-Ni double hydroxide nanopetals on the graphene atop CEG. The double hydroxide in the obtained electrode with the optimized Co2+/Ni2+ molar ratio, Co0.75Ni0.25(OH)2-CEG, displays much improved rate capability and so can deliver a high specific capacitance of 1460 F g-1 at an ultra-high current density of 100 A g-1. An asymmetric device is assembled by using Co0.75Ni0.25(OH)2-CEG as cathode, which demonstrates a high energy density of 31.6 Wh kg-1 at an ultra-high power density of 21.5 kW kg-1, showing the potential of the hierarchical composite electrode for high power application. The device also displays good stability, it can retain more than 90% of its capacitance after 10000 galvanostatic charge-discharge cycles.

An Ultrahigh Capacity Graphite/Li 2S Battery with Holey-Li 2S Nanoarchitectures

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

Ye, Fangmin; Noh, Hyungjun; Lee, Hongkyung

The pairing of high-capacity Li 2S cathode (1166 mAh g -1) and lithium-free anode (LFA) provides an unparalleled potential in developing safe and energy-dense next-generation secondary batteries. However, the low utilization of the Li 2S cathode and the lack of electrolytes compatible to both electrodes are impeding the development. Here, a novel graphite/Li 2S battery system, which features a self-assembled, holey-Li 2S nanoarchitecture and a stable solid electrolyte interface (SEI) on the graphite electrode, is reported. The holey structure on Li 2S is beneficial in decomposing Li 2S at the first charging process due to the enhanced Li ion extractionmore » and transfer from the Li 2S to the electrolyte. In addition, the concentrated dioxolane (DOL)-rich electrolyte designed lowers the irreversible capacity loss for SEI formation. By using the combined strategies, the graphite/holey-Li 2S battery delivers an ultrahigh discharge capacity of 810 mAh g -1 at 0.1 C (based on the mass of Li 2S) and of 714 mAh g -1 at 0.2 C. Moreover, it exhibits a reversible capacity of 300 mAh g -1 after a record lifecycle of 600 cycles at 1 C. These results suggest the great potential of the designed LFA/holey-Li 2S batteries for practical use.« less

An Ultrahigh Capacity Graphite/Li 2S Battery with Holey-Li 2S Nanoarchitectures

DOE PAGES

Ye, Fangmin; Noh, Hyungjun; Lee, Hongkyung; ...

2018-05-07

The pairing of high-capacity Li 2S cathode (1166 mAh g -1) and lithium-free anode (LFA) provides an unparalleled potential in developing safe and energy-dense next-generation secondary batteries. However, the low utilization of the Li 2S cathode and the lack of electrolytes compatible to both electrodes are impeding the development. Here, a novel graphite/Li 2S battery system, which features a self-assembled, holey-Li 2S nanoarchitecture and a stable solid electrolyte interface (SEI) on the graphite electrode, is reported. The holey structure on Li 2S is beneficial in decomposing Li 2S at the first charging process due to the enhanced Li ion extractionmore » and transfer from the Li 2S to the electrolyte. In addition, the concentrated dioxolane (DOL)-rich electrolyte designed lowers the irreversible capacity loss for SEI formation. By using the combined strategies, the graphite/holey-Li 2S battery delivers an ultrahigh discharge capacity of 810 mAh g -1 at 0.1 C (based on the mass of Li 2S) and of 714 mAh g -1 at 0.2 C. Moreover, it exhibits a reversible capacity of 300 mAh g -1 after a record lifecycle of 600 cycles at 1 C. These results suggest the great potential of the designed LFA/holey-Li 2S batteries for practical use.« less

Preparation and characterization of superporous agarose-reticulated vitreous carbon electrodes as platforms for electrochemical bioassays.

PubMed

Rao, Ashwin K; Creager, Stephen E

2008-08-01

Three-dimensional flow-through electrodes were fabricated using superporous agarose (SPA) and reticulated vitreous carbon (RVC) composite materials that were suitable as a platform for sandwich assays. These SPA-RVC composite electrodes were fabricated by fitting a SPA-RVC composite cylinder inside a graphite tube and subsequently fixing the graphite tube onto a polypropylene micropipette tip. The electrode design allows for ease in reagent/washing steps involved in sandwich assay protocols and could easily be made portable. The electrode materials were characterized with respect to pore-size distribution, total free volume, ligament and bulk densities of the RVC, and physical structural characteristics. Coulometric detection of redox molecules such as K(3)Fe(CN)(6) and 4-aminophenol was possible using SPA-RVC electrodes by the trapping of these redox molecules inside the SPA-RVC electrodes. Avidin affinity molecules were covalently immobilized onto the SPA matrix inside the RVC electrodes by periodate-activation followed by reductive amination. The amount of avidin immobilized inside the SPA-RVC electrodes was (5+/-0.06)x10(-11) mol, which was determined by saturating the avidin sites with biotinylated fluorescein (b-fluo) and subsequently determining the amount of immobilized b-fluo via a standard addition method using fluorescence spectroscopy. Non-specific binding of labeled enzymes such as biotinylated alkaline phosphatase (b-ALP) onto the SPA-RVC electrodes without avidin capture sites was determined to be less than 1% compared to the specific binding of b-ALP on avidinylated SPA-RVC electrodes.

Multilayer core-shell structured composite paper electrode consisting of copper, cuprous oxide and graphite assembled on cellulose fibers for asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wan, Caichao; Jiao, Yue; Li, Jian

2017-09-01

An easily-operated and inexpensive strategy (pencil-drawing-electrodeposition-electro-oxidation) is proposed to synthesize a novel class of multilayer core-shell structured composite paper electrode, which consists of copper, cuprous oxide and graphite assembled on cellulose fibers. This interesting electrode structure plays a pivotal role in providing more active sites for electrochemical reactions, facilitating ion and electron transport and shorting their diffusion pathways. This electrode demonstrates excellent electrochemical properties with a high specific capacitance of 601 F g-1 at 2 A g-1 and retains 83% of this capacitance when operated at an ultrahigh current density of 100 A g-1. In addition, a high energy density of 13.4 W h kg-1 at the power density of 0.40 kW kg-1 and a favorable cycling stability (95.3%, 8000 cycles) were achieved for this electrode. When this electrode was assembled into an asymmetric supercapacitor with carbon paper as negative electrode, the device displays remarkable electrochemical performances with a large areal capacitances (122 mF cm-2 at 1 mA cm-2), high areal energy density (10.8 μW h cm-2 at 402.5 μW cm-2) and outstanding cycling stability (91.5%, 5000 cycles). These results unveil the potential of this composite electrode as a high-performance electrode material for supercapacitors.

A structural study of solid electrolyte interface on negative electrode of lithium-Ion battery by electron microscopy.

PubMed

Matsushita, Tadashi; Watanabe, Jiro; Nakao, Tatsuya; Yamashita, Seiichi

2014-11-01

For the last decades, the performance of the lithium-ion battery (LIB) has been significantly improved and its applications have been expanding rapidly. However, its performance has yet to be enhanced.In the lithium-ion battery development, it is important to elucidate the electrode structure change in detail during the charge and discharge cycling. In particular, solid electrolyte interface (SEI) formed by decomposition of the electrolytes on the graphite negative electrode surface should play an important role for battery properties. Therefore, it is essential to control the structure and composition of SEI to improve the battery performance. Here, we conducted a scanning electron microscope (SEM) and transmission electron microscope (TEM) study to elucidate the structures of the SEI during the charge and discharge process using LiNi1/3Co1/3Mn1/3O2 [1] cathode and graphite anode. [2] Since SEI is a lithium-containing compound with high activity, it was observed without being exposed to the atmosphere. The electrodes including SEI were sampled after dismantling batteries with cutoff voltages of 3V and 4.2V for the charge process and 3V for the discharge process. Fig.1 shows SEM images of the graphite electrode surface during the charge and discharge process. The change of the SEI structure during the process was clearly observed. Further, TEM images showed that the SEI grew thicker during the charge process and becomes thinner when discharged. These results with regard to the reversible SEI structure could give a new insight for the battery development.jmicro;63/suppl_1/i21/DFU056F1F1DFU056F1Fig. 1.SEM images of the graphite electrode surface:(a) before charge process;(b) with charge-cutoff voltage of 3.0V; (c) with charge-cutoff voltage of 4.2V; (d) with discharge-cutoff voltage of 3.0V. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Electrochemical oxidation of textile industry wastewater by graphite electrodes.

PubMed

Bhatnagar, Rajendra; Joshi, Himanshu; Mall, Indra D; Srivastava, Vimal C

2014-01-01

In the present article, studies have been performed on the electrochemical (EC) oxidation of actual textile industry wastewater by graphite electrodes. Multi-response optimization of four independent parameters namely initial pH (pHo): 4-10, current density (j): 27.78-138.89 A/m(2), NaCl concentration (w): 0-2 g/L and electrolysis time (t): 10-130 min have been performed using Box-Behnken (BB) experimental design. It was aimed to simultaneously maximize the chemical oxygen demand (COD) and color removal efficiencies and minimize specific energy consumption using desirability function approach. Pareto analysis of variance (ANOVA) showed a high coefficient of determination value for COD (R(2) = 0.8418), color (R(2) = 0.7010) and specific energy (R(2) = 0.9125) between the experimental values and the predicted values by a second-order regression model. Maximum COD and color removal and minimum specific energy consumed was 90.78%, 96.27% and 23.58 kWh/kg COD removed, respectively, were observed at optimum conditions. The wastewater, sludge and scum obtained after treatment at optimum condition have been characterized by various techniques. UV-visible study showed that all azo bonds of the dyes present in the wastewater were totally broken and most of the aromatic rings were mineralized during EC oxidation with graphite electrode. Carbon balance showed that out of the total carbon eroded from the graphite electrodes, 27-29.2% goes to the scum, 71.1-73.3% goes into the sludge and rest goes to the treated wastewater. Thermogravimetric analysis showed that the generated sludge and scum can be dried and used as a fuel in the boilers/incinerators.

76 FR 14910 - Small Diameter Graphite Electrodes From the People's Republic of China: Initiation of Anti...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

... correct grade of petroleum coke mix, and have been baked, formed, carbonized, impregnated, and graphitized... required for the production of SDGE (e.g., raw material handling, mixing, forming, baking, impregnating... production process, demonstrating how raw materials are formed, baked, impregnated (if needed), re-baked...

Inert gas rejection device for zinc-halogen battery systems

DOEpatents

Hammond, Michael J.; Arendell, Mark W.

1981-01-01

An electrolytic cell for separating chlorine gas from other (foreign) gases, having an anode, a cathode assembly, an aqueous electrolyte, a housing, and a constant voltage power supply. The cathode assembly is generally comprised of a dense graphite electrode having a winding channel formed in the face opposing the anode, a gas impermeable (but liquid permeable) membrane sealed into the side of the cathode electrode over the channel, and a packing of graphite particles contained in the channel of the cathode electrode. The housing separates and parallelly aligns the anode and cathode assembly, and provides a hermetic seal for the cell. In operation, a stream of chlorine and foreign gases enters the cell at the beginning of the cathode electrode channel. The chlorine gas is dissolved into the electrolyte and electrochemically reduced into chloride ions. The chloride ions disfuse through the gas impermeable membrane, and are electrochemically oxidized at the anode into purified chlorine gas. The foreign gases do not participate in the above electrochemical reactions, and are vented from the cell at the end of the cathode electrode channel.

A Reusable Impedimetric Aptasensor for Detection of Thrombin Employing a Graphite-Epoxy Composite Electrode

PubMed Central

Ocaña, Cristina; Pacios, Mercè; del Valle, Manel

2012-01-01

Here, we report the application of a label-free electrochemical aptasensor based on a graphite-epoxy composite electrode for the detection of thrombin; in this work, aptamers were immobilized onto the electrodes surface using wet physical adsorption. The detection principle is based on the changes of the interfacial properties of the electrode; these were probed in the presence of the reversible redox couple [Fe(CN)6]3−/[Fe(CN)6]4− using impedance measurements. The electrode surface was partially blocked due to formation of aptamer-thrombin complex, resulting in an increase of the interfacial electron-transfer resistance detected by Electrochemical Impedance Spectroscopy (EIS). The aptasensor showed a linear response for thrombin in the range of 7.5 pM to 75 pM and a detection limit of 4.5 pM. The aptasensor was regenerated by breaking the complex formed between the aptamer and thrombin using 2.0 M NaCl solution at 42 °C, showing its operation for different cycles. The interference response caused by main proteins in serum has been characterized. PMID:22736991

What makes lithium substituted polyacrylic acid a better binder than polyacrylic acid for silicon-graphite composite anodes?

DOE PAGES

Hays, Kevin A.; Ruther, Rose E.; Kukay, Alexander J.; ...

2018-03-04

Lithium substituted polyacrylic acid (LiPAA) has previously been demonstrated as a superior binder over polyacrylic acid (PAA) for Si anodes, but from where does this enhanced performance arise? In this paper, full cells are assembled with PAA and LiPAA based Si-graphite composite anodes that dried at temperatures from 100 °C to 200 °C. The performance of full cells containing PAA based Si-graphite anodes largely depend on the secondary drying temperature, as decomposition of the binder is correlated to increased electrode moisture and a rise in cell impedance. Full cells containing LiPAA based Si-graphite composite electrodes display better Coulombic efficiency thanmore » those with PAA, because of the electrochemical reduction of the PAA binder. This is identified by attenuated total reflectance Fourier transform infrared spectrometry and observed gassing during the electrochemical reaction. Finally, Coulombic losses from the PAA and Si SEI, along with depletion of the Si capacity in the anode results in progressive underutilization of the cathode and full cell capacity loss.« less

What makes lithium substituted polyacrylic acid a better binder than polyacrylic acid for silicon-graphite composite anodes?

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

Hays, Kevin A.; Ruther, Rose E.; Kukay, Alexander J.

Lithium substituted polyacrylic acid (LiPAA) has previously been demonstrated as a superior binder over polyacrylic acid (PAA) for Si anodes, but from where does this enhanced performance arise? In this paper, full cells are assembled with PAA and LiPAA based Si-graphite composite anodes that dried at temperatures from 100 °C to 200 °C. The performance of full cells containing PAA based Si-graphite anodes largely depend on the secondary drying temperature, as decomposition of the binder is correlated to increased electrode moisture and a rise in cell impedance. Full cells containing LiPAA based Si-graphite composite electrodes display better Coulombic efficiency thanmore » those with PAA, because of the electrochemical reduction of the PAA binder. This is identified by attenuated total reflectance Fourier transform infrared spectrometry and observed gassing during the electrochemical reaction. Finally, Coulombic losses from the PAA and Si SEI, along with depletion of the Si capacity in the anode results in progressive underutilization of the cathode and full cell capacity loss.« less

Dendrite-free Li metal anode enabled by a 3D free-standing lithiophilic nitrogen-enriched carbon sponge

NASA Astrophysics Data System (ADS)

Hou, Guangmei; Ren, Xiaohua; Ma, Xiaoxin; Zhang, Le; Zhai, Wei; Ai, Qing; Xu, Xiaoyan; Zhang, Lin; Si, Pengchao; Feng, Jinkui; Ding, Fei; Ci, Lijie

2018-05-01

Lithium metal is considered as the ultimate anode material for high-energy Li battery systems. However, the commercial application of lithium anode is impeded by issues with safety and low coulombic efficiency induced by Li dendrite growth. Herein, a free-standing three-dimensional nitrogen-enriched graphitic carbon sponge with a high nitrogen content is proposed as a multifunctional current collect for Lithium accommodation. The abundant lithiophilic N-containing functional groups are served as preferred nucleation sites to guide a uniform Li deposition. In addition, the nitrogen-enriched graphitic carbon sponge with a high specific surface area can effectively reduce the local current density. As a result of the synergistic effect, the nitrogen-enriched graphitic carbon sponge electrode realizes a long-term stable cycling without dendrites formation. Notably, the as-obtained composite electrode can deliver an ultra-high specific capacity of ∼3175 mA h g-1. The nitrogen-enriched graphitic carbon sponge might provide innovative insights to design a superior matrix for dendrite-free Li anode.

Graphite to Graphene via Graphene Oxide: An Overview on Synthesis, Properties, and Applications

NASA Astrophysics Data System (ADS)

Hansora, D. P.; Shimpi, N. G.; Mishra, S.

2015-12-01

This work represents a state-of-the-art technique developed for the preparation of graphene from graphite-metal electrodes by the arc-discharge method carried out in a continuous flow of water. Because of continuous arcing of graphite-metal electrodes, the graphene sheets were observed in water with uniformity and little damage. These nanosheets were subjected to various purification steps such as acid treatment, oxidation, water washing, centrifugation, and drying. The pure graphene sheets were analyzed using Raman spectrophotometry, x-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and tunneling electron microscopy (TEM). Peaks of Raman spectra were recorded at (1300-1400 cm-1) and (1500-1600 cm-1) for weak D-band and strong G-band, respectively. The XRD pattern showed 85.6% crystallinity of pure graphite, whereas pure graphene was 66.4% crystalline. TEM and FE-SEM micrographs revealed that graphene sheets were overlapped to each other and layer-by-layer formation was also observed. Beside this research work, we also reviewed recent developments of graphene and related nanomaterials along with their preparations, properties, functionalizations, and potential applications.

What makes lithium substituted polyacrylic acid a better binder than polyacrylic acid for silicon-graphite composite anodes?

NASA Astrophysics Data System (ADS)

Hays, Kevin A.; Ruther, Rose E.; Kukay, Alexander J.; Cao, Pengfei; Saito, Tomonori; Wood, David L.; Li, Jianlin

2018-04-01

Lithium substituted polyacrylic acid (LiPAA) has previously been demonstrated as a superior binder over polyacrylic acid (PAA) for Si anodes, but from where does this enhanced performance arise? In this study, full cells are assembled with PAA and LiPAA based Si-graphite composite anodes that dried at temperatures from 100 °C to 200 °C. The performance of full cells containing PAA based Si-graphite anodes largely depend on the secondary drying temperature, as decomposition of the binder is correlated to increased electrode moisture and a rise in cell impedance. Full cells containing LiPAA based Si-graphite composite electrodes display better Coulombic efficiency than those with PAA, because of the electrochemical reduction of the PAA binder. This is identified by attenuated total reflectance Fourier transform infrared spectrometry and observed gassing during the electrochemical reaction. Coulombic losses from the PAA and Si SEI, along with depletion of the Si capacity in the anode results in progressive underutilization of the cathode and full cell capacity loss.

Study of Drug Metabolism by Xanthine Oxidase

PubMed Central

Zhao, Jing; He, Xiaolin; Yang, Nana; Sun, Lizhou; Li, Genxi

2012-01-01

In this work, we report the studies of drug metabolism by xanthine oxidase (XOD) with electrochemical techniques. Firstly, a pair of stable, well-defined and quasi-reversible oxidation/reduction peaks is obtained with the formal potential at −413.1 mV (vs. SCE) after embedding XOD in salmon sperm DNA membrane on the surface of pyrolytic graphite electrode. Then, a new steady peak can be observed at −730 mV (vs. SCE) upon the addition of 6-mercaptopurine (6-MP) to the electrochemical system, indicating the metabolism of 6-MP by XOD. Furthermore, the chronoamperometric response shows that the current of the catalytic peak located at −730 mV increases with addition of 6-MP in a concentration-dependent manner, and the increase of the chronoamperometric current can be inhibited by an XOD inhibitor, quercetin. Therefore, our results prove that XOD/DNA modified electrode can be efficiently used to study the metabolism of 6-MP, which may provide a convenient approach for in vitro studies on enzyme-catalyzed drug metabolism. PMID:22606015

Preparation of thin film silver fluoride electrodes from constituent elements

NASA Technical Reports Server (NTRS)

Odonnell, P. M.

1972-01-01

The feasibility of preparing thin-film metal fluoride electrodes from the elemental constituents has been demonstrated. Silver fluoride cathodes were prepared by deposition of silver on a conducting graphite substrate followed by fluorination under controlled conditions using elemental fluorine. The resulting electrodes were of high purity, and the variables such as size, shape, and thickness were easily controlled.

Fabrication of novel coated pyrolytic graphite electrodes for the selective nano-level monitoring of Cd²⁺ ions in biological and environmental samples using polymeric membrane of newly synthesized macrocycle.

PubMed

Sahani, Manoj Kumar; Singh, A K; Jain, A K; Upadhyay, Anjali; Kumar, Amit; Singh, Udai P; Narang, Shikha

2015-02-20

Novel 5-amino-1,3,4-thiadiazole-2-thiol unit based macrocyclic ionophore 5,11,17-trithia-1,3,7,9,13,15,19,20,21-nonaazatetracyclo[14.2.1.1(4,7).1(10,13)]henicosa-4(20),10(21),16(19)-triene-6,12,18-trithione (M1), was synthesized and characterized. Preliminary studies on M1 have showed that it has more the affinity toward Cd(2+) ion. Thus, the macrocyclic ionophore (M1) was used as electroactive material in the fabrication of PVC-membrane electrodes such as polymeric membrane electrode (PME), coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) were prepared and its performance characteristic were compared with. The electroanalytical studies performed on PME, CGE and CPGE revealed that CPGE having membrane composition M1:PVC:1-CN:NaTPB in the ratio of 7:37:54:2 exhibits the best potentiometric characteristics in terms of detection limit of 7.58×10(-9) mol L(-1), Nernstian slope of 29.6 mV decade(-1) of activity. The sensor was found to be independent of pH in the range 2.5-8.5. The sensor showed a fast response time of 10s and could be used over a period of 4 months without any significant divergence in its potentiometric characteristics. The sensor has been employed for monitoring of the Cd(2+) ion in real samples and also used as an indicator electrode in the potentiometric titration of Cd(2+) ion with EDTA. Copyright © 2014. Published by Elsevier B.V.

Water-activated graphite felt as a high-performance electrode for vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Kabtamu, Daniel Manaye; Chen, Jian-Yu; Chang, Yu-Chung; Wang, Chen-Hao

2017-02-01

A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as sbnd OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge-discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm-2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.

Design and Manufacturing of Desalination System Powered by Solar Energy Using CDI Technique

NASA Astrophysics Data System (ADS)

Rostami, Mohammad Sajjad; Khashehchi, Morteza; Pipelzadeh, Ehsan

2017-11-01

Capacitive deionization (CDI) is an emerging energy efficient, low pressure and low capital intensive desalination process where ions are separated by a pure electrostatic force imposed by a small bias potential as low as 1 V That funded by an external Renewable (Solar) power supply to materials with high specific surface area. The main objective of this configuration is to separate the cation and anions on oppositely charged electrodes. One of the key parameters for commercial realization of CDI is the salt adsorption capacity of the electrodes. State-of-the-art electrode materials are based on porous activated carbon particles or carbon aerogels. Various electrode materials have been developed in the past, which have suffered from instability and lack of performance. Preliminary experimental results using carbon black, graphite powder, graphene ∖ graphite ∖ PTFE (Active ∖ Conductive ∖ binder) show that the graphene reduced via urea method is a suitable method to develop CDI electrode materials. Although some progress has been made, production of efficient and stable carbon based electrode materials for large scale desalination has not been fully realized. A new desalination technique using capacitive deionization.

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.

A dual-ion imprinted polymer embedded in sol-gel matrix for the ultra trace simultaneous analysis of cadmium and copper.

PubMed

Bali Prasad, Bhim; Jauhari, Darshika; Verma, Archana

2014-03-01

In simultaneous determination of group of elements, there are inter-metallic interactions which result in a non-linear relationship between the peak current and ionic concentration for each of the element, at bare (unmodified) electrode. To resolve this problem, we have resorted, for the first time, to develop a modified pencil graphite electrode using a typical ion imprinted polymer network (dual-ion imprinted polymer embedded in sol-gel matrix (inorganic-organic hybrid nano-material)) for the simultaneous analysis of a binary mixture of Cd(II) and Cu(II) ions, without any complication of inter-metallic interactions and competitive bindings, in real samples. The adequate resolution of differential pulse anodic stripping voltammetry peaks by 725 mV (cf, 615 mV with unmodified electrode), without any cross-reactivity and the stringent detection limits as low as, 0.050 and 0.034 ng mL(-1) (S/N=3) for Cd(II) and Cu(II) ions, respectively by the proposed sensor can be considered useful for the primitive diagnosis of several chronic diseases in clinical settings. Copyright © 2013 Elsevier B.V. All rights reserved.

Multiple-element semiquantitative analysis of one-milligram geochemical samples by D.C. arc emission spectrography

USGS Publications Warehouse

Rait, N.

1981-01-01

A modified method is described for a 1-mg sample multi-element semiquantitative spectrographic analysis. This method uses a direct-current arc source, carbon instead of graphite electrodes, and an 80% argon-20% oxygen atmosphere instead of air. Although this is a destructive method, an analysis can be made for 68 elements in all mineral and geochemical samples. Carbon electrodes have been an aid in improving the detection limits of many elements. The carbon has a greater resistance to heat conductance and develops a better tip, facilitating sample volatilization and counter balancing the cooling effect of a flow of the argon-oxygen mixture around the anode. Where such an argon-oxygen atmosphere is used instead of air, the cyanogen band lines are greatly diminished in intensity, and thus more spectral lines of analysis elements are available for use; the spectral background is also lower. The main advantage of using the carbon electrode and the 80% argon-20% oxygen atmosphere is the improved detection limits of 36 out of 68 elements. The detection limits remain the same for 23 elements, and are not as good for only nine elements. ?? 1981.

2D Hexagonal Boron Nitride (2D-hBN) Explored for the Electrochemical Sensing of Dopamine.

PubMed

Khan, Aamar F; Brownson, Dale A C; Randviir, Edward P; Smith, Graham C; Banks, Craig E

2016-10-04

Crystalline 2D hexagonal boron nitride (2D-hBN) nanosheets are explored as a potential electrocatalyst toward the electroanalytical sensing of dopamine (DA). The 2D-hBN nanosheets are electrically wired via a drop-casting modification process onto a range of commercially available carbon supporting electrodes, including glassy carbon (GC), boron-doped diamond (BDD), and screen-printed graphitic electrodes (SPEs). 2D-hBN has not previously been explored toward the electrochemical detection/electrochemical sensing of DA. We critically evaluate the potential electrocatalytic performance of 2D-hBN modified electrodes, the effect of supporting carbon electrode platforms, and the effect of "mass coverage" (which is commonly neglected in the 2D material literature) toward the detection of DA. The response of 2D-hBN modified electrodes is found to be largely dependent upon the interaction between 2D-hBN and the underlying supporting electrode material. For example, in the case of SPEs, modification with 2D-hBN (324 ng) improves the electrochemical response, decreasing the electrochemical oxidation potential of DA by ∼90 mV compared to an unmodified SPE. Conversely, modification of a GC electrode with 2D-hBN (324 ng) resulted in an increased oxidation potential of DA by ∼80 mV when compared to the unmodified electrode. We explore the underlying mechanisms of the aforementioned examples and infer that electrode surface interactions and roughness factors are critical considerations. 2D-hBN is utilized toward the sensing of DA in the presence of the common interferents ascorbic acid (AA) and uric acid (UA). 2D-hBN is found to be an effective electrocatalyst in the simultaneous detection of DA and UA at both pH 5.0 and 7.4. The peak separations/resolution between DA and UA increases by ∼70 and 50 mV (at pH 5.0 and 7.4, respectively, when utilizing 108 ng of 2D-hBN) compared to unmodified SPEs, with a particularly favorable response evident in pH 5.0, giving rise to a significant increase in the peak current of DA. The limit of detection (3σ) is found to correspond to 0.65 μM for DA in the presence of UA. However, it is not possible to deconvolute the simultaneous detection of DA and AA. The observed electrocatalytic effect at 2D-hBN has not previously been reported in the literature when supported upon carbon or any other electrode. We provide valuable insights into the modifier-substrate interactions of this material, essential for those designing, fabricating, and consequently performing electrochemical experiments utilizing 2D-hBN and related 2D materials.

Electrochemical and thermal studies of lithium ion batteries

NASA Astrophysics Data System (ADS)

Lu, Wenquan

The structural, electrochemical, and thermal characteristics of carbonaceous anodes and LiNi0.8Co0.2O2 cathode in Li-ion cells were investigated using various electrochemical and calorimetric techniques. The electrode-electrolyte interface was investigated for various carbonaceous materials such as graphite with different shapes, surface modified graphite with copper, and novel carbon material derived from sepiolite template. The structural and morphological properties were determined using XRD, TGA, SEM, BET techniques. The electrochemical characteristics were studied using conventional electrochemical techniques such as galvanostatic charge/discharge cycling, cyclic voltammetry, and impedance (AC and DC) methods. It was observed that the electrochemical active surface area instead of the BET area plays a critical role in the irreversible capacity loss associated with the carbonaceous anodes. It was also found that the exfoliation of carbon anodes especially in PC based electrolyte could be significantly reduced by protective copper coating of the natural graphite. LiNi0.8Co0.2O2 cathode material was found to possess high energy density and excellent cycling characteristics. The structural and electrochemical properties of LiNi0.8Co 0.2O2 synthesized by sol-gel and solid-state methods were studied. Results of the AC impedance spectroscopy carried out on LiNi 0.8Co0.2O2 cathodes revealed that the charge transfer resistance is a function of the state of charge. The solid state Li + diffusion was calculated to be around 10-13 cm2/s in the oxide particle by Warburg impedance method. In addition, the cell fabricated with LiNi0.8Co0.2O 2 cathode showed excellent energy and power performance under static and dynamic load conditions that prevail in Electric and Hybrid Vehicles. Thermal properties of the LiNi0.8Co0.2O2 cathode, carbonaceous anodes, and Li-ion cells fabricated with these electrodes were also investigated using isothermal microcalorimetry (IMC), differential scanning calorimetry (DSC) and accelerated rate calorimetry (ARC). Isothermal micro-calorimeter was used to investigate the thermal behavior of the Li-ion cell and its electrodes. The overall heat changes during charge-discharge processes were explained in terms of the irreversible (resistive) and reversible (entropic) heats. It was observed that the reversible heat strongly depends on the structural or phase change occurring in the electrodes during Li-ion insertion and extraction reactions. It was also found that the contribution of the reversible heat to the overall cell heat generation rate was significant only at low cycling rates.

A biosensor based on graphite epoxy composite electrode for aspartame and ethanol detection.

PubMed

Kirgöz, Ulkü Anik; Odaci, Dilek; Timur, Suna; Merkoçi, Arben; Alegret, Salvador; Beşün, Nurgün; Telefoncu, Azmi

2006-06-16

A gelatin membrane with carboxyl esterase and alcohol oxidase was subsequently integrated onto the surface of a graphite epoxy composite electrode (GECE). The developed biosensors showed linearity in the range of 2.5-400 microM for aspartame and 2.5-25 microM for ethanol with response times of 170 and 70s for each analyte, respectively. The resulting bienzyme biosensor was used for aspartame detection in diet coke samples and ethanol detection in beer and wine samples. From the obtained results, it can be concluded that the developed biosensor is a selective, practical and economic tool for aspartame and ethanol detection in real samples.

Dross treatment in a rotary arc furnace with graphite electrodes

NASA Astrophysics Data System (ADS)

Drouet, Michel G.; Handfield, My; Meunier, Jean; Laflamme, Claude B.

1994-05-01

Aluminum baths are always covered with a layer of dross resulting from the aluminum surface oxidation. This dross represents 1-10% of the melt and may contain up to 75wt.% aluminum. Since aluminum production is highly energy intensive, dross recycling is very attractive from both energy and economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally unacceptable because of the production of salt slags. Hydro-Quebec has developed a new technology using a rotary arc furnace with graphite electrodes. This process provides aluminum recovery rates of 80-90%, using a highly energy efficient, environmentally sound production method.

Silicone modified resins for graphite fiber laminates

NASA Technical Reports Server (NTRS)

Frost, L. W.; Bower, G. M.

1979-01-01

The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.

Fabrication of TiO2/Carbon Photocatalyst using Submerged DC Arc Discharged in Ethanol/Acetic Acid Medium

NASA Astrophysics Data System (ADS)

Saraswati, T. E.; Nandika, A. O.; Andhika, I. F.; Patiha; Purnawan, C.; Wahyuningsih, S.; Rahardjo, S. B.

2017-05-01

This study aimed to fabricate a modified photocatalyst of TiO2/C to enhance its performance. The fabrication was achieved using the submerged direct current (DC) arc-discharge method employing two graphite electrodes, one of which was filled with a mixture of carbon powder, TiO2, and binder, in ethanol with acetic acid added in various concentrations. The arc-discharge method was conducted by flowing a current of 10-20 A (~20 V). X-ray diffraction (XRD) patterns showed significant placements of the main peak characteristics of TiO2, C graphite, and titanium carbide. The surface analysis using Fourier transform infrared spectroscopy (FTIR) revealed that fabricated TiO2/C nanoparticles had stretching vibrations of Ti-O, C-H, C═O, C-O, O-H and C═C in the regions of 450-550 cm-1, 2900-2880 cm-1, 1690-1760 cm-1, 1050-1300 cm-1, 3400-3700 cm-1 and ~1600 cm-1, respectively. In addition, the study investigated the photocatalysts of unmodified and modified TiO2/C for photodegradation of methylene blue (MB) dye solution under mercury lamp irradiation. The effectiveness of the degradation was defined by the decrease in 60-minute absorbance under a UV-Vis spectrophotometer. Modified TiO2/C proved to be significantly more efficient in reducing dye concentrations, reaching ~70%. It indicated that the oxygen-containing functional groups have been successfully attached to the surface of the nanoparticles and played a role in enhancing photocatalytic activity.

A Novel Method for Fabricating Wearable, Piezoresistive, and Pressure Sensors Based on Modified-Graphite/Polyurethane Composite Films

PubMed Central

He, Yin; Li, Wei; Yang, Guilin; Liu, Hao; Lu, Junyu; Zheng, Tongtong; Li, Xiaojiu

2017-01-01

A wearable, low-cost, highly repeatable piezoresistive sensor was fabricated by the synthesis of modified-graphite and polyurethane (PU) composites and polydimethylsiloxane (PDMS). Graphite sheets functionalized by using a silane coupling agent (KH550) were distributed in PU/N,N-dimethylformamide (DMF) solution, which were then molded to modified-graphite/PU (MG/PU) composite films. Experimental results show that with increasing modified-graphite content, the tensile strength of the MG/PU films first increased and then decreased, and the elongation at break of the composite films showed a decreasing trend. The electrical conductivity of the composite films can be influenced by filler modification and concentration, and the percolation threshold of MG/PU was 28.03 wt %. Under liner uniaxial compression, the 30 wt % MG/PU composite films exhibited 0.274 kPa−1 piezoresistive sensitivity within the range of low pressure, and possessed better stability and hysteresis. The flexible MG/PU composite piezoresistive sensors have great potential for body motion, wearable devices for human healthcare, and garment pressure testing. PMID:28773047

Graphite//LiNi0.5 Mn1.5 O4 Cells Based on Environmentally Friendly Made-in-Water Electrodes.

PubMed

De Giorgio, Francesca; Laszczynski, Nina; von Zamory, Jan; Mastragostino, Marina; Arbizzani, Catia; Passerini, Stefano

2017-01-20

The performance of graphite//LiNi 0.5 Mn 1.5 O 4 (LNMO) cells, both electrodes of which are made using water-soluble sodium carboxymethyl cellulose (CMC) binder, is reported for the first time. The full cell performed outstandingly over 400 cycles in the conventional electrolyte ethylene carbonate/dimethyl carbonate-1 m LiPF 6 , and the delivered specific energy at the 100th, 200th, 300th, and 400th cycle corresponded to 82, 78, 73, and 66 %, respectively, of the initial energy value of 259 Wh kg -1 (referring to the sum of the two electrode-composite weights). The good stability of high-voltage, LNMO-CMC-based electrodes upon long-term cycling is discussed and the results are compared to those of LNMO-composite electrodes with polyvinylidene fluoride (PVdF). LNMO-CMC electrodes outperformed those with PVdF binder, displaying a capacity retention of 83 % compared to 62 % for the PVdF-based electrodes after 400 cycles at 1 C. CMC promotes a more compact and stable electrode surface than PVdF; undesired interfacial reactions at high operating voltages are mitigated, and the thickness of the passivation layer on the LNMO surface is reduced, thereby enhancing its cycling stability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nucleation/Growth Mechanisms and Morphological Evolution of Porous MnO₂ Coating Deposited on Graphite for Supercapacitor.

PubMed

Huang, Wenxin; Li, Jun; Xu, Yunhe

2017-10-19

The nucleation and growth mechanisms of porous MnO₂ coating deposited on graphite in MnSO₄ solution were investigated in detail by cyclic voltammetry, chronoamperometry and scanning electron microscopy. The electrochemical properties of honeycomb-like MnO₂ were evaluated by cycle voltammetry and galvanostatic charge-discharge. Results indicated that MnO₂ was synthesized by the following steps: Mn 2+ → Mn 3+ + e⁻, Mn 3+ +2H2O → MnOOH + 3H⁺, and MnOOH → MnO₂ + H⁺+ e⁻. The deposition of MnO₂ was divided into four stages. A short incubation period (approximately 1.5 s) was observed, prior to nucleation. The decreasing trend of the current slowed as time increased due to nucleation and MnO₂ growth in the second stage. A huge number of nuclei were formed by instantaneous nucleation, and these nuclei grew and connected with one another at an exceedingly short time (0.5 s). In the third stage, the gaps in-between initial graphite flakes were filled with MnO₂ until the morphology of the flakes gradually became similar to that of the MnO₂-deposited layer. In the fourth stage, the graphite electrode was covered completely with a thick and dense layer of MnO₂ deposits. All MnO₂ electrodes at different deposition times obtained nearly the same specific capacitance of approximately 186 F/g, thus indicating that the specific capacitance of the electrodes is not related with deposition time.

Perfluoroalkyl-substituted ethylene carbonates: Novel electrolyte additives for high-voltage lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhu, Ye; Casselman, Matthew D.; Li, Yan; Wei, Alexander; Abraham, Daniel P.

2014-01-01

A new family of polyfluoroalkyl-substituted ethylene carbonates is synthesized and tested as additives in lithium-ion cells containing EC:EMC + LiPF6-based electrolyte. The influence of these compounds is investigated in Li1.2Ni0.15Mn0.55Co0.1O2//graphite cells via a combination of galvanostatic cycling and electrochemical impedance spectroscopy (EIS) tests. Among the four additives studied in this work (4-(trifluoromethyl)-1,3-dioxolan-2-one (TFM-EC), 4-(perfluorobutyl)-1,3-dioxolan-2-one (PFB-EC), 4-(perfluorohexyl)-1,3-dioxolan-2-one (PFH-EC), and 4-(perfluorooctyl)-1,3-dioxolan-2-one (PFO-EC)), small amounts (0.5 wt%) of PFO-EC is found to be most effective in lessening cell performance degradation during extended cycling. Linear sweep voltammetry (LSV), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are used to further characterize the effects of PFO-EC on the positive and negative electrodes. LSV data from the electrolyte, and XPS analyses of electrodes harvested after cycling, suggest that PFO-EC is oxidized on the cathode forming surface films that slow electrode/cell impedance rise. Differential capacity (dQ/dV) plots from graphite//Li cells suggest that PFO-EC is involved in solid electrolyte interphase (SEI) formation. Raman data from anodes after cycling suggest that structural disordering of graphite is reduced by the addition of PFO-EC, which may explain the improved cell capacity retention.

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

Estevez, Luis; Reed, David; Nie, Zimin

We decorated the surfaces of graphite felts with some oxygen-containing functional groups, such as C-OH, O=C and HO-C=O. And the mole ratios and amounts of these functional groups were effectively adjusted on the graphite surface by a particular method. The catalytic effects of amounts and mole ratio of different kinds of functional groups on VRB electrode performances were investigated in detail.

Preparation of Crumpled Graphite Oxide from Recycled Graphite Using Plasma Electrolysis and Its Application for Adsorption of Cadmium in Aqueous Environment

NASA Astrophysics Data System (ADS)

Hong, Phan Ngoc; Tuoi, Tran Thi; Ngan, Nguyen Thi Kim; Trang, Bui Thi; Minh, Phan Ngoc; Lam, Tran Dai; Hanh, Nguyen Thi; Van Thanh, Dang

2016-05-01

Household battery waste is considered hazardous and needs to be collected, managed, and recycled appropriately. In this study, using a plasma electrolysis method, we recycled graphite electrodes of exhausted dry batteries to prepare crumpled graphite oxide (CGO). Scanning electron microscopy revealed that the CGO possessed spherical morphology with average dimensions of 0.5 μm to 5 μm. The as-prepared CGO was then applied to absorb cadmium in aqueous environment. The results showed that CGO appears to be a promising adsorbent for removal of toxic waste from polluted water.

Graphite based Schottky diodes formed semiconducting substrates

NASA Astrophysics Data System (ADS)

Schumann, Todd; Tongay, Sefaattin; Hebard, Arthur

2010-03-01

We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). The fabrication can be as easy as allowing a dab of graphite paint to air dry on any one of the investigated semiconductors. Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

In situ, one step removal of ammonia from onshore and offshore formation water of petroleum production fields.

PubMed

Awad Abouelata, Ahmed M; Elhadad, Adel M A; Hammad, Samir

2018-04-21

Fish, crustaceans and other living organisms are threatened due to disposal of harmful contaminants in sea water. Ammonia is considered one of harmful contaminants due to industrial activities of oil companies, where excess ammonia in the formation water is discharged into sea water. Electrochemical treatment (EC) was used in one step for total removal of ammonia and remediation of other contaminants. Three working electrodes were examined EC cell, aluminum, iron and modified electrode (Ti/IrO 2 ). Graphite electrode was used as counter electrode in all processes of binary system. Both ionized and unionized ammonia of onshore (5.54 mg L -1 ) and off shore (110 mg L -1 ) were totally undetected after one step using all types of electrodes. The study was extended also to check the removal efficiency of other contaminants, where the analysis indicated the alleviation of them. Total suspended solid (TSS) of both onshore 64 mg L -1 and offshore 228 mg L -1 samples was reduced to 4 mg L -1 . Total dissolved solids (TDS), chemical oxygen demand (COD) and biological oxygen demand (BOD) of high values, 232,000, 8500 and 2442 mg L -1 were also reduced to lower levels 18,400, 4000 and 1600 mg L -1 , respectively. The formed sludge after EC treatment was also investigated using XRD. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nanoscale Electrochemistry of sp(2) Carbon Materials: From Graphite and Graphene to Carbon Nanotubes.

PubMed

Unwin, Patrick R; Güell, Aleix G; Zhang, Guohui

2016-09-20

Carbon materials have a long history of use as electrodes in electrochemistry, from (bio)electroanalysis to applications in energy technologies, such as batteries and fuel cells. With the advent of new forms of nanocarbon, particularly, carbon nanotubes and graphene, carbon electrode materials have taken on even greater significance for electrochemical studies, both in their own right and as components and supports in an array of functional composites. With the increasing prominence of carbon nanomaterials in electrochemistry comes a need to critically evaluate the experimental framework from which a microscopic understanding of electrochemical processes is best developed. This Account advocates the use of emerging electrochemical imaging techniques and confined electrochemical cell formats that have considerable potential to reveal major new perspectives on the intrinsic electrochemical activity of carbon materials, with unprecedented detail and spatial resolution. These techniques allow particular features on a surface to be targeted and models of structure-activity to be developed and tested on a wide range of length scales and time scales. When high resolution electrochemical imaging data are combined with information from other microscopy and spectroscopy techniques applied to the same area of an electrode surface, in a correlative-electrochemical microscopy approach, highly resolved and unambiguous pictures of electrode activity are revealed that provide new views of the electrochemical properties of carbon materials. With a focus on major sp(2) carbon materials, graphite, graphene, and single walled carbon nanotubes (SWNTs), this Account summarizes recent advances that have changed understanding of interfacial electrochemistry at carbon electrodes including: (i) Unequivocal evidence for the high activity of the basal surface of highly oriented pyrolytic graphite (HOPG), which is at least as active as noble metal electrodes (e.g., platinum) for outer-sphere redox processes. (ii) Demonstration of the high activity of basal plane HOPG toward other reactions, with no requirement for catalysis by step edges or defects, as exemplified by studies of proton-coupled electron transfer, redox transformations of adsorbed molecules, surface functionalization via diazonium electrochemistry, and metal electrodeposition. (iii) Rationalization of the complex interplay of different factors that determine electrochemistry at graphene, including the source (mechanical exfoliation from graphite vs chemical vapor deposition), number of graphene layers, edges, electronic structure, redox couple, and electrode history effects. (iv) New methodologies that allow nanoscale electrochemistry of 1D materials (SWNTs) to be related to their electronic characteristics (metallic vs semiconductor SWNTs), size, and quality, with high resolution imaging revealing the high activity of SWNT sidewalls and the importance of defects for some electrocatalytic reactions (e.g., the oxygen reduction reaction). The experimental approaches highlighted for carbon electrodes are generally applicable to other electrode materials and set a new framework and course for the study of electrochemical and interfacial processes.

Electrolyte Structure near Electrode Interfaces in Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Lordi, Vincenzo; Ong, Mitchell; Verners, Osvalds; van Duin, Adri; Draeger, Erik; Pask, John

2014-03-01

The performance of lithium-ion secondary batteries (LIBs) is strongly tied to electrochemistry and ionic transport near the electrode-electrolyte interface. Changes in ion solvation near the interface affect ion conductivity and also are associated with the formation and evolution of solid-electrolyte interphase (SEI) layers, which impede transport but also passivate the interface. Thus, understanding these effects is critical to optimizing battery performance. Here we present molecular dynamics (MD) simulations of typical organic liquid LIB electrolytes in contact with graphite electrodes to understand differences in molecular structure and solvation near the interface compared to the bulk electrolyte. Results for different graphite terminations are presented. We compare the results of density-functional based MD to the empirical reactive forcefield ReaxFF and the non-reactive, non-polarizable COMPASS forcefield. Notable differences in the predictive power of each of these techniques are discussed. Prepared by LLNL under Contract DE-AC52-07NA27344.

Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

PubMed

Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

2016-08-01

This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Inverse opal carbons for counter electrode of dye-sensitized solar cells.

PubMed

Kang, Da-Young; Lee, Youngshin; Cho, Chang-Yeol; Moon, Jun Hyuk

2012-05-01

We investigated the fabrication of inverse opal carbon counter electrodes using a colloidal templating method for DSSCs. Specifically, bare inverse opal carbon, mesopore-incoporated inverse opal carbon, and graphitized inverse opal carbon were synthesized and stably dispersed in ethanol solution for spray coating on a FTO substrate. The thickness of the electrode was controlled by the number of coatings, and the average relative thickness was evaluated by measuring the transmittance spectrum. The effect of the counter electrode thickness on the photovoltaic performance of the DSSCs was investigated and analyzed by interfacial charge transfer resistance (R(CT)) under EIS measurement. The effect of the surface area and conductivity of the inverse opal was also investigated by considering the increase in surface area due to the mesopore in the inverse opal carbon and conductivity by graphitization of the carbon matrix. The results showed that the FF and thereby the efficiency of DSSCs were increased as the electrode thickness increased. Consequently, the larger FF and thereby the greater efficiency of the DSSCs were achieved for mIOC and gIOC compared to IOC, which was attributed to the lower R(CT). Finally, compared to a conventional Pt counter electrode, the inverse opal-based carbon showed a comparable efficiency upon application to DSSCs.

From coin cells to 400 mAh pouch cells: Enhancing performance of high-capacity lithium-ion cells via modifications in electrode constitution and fabrication

NASA Astrophysics Data System (ADS)

Trask, Stephen E.; Li, Yan; Kubal, Joseph J.; Bettge, Martin; Polzin, Bryant J.; Zhu, Ye; Jansen, Andrew N.; Abraham, Daniel P.

2014-08-01

In this article we describe efforts to improve performance and cycle life of cells containing Li1.2Ni0.15Mn0.55Co0.1O2-based positive and graphite-based negative electrodes. Initial work to identify high-performing materials, compositions, fabrication variables, and cycling conditions is conducted in coin cells. The resulting information is then used for the preparation of double-sided electrodes, assembly of pouch cells, and electrochemical testing. We report the cycling performance of cells with electrodes prepared under various conditions. Our data indicate that cells with positive electrodes containing 92 wt.% Li1.2Ni0.15Mn0.55Co0.1O2, 4 wt.% carbons (no graphite), and 4 wt.% PVdF (92-4-4) show ∼20% capacity fade after 1000 cycles in the 2.5-4.4 V range, significantly better than our baseline cells that show the same fade after only 450 cycles. Our analyses indicate that the major contributors to cell energy fade are capacity loss and impedance rise. Therefore incorporating approaches that minimize capacity fade and impedance rise, such as electrode coatings and electrolyte additives, can significantly enhance calendar and cycle life of this promising cell chemistry.

From coin cells to 400 mAh pouch cells: Enhancing performance of high-capacity lithium-ion cells via modifications in electrode constitution and fabrication

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

Trask, Stephen E.; Li, Yan; Kubal, Joseph J.

2014-08-01

In this article we describe efforts to improve performance and cycle life of cells containing Li1.2Ni0.15Mn0.55Co0.1O2-based positive and graphite-based negative electrodes. Initial work to identify high-performing materials, compositions, fabrication variables, and cycling conditions is conducted in coin cells. The resulting information is then used for the preparation of double-sided electrodes, assembly of pouch cells, and electrochemical testing. We report the cycling performance of cells with electrodes prepared under various conditions. Our data indicate that cells with positive electrodes containing 92 wt% Li1.2Ni0.15Mn0.55Co0.1O2, 4 wt% carbons (no graphite), and 4 wt% PVdF (92-4-4) show ~20% capacity fade after 1000 cycles inmore » the 2.5-4.4V range, significantly better than our baseline cells that show the same fade after only 450 cycles. Our analyses indicate that the major contributors to cell energy fade are capacity loss and impedance rise. Therefore incorporating approaches that minimize capacity fade and impedance rise, such as electrode coatings and electrolyte additives, can significantly enhance calendar and cycle life of this promising cell chemistry.« less

Capillary suspensions as beneficial formulation concept for high energy density Li-ion battery electrodes

NASA Astrophysics Data System (ADS)

Bitsch, Boris; Gallasch, Tobias; Schroeder, Melanie; Börner, Markus; Winter, Martin; Willenbacher, Norbert

2016-10-01

We introduce a novel formulation concept to prepare high capacity graphite electrodes for lithium ion batteries. The concept is based on the capillary suspension phenomenon: graphite and conductive agent are dispersed in an aqueous binder solution and the organic solvent octanol is added as immiscible, secondary fluid providing the formation of a sample-spanning network resulting in unique stability and coating properties. No additional processing steps compared to conventional slurry preparation are required. The resulting ultra-thick electrodes comprise mass loadings of about 16.5 mg cm-2, uniform layer thickness, and superior edge contours. The adjustment of mechanical energy input ensures uniform distribution of the conductive agent and sufficient electronic conductivity of the final dry composite electrode. The resulting pore structure is due to the stable network provided by the secondary fluid which evaporates residue-free during drying. Constant current-constant potential (CC-CP) cycling clearly indicates that the corresponding microstructure significantly improves the kinetics of reversible Li+ (de-) intercalation. A double layer electrode combining a conventionally prepared layer coated directly onto the Cu current collector with an upper layer stabilized with octanol was prepared applying wet-on-wet coating. CC-CP cycling data confirms that staged porosity within the electrode cross section results in superior electrochemical performance.

Development of a Novel, Low-Cost, Disposable Wooden Pencil Graphite Electrode for Use in the Determination of Antioxidants and Other Biological Compounds.

PubMed

Kariuki, James; Ervin, Emily; Olafson, Carly

2015-07-31

The development of portable sensors that can be used outside the lab is an active area of research in the electroanalytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy-carbon electrodes (GCEs), are costly and require time-consuming preparation. Alternatives have been proposed, including mechanical pencil-lead electrodes (MPEs). However, MPEs themselves possess numerous drawbacks, particularly structural fragility. In this paper, we present a novel pencil-graphite electrode (PGE) fabricated from a regular HB#2 pencil. This PGE is a simple, disposable, extremely low-cost alternative to GCEs ($0.30 per PGE, vs. $190 + per GCE), and possesses the structural stability that MPEs lack. PGEs were characterized by square-wave voltammetry of ferricyanide, gallic acid, uric acid, dopamine, and several foodstuffs. In all cases, PGEs demonstrated sensitivities comparable or superior to those of the GCE and MPE (LOD = 5.62 × 10(-4) M PGE, 4.80 × 10(-4) M GCE, 2.93 × 10(-4) M MPE). Signal areas and peak heights were typically four to ten times larger for the PGE relative to the GCE.

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.

A Novel In-situ Electrochemical Cell for Neutron Diffraction Studies of Phase Transitions in Small Volume Electrodes of Li-ion Batteries

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

Vadlamani, Bhaskar S; An, Ke; Jagannathan, M.

2014-01-01

The design and performance of a novel in-situ electrochemical cell that greatly facilitates the neutron diffraction study of complex phase transitions in small volume electrodes of Li-ion cells, is presented in this work. Diffraction patterns that are Rietveld-refinable could be obtained simultaneously for all the electrodes, which demonstrates that the cell is best suited to explore electrode phase transitions driven by the lithiation and delithiation processes. This has been facilitated by the use of single crystal (100) Si sheets as casing material and the planar cell configuration, giving improved signal-to-noise ratio relative to other casing materials. The in-situ cell hasmore » also been designed for easy assembly and to facilitate rapid experiments. The effectiveness of cell is demonstrated by tracking the neutron diffraction patterns during the charging of graphite/LiCoO2 and graphite/LiMn2O4 cells. It is shown that good quality neutron diffraction data can be obtained and that most of the finer details of the phase transitions, and the associated changes in crystallographic parameters in these electrodes, can be captured.« less

Imidazolium-organic solvent mixtures as electrolytes for lithium batteries

NASA Astrophysics Data System (ADS)

Chagnes, A.; Diaw, M.; Carré, B.; Willmann, P.; Lemordant, D.

γ-Butyrolactone (BL) has been mixed to the room temperature ionic liquid (RTIL) 1-butyl 3-methyl-imidazolium tetrafluoroborate (BMIBF 4) (ratio: 3/2, v/v) in the presence of lithium tetrafluoroborate (LiBF 4) for use as electrolyte in lithium-ion batteries. This mixture exhibits a larger thermal stability than the reference electrolyte EC/DEC/DMC (2/2/1) + LiPF 6 (1 M) and can be considered as a new RTIL as no free BL molecules are present in the liquid phase. The cycling ability of this electrolyte has been investigated at a graphite, a titanate oxide (Li 4Ti 5O 12) and a cobalt oxide (Li xCoO 2) electrodes. The ionic liquid is strongly reduced at the graphite electrode near 1 V and leads to the formation of a blocking film, which prevents any further cycling. The titanate oxide electrode can be cycled with a high capacity without any significant fading. Cycling of the positive cobalt oxide electrode was unsuccessfully owing to an oxidation reaction at the electrode surface, which prevents the intercalation or de-intercalation of Li ions in and from the host material. Less reactive cathode material than cobalt oxide must be employed with this RTIL.

Electrochemical characterisation of CaCl2 deficient LiCl-KCl-CaCl2 eutectic melt and electro-deoxidation of solid UO2

NASA Astrophysics Data System (ADS)

Sri Maha Vishnu, D.; Sanil, N.; Mohandas, K. S.; Nagarajan, K.

2016-03-01

The CaCl2 deficient ternary eutectic melt LiCl-KCl-CaCl2 (50.5: 44.2: 5.3 mol %) was electrochemically characterised by cyclic voltammetry and polarization techniques in the context of its probable use as the electrolyte in the electrochemical reduction of solid UO2 to uranium metal. Tungsten (cathodic polarization) and graphite (anodic polarization) working electrodes were used in these studies carried out in the temperature range 623 K-923 K. The cathodic limit of the melt was observed to be set by the deposition of Ca2+ ions followed by Li+ ions on the tungsten electrode and the anodic limit by oxidation of chloride ions on the graphite electrode (chlorine evolution). The difference between the onset potential of deposition of Ca2+ and Li+ was found to be 0.241 V at a scan rate of 20 mV/s at 623 K and the difference decreased with increase in temperature and vanished at 923 K. Polarization measurements with stainless steel (SS) cathode and graphite anode at 673 K showed the possibility of low-energy reactions occurring on the UO2 electrode in the melt. UO2 pellets were cathodically polarized at 3.9 V for 25 h to test the feasibility of electro-reduction to uranium in the melt. The surface of the pellets was found reduced to U metal.

Preliminary Development of Electrodes for an Electric-Arc Wind Tunnel

NASA Technical Reports Server (NTRS)

Shepard, Charles E.; Boldman, Donald R.

1959-01-01

Two electrode configurations were tested in an electric-arc wind tunnel at the NASA Lewis Research Center. The results indicated approximately the same heat-loss rate per unit of arc power input for each of the configurations. Measured heat-loss rates were on the order of 40 percent of the arc power input. Nearly all this loss occurred at the anode. The power input and arc current limitations of the electrodes appear to be the critical design factors. Up to now, the maximum power to the stream has been 115 kilowatts with a cooled tungsten cathode and a cooled cylindrical anode incorporating a magnetic field. The maximum power input to this anode could not be established with the cooled tungsten cathode because cathode failures occurred at a gross power level of approximately 175 kilowatts. It was necessary to use a graphite cathode to seek the limitation of the anode. The results indicated that the anode limitation was primarily a function of arc current rather than power input. The anode was successfully operated at a power of 340 kilowatts at 1730 amperes; however, the anode failed with a power input of 324 kilowatts and a current of 2140 amperes. The magnetic flux density at the time of failure was 0.32 weber per square meter, or 3200 gauss. The graphite cathode was used only to establish the anode limitation; further investigation of graphite cathodes was discontinued because of the large amount of stream contamination associated with this type of electrode.

Exploring electrolyte preference of vanadium nitride supercapacitor electrodes

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

Wang, Bo; Chen, Zhaohui; Lu, Gang

Highlights: • Hierarchical VN nanostructures were prepared on graphite foam. • Electrolyte preference of VN supercapacitor electrodes was explored. • VN showed better capacitive property in organic and alkaline electrolytes than LiCl. - Abstract: Vanadium nitride hierarchical nanostructures were prepared through an ammonia annealing procedure utilizing vanadium pentoxide nanostructures grown on graphite foam. The electrochemical properties of hierarchical vanadium nitride was tested in aqueous and organic electrolytes. As a result, the vanadium nitride showed better capacitive energy storage property in organic and alkaline electrolytes. This work provides insight into the charge storage process of vanadium nitride and our findings canmore » shed light on other transition metal nitride-based electrochemical energy storage systems.« less

Electrodeposition of Manganese-Nickel Oxide Films on a Graphite Sheet for Electrochemical Capacitor Applications.

PubMed

Lee, Hae-Min; Lee, Kangtaek; Kim, Chang-Koo

2014-01-09

Manganese-nickel (Mn-Ni) oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers. The X-ray diffractometer pattern revealed the presence of separate manganese oxide (g-MnO₂) and nickel oxide (NiO) in the films. The electrodeposited Mn-Ni oxide electrode exhibited a specific capacitance of 424 F/g in Na₂SO₄ electrolyte. This electrode maintained 86% of its initial specific capacitance over 2000 cycles of the charge-discharge operation, showing good cycling stability.

Effect of anode polarization on biofilm formation and electron transfer in Shewanella oneidensis/graphite felt microbial fuel cells.

PubMed

Pinto, David; Coradin, Thibaud; Laberty-Robert, Christel

2018-04-01

In microbial fuel cells, electricity generation is assumed by bacterial degradation of low-grade organics generating electrons that are transferred to an electrode. The nature and efficiency of the electron transfer from the bacteria to the electrodes are determined by several chemical, physical and biological parameters. Specifically, the application of a specific potential at the bioanode has been shown to stimulate the formation of an electro-active biofilm, but the underlying mechanisms remain poorly understood. In this study, we have investigated the effect of an applied potential on the formation and electroactivity of biofilms established by Shewanella oneidensis bacteria on graphite felt electrodes in single- and double-chamber reactor configurations in oxic conditions. Using amperometry, cyclic voltammetry, and OCP/Power/Polarization curves techniques, we showed that a potential ranging between -0.3V and +0.5V (vs. Ag/AgCl/KCl sat.) and its converse application to a couple of electrodes leads to different electrochemical behaviors, anodic currents and biofilm architectures. For example, when the bacteria were confined in the anodic compartment of a double-chamber cell, a negative applied potential (-0.3V) at the bioanode favors a mediated electron transfer correlated with the progressive formation of a biofilm that fills the felt porosity and bridges the graphite fibers. In contrast, a positive applied potential (+0.3V) at the bioanode stimulates a direct electron transfer resulting in the fast-bacterial colonization of the fibers only. These results provide significant insight for the understanding of the complex bacteria-electrode interactions in microbial fuel cells. Copyright © 2017 Elsevier B.V. All rights reserved.

DETERMINING BERYLLIUM IN DRINKING WATER BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROSCOPY

EPA Science Inventory

A direct graphite furnace atomic absorption spectroscopy method for the analysis of beryllium in drinking water has been derived from a method for determining beryllium in urine. Ammonium phosphomolybdate and ascorbic acid were employed as matrix modifiers. The matrix modifiers s...

A High Performance Lithium-Ion Capacitor with Both Electrodes Prepared from Sri Lanka Graphite Ore.

PubMed

Gao, Xiaoyu; Zhan, Changzhen; Yu, Xiaoliang; Liang, Qinghua; Lv, Ruitao; Gai, Guosheng; Shen, Wanci; Kang, Feiyu; Huang, Zheng-Hong

2017-04-14

The natural Sri Lanka graphite (vein graphite) is widely-used as anode material for lithium-ion batteries (LIBs), due to its high crystallinity and low cost. In this work, graphitic porous carbon (GPC) and high-purity vein graphite (PVG) were prepared from Sri Lanka graphite ore by KOH activation, and high temperature purification, respectively. Furthermore, a lithium-ion capacitor (LIC) is fabricated with GPC as cathode, and PVG as anode. The assembled GPC//PVG LIC shows a notable electrochemical performance with a maximum energy density of 86 W·h·kg -1 at 150 W·kg -1 , and 48 W·h·kg -1 at a high-power density of 7.4 kW·kg -1 . This high-performance LIC based on PVG and GPC is believed to be promising for practical applications, due to its low-cost raw materials and industrially feasible production.

A High Performance Lithium-Ion Capacitor with Both Electrodes Prepared from Sri Lanka Graphite Ore

PubMed Central

Gao, Xiaoyu; Zhan, Changzhen; Yu, Xiaoliang; Liang, Qinghua; Lv, Ruitao; Gai, Guosheng; Shen, Wanci; Kang, Feiyu; Huang, Zheng-Hong

2017-01-01

The natural Sri Lanka graphite (vein graphite) is widely-used as anode material for lithium-ion batteries (LIBs), due to its high crystallinity and low cost. In this work, graphitic porous carbon (GPC) and high-purity vein graphite (PVG) were prepared from Sri Lanka graphite ore by KOH activation, and high temperature purification, respectively. Furthermore, a lithium-ion capacitor (LIC) is fabricated with GPC as cathode, and PVG as anode. The assembled GPC//PVG LIC shows a notable electrochemical performance with a maximum energy density of 86 W·h·kg−1 at 150 W·kg−1, and 48 W·h·kg−1 at a high-power density of 7.4 kW·kg−1. This high-performance LIC based on PVG and GPC is believed to be promising for practical applications, due to its low-cost raw materials and industrially feasible production. PMID:28772773

Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

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

Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen

2011-12-01

Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphitemore » content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present« less

Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters

NASA Astrophysics Data System (ADS)

Žumer, Marko; Zajec, Bojan; Rozman, Robert; Nemanič, Vincenc

2012-04-01

Gas-discharge tube (GDT) surge protectors are known for many decades as passive units used in low-voltage telecom networks for protection of electrical components from transient over-voltages (discharging) such as lightning. Unreliability of the mean turn-on DC breakdown voltage and the run-to-run variability has been overcome successfully in the past by adding, for example, a radioactive source inside the tube. Radioisotopes provide a constant low level of free electrons, which trigger the breakdown. In the last decades, any concept using environmentally harmful compounds is not acceptable anymore and new solutions were searched. In our application, a cold field electron emitter source is used as the trigger for the gas discharge but with no activating compound on the two main electrodes. The patent literature describes in details the implementation of the so-called trigger wires (auxiliary electrodes) made of graphite, placed in between the two main electrodes, but no physical explanation has been given yet. We present experimental results, which show that stable cold field electron emission current in the high vacuum range originating from the nano-structured edge of the graphite layer is well correlated to the stable breakdown voltage of the GDT surge protector filled with a mixture of clean gases.

Characteristics of cold atmospheric plasma source based on low-current pulsed discharge with coaxial electrodes

NASA Astrophysics Data System (ADS)

Bureyev, O. A.; Surkov, Yu S.; Spirina, A. V.

2017-05-01

This work investigates the characteristics of the gas discharge system used to create an atmospheric pressure plasma flow. The plasma jet design with a cylindrical graphite cathode and an anode rod located on the axis of the system allows to realize regularly reproducible spark breakdowns mode with a frequency ∼ 5 kHz and a duration ∼ 40 μs. The device generates a cold atmospheric plasma flame with 1 cm in diameter in the flow of various plasma forming gases including nitrogen and air at about 100 mA average discharge current. In the described construction the cathode spots of individual spark channels randomly move along the inner surface of the graphite electrode creating the secondary plasma stream time-average distributed throughout the whole exit aperture area after the decay of numerous filamentary discharge channels. The results of the spectral diagnostics of plasma in the discharge gap and in the stream coming out of the source are presented. Despite the low temperature of atoms and molecules in plasma stream the cathode spots operation with temperature of ∼ 4000 °C at a graphite electrode inside a discharge system enables to saturate the plasma by CN-radicals and atomic carbon in the case of using nitrogen as the working gas.

Macroporous graphitic carbon foam decorated with polydopamine as a high-performance anode for microbial fuel cell

NASA Astrophysics Data System (ADS)

Jiang, Hongmei; Yang, Lu; Deng, Wenfang; Tan, Yueming; Xie, Qingji

2017-09-01

Herein, a macroporous graphitic carbon foam (MGCF) electrode decorated with polydopamine (PDA) is used as a high-performance anode for microbial fuel cell (MFC) applications. The MGCF is facilely prepared by pyrolysis of a powder mixture comprising maltose, nickel nitrate, and ammonia chloride, without using solid porous template. The MGCF is coated with PDA by self-polymerization of dopamine in a basic solution. The MGCF can provide a large surface area for bacterial attachment, and PDA coated on the MGCF electrode can further promote bacterial adhesion resulting from the improved hydrophility, so the MGCF-PDA electrode as an anode in a MFC can show ultrahigh bacterial loading capacity. Moreover, the electrochemical oxidation of flavins at the MGCF-PDA electrode is greatly accelerated, so the extracellular electron transfer mediated by flavins is improved. As a result, the MFC equipped with a MGCF-PDA anode can show a maximum power density of 1735 mW cm-2, which is 6.7 times that of a MFC equipped with a commercial carbon felt anode, indicating a promising anode for MFC applications.

Voltammetric studies of hemoglobin-coated polystyrene latex bead films on pyrolytic graphite electrodes.

PubMed

Sun, Hong; Hu, Naifei

2004-08-01

A novel hemoglobin (Hb)-coated polystyrene (PS) latex bead film was deposited on pyrolytic graphite (PG) electrode surface. In the first step, positively charged Hb molecules in pH 5.0 buffers were adsorbed on the surface of negatively charged, 500 nm diameter PS latex beads bearing sulfate groups by electrostatic interaction. The aqueous dispersion of Hb-coated PS particles was then deposited on the surface of PG electrodes and, after evaporation of the solvent, Hb-PS films were formed. The Hb-PS film electrodes exhibited a pair of well-defined, quasi-reversible cyclic voltammetric (CV) peaks at about -0.36 V vs. SCE in pH 7.0 buffers, characteristic of Hb heme Fe(III)/Fe(II) redox couples. Positions of Soret absorption band of Hb-PS films suggest that Hb retains its near-native structure in the films in its dry form and in solution at medium pH. The Hb in PS films was also acted as a catalyst to catalyze electrochemical reduction of various substrates such as trichloroacetic acid (TCA), nitrite, oxygen and hydrogen peroxide.

Self-Supporting GaN Nanowires/Graphite Paper: Novel High-Performance Flexible Supercapacitor Electrodes.

PubMed

Wang, Shouzhi; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Zhang, Lei; Hao, Xiaopeng

2017-02-01

Flexible supercapacitors have attracted great interest as energy storage devices because of their promise in applications such as wearable and smart electronic devices. Herein, a novel flexible supercapacitor electrode based on gallium nitride nanowire (GaN NW)/graphite paper (GP) nanocomposites is reported. The outstanding electrical conductivities of the GaN NW (6.36 × 10 2 S m -1 ) and GP (7.5 × 10 4 S m -1 ) deliver a synergistically enhanced electrochemical performance that cannot be achieved by either of the components alone. The composite electrode exhibits excellent specific capacitance (237 mF cm -2 at 0.1 mA cm -2 ) and outstanding cycling performance (98% capacitance retention after 10 000 cycles). The flexible symmetric supercapacitor also manifests high energy and power densities (0.30 mW h cm -3 and 1000 mW cm -3 ). These findings demonstrate that the GaN/GP composite electrode has significant potential as a candidate for the flexible energy storage devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pb2+ ions mobility perturbation by iron particles during electrokinetic remediation of contaminated soil.

PubMed

Zulfiqar, Waqas; Iqbal, Muhammad Asad; Butt, Mehwish Khalid

2017-02-01

Electrokinetic (EK) remediation is one of the most useful approaches for de-contamination of soils. However, it is unclear that how and when the electrokinetic remediation gives advantages over other remediation techniques in soil. This study was designed to find the influence of Fe 2+ particles on the mobility of Pb 2+ ions, during electrokinetic remediation, in soil contaminated purposely by lead nitrate Pb(NO 3 ) 2 . Two types of electrokinetic experiments were performed, by using iron and graphite electrodes. The Fe 2+ ions from the iron electrodes, produced due to acidic environment in anode compartment, affected the mobility of lead particles by precipitating as Fe(OH) 2 . Fe 2+ ions enhance the adsorption of lead ions in soil. The results show Fe 2+ ions of lower ionic conductivity decreased mobility of other particles in soil. Electrokinetic remediation for up to 120 h with iron electrodes is shown to be less effective for removal of lead. In contrast, graphite electrodes were 15 times more effective in lead removal from soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Differential pulse voltammetric determination of acyclovir in pharmaceutical preparations using a pencil graphite electrode.

PubMed

Dilgin, Didem Giray; Karakaya, Serkan

2016-06-01

In this study, a new selective and sensitive voltammetric procedure for determination of acyclovir (ACV) was proposed using a disposable electrode, pencil graphite electrode (PGE). Cyclic and differential pulse voltammograms of ACV were recorded in Britton-Robinson buffer solution containing 0.10 M KCl with pH of 4.0 at PGE. The PGE displayed a very good electrochemical behavior with significant enhancement of the peak current compared to a glassy carbon electrode (GCE). Under experimental conditions, the PGE had a linear response range from 1.0 μM to 100.0 μM ACV with a detection limit of 0.3 μM (based on 3 Sb). Relative standard deviations of 4.8 and 3.6% were obtained for five successive determinations of 10.0 and 50.0 μM ACV, respectively, which indicate acceptable repeatability. This voltammetric method was successfully applied to the direct determination of ACV in real pharmaceutical samples. The effect of various interfering compounds on the ACV peak current was studied. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultra-thin passivating film induced by vinylene carbonate on highly oriented pyrolytic graphite negative electrode in lithium-ion cell

NASA Astrophysics Data System (ADS)

Matsuoka, O.; Hiwara, A.; Omi, T.; Toriida, M.; Hayashi, T.; Tanaka, C.; Saito, Y.; Ishida, T.; Tan, H.; Ono, S. S.; Yamamoto, S.

We investigated the influence of vinylene carbonate, as an additive molecule, on the decomposition phenomena of electrolyte solution [ethylene carbonate (EC)—ethyl methyl carbonate (EMC) (1:2 by volume) containing 1 M LiPF 6] on a highly oriented pyrolytic graphite (HOPG) negative electrode by using cyclic voltammetry (CV) and atomic force microscopy (AFM). Vinylene carbonate deactivated reactive sites (e.g. radicals and oxides at the defects and the edge of carbon layer) on the cleaved surface of the HOPG negative electrode, and prevented further decomposition of the other solvents there. Further, vinylene carbonate induced an ultra-thin film (less than 1.0 nm in thickness) on the terrace of the basal plane of the HOPG negative electrode, and this film suppressed the decomposition of electrolyte solution on the terraces of the basal plane. We consider that this ultra-thin passivating film is composed of a reduction product of vinylene carbonate (VC), and might have a polymer structure. These induced effects might explain how VC improves the life performance of lithium-ion cells.

Nano-graphite functionalized mesocellular carbon foam with enhanced intra-penetrating electrical percolation networks for high performance electrochemical energy storage electrode materials.

PubMed

Jo, Changshin; An, Sunhyung; Kim, Younghoon; Shim, Jongmin; Yoon, Songhun; Lee, Jinwoo

2012-04-28

Mesocellular carbon foam (MSU-F-C) is functionalized with hollow nanographite by a simple solution-phase method to enhance the intrapenetrating electrical percolation network. The electrical conductivity of the resulting material, denoted as MSU-F-C-G, is increased by a factor of 20.5 compared with the pristine MSU-F-C. Hollow graphite nanoparticles are well-dispersed in mesocellular carbon foam, as confirmed by transmission electron microscopy (TEM), and the d spacing of the (002) planes is 0.343 nm, which is only slightly larger than that of pure graphite (0.335 nm), suggesting a random combination of graphitic and turbostratic stacking. After nanographitic functionalization, the BET surface area and total pore volume decreased from 928 m(2) g(-1) and 1.5 cm(3) g(-1) to 394 m(2) g(-1) and 0.7 cm(3) g(-1), respectively. Thermogravimetric analysis in air shows that the thermal stability of MSU-F-C-G is improved relative to that of MSU-F-C, and the one-step weight loss indicates that the nanographite is homogeneously functionalized on the MSU-F-C particles. When the resulting mesocellular carbon materials are used as electrode materials for an electric double layer capacitor (EDLC), the specific capacitances (C(sp)) of the MSU-F-C and MSU-F-C-G electrodes at 4 mV s(-1) are 109 F g(-1) and 93 F g(-1), respectively. The MSU-F-C-G electrode exhibited a very high area capacitance (C(area), 23.5 μF cm(-2)) compared with that of the MSU-F-C electrode (11.7 μF cm(-2)), which is attributed to the enhanced intraparticle conductivity by the nanographitic functionalization. MSU-F-C-G exhibited high capacity retention (52%) at a very high scan rate of 512 mV s(-1), while only a 23% capacity retention at 512 mV s(-1) was observed in the case of the MSU-F-C electrode. When applied as an anode in a lithium ion battery, a significant increase in the initial efficiency (44%), high reversible discharge capacity (580 mA h g(-1)) in the lower voltage region, and a higher rate capability were observed. The high rate capability of the MSU-F-C-G electrode as charge storage was due to the low resistance derived from the nanographitic functionalization. This journal is © the Owner Societies 2012

Nucleation/Growth Mechanisms and Morphological Evolution of Porous MnO2 Coating Deposited on Graphite for Supercapacitor

PubMed Central

Huang, Wenxin; Xu, Yunhe

2017-01-01

The nucleation and growth mechanisms of porous MnO2 coating deposited on graphite in MnSO4 solution were investigated in detail by cyclic voltammetry, chronoamperometry and scanning electron microscopy. The electrochemical properties of honeycomb-like MnO2 were evaluated by cycle voltammetry and galvanostatic charge-discharge. Results indicated that MnO2 was synthesized by the following steps: Mn2+→Mn3++e−, Mn3++2H2O→MnOOH+3H+, and MnOOH→MnO2+H++e−. The deposition of MnO2 was divided into four stages. A short incubation period (approximately 1.5 s) was observed, prior to nucleation. The decreasing trend of the current slowed as time increased due to nucleation and MnO2 growth in the second stage. A huge number of nuclei were formed by instantaneous nucleation, and these nuclei grew and connected with one another at an exceedingly short time (0.5 s). In the third stage, the gaps in-between initial graphite flakes were filled with MnO2 until the morphology of the flakes gradually became similar to that of the MnO2-deposited layer. In the fourth stage, the graphite electrode was covered completely with a thick and dense layer of MnO2 deposits. All MnO2 electrodes at different deposition times obtained nearly the same specific capacitance of approximately 186 F/g, thus indicating that the specific capacitance of the electrodes is not related with deposition time. PMID:29048377

Multilayer Approach for Advanced Hybrid Lithium Battery.

PubMed

Ming, Jun; Li, Mengliu; Kumar, Pushpendra; Li, Lain-Jong

2016-06-28

Conventional intercalated rechargeable batteries have shown their capacity limit, and the development of an alternative battery system with higher capacity is strongly needed for sustainable electrical vehicles and hand-held devices. Herein, we introduce a feasible and scalable multilayer approach to fabricate a promising hybrid lithium battery with superior capacity and multivoltage plateaus. A sulfur-rich electrode (90 wt % S) is covered by a dual layer of graphite/Li4Ti5O12, where the active materials S and Li4Ti5O12 can both take part in redox reactions and thus deliver a high capacity of 572 mAh gcathode(-1) (vs the total mass of electrode) or 1866 mAh gs(-1) (vs the mass of sulfur) at 0.1C (with the definition of 1C = 1675 mA gs(-1)). The battery shows unique voltage platforms at 2.35 and 2.1 V, contributed from S, and 1.55 V from Li4Ti5O12. A high rate capability of 566 mAh gcathode(-1) at 0.25C and 376 mAh gcathode(-1) at 1C with durable cycle ability over 100 cycles can be achieved. Operando Raman and electron microscope analysis confirm that the graphite/Li4Ti5O12 layer slows the dissolution/migration of polysulfides, thereby giving rise to a higher sulfur utilization and a slower capacity decay. This advanced hybrid battery with a multilayer concept for marrying different voltage plateaus from various electrode materials opens a way of providing tunable capacity and multiple voltage platforms for energy device applications.

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

Cellulose Derived Graphenic Fibers for Capacitive Desalination of Brackish Water.

PubMed

Pugazhenthiran, Nalenthiran; Sen Gupta, Soujit; Prabhath, Anupama; Manikandan, Muthu; Swathy, Jakka Ravindran; Raman, V Kalyan; Pradeep, Thalappil

2015-09-16

We describe a simple and inexpensive cellulose-derived and layer-by-layer stacked carbon fiber network electrode for capacitive deionization (CDI) of brackish water. The microstructure and chemical composition were characterized using spectroscopic and microscopic techniques; electrochemical/electrical performance was evaluated by cyclic voltammetry and 4-probe electrical conductivity and surface area by Brunauer-Emmett-Teller analysis, respectively. The desalination performance was investigated using a laboratory batch model CDI unit, under fixed applied voltage and varying salt concentrations. Electro-adsorption of NaCl on the graphite reinforced-cellulose (GrC) electrode reached equilibrium quickly (within 90 min) and the adsorbed salts were released swiftly (in 40 min) back into the solution, during reversal of applied potential. X-ray photoelectron spectroscopic studies clearly illustrate that sodium and chloride ions were physisorbed on the negative and positive electrodes, respectively during electro-adsorption. This GrC electrode showed an electro-adsorption capacity of 13.1 mg/g of the electrode at a cell potential of 1.2 V, with excellent recyclability and complete regeneration. The electrode has a high tendency for removal of specific anions, such as fluoride, nitrate, chloride, and sulfate from water in the following order: Cl->NO3->F->SO4(2-). GrC electrodes also showed resistance to biofouling with negligible biofilm formation even after 5 days of incubation in Pseudomonas putida bacterial culture. Our unique cost-effective methodology of layer-by-layer stacking of carbon nanofibers and concurrent reinforcement using graphite provides uniform conductivity throughout the electrode with fast electro-adsorption, rapid desorption, and extended reuse, making the electrode affordable for capacitive desalination of brackish water.

Electrometallurgy of Silicon

DTIC Science & Technology

1988-01-01

wind, plants, and water impounded in elevated reservoirs. Photovoltaic or solar cells, which convert sunlight directly to electricity, belongs tc, the...on record is that of St. Claire DeVille, who claimed that silicon was produced by electrolysing an impure melt of NaAlC14, but his material did not...this composition and purified melts were electrolysed at about 14500C in graphite crucible and using graphite electrodes. Applied potentials were

High-volumetric performance aligned nano-porous microwave exfoliated graphite oxide-based electrochemical capacitors.

PubMed

Ghaffari, Mehdi; Zhou, Yue; Xu, Haiping; Lin, Minren; Kim, Tae Young; Ruoff, Rodney S; Zhang, Q M

2013-09-20

Ultra-high volumetric performance electrochemical double layer capacitors based on high density aligned nano-porous microwave exfoliated graphite oxide have been studied. Elimination of macro-, meso-, and larger micro-pores from electrodes and controlling the nano-morphology results in very high volumetric capacitance, energy, and power density values. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Separation medium containing thermally exfoliated graphite oxide

NASA Technical Reports Server (NTRS)

Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

2012-01-01

A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

Packaging material and flexible medical tubing containing thermally exfoliated graphite oxide

NASA Technical Reports Server (NTRS)

Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

2011-01-01

A packaging material or flexible medical tubing containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

Metal-Organic Frameworks as Highly Active Electrocatalysts for High-Energy Density, Aqueous Zinc-Polyiodide Redox Flow Batteries.

PubMed

Li, Bin; Liu, Jian; Nie, Zimin; Wang, Wei; Reed, David; Liu, Jun; McGrail, Pete; Sprenkle, Vincent

2016-07-13

The new aqueous zinc-polyiodide redox flow battery (RFB) system with highly soluble active materials as well as ambipolar and bifunctional designs demonstrated significantly enhanced energy density, which shows great potential to reduce RFB cost. However, the poor kinetic reversibility and electrochemical activity of the redox reaction of I3(-)/I(-) couples on graphite felts (GFs) electrode can result in low energy efficiency. Two nanoporous metal-organic frameworks (MOFs), MIL-125-NH2 and UiO-66-CH3, that have high surface areas when introduced to GF surfaces accelerated the I3(-)/I(-) redox reaction. The flow cell with MOF-modified GFs serving as a positive electrode showed higher energy efficiency than the pristine GFs; increases of about 6.4% and 2.7% occurred at the current density of 30 mA/cm(2) for MIL-125-NH2 and UiO-66-CH3, respectively. Moreover, UiO-66-CH3 is more promising due to its excellent chemical stability in the weakly acidic electrolyte. This letter highlights a way for MOFs to be used in the field of RFBs.

Graphene Transparent Conductive Electrodes for Next- Generation Microshutter Arrays

NASA Technical Reports Server (NTRS)

Li, Mary; Sultana, Mahmooda; Hess, Larry

2012-01-01

Graphene is a single atomic layer of graphite. It is optically transparent and has high electron mobility, and thus has great potential to make transparent conductive electrodes. This invention contributes towards the development of graphene transparent conductive electrodes for next-generation microshutter arrays. The original design for the electrodes of the next generation of microshutters uses indium-tin-oxide (ITO) as the electrode material. ITO is widely used in NASA flight missions. The optical transparency of ITO is limited, and the material is brittle. Also, ITO has been getting more expensive in recent years. The objective of the invention is to develop a graphene transparent conductive electrode that will replace ITO. An exfoliation procedure was developed to make graphene out of graphite crystals. In addition, large areas of single-layer graphene were produced using low-pressure chemical vapor deposition (LPCVD) with high optical transparency. A special graphene transport procedure was developed for transferring graphene from copper substrates to arbitrary substrates. The concept is to grow large-size graphene sheets using the LPCVD system through chemical reaction, transfer the graphene film to a substrate, dope graphene to reduce the sheet resistance, and pattern the film to the dimension of the electrodes in the microshutter array. Graphene transparent conductive electrodes are expected to have a transparency of 97.7%. This covers the electromagnetic spectrum from UV to IR. In comparison, ITO electrodes currently used in microshutter arrays have 85% transparency in mid-IR, and suffer from dramatic transparency drop at a wavelength of near-IR or shorter. Thus, graphene also has potential application as transparent conductive electrodes for Schottky photodiodes in the UV region.

Nickel as a catalyst for the electro-oxidation of methanol in alkaline medium

NASA Astrophysics Data System (ADS)

Abdel Rahim, M. A.; Abdel Hameed, R. M.; Khalil, M. W.

The use of Ni as a catalyst for the electro-oxidation of methanol in alkaline medium was studied by cyclic voltammetry. It was found that only Ni dispersed on graphite shows a catalytic activity towards methanol oxidation but massive Ni does not. Ni was dispersed on graphite by the electro-deposition from acidic NiSO 4 solution using potentiostatic and galvanostatic techniques. The catalytic activity of the C/Ni electrodes towards methanol oxidation was found to vary with the amount of electro-deposited Ni. The dependence of the oxidation current on methanol concentration and scan rate was discussed. It was concluded from the electro-chemical measurements and SEM analysis that methanol oxidation starts as Ni-oxide is formed on the electrode surface.

High-capacity nanostructured germanium-containing materials and lithium alloys thereof

DOEpatents

Graetz, Jason A.; Fultz, Brent T.; Ahn, Channing; Yazami, Rachid

2010-08-24

Electrodes comprising an alkali metal, for example, lithium, alloyed with nanostructured materials of formula Si.sub.zGe.sub.(z-1), where 0

Development and characterization of a rechargeable carbon foam electrode containing nickel oxyhydroxide active mass

NASA Astrophysics Data System (ADS)

Chye, Matthew B.

2011-12-01

Batteries and asymmetric electrochemical capacitors using nickel-based positive electrodes can provide high currents due to their defect structure and low internal resistance. Nickel-based positive electrodes, therefore, are ideal for high current applications such as power tools and electric vehicles (EVs). The positive electrodes prepared in this research are monolithic graphitic foams electrochemically impregnated with nickel oxyhydroxide active mass and select additives that enhance electrode performance. Carbon foam is a good current collector due to its light-weight, porous, and graphitic nature, which give its good electrical properties and the ability to be used as a current collector. Replacing sintered nickel current collectors in nickel-based batteries with a low cost, readily available material, carbon foam, can reduce the mass of a rechargeable battery. The goal of this research has been to contribute to fundamental science through better understanding of optimizing the deposition and formation processes of the active mass onto carbon foams as well as investigating the active mass behavior under deposition, formation, and cycling conditions. Flooded cells and a PFA sealed asymmetric capacitor have been used. The effects of carbon foam surface pretreatments and how they affect the active material/carbon foam performance are demonstrated. Also the feasibility of this positive electrode as a component in nickel-based batteries, a Ni-Zn cells and an asymmetric capacitor pouch cell, is demonstrated.

Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

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

Taer, E.; Awitdrus,; Farma, R.

Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance ofmore » the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.« less

Alkaline deoxygenated graphene oxide for supercapacitor applications: An effective green alternative for chemically reduced graphene

NASA Astrophysics Data System (ADS)

Perera, Sanjaya D.; Mariano, Ruperto G.; Nijem, Nour; Chabal, Yves; Ferraris, John P.; Balkus, Kenneth J.

2012-10-01

Graphene is a promising electrode material for energy storage applications. The most successful method for preparing graphene from graphite involves the oxidation of graphite to graphene oxide (GO) and reduction back to graphene. Even though different chemical and thermal methods have been developed to reduce GO to graphene, the use of less toxic materials to generate graphene still remains a challenge. In this study we developed a facile one-pot synthesis of deoxygenated graphene (hGO) via alkaline hydrothermal process, which exhibits similar properties to the graphene obtained via hydrazine reduction (i.e. the same degree of deoxygenation found in hydrazine reduced GO). Moreover, the hGO formed freestanding, binder-free paper electrodes for supercapacitors. Coin cell type (CR2032) symmetric supercapacitors were assembled using the hGO electrodes. Electrochemical characterization of hGO was carried out using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and ethylmethylimidazolium bis-(trifluoromethanesulfonyl)imide (EMITFSI) electrolytes. The results for the hGO electrodes were compared with the hydrazine reduced GO (rGO) electrode. The hGO electrode exhibits a energy density of 20 W h kg-1 and 50 W h kg-1 in LiTFSI and EMITFSI respectively, while delivering a maximum power density of 11 kW kg-1 and 14.7 kW kg-1 in LiTFSI and EMITFSI, respectively.

Design of a new nanocomposite between bismuth nanoparticles and graphene oxide for development of electrochemical sensors.

PubMed

Bindewald, Eduardo H; Schibelbain, Arthur F; Papi, Maurício A P; Neiva, Eduardo G C; Zarbin, Aldo J G; Bergamini, Márcio F; Marcolino-Júnior, Luiz H

2017-10-01

This study describes a new route for preparation of a nanocomposite between graphene oxide (GO) and bismuth nanoparticles (BiNPs) and its evaluation as modifier electrode for development of electrochemical sensors. BiNPs were synthesized under ultrasound conditions using Bi(NO 3 ) 3 as metal precursor and ascorbic acid (AA) as reducing agent/passivating. Some experimental parameters of BiNPs synthesis such as Bi 3+ :AA molar ratio and reaction time were conducted aiming the best voltammetric performance of the sensor. Glassy carbon electrodes (GCE) were modified by drop-casting with the BiNPs dispersions and anodic stripping voltammetry measurements were performed and revealed an improvement in the sensitivityfor determination of Cd(II) and Pb(II) compared to an unmodified electrode. The best electrochemical response was obtained for a BiNPs synthesis with Bi 3+ :AA molar ratio of 1:6 and reaction time of 10min, which yielded Bi metallic nanoparticles with average size of 5.4nm confirmed by XRD and TEM images, respectively. GO was produced by graphite oxidation using potassium permanganate and exfoliated with an ultrasound tip. GO-BiNPs nanocomposite was obtained by a simple mixture of GO and BiNPs dispersions in water and kept under ultrasonic bath for 1h. GCE were modified with a nanocomposite suspension containing 0.3 and 1.5mgmL -1 of GO and BiNPs in water, respectively. Under optimized conditions, the proposed nanocomposite was evaluated on the voltammetric determination of Pb (II) and Cd (II), leading to a linear response range between 0.1 and 1.4μmolL -1 for both cations, with limit of detection of 30 and 27nmolL -1 , respectively. These results indicate the great potential of the GO-BiNPs nanocomposite for improving the sensitivity of voltammetric procedures. Copyright © 2017 Elsevier B.V. All rights reserved.

Novel composite material polyoxovanadate@MIL-101(Cr): a highly efficient electrocatalyst for ascorbic acid oxidation.

PubMed

Fernandes, Diana M; Barbosa, André D S; Pires, João; Balula, Salete S; Cunha-Silva, Luís; Freire, Cristina

2013-12-26

A novel hybrid composite material, PMo10V2@MIL-101 was prepared by the encapsulation of the tetra-butylammonium (TBA) salt of the vanadium-substituted phosphomolybdate [PMo10V2O40](5-) (PMo10V2) into the porous metal-organic framework (MOF) MIL-101(Cr). The materials characterization by powder X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy confirmed the preparation of the composite material without disruption of the MOF porous structure. Pyrolytic graphite electrodes modified with the original components (MIL-101(Cr), PMo10V2), and the composite material PMo10V2@MIL-101 were prepared and their electrochemical responses were studied by cyclic voltammetry. Surface confined redox processes were observed for all the immobilized materials. MIL-101(Cr) showed one-electron reduction process due to chromium centers (Cr(III) → Cr(II)), while PMo10V2 presented five reduction processes: the peak at more positive potentials is attributed to two superimposed 1-electron vanadium reduction processes (V(V) → V(IV)) and the other four peaks to Mo-centred two-electron reduction processes (Mo(VI) → Mo(V)). The electrochemical behavior of the composite material PMo10V2@MIL-101 showed both MIL-101(Cr) and PMo10V2 redox features, although with the splitting of the two vanadium processes and the shift of the Mo- and Cr- centered processes to more negative potentials. Finally, PMo10V2@MIL-101 modified electrode showed outstanding enhanced vanadium-based electrocatalytic properties towards ascorbic acid oxidation, in comparison with the free PMo10V2, as a result of its immobilization into the porous structure of the MOF. Furthermore, PMo10V2@MIL-101 modified electrode showed successful simultaneous detection of ascorbic acid and dopamine.

Biodegradation of phenol in batch and continuous flow microbial fuel cells with rod and granular graphite electrodes.

PubMed

Moreno, Lyman; Nemati, Mehdi; Predicala, Bernardo

2018-01-01

Phenol biodegradation was evaluated in batch and continuous flow microbial fuel cells (MFCs). In batch-operated MFCs, biodegradation of 100-1000 mg L -1 phenol was four to six times faster when graphite granules were used instead of rods (3.5-4.8 mg L -1  h -1 vs 0.5-0.9 mg L -1  h -1 ). Similarly maximum phenol biodegradation rates in continuous MFCs with granular and single-rod electrodes were 11.5 and 0.8 mg L -1  h -1 , respectively. This superior performance was also evident in terms of electrochemical outputs, whereby continuous flow MFCs with granular graphite electrodes achieved maximum current and power densities (3444.4 mA m -3 and 777.8 mW m -3 ) that were markedly higher than those with single-rod electrodes (37.3 mA m -3 and 0.8 mW m -3 ). Addition of neutral red enhanced the electrochemical outputs to 5714.3 mA m -3 and 1428.6 mW m -3 . Using the data generated in the continuous flow MFC, biokinetic parameters including μ m , K S , Y and K e were determined as 0.03 h -1 , 24.2 mg L -1 , 0.25 mg cell (mg phenol) -1 and 3.7 × 10 -4  h -1 , respectively. Access to detailed kinetic information generated in MFC environmental conditions is critical in the design, operation and control of large-scale treatment systems utilizing MFC technology.

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.

Highly Flexible Freestanding Porous Carbon Nanofibers for Electrodes Materials of High-Performance All-Carbon Supercapacitors.

PubMed

Liu, Ying; Zhou, Jinyuan; Chen, Lulu; Zhang, Peng; Fu, Wenbin; Zhao, Hao; Ma, Yufang; Pan, Xiaojun; Zhang, Zhenxing; Han, Weihua; Xie, Erqing

2015-10-28

Highly flexible porous carbon nanofibers (P-CNFs) were fabricated by electrospining technique combining with metal ion-assistant acid corrosion process. The resultant fibers display high conductivity and outstanding mechanical flexibility, whereas little change in their resistance can be observed under repeatedly bending, even to 180°. Further results indicate that the improved flexibility of P-CNFs can be due to the high graphitization degree caused by Co ions. In view of electrode materials for high-performance supercapacitors, this type of porous nanostructure and high graphitization degree could synergistically facilitate the electrolyte ion diffusion and electron transportation. In the three electrodes testing system, the resultant P-CNFs electrodes can exhibit a specific capacitance of 104.5 F g(-1) (0.2 A g(-1)), high rate capability (remain 56.5% at 10 A g(-1)), and capacitance retention of ∼94% after 2000 cycles. Furthermore, the assembled symmetric supercapacitors showed a high flexibility and can deliver an energy density of 3.22 Wh kg(-1) at power density of 600 W kg(-1). This work might open a way to improve the mechanical properties of carbon fibers and suggests that this type of freestanding P-CNFs be used as effective electrode materials for flexible all-carbon supercapacitors.

Resistance welding graphite-fiber composites

NASA Technical Reports Server (NTRS)

Lamoureux, R. T.

1980-01-01

High-strength joints are welded in seconds in carbon-reinfored thermoplastic beams. Resistance-welding electrode applies heat and pressure to joint and is spring-loaded to follow softening material to maintain contact; it also holds parts together for cooling and hardening. Both transverse and longitudinal configurations can be welded. Adhesive bonding and encapsulation are more time consuming methods and introduce additional material into joint, while ultrasonic heating can damage graphite fibers in composite.

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: circuitry and mechanical design.

PubMed

Kia, Kaveh Kazemi; Bonabi, Fahimeh

2012-12-01

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

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

Kia, Kaveh Kazemi; Bonabi, Fahimeh

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 {mu}s. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through themore » graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.« less

A Nanoporous Carbon/Exfoliated Graphite Composite For Supercapacitor Electrodes

NASA Astrophysics Data System (ADS)

Rosi, Memoria; Ekaputra, Muhamad P.; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

2010-12-01

Nanoporous carbon was prepared from coconut shells using a simple heating method. The nanoporous carbon is subjected to different treatments: without activation, activation with polyethylene glycol (PEG), and activation with sodium hydroxide (NaOH)-PEG. The exfoliated graphite was synthesized from graphite powder oxidized with zinc acetate (ZnAc) and intercalated with polyvinyl alcohol (PVA) and NaOH. A composite was made by mixing the nanoporous carbon with NaOH-PEG activation, the exfoliated graphite and a binder of PVA solution, grinding the mixture, and annealing it using ultrasonic bath for 1 hour. All of as-synthesized materials were characterized by employing a scanning electron microscope (SEM), a MATLAB's image processing toolbox, and an x-ray diffractometer (XRD). It was confirmed that the composite is crystalline with (002) and (004) orientations. In addition, it was also found that the composite has a high surface area, a high distribution of pore sizes less than 40 nm, and a high porosity (67%). Noting that the pore sizes less than 20 nm are significant for ionic species storage and those in the range of 20 to 40 nm are very accessible for ionic clusters mobility across the pores, the composite is a promising material for the application as supercapacitor electrodes.

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

NASA Astrophysics Data System (ADS)

Kia, Kaveh Kazemi; Bonabi, Fahimeh

2012-12-01

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

Electronically conductive polymer binder for lithium-ion battery electrode

DOEpatents

Liu, Gao; Xun, Shidi; Battaglia, Vincent S.; Zheng, Honghe; Wu, Mingyan

2015-07-07

A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

Electronically conductive polymer binder for lithium-ion battery electrode

DOEpatents

Liu, Gao; Battaglia, Vincent S.; Park, Sang -Jae

2015-10-06

A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

Electronically conductive polymer binder for lithium-ion battery electrode

DOEpatents

Liu, Gao; Xun, Shidi; Battaglia, Vincent S.; Zheng, Honghe; Wu, Mingyan

2017-08-01

A family of carboxylic acid groups containing fluorene/fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries. Triethyleneoxide side chains provide improved adhesion to materials such as, graphite, silicon, silicon alloy, tin, tin alloy. These binders enable the use of silicon as an electrode material as they significantly improve the cycle-ability of silicon by preventing electrode degradation over time. In particular, these polymers, which become conductive on first charge, bind to the silicon particles of the electrode, are flexible so as to better accommodate the expansion and contraction of the electrode during charge/discharge, and being conductive promote the flow battery current.

Uneven biofilm and current distribution in three-dimensional macroporous anodes of bio-electrochemical systems composed of graphite electrode arrays.

PubMed

Li, Jun; Hu, Linbin; Zhang, Liang; Ye, Ding-Ding; Zhu, Xun; Liao, Qiang

2017-03-01

A 3-D macroporous anode was constructed using different numbers of graphite rod arrays in fixed-volume bio-electrochemical systems (BESs), and the current and biofilm distribution were investigated by dividing the 3-D anode into several subunits. In the fixed-volume chamber, current production was not significantly improved after the electrode number increased to 36. In the case of 100 electrodes, a significant uneven current distribution was found in the macroporous anode. This was attributed to a differential pH distribution, which resulted from proton accumulation inside the macroporous anode. The pH distribution influenced the biofilm development and led to an uneven biofilm distribution. With respect to current generation, the uneven distribution of both the pH and biofilm contributed to the uneven current distribution. The center had a low pH, which led to less biofilm and a lower contribution to the total current, limiting the performance of the BESs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt.

PubMed

Jeżowski, P; Crosnier, O; Deunf, E; Poizot, P; Béguin, F; Brousse, T

2018-02-01

Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO 2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.

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.

Safe and recyclable lithium-ion capacitors using sacrificial organic lithium salt

NASA Astrophysics Data System (ADS)

Jeżowski, P.; Crosnier, O.; Deunf, E.; Poizot, P.; Béguin, F.; Brousse, T.

2018-02-01

Lithium-ion capacitors (LICs) shrewdly combine a lithium-ion battery negative electrode capable of reversibly intercalating lithium cations, namely graphite, together with an electrical double-layer positive electrode, namely activated carbon. However, the beauty of this concept is marred by the lack of a lithium-cation source in the device, thus requiring a specific preliminary charging step. The strategies devised thus far in an attempt to rectify this issue all present drawbacks. Our research uncovers a unique approach based on the use of a lithiated organic material, namely 3,4-dihydroxybenzonitrile dilithium salt. This compound can irreversibly provide lithium cations to the graphite electrode during an initial operando charging step without any negative effects with respect to further operation of the LIC. This method not only restores the low CO2 footprint of LICs, but also possesses far-reaching potential with respect to designing a wide range of greener hybrid devices based on other chemistries, comprising entirely recyclable components.

Graphene Oxide-Assisted Liquid Phase Exfoliation of Graphite into Graphene for Highly Conductive Film and Electromechanical Sensors.

PubMed

Tung, Tran Thanh; Yoo, Jeongha; Alotaibi, Faisal K; Nine, Md J; Karunagaran, Ramesh; Krebsz, Melinda; Nguyen, Giang T; Tran, Diana N H; Feller, Jean-Francois; Losic, Dusan

2016-06-29

Here, we report a new method to prepare graphene from graphite by the liquid phase exfoliation process with sonication using graphene oxide (GO) as a dispersant. It was found that GO nanosheets act a as surfactant to the mediated exfoliation of graphite into a GO-adsorbed graphene complex in the aqueous solution, from which graphene was separated by an additional process. The preparation of isolated graphene from a single to a few layers is routinely achieved with an exfoliation yield of up to higher than 40% from the initial graphite material. The prepared graphene sheets showed a high quality (C/O ∼ 21.5), low defect (ID/IG ∼ 0.12), and high conductivity (6.2 × 10(4) S/m). Moreover, the large lateral size ranging from 5 to 10 μm of graphene, which is believed to be due to the shielding effect of GO avoiding damage under ultrasonic jets and cavitation formed by the sonication process. The thin graphene film prepared by the spray-coating technique showed a sheet resistance of 668 Ω/sq with a transmittance of 80% at 550 nm after annealing at 350 °C for 3 h. The transparent electrode was even greater with the resistance only 66.02 Ω when graphene is deposited on an interdigitated electrode (1 mm gap). Finally, a flexible sensor based on a graphene spray-coating polydimethylsiloxane (PDMS) is demonstrated showing excellent performance working under human touch pressure (<10 kPa). The graphene prepared by this method has some distinct properties showing it as a promising material for applications in electronics including thin film coatings, transparent electrodes, wearable electronics, human monitoring sensors, and RFID tags.

Automotive body panel containing thermally exfoliated graphite oxide

NASA Technical Reports Server (NTRS)

Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor); Prud'Homme, Robert K. (Inventor); Adamson, Douglas (Inventor)

2011-01-01

An automotive body panel containing a polymer composite formed of at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

Effect of electrolyte composition on initial cycling and impedance characteristics of lithium-ion cells

NASA Astrophysics Data System (ADS)

Abraham, D. P.; Furczon, M. M.; Kang, S.-H.; Dees, D. W.; Jansen, A. N.

Hybrid-electric vehicles require lithium-battery electrolytes that form stable, low impedance passivation layers to protect the electrodes, while allowing rapid lithium-ion transport under high current charge/discharge pulses. In this article, we describe data acquired on cells containing LiNi 0.8Co 0.15Al 0.05O 2-based positive electrodes, graphite-based negative electrodes, and electrolytes with lithium hexafluorophosphate (LiPF 6), lithium tetrafluoroborate (LiBF 4), lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato) borate (LiF 2OB) salts. The impedance data were collected in cells containing a Li-Sn reference electrode to determine effect of electrolyte composition and testing temperature on individual electrode impedance. The full cell impedance data showed the following trend: LiBOB > LiBF 4 > LiF 2OB > LiPF 6. The negative electrode impedance showed a trend similar to that of the full cell; this electrode was the main contributor to impedance in the LiBOB and LiBF 4 cells. The positive electrode impedance values for the LiBF 4, LiF 2OB, and LiPF 6 cells were comparable; the values were somewhat higher for the LiBOB cell. Cycling and impedance data were also obtained for cells containing additions of LiBF 4, LiBOB, LiF 2OB, and vinylene carbonate (VC) to the EC:EMC (3:7 by wt.) + 1.2 M LiPF 6 electrolyte. Our data indicate that the composition and morphology of the graphite SEI formed during the first lithiation cycle is an important determinant of the negative electrode impedance, and hence full cell impedance.

Unraveling the Reactivity of Minium toward Bicarbonate and the Role of Lead Oxides Therein.

PubMed

Ayalew, Eyasu; Janssens, Koen; De Wael, Karolien

2016-02-02

Understanding the reactivity of (semiconductor) pigments provides vital information on how to improve conservation strategies for works of art to avoid rapid degradation of the pigments. This study focuses on the photoactivity of minium (Pb3O4), a semiconductor pigment that gives rise to strong discoloration phenomena upon exposure to various environmental conditions. For demonstrating its photoactivity, an electrochemical setup with a minium-modified graphite electrode (C|Pb3O4) was used. It is confirmed that minium is a p-type semiconductor that is photoactive during illumination and becomes inactive in the dark. Raman measurements confirm the formation of degradation products. The photoactivity of a semiconductor pigment is partly defined by the presence of lead oxide (PbO) impurities; these introduce new states in the original band gap. It will be experimentally evidenced that the presence of PbO particles in minium leads to an upward shift of the valence band that reduces the band gap. Thus, upon photoexcitation, the electron/hole separation is more easily initialized. The PbO/Pb3O4 composite electrodes demonstrate a higher reductive photocurrent compared to the photocurrent registered at pure PbO or Pb3O4-modified electrodes. Upon exposure to light with energy close to and above the band gap, electrons are excited from the valence band to the conduction band to initialize the reduction of Pb(IV) to Pb(II), resulting in the initial formation of PbO. However, in the presence of bicarbonate ions, a significantly higher photoreduction current is recorded because the PbO reacts further to form hydrocerussite. Therefore, the presence of bicarbonates in the environment stimulates the photodecomposition process of minium and plays an important role in the degradation process.

Proposal of simple and novel method of capacity fading analysis using pseudo-reference electrode in lithium ion cells: Application to solvent-free lithium ion polymer batteries

NASA Astrophysics Data System (ADS)

Shono, Kumi; Kobayashi, Takeshi; Tabuchi, Masato; Ohno, Yasutaka; Miyashiro, Hajime; Kobayashi, Yo

2014-02-01

We propose a simple procedure for introducing a pseudo-reference electrode (PRE) to lithium ion batteries using isometric lithium metal placed between the cathode and anode, and we successfully obtained the cathode and anode voltage profiles, individual interfacial impedances, and the misalignment of the operation range between the cathode and anode after cycle operation. The proposed procedure is applicable to lithium ion battery systems using a solid electrolyte to prepare two cells with a lithium counter electrode. We determined the capacity decrease of a solvent-free lithium ion polymer battery consisting of a LiNi1/3Mn1/3Co1/3O2 (NMC), a polyether-based solid polymer electrolyte (SPE), and a graphite (Gr) with the proposed PRE over 1000 cycles. The capacity retention of the [Gr|SPE|NMC] cell reached 50% at the 1000th cycle upon the optimization of cell preparation, and we found that the main factor of the capacity decrease was the continuous irreversible loss of active lithium at the graphite anode, not the oxidation of the SPE. Our findings suggest that we should reconsider combining a polyether-based SPE with a conventionally used 4 V class cathode and a graphite anode to develop an innovative, safe, and low-cost battery for the expected large lithium ion battery systems for stationary use.

Improvement of Ion/Ioff for h-BN encapsulated bilayer graphene by graphite local back gate electrode

NASA Astrophysics Data System (ADS)

Uwanno, Teerayut; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

The critical issue for bilayer graphene (BLG) devices is low Ion/Ioff even at the band gap of 0.3eV. Band gap in BLG can be formed by creating potential difference between the two layers of BLG. This can be done by applying external electric field perpendicularly to BLG to induce different carrier densities in the two layers. Due to such origin, the spatial uniformity of band gap in the channel is quite sensitive to charge inhomogeneity in BLG. In order to apply electric field of 3V/nm to open the maximum band gap of 0.3eV, high- k gate stack has been utilized so far. However, oxide dielectrics usually have large charge inhomogeneity causing in-plane potential fluctuation in BLG channel. Due to surface flatness and small charge inhomogeneity, h-BN has been used as dielectrics to achieve high quality graphene devices, however, Ion/Iofffor BLG/ h-BN heterostuctures has not been reported yet. In this study, we used graphite as local back gate electrode to BLG encapsulated with h-BN. This resulted in much higher Ion/Ioff, indicating the importance of screening of charge inhomogeneity from SiO2 substrate surface by local graphite back gate electrode. This research was partly supported by JSPS Core-to-Core Program, A. Advanced Research Networks.

Carbon-oxygen reaction efficiency in air gap switch with graphite electrodes under high current pulse discharge

NASA Astrophysics Data System (ADS)

Dai, Hongyu; Li, Lee; Peng, Ming-yang; Xiong, Jiaming; Wu, Haibo; Yu, Bin

2017-12-01

In order to reduce the effect of residual carbon on the insulation performance, after the GW-hundreds kiloampere graphite-electrode switch turning on, the chemical kinetics of the carbon-oxygen reaction is analyzed. The capacitive pulsed experimental circuit is used to reconstruct the actual condition of high power and high current discharge. The carbon-oxygen reaction efficiency is analyzed using a Fourier transform infrared spectrometer and a flue gas analyzer. The research shows that the gas products include NOX, O3, CH4, and COX. Through the quantitative analysis, the conversion efficiency of COX increases with the augment of the accumulated transferred charge, and the change law of the CO generation efficiency has an extreme value. With the corresponding calculation and the observation of the scanning electron microscope, it is found that most of the carbon consumed from the graphite electrodes is converted to amorphous elemental carbon, and the insufficiency of the carbon-oxygen reaction leads to the problem of carbon residue, for 20%-45% of elemental carbon is not oxidized. The size of amorphous elemental carbon is about several micrometers to tens micrometers by the analysis of metallographic microscope. In the condition of compressed air, changing the amount of transferred charge is helpful to improve the carbon-oxygen reaction efficiency and inhibit the problem of carbon residue.

Label-free voltammetric detection of MicroRNAs at multi-channel screen printed array of electrodes comparison to graphite sensors.

PubMed

Erdem, Arzum; Congur, Gulsah

2014-01-01

The multi-channel screen-printed array of electrodes (MUX-SPE16) was used in our study for the first time for electrochemical monitoring of nucleic acid hybridization related to different miRNA sequences (miRNA-16, miRNA-15a and miRNA-660, i.e, the biomarkers for Alzheimer disease). The MUX-SPE16 was also used for the first time herein for the label-free electrochemical detection of nucleic acid hybridization combined magnetic beads (MB) assay in comparison to the disposable pencil graphite electrode (PGE). Under the principle of the magnetic beads assay, the biotinylated inosine substituted DNA probe was firstly immobilized onto streptavidin coated MB, and then, the hybridization process between probe and its complementary miRNA sequence was performed at MB surface. The voltammetric transduction was performed using differential pulse voltammetry (DPV) technique in combination with the single-use graphite sensor technologies; PGE and MUX-SPE16 for miRNA detection by measuring the guanine oxidation signal without using any external indicator. The features of single-use sensor technologies, PGE and MUX-SPE16, were discussed concerning to their reproducibility, detection limit, and selectivity compared to the results in the earlier studies presenting the electrochemical miRNA detection related to different miRNA sequences. © 2013 Elsevier B.V. All rights reserved.

Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction.

PubMed

Huang, K; Bi, K; Liang, C; Lin, S; Wang, W J; Yang, T Z; Liu, J; Zhang, R; Fan, D Y; Wang, Y G; Lei, M

2015-01-01

Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR) benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon.

Construction of 3D nanostructure hierarchical porous graphitic carbons by charge-induced self-assembly and nanocrystal-assisted catalytic graphitization for supercapacitors.

PubMed

Ma, Fangwei; Ma, Di; Wu, Guang; Geng, Weidan; Shao, Jinqiu; Song, Shijiao; Wan, Jiafeng; Qiu, Jieshan

2016-05-10

A smart and sustainable strategy based on charge-induced self-assembly and nanocrystal-assisted catalytic graphitization is explored for the efficient construction of 3D nanostructure hierarchical porous graphitic carbons from the pectin biopolymer. The electrostatic interaction between the negatively charged pectin chains and magnesium ions plays a crucial role in the formation of 3D architectures. The 3D HPGCs possess a three-dimensional carbon framework with a hierarchical porous structure, flake-like graphitic carbon walls and high surface area (1320 m(2) g(-1)). The 3D HPGCs show an outstanding specific capacitance of 274 F g(-1) and excellent rate capability with a high capacitance retention of 85% at a high current density of 50 A g(-1) for supercapacitor electrodes. This strategy provided a novel approach to effectively construct 3D porous carbon nanostructures from biopolymers.

Pillared graphite anodes for reversible sodiation.

PubMed

Zhang, Hanyang; Li, Zhifei; Xu, Wei; Chen, Yicong; Ji, Xiulei; Lerner, Michael M

2018-08-10

There has been a major effort recently to develop new rechargeable sodium-ion electrodes. In lithium ion batteries, LiC 6 forms from graphite and desolvated Li cations during the first charge. With sodium ions, graphite only shows a significant capacity when Na + intercalates as a solvated complex, resulting in ternary graphite intercalation compounds (GICs). Although this chemistry has been shown to be highly reversible and to support high rates in small test cells, these GICs can require >250% volume expansion and contraction during cycling. Here we demonstrate the first example of GICs that reversibly sodiate/desodiate without any significant volume change. These pillared GICs are obtained by electrochemical reduction of graphite in an ether/amine co-solvent electrolyte. The initial gallery expansion, 0.36 nm, is less than half of that in diglyme-based systems, and shows a similar capacity. Thermal analyses suggest the pillaring phenomenon arises from stronger co-intercalate interactions in the GIC galleries.

In situ oxygen plasma cleaning of microswitch surfaces—comparison of Ti and graphite electrodes

NASA Astrophysics Data System (ADS)

Oh, Changho; Streller, Frank; Ashurst, W. Robert; Carpick, Robert W.; de Boer, Maarten P.

2016-11-01

Ohmic micro- and nanoswitches are of interest for a wide variety of applications including radio frequency communications and as low power complements to transistors. In these switches, it is of paramount importance to maintain surface cleanliness in order to prevent frequent failure by tribopolymer growth. To prepare surfaces, an oxygen plasma clean is expected to be beneficial compared to a high temperature vacuum bakeout because of shorter cleaning time (<5 min compared to ~24 h) and active removal of organic contaminants. We demonstrate that sputtering of the electrode material during oxygen plasma cleaning is a critical consideration for effective cleaning of switch surfaces. With Ti electrodes, a TiO x layer forms that increases electrical contact resistance. When plasma-cleaned using graphite electrodes, the resistance of Pt-coated microswitches exhibit a long lifetime with consistently low resistance (<0.5 Ω variation over 300 million cycles) if the test chamber is refilled with ultra-high purity nitrogen and if the devices are not exposed to laboratory air. Their current-voltage characteristic is also linear at the millivolt level. This is important for nanoswitches which will be operated in that range.

The application of phase contrast X-ray techniques for imaging Li-ion battery electrodes

NASA Astrophysics Data System (ADS)

Eastwood, D. S.; Bradley, R. S.; Tariq, F.; Cooper, S. J.; Taiwo, O. O.; Gelb, J.; Merkle, A.; Brett, D. J. L.; Brandon, N. P.; Withers, P. J.; Lee, P. D.; Shearing, P. R.

2014-04-01

In order to accelerate the commercialization of fuel cells and batteries across a range of applications, an understanding of the mechanisms by which they age and degrade at the microstructural level is required. Here, the most widely commercialized Li-ion batteries based on porous graphite based electrodes which de/intercalate Li+ ions during charge/discharge are studied by two phase contrast enhanced X-ray imaging modes, namely in-line phase contrast and Zernike phase contrast at the micro (synchrotron) and nano (laboratory X-ray microscope) level, respectively. The rate of charge cycling is directly dependent on the nature of the electrode microstructure, which are typically complex multi-scale 3D geometries with significant microstructural heterogeneities. We have been able to characterise the porosity and the tortuosity by micro-CT as well as the morphology of 5 individual graphite particles by nano-tomography finding that while their volume varied significantly their sphericity was surprisingly similar. The volume specific surface areas of the individual grains measured by nano-CT are significantly larger than the total volume specific surface area of the electrode from the micro-CT imaging, which can be attributed to the greater particle surface area visible at higher resolution.

In-situ synthesis of Co3O4/graphite nanocomposite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Gopalakrishnan, M.; Srikesh, G.; Mohan, A.; Arivazhagan, V.

2017-05-01

In this work, a low cost and pollution free in-situ synthesis of phase pure Co3O4 nanoparticles and Co3O4/graphite nanocomposite have been successfully developed via co-precipitation method followed by the thermal treatment process. The prepared samples were characterized by powder X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Fourier Transform Infrared Spectroscopy and electrochemical measurements. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy were carried out in 6 M KOH aqueous electrolytic solution. The results show the excellent maximum specific capacitive behavior of 239.5 F g-1 for pure and 395.04 F g-1 for Co3O4/graphite nanocomposite at a current density of 0.5 A g-1. This composite exhibits a good cyclic stability, with a small loss of 2.68% of maximum capacitance over a consecutive 1000 cycles. The investigation indicates that the prepared electrode material could be a potential and promising candidate for electrochemical supercapacitors.

Hindered Glymes for Graphite-Compatible Electrolytes.

PubMed

Shanmukaraj, Devaraj; Grugeon, Sylvie; Laruelle, Stephane; Armand, Michel

2015-08-24

Organic carbonate mixtures are used almost exclusively as lithium battery electrolyte solvents. The linear compounds (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) act mainly as thinner for the more viscous and high-melting ethylene carbonate but are the least stable component and have low flash points; these are serious handicaps for lifetime and safety. Polyethers (glymes) are useful co-solvents, but all formerly known representatives solvate Li(+) strongly enough to co-intercalate in the graphite negative electrode and exfoliate it. We have put forward a new electrolyte composition comprising a polyether to which a bulky tert-butyl group is attached ("hindered glyme"), thus completely preventing co-intercalation while maintaining good conductivity. This alkyl-carbonate-free electrolyte shows remarkable cycle efficiency of the graphite electrode, not only at room temperature, but also at 50 and 70 °C in the presence of lithium bis(fluorosulfonimide). The two-ethylene-bridge hindered glyme has a high boiling point and a flash point of 80 °C, a considerable advantage for safety. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of glucose biosensor based on reconstitution of glucose oxidase onto polymeric redox mediator coated pencil graphite electrodes.

PubMed

Dervisevic, Muamer; Cevik, Emre; Senel, Mehmet

2015-01-01

In this study, a novel glucose biosensor was fabricated by reconstitutional immobilization of glucose oxidase (GOx) onto a poly(glycidyl methacrylate-co-vinylferrocene) (poly(GMA-co-VFc)) film coated pencil graphite electrode (PGE). The amperometric current response of poly(GMA-co-VFc)-GOx to glucose is linear in the concentration range between 1 and 16mM (correlation coefficient of 0.9998) with a detection limit of 2.7μM (S/N=3). Experimental parameters were studied in detail and optimized, including the pH and temperature governing the analytical performance of the biosensor. The stability and reusability of the biosensor as well as its kinetic parameters have also been studied. Copyright © 2014 Elsevier Inc. All rights reserved.

Sequence-specific label-free nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a using a disposable pencil graphite electrode.

PubMed

Donmez, Soner; Arslan, Fatma; Arslan, Halit

2016-05-01

In this paper, we demonstrate a simple, sensitive, inexpensive, disposable and label-free electrochemical nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a (HCV1a). The nucleic acid biosensor was designed with the amino-linked inosine-substituted 20-mer probes, which were immobilized onto a disposable pencil graphite electrode (PGE) by covalent linking. The proposed nucleic acid biosensor was linear in the range of 0.05 and 0.75 μM, exhibiting a limit of detection of 54.9 nM. The single-stranded synthetic PCR product analogs of HCV1a were also detected with satisfactory results under optimal conditions, showing the potential application of this biosensor.

Electrochemical treatment of evaporated residue of soak liquor generated from leather industry.

PubMed

Boopathy, R; Sekaran, G

2013-09-15

The organic and suspended solids present in soak liquor, generated from leather industry, demands treatment. The soak liquor is being segregated and evaporated in solar evaporation pans/multiple effect evaporator due to non availability of viable technology for its treatment. The residue left behind in the pans/evaporator does not carry any reuse value and also faces disposal threat due to the presence of high concentration of sodium chloride, organic and bacterial impurities. In the present investigation, the aqueous evaporated residue of soak liquor (ERSL) was treated by electrochemical oxidation. Graphite/graphite and SS304/graphite systems were used in electrochemical oxidation of organics in ERSL. Among these, graphite/graphite system was found to be effective over SS304/graphite system. Hence, the optimised conditions for the electrochemical oxidation of organics in ERSL using graphite/graphite system was evaluated by response surface methodology (RSM). The mass transport coefficient (km) was calculated based on pseudo-first order rate kinetics for both the electrode systems (graphite/graphite and SS304/graphite). The thermodynamic properties illustrated the electrochemical oxidation was exothermic and non-spontaneous in nature. The calculated specific energy consumption at the optimum current density of 50 mA cm(-2) was 0.41 kWh m(-3) for the removal of COD and 2.57 kWh m(-3) for the removal of TKN. Copyright © 2013 Elsevier B.V. All rights reserved.

Tire containing thermally exfoliated graphite oxide

NASA Technical Reports Server (NTRS)

Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

2011-01-01

A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

One-pot hydrothermal synthesis, characterization, and electrochemical properties of rGO/MnFe2O4 nanocomposites

NASA Astrophysics Data System (ADS)

Kotutha, Isara; Swatsitang, Ekaphan; Meewassana, Worawat; Maensiri, Santi

2015-06-01

In this work, a simple facile route for preparing an rGO/MnFe2O4 nanocomposite through a one-pot hydrothermal approach was demonstrated. Graphite oxide (GO) was prepared from graphite powder by a modified Hummers method. Fe(NO3)2 • 9H2O and Mn(NO3)2 • H2O were used as the precursors for the preparation of the rGO/MnFe2O4 nanocomposite. The formation of the rGO/MnFe2O4 nanocomposite was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Rama spectroscopy (Raman). The specific surface area of the prepared composite obtained by Brunauer-Emmett-Teller (BET) analysis was lower than that of pure rGO but higher than that of pure MnFe2O4. Consequently, the electrochemical performance was investigated by using a three-electrode cell system in 6.0 M KOH. The results show that the specific capacitance was determined to be 190.3, 276.9, and 144.5 F/g at a scan rate of 10 mV/s, and 194.9, 274.6, and 134.4 F/g at a current density of 5.0 A/g for rGO, rGO/(5 mmol) MnFe2O4, and rGO/(10 mmol) MnFe2O4, respectively. These results suggest that the composite of MnFe2O4 nanoparticles on an rGO nanosheet can improve the capacitive behavior of the fabricated electrode, but the electrochemical properties are reduced when the MnFe2O4 concentration ratio is high.

Nano-level monitoring of Mn(2+) ion by fabrication of coated pyrolytic graphite electrode based on isonicotinohydrazide derivatives.

PubMed

Sahani, Manoj Kumar; Singh, A K; Jain, A K

2015-05-01

The two ionophores N'(N',N‴E,N',N‴E)-N',N‴-((((oxybis(ethane-2,1-diyl))bis(oxy)) bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I1) and (N',N‴E,N',N‴E)-N',N‴-(((propane-1,3-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I2) were synthesised and investigated as neutral carrier in the fabrication of Mn(2+) ion selective sensor. Several membranes were prepared by incorporating different plasticizers and anionic excluders and their effect on potentiometric response was studied. The best analytical performance was obtained with the electrode having a membrane of composition of I2: PVC: o-NPOE: NaTPB in the ratio of 6:34:58:2 (w/w, mg). Comparative studies of coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) based on I2 reveal the superiority of CPGE. The CPGE exhibits wide working concentration range of 1.23×10(-8)-1.0×10(-1) mol L(-1) and a detection limit down to 4.78×10(-9) mol L(-1) with a Nernstian slope of 29.5±0.4 mV decade(-1) of activity. The sensor performs satisfactorily over a wide pH range (3.5-9.0) and exhibited a quick response time (9s). The sensor can work satisfactorily in water-acetonitrile and water-methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor could be used for a period of four months without any significant divergence in performance. The sensor reflects its utility in the quantification of Mn(2+) ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Mn(2+) ion with ethylenediaminetetraacetic acid (EDTA). Copyright © 2015 Elsevier B.V. All rights reserved.

Nitrogen-doped porous graphitic carbon as an excellent electrode material for advanced supercapacitors.

PubMed

Sun, Li; Tian, Chungui; Fu, Yu; Yang, Ying; Yin, Jie; Wang, Lei; Fu, Honggang

2014-01-07

An advanced supercapacitor material based on nitrogen-doped porous graphitic carbon (NPGC) with high a surface area was synthesized by means of a simple coordination-pyrolysis combination process, in which tetraethyl orthosilicate (TEOS), nickel nitrate, and glucose were adopted as porogent, graphitic catalyst precursor, and carbon source, respectively. In addition, melamine was selected as a nitrogen source owing to its nitrogen-enriched structure and the strong interaction between the amine groups and the glucose unit. A low-temperature treatment resulted in the formation of a NPGC precursor by combination of the catalytic precursor, hydrolyzed TEOS, and the melamine-glucose unit. Following pyrolysis and removal of the catalyst and porogent, the NPGC material showed excellent electrical conductivity owing to its high crystallinity, a large Brunauer-Emmett-Teller surface area (SBET =1027 m(2)  g(-1) ), and a high nitrogen level (7.72 wt %). The unusual microstructure of NPGC materials could provide electrochemical energy storage. The NPGC material, without the need for any conductive additives, showed excellent capacitive behavior (293 F g(-1) at 1 A g(-1) ), long-term cycling stability, and high coulombic efficiency (>99.9 % over 5000 cycles) in KOH when used as an electrode. Notably, in a two-electrode symmetric supercapacitor, NPGC energy densities as high as 8.1 and 47.5 Wh kg(-1) , at a high power density (10.5 kW kg(-1) ), were achieved in 6 M KOH and 1 M Et4 NBF4 -PC electrolytes, respectively. Thus, the synthesized NPGC material could be a highly promising electrode material for advanced supercapacitors and other conversion devices. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Construction and performance characteristics of polymeric membrane electrode and coated graphite electrode for the selective determination of Fe³⁺ ion.

PubMed

Bandi, Koteswara Rao; Singh, Ashok K; Upadhyay, Anjali

2014-03-01

Novel Fe(3+) ion-selective polymeric membrane electrodes (PMEs) were prepared using three different ionophores N-(4-(dimethylamino)benzylidene)thiazol-2-amine [L1], 5-((3-methylthiophene-2yl) methyleneamino)-1,3,4-thiadiazole-2-thiol [L2] and N-((3-methylthiophene-2yl)methylene)thiazol-2-amine [L3] and their potentiometric characteristics were discussed. Effect of various plasticizers and anion excluders was also studied in detail and improved performance was observed. The best performance was obtained for the membrane electrode having a composition of L2:PVC:o-NPOE:NaTPB as 3:38.5:56:2.5 (w/w; mg). A coated graphite electrode (CGE) was also prepared with the same composition and compared. CGE is found to perform better as it shows a wider working concentration range of 8.3×10(-8)-1.0×10(-1)molL(-1), a lower detection limit of 2.3×10(-8)molL(-1), and a near Nernstian slope of 19.5 ± 0.4 mVdecade(-1) of activity with a response time of 10s. The CGE shows a shelf life of 6 weeks and in view of high selectivity, it can be used to quantify Fe(3+) ion in water, soil, vegetable and medicinal plants. It can also be used as an indicator electrode in potentiometric titration of EDTA with Fe(3+) ion. Copyright © 2013. Published by Elsevier B.V.

Electrode wells for powerline-frequency electrical heating of soils

DOEpatents

Buettner, H.M.; Daily, W.D.; Aines, R.D.; Newmark, R.L.; Ramirez, A.L.; Siegel, W.H.

1999-05-25

An electrode well is described for use in powerline-frequency heating of soils for decontamination of the soil. Heating of soils enables the removal of volatile organic compounds from soil when utilized in combination with vacuum extraction. A preferred embodiment of the electrode well utilizes a mild steel pipe as the current-carrying conductor to at least one stainless steel electrode surrounded by a conductive backfill material, preferably graphite or steel shot. A covering is also provided for electrically insulating the current-carrying pipe. One of the electrode wells is utilized with an extraction well which is under subatmospheric pressure to withdraw the volatile material, such as gasoline and trichloroethylene (TCE) as it is heated. 4 figs.

Electrode wells for powerline-frequency electrical heating of soils

DOEpatents

Buettner, Harley M.; Daily, William D.; Aines, Roger D.; Newmark, Robin L.; Ramirez, Abelardo L.; Siegel, William H.

1999-01-01

An electrode well for use in powerline-frequency heating of soils for decontamination of the soil. Heating of soils enables the removal of volatile organic compounds from soil when utilized in combination with vacuum extraction. A preferred embodiment of the electrode well utilizes a mild steel pipe as the current-carrying conductor to at least one stainless steel electrode surrounded by a conductive backfill material, preferably graphite or steel shot. A covering is also provided for electrically insulating the current-carrying pipe. One of the electrode wells is utilized with an extraction well which is under subatmospheric pressure to withdraw the volatile material, such as gasoline and trichioroethylene (TCE) as it is heated.

Transient photoresponse of nitrogen-doped ultrananocrystalline diamond electrodes in saline solution

NASA Astrophysics Data System (ADS)

Ahnood, Arman; Simonov, Alexandr N.; Laird, Jamie S.; Maturana, Matias I.; Ganesan, Kumaravelu; Stacey, Alastair; Ibbotson, Michael R.; Spiccia, Leone; Prawer, Steven

2016-03-01

Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamond nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm-2, charge injection capacity of 0.01 mC cm-2 is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.

One-Step Catalytic Synthesis of CuO/Cu2O in a Graphitized Porous C Matrix Derived from the Cu-Based Metal-Organic Framework for Li- and Na-Ion Batteries.

PubMed

Kim, A-Young; Kim, Min Kyu; Cho, Keumnam; Woo, Jae-Young; Lee, Yongho; Han, Sung-Hwan; Byun, Dongjin; Choi, Wonchang; Lee, Joong Kee

2016-08-03

The hybrid composite electrode comprising CuO and Cu2O micronanoparticles in a highly graphitized porous C matrix (CuO/Cu2O-GPC) has a rational design and is a favorable approach to increasing the rate capability and reversible capacity of metal oxide negative materials for Li- and Na-ion batteries. CuO/Cu2O-GPC is synthesized through a Cu-based metal-organic framework via a one-step thermal transformation process. The electrochemical performances of the CuO/Cu2O-GPC negative electrode in Li- and Na-ion batteries are systematically studied and exhibit excellent capacities of 887.3 mAh g(-1) at 60 mA g(-1) after 200 cycles in a Li-ion battery and 302.9 mAh g(-1) at 50 mA g(-1) after 200 cycles in a Na-ion battery. The high electrochemical stability was obtained via the rational strategy, mainly owing to the synergy effect of the CuO and Cu2O micronanoparticles and highly graphitized porous C formed by catalytic graphitization of Cu nanoparticles. Owing to the simple one-step thermal transformation process and resulting high electrochemical performance, CuO/Cu2O-GPC is one of the prospective negative active materials for rechargeable Li- and Na-ion batteries.

Electrospun N-doped Hierarchical Porous Carbon Nanofiber with Improved Graphitization Degree for High Performance Lithium Ion Capacitor.

PubMed

Li, Baohua; Shi, Ruiying; Han, Cuiping; Xu, Xiaofu; Qing, Xianying; Xu, Lei; Li, Hongfei; Li, Junqin; Wong, Ching-Ping

2018-05-14

Lithium ion capacitor (LIC) has been regarded as a promising device to combine the merits of lithium ion batteries and supercapacitors, which can meet the requirements for both high energy and power density. The development of advanced electrode is the key. Herein, we demonstrate the bottom-up synthesis of activated carbon nanofiber (a-PANF) with hierarchical porous structure and high graphitization degree. Electrospinning is employed to prepare interconnected fiber network with macropores and ferric acetylacetonate is introduced as both mesopore creating agent and graphitic catalyst to increase the graphitization degree. Furthermore, chemical activation enlarges the specific surface area by producing rich micropores. Half cell evaluation of the as-prepared a-PANF displays a discharge capacity of 80 mAh g-1 at 0.1 A g-1 within 2~4.5 V and no capacity fading after 1000 cycles at 2 A g-1, which is significantly higher than conventional activated carbon. Furthermore, the as-assembled LIC with a-PANF cathode and Fe3O4 anode achieves a superior energy density of 124.6 Wh kg-1 at a specific power of 93.8 W kg-1, and remains 103.7 Wh kg-1 at 4687.5 W kg-1, demonstrating the promising application of a-PANF as potential electrode candidates for efficient energy storage systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas storage cylinder formed from a composition containing thermally exfoliated graphite

NASA Technical Reports Server (NTRS)

Aksay, Ilhan A. (Inventor); Prud'Homme, Robert K. (Inventor)

2012-01-01

A gas storage cylinder or gas storage cylinder liner, formed from a polymer composite, containing at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m(exp 2)/g to 2600 m(exp 2)2/g.

Polymerization method for formation of thermally exfoliated graphite oxide containing polymer

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Adamson, Douglas (Inventor)

2010-01-01

A process for polymerization of at least one monomer including polymerizing the at least one monomer in the presence of a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m(esp 2)/g to 2600 m(esp 2/g.

Enhanced electrocatalytic activity of reduced graphene oxide-Os nanoparticle hybrid films obtained at a liquid/liquid interface

NASA Astrophysics Data System (ADS)

Bramhaiah, K.; Pandey, Indu; Singh, Vidya N.; Kavitha, C.; John, Neena S.

2018-03-01

Hybrid films of reduced graphene oxide-osmium nanoparticles (rGO-Os NPs) synthesized at a liquid/liquid interface are explored for their electrocatalytic activity towards the oxidation of rhodamine B (RhB), a popular colourant found in textile industry effluents and a non-permitted food colour. The free-standing nature of the films enables them to be lifted directly on to electrodes without the aid of any binders. The films consist of aggregates of ultra-small Os NPs interspersed with rGO layers. The hybrid film exhibits enhanced RhB oxidation when compared to its constituents arising from the synergic effect between rGO and Os NPs, Os contributing to electrocatalysis and rGO contributing to high surface area and conductance as well as stabilization of Os nanoparticles. The electrochemical sensor based on rGO-Os NP hybrid film on pencil graphite electrode shows a remarkable performance for the quantitative detection of RhB with a linear variation in a wide range of concentrations, 4-1300 ppb (8.3 nM-2.71 μM). The modified electrode presents good stability over more than 6 months, reproducibility and anti-interference capability. The use of developed sensor for adequate detection of RhB in real samples such as food samples and pen markers is also demonstrated.

A facile approach to fabricate flexible all-solid-state supercapacitors based on MnFe2O4/graphene hybrids

NASA Astrophysics Data System (ADS)

Cai, Weihua; Lai, Ting; Dai, Wanlin; Ye, Jianshan

2014-06-01

A critical challenge for the construction of flexible electrochemical capacitors is the preparation of flexible electrodes with large specific capacitance and robust mechanical strength. Here, we demonstrate a facile approach to make high performance and flexible electrodes by dropping MnFe2O4/graphene hybrid inks onto flexible graphite sheets (as current collectors and substrates) and drying under an infrared lamp. MnFe2O4/graphene hybrid inks are synthesized by immobilizing the MnFe2O4 microspheres on the graphene nanosheets via a simple solvothermal route. Electrochemical studies show that MnFe2O4/graphene exhibits a high capacitance of 300 F g-1 at a current density of 0.3 A g-1. In addition, the excellent electrochemical performance of a supercapacitor consisting of a sandwich structure of two pieces of MnFe2O4/graphene hybrids modified electrodes separated by polyvinyl alcohol (PVA)-H2SO4 gel electrolyte is further explored. Our studies reveal that the flexible supercapacitor device with 227 μm thickness can achieve a maximum specific capacitance of 120 F g-1 at a current density of 0.1 A g-1 and excellent cycle performance retaining 105% capacitance after 5000 cycles. This research may offer a method for the fabrication of lightweight, stable, flexible and high performance energy storage devices.

Transparent, flexible supercapacitors from nano-engineered carbon films.

PubMed

Jung, Hyun Young; Karimi, Majid B; Hahm, Myung Gwan; Ajayan, Pulickel M; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Transparent, flexible supercapacitors from nano-engineered carbon films

PubMed Central

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications. PMID:23105970

Transparent, flexible supercapacitors from nano-engineered carbon films

NASA Astrophysics Data System (ADS)

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-10-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Coupling Graphene Sheets with Iron Oxide Nanoparticles for Energy Storage and Microelectronics

DTIC Science & Technology

2015-08-13

of highly oriented pyrolytic graphite ( HOPG ) flake. Two electrode system containing platinum as counter electrode and HOPG as working electrode is... XRD ) patterns of the HOPG , exfoliated graphene, PyDop1-ɤ-Fe2O3 and PyDop1-ɤ-Fe2O3-graphene are given in Figure 1e. HOPG show a very sharp diffraction...atoms arranged in hexagonal pattern in honey comb crystal lattice, (c) TEM (d) HRTEM image of graphene- PyDop1-MNP hybrid, (e) XRD pattern of the HOPG

Final Technical Report: Application of in situ Neutron Diffraction to Understand the Mechanism of Phase Transitions

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

Chandran, Ravi

In this research, phase transitions in the bulk electrodes for Li-ion batteries were investigated using neutron diffraction (ND) as well as neutron imaging techniques. The objectives of this research is to design of a novel in situ electrochemical cell to obtain Rietveld refinable neutron diffraction experiments using small volume electrodes of various laboratory/research-scale electrodes intended for Li-ion batteries. This cell is also to be used to investigate the complexity of phase transitions in Li(Mg) alloy electrodes, either by diffraction or by neutron imaging, which occur under electrochemical lithiation and delithiation, and to determine aspects of phase transition that enable/limit energymore » storage capacity. Additional objective is to investigate the phase transitions in electrodes made of etched micro-columns of silicon and investigate the effect of particle/column size on phase transitions and nonequilibrium structures. An in situ electrochemical cell was designed successfully and was used to study the phase transitions under in-situ neutron diffraction in both the electrodes (anode/cathode) simultaneously in graphite/LiCoO 2 and in graphite/LiMn 2O 4 cells each with two cells. The diffraction patterns fully validated the working of the in situ cell. Additional experimental were performed using the Si micro-columnar electrodes. The results revealed new lithiation phenomena, as evidenced by mosaicity formation in silicon electrode. These experiments were performed in Vulcan diffractometer at SNS, Oak Ridge National Laboratory. In parallel, the spatial distribution of Li during lithiation and delithiation processes in Li-battery electrodes were investigated. For this purpose, neutron tomographic imaging technique has been used for 3D mapping of Li distribution in bulk Li(Mg) alloy electrodes. It was possible to observe the phase boundary of Li(Mg) alloy indicating phase transition from Li-rich BCC β-phase to Li-lean α-phase. These experiments have been performed at CG-1D Neutron Imaging Prototype Station at SNS.« less

Supercapacitors based on 3D network of activated carbon nanowhiskers wrapped-on graphitized electrospun nanofibers

NASA Astrophysics Data System (ADS)

He, Shuijian; Chen, Linlin; Xie, Chencheng; Hu, Huan; Chen, Shuiliang; Hanif, Muddasir; Hou, Haoqing

2013-12-01

Due to their cycling stability and high power density, the supercapacitors bridge the power/energy gap between traditional dielectric capacitors and batteries/fuel cells. Electrode materials are key components for making high performance supercapacitors. An activated carbon nanowhiskers (ACNWs) wrapped-on graphitized electrospun nanofiber (GENF) network (ACNWs/GENFN) with 3D porous structure is prepared as a new type of binder-free electrode material for supercapacitors. The supercapacitor based on the ACNWs/GENFN composite material displays an excellent performance with a specific capacitance of 176.5 F g-1 at current density of 0.5 A g-1, an ultrahigh power density of 252.8 kW kg-1 at current density of 800 A g-1 and an outstanding cycling stability of no capacitance loss after 10,000 charge/discharge cycles.

Homogeneity of lithium distribution in cylinder-type Li-ion batteries

PubMed Central

Senyshyn, A.; Mühlbauer, M. J.; Dolotko, O.; Hofmann, M.; Ehrenberg, H.

2015-01-01

Spatially-resolved neutron powder diffraction with a gauge volume of 2 × 2 × 20 mm3 has been applied as an in situ method to probe the lithium concentration in the graphite anode of different Li-ion cells of 18650-type in charged state. Structural studies performed in combination with electrochemical measurements and X-ray computed tomography under real cell operating conditions unambiguously revealed non-homogeneity of the lithium distribution in the graphite anode. Deviations from a homogeneous behaviour have been found in both radial and axial directions of 18650-type cells and were discussed in the frame of cell geometry and electrical connection of electrodes, which might play a crucial role in the homogeneity of the lithium distribution in the active materials within each electrode. PMID:26681110

Nickel cobalt oxide nanowire-reduced graphite oxide composite material and its application for high performance supercapacitor electrode material.

PubMed

Wang, Xu; Yan, Chaoyi; Sumboja, Afriyanti; Lee, Pooi See

2014-09-01

In this paper, we report a facile synthesis method of mesoporous nickel cobalt oxide (NiCo2O4) nanowire-reduced graphite oxide (rGO) composite material by urea induced hydrolysis reaction, followed by sintering at 300 degrees C. P123 was used to stabilize the GO during synthesis, which resulted in a uniform coating of NiCo2O4 nanowire on rGO sheet. The growth mechanism of the composite material is discussed in detail. The NiCo2O4-rGO composite material showed an outstanding electrochemical performance of 873 F g(-1) at 0.5 A g(-1) and 512 F g(-1) at 40 A g(-1). This method provides a promising approach towards low cost and large scale production of supercapacitor electrode material.

Metal-free supercapacitor with aqueous electrolyte and low-cost carbon materials

NASA Astrophysics Data System (ADS)

Blomquist, Nicklas; Wells, Thomas; Andres, Britta; Bäckström, Joakim; Forsberg, Sven; Olin, Håkan

2017-01-01

Electric double-layer capacitors (EDLCs) or supercapacitors (SCs) are fast energy storage devices with high pulse efficiency and superior cyclability, which makes them useful in various applications including electronics, vehicles and grids. Aqueous SCs are considered to be more environmentally friendly than those based on organic electrolytes. Because of the corrosive nature of the aqueous environment, however, expensive electrochemically stable materials are needed for the current collectors and electrodes in aqueous SCs. This results in high costs for a given energy-storage capacity. To address this, we developed a novel low-cost aqueous SC using graphite foil as the current collector and a mix of graphene, nanographite, simple water-purification carbons and nanocellulose as electrodes. The electrodes were coated directly onto the graphite foil by using casting frames and the SCs were assembled in a pouch cell design. With this approach, we achieved a material cost reduction of greater than 90% while maintaining approximately one-half of the specific capacitance of a commercial unit, thus demonstrating that the proposed SC can be an environmentally friendly, low-cost alternative to conventional SCs.

Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

PubMed Central

Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang; Pan, Chun-Jern; Chou, Hung-Lung; Chen, Hsin-An; Gong, Ming; Wu, Yingpeng; Yuan, Chunze; Angell, Michael; Hsieh, Yu-Ju; Chen, Yu-Hsun; Wen, Cheng-Yen; Chen, Chun-Wei; Hwang, Bing-Joe; Chen, Chia-Chun; Dai, Hongjie

2017-01-01

Recently, interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. Here, an aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of ∼110 mAh g−1 with Coulombic efficiency ∼98%, at a current density of 99 mA g−1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60 mAh g−1 at 6 C, over 6,000 cycles with Coulombic efficiency ∼ 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Finally, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode. PMID:28194027

Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

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

Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang

There has been some interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. An aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of B110 mAhg -1 with Coulombic efficiency B98%, at a current density of 99mAg -1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60mAhg -1 at 6 C, over 6,000 cycles with Coulombic efficiency Bmore » 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Lastly, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.« less

Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

DOE PAGES

Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang; ...

2017-02-13

There has been some interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. An aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of B110 mAhg -1 with Coulombic efficiency B98%, at a current density of 99mAg -1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60mAhg -1 at 6 C, over 6,000 cycles with Coulombic efficiency Bmore » 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Lastly, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.« less

Biotin determination in food supplements by an electrochemical magneto biosensor.

PubMed

Kergaravat, Silvina V; Gómez, Gabriel A; Fabiano, Silvia N; Laube Chávez, Tamara I; Pividori, María I; Hernández, Silvia R

2012-08-15

An electrochemical magneto biosensor for the rapid determination of biotin in food samples is reported. The affinity reaction was performed on streptavidin-modified magnetic microbeads as a solid support in a direct competitive format. The biotinylated horseradish peroxidase enzyme (biotin-HRP) competes with free biotin in the sample for the binding sites of streptavidin on the magnetic microbeads. The modified magnetic beads were then easily captured by a magneto graphite-epoxy composite electrode and the electrochemical signal was based on the enzymatic activity of the HRP enzyme under the addition of H(2)O(2) as the substrate and o-phenilendiamine as cosubstrate. The response was electrochemically detected by square wave voltammetry. The limit of detection was 8.4×10(-8) mol L(--1) of biotin (20 μg L(--1)) with a dynamic range from 0.94 to 2.4×10(-7) mol L(--1). Biotin-fortified commercial dietary supplement and infant formula samples were evaluated obtaining good performances in the results. Total time of analysis was 40 min per 20 assays. Copyright © 2012 Elsevier B.V. All rights reserved.

More About Arc-Welding Process for Making Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M.; Leidecker, Henning

2005-01-01

High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

Dielectric elastomers with novel highly-conducting electrodes

NASA Astrophysics Data System (ADS)

Böse, Holger; Uhl, Detlev

2013-04-01

Beside the characteristics of the elastomer material itself, the performance of dielectric elastomers in actuator, sensor as well as generator applications depends also on the properties of the electrode material. Various electrode materials based on metallic particles dispersed in a silicone matrix were manufactured and investigated. Anisotropic particles such as silver-coated copper flakes and silver-coated glass flakes were used for the preparation of the electrodes. The concentration of the metallic particles and the thickness of the electrode layers were varied. Specific conductivities derived from resistance measurements reached about 100 S/cm and surmount those of the reference materials based on graphite and carbon black by up to three orders of magnitude. The high conductivities of the new electrode materials can be maintained even at very large stretch deformations up to 200 %.

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

Fire test method for graphite fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1980-01-01

A potential problem in the use of graphite fiber reinforced resin matrix composites is the dispersal of graphite fibers during accidential fires. Airborne, electrically conductive fibers originating from the burning composites could enter and cause shorting in electrical equipment located in surrounding areas. A test method for assessing the burning characteristics of graphite fiber reinforced composites and the effectiveness of the composites in retaining the graphite fibers has been developed. The method utilizes a modified rate of heat release apparatus. The equipment and the testing procedure are described. The application of the test method to the assessment of composite materials is illustrated for two resin matrix/graphite composite systems.

Conductive Circuit Containing a Polymer Composition Containing Thermally Exfoliated Graphite Oxide and Method of Making the Same

NASA Technical Reports Server (NTRS)

Aksay, Ilhan A. (Inventor); Prud'Homme, Robert K. (Inventor)

2017-01-01

A conductive circuit containing a polymer composite, which contains at least one polymer and a modified graphite oxide material, containing thermally exfoliated graphite oxide having a surface area of from about 300 sq m/g to 2600 sq m/g, and a method of making the same.

Conductive Circuit Containing a Polymer Composition Containing Thermally Exfoliated Graphite Oxide and Method of Making the Same

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

2014-01-01

A conductive circuit containing a polymer composite, which contains at least one polymer and a modified graphite oxide material, containing thermally exfoliated graphite oxide having a surface area of from about 300 m(sup.2)/g to 2600 m(sup.2)/g, and a method of making the same.

Electrospray painted article containing thermally exfoliated graphite oxide and method for their manufacture

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel (Inventor)

2011-01-01

A painted polymer part containing a conductive polymer composition containing at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the painted polymer part has been electrospray painted.

Determination of platinum in mineral raw materials by switching chronoamperometry

NASA Astrophysics Data System (ADS)

Pakrieva, E.; Oskina, Y.; Ustinova, E.

2014-08-01

The technique of platinum (IV) determination in mineral raw materials with the application of switching chronoamperometry has been offered. The graphite electrode impregnated with polyethylene was used as the working electrode. The hydrolytic precipitation method with 3% NaOH solution has been developed to separate platinum from the sample matrix. The use of switching chronoamperometry applied to the assessment of the platinum content in geological objects has been demonstrated.

Plastic-bonded electrodes for nickel-cadmium accumulators. IV - Some specific problems of the positive active layer

NASA Astrophysics Data System (ADS)

Micka, K.; Mrha, J.; Klapste, B.

1980-06-01

The active layer of plastic-bonded nickel oxide electrodes undergoes expansion during discharging and contraction during charging; the latter however does not fully compensate for the expansion. These volume changes can be made reversible by the action of an external pressure. The electro-chemical behavior of the conductive components, carbon black and graphite, shows more or less severe corrosion during anodic current loading.

Electrochemical Interfaces and Electrode Processes.

DTIC Science & Technology

1984-08-15

reduction of 02 on such surfaces has been of special interest. Some of these complexes such as the iron tetrasulfonated phthalocyanines (TSPc) have high...high area carbon electrodes in porous carbon electrolyte structures (14,22,27). We have been successful in examining the Fe phthalocyanine and Co...Zagal, B. Z. Nikolic and R. R. Adzic, 1 May 1979. 50. A Mechanistic Study of 02 Reduction on Water Soluble Phthalocyanines Adsorbed on Graphite

Self-Activating, Capacitive Anion Intercalation Enables High-Power Graphite Cathodes.

PubMed

Wang, Gang; Yu, Minghao; Wang, Jungang; Li, Debao; Tan, Deming; Löffler, Markus; Zhuang, Xiaodong; Müllen, Klaus; Feng, Xinliang

2018-05-01

Developing high-power cathodes is crucial to construct next-generation quick-charge batteries for electric transportation and grid applications. However, this mainly relies on nanoengineering strategies at the expense of low scalability and high battery cost. Another option is provided herein to build high-power cathodes by exploiting inexpensive bulk graphite as the active electrode material, where anion intercalation is involved. With the assistance of a strong alginate binder, the disintegration problem of graphite cathodes due to the large volume variation of >130% is well suppressed, making it possible to investigate the intrinsic electrochemical behavior and to elucidate the charge storage kinetics of graphite cathodes. Ultrahigh power capability up to 42.9 kW kg -1 at the energy density of >300 Wh kg -1 (based on graphite mass) and long cycling life over 10 000 cycles are achieved, much higher than those of conventional cathode materials for Li-ion batteries. A self-activating and capacitive anion intercalation into graphite is discovered for the first time, making graphite a new intrinsic intercalation-pseudocapacitance cathode material. The finding highlights the kinetical difference of anion intercalation (as cathode) from cation intercalation (as anode) into graphitic carbon materials, and new high-power energy storage devices will be inspired. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate.

PubMed

Akerdi, Abdollah Gholami; Bahrami, S Hajir; Arami, Mokhtar; Pajootan, Elmira

2016-09-01

Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated. Copyright © 2016 Elsevier Ltd. All rights reserved.

An electrochemical label-free and sensitive thrombin aptasensor based on graphene oxide modified pencil graphite electrode.

PubMed

Ahour, F; Ahsani, M K

2016-12-15

In this work, we tactfully constructed a novel label-free electrochemical aptasensor for rapid and facile detection of thrombin using graphene oxide (GO) and thrombin binding aptamer (TBA). The strategy relies on the preferential adsorption of single-stranded DNA (ssDNA) to GO over aptamer-target complexes. The TBA-thrombin complex formation was monitored by differential pulse voltammetry (DPV) using the guanine oxidation signal. In the absence of thrombin, the aptamers adsorbed onto the surface of GO leading to a strong background guanine oxidation signal. Conversely, in the presence of thrombin, the conformational transformation of TBA after incubating with the thrombin solution and formation of the aptamer-thrombin complexes which had weak binding ability to GO, leads to the desorption of TBA-thrombin complex from electrode surface and significant oxidation signal decrease. The selectivity of the biosensor was studied using other biological substances. The biosensor's signal was proportional to the thrombin concentration from 0.1 to 10nM with a detection limit of 0.07nM. Particularly, the proposed method could be widely applied to the aptamer-based determination of other target analytes. Copyright © 2016 Elsevier B.V. All rights reserved.

Non-activated high surface area expanded graphite oxide for supercapacitors

NASA Astrophysics Data System (ADS)

Vermisoglou, E. C.; Giannakopoulou, T.; Romanos, G. E.; Boukos, N.; Giannouri, M.; Lei, C.; Lekakou, C.; Trapalis, C.

2015-12-01

Microwave irradiation of graphite oxide constitutes a facile route toward production of reduced graphene oxide, since during this treatment both exfoliation and reduction of graphite oxide occurs. In this work, the effect of pristine graphite (type, size of flakes), pretreatment and oxidation cycles on the finally produced expanded material was examined. All the types of graphite that were tested afforded materials with high BET surface areas ranging from 940 m2/g to 2490 m2/g, without intervening an activation stage at elevated temperature. SEM and TEM images displayed exfoliated structures, where the flakes were significantly detached and curved. The quality of the reduced graphene oxide sheets was evidenced both by X-ray photoelectron spectroscopy and Raman spectroscopy. The electrode material capacitance was determined via electrochemical impedance spectroscopy and cyclic voltammetry. The materials with PEDOT binder had better performance (∼97 F/g) at low operation rates while those with PVDF binder performed better (∼20 F/g) at higher rates, opening up perspectives for their application in supercapacitors.

Beam impingement angle effects on secondary electron emission characteristics of textured pyrolytic graphite

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1984-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion-textured pyrolytic graphite over a range of primary electron energy levels and electron beam impingement angles are presented. Information required to develop high efficiency multistage depressed collectors (MDC's) for microwave amplifier traveling-wave tubes for space communication and aircraft applications is provided. To attain the highest possible MDC efficiencies, the electrode surfaces must have low secondary electron emission characteristics. Pyrolytic graphite, a chemically vapor-deposited material, is a particularly promising candidate for this application. The pyrolytic graphite surfaces studied were tested over a range of primary electron beam energies and beam impingement angles from 200 to 2000 eV and direct (0 deg) to near-grazing angles (85 deg), respectively. Surfaces both parallel to and normal to the planes of material deposition were examined. The true secondary electron emission and reflected primary electron yield characteristics of the pyrolytic graphite surfaces are compared to those of sooted control surfaces.

Purification and preparation of graphite oxide from natural graphite

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

Panatarani, C., E-mail: c.panatarani@phys.unpad.ac.id; Muthahhari, N.; Joni, I. Made

2016-03-11

Graphite oxide has attracted much interest as a possible route for preparation of natural graphite in the large-scale production and manipulation of graphene as a material with extraordinary electronic properties. Graphite oxide was prepared by modified Hummers method from purified natural graphite sample from West Kalimantan. We demonstrated that natural graphite is well-purified by acid leaching method. The purified graphite was proceed for intercalating process by modifying Hummers method. The modification is on the reaction time and temperature of the intercalation process. The materials used in the intercalating process are H{sub 2}SO{sub 4} and KMNO{sub 4}. The purified natural graphitemore » is analyzed by carbon content based on Loss on Ignition test. The thermo gravimetricanalysis and the Fouriertransform infrared spectroscopy are performed to investigate the oxidation results of the obtained GO which is indicated by the existence of functional groups. In addition, the X-ray diffraction and energy dispersive X-ray spectroscopy are also applied to characterize respectively for the crystal structure and elemental analysis. The results confirmed that natural graphite samples with 68% carbon content was purified into 97.68 % carbon content. While the intercalation process formed a formation of functional groups in the obtained GO. The results show that the temperature and reaction times have improved the efficiency of the oxidation process. It is concluded that these method could be considered as an important route for large-scale production of graphene.« less

Atomic Layer Deposition of Metal Oxides on sp2-Graphitic Carbon Substrates

DTIC Science & Technology

2014-03-31

supercapacitors . The research explored the ALD nucleation procedure based on NO2 and TMA. Al2O3 ALD films resulting from the nucleation procedure were...TiO2 and ZnO were used for electrodes for Li ion batteries and pseudocapacitance supercapacitors . 15. SUBJECT TERMS F-16 Aircraft, High Power...sp2 Graphitic Carbon Substrates 11 4.4.1 TiO2 ALD as Anode Material for Li Ion Batteries 11 4.4.2 TiO2 ALD for Pseudocapacitance Supercapacitors

Energy-Saving Sintering of Electrically Conductive Powders by Modified Pulsed Electric Current Heating Using an Electrically Nonconductive Die

NASA Astrophysics Data System (ADS)

Ito, Mikio; Kawahara, Kenta; Araki, Keita

2014-04-01

Sintering of Cu and thermoelectric Ca3Co4O9 was tried using a modified pulsed electric current sintering (PECS) process, where an electrically nonconductive die was used instead of a conventional graphite die. The pulsed electric current flowed through graphite punches and sample powder, which caused the Joule heating of the powder compact itself, resulting in sintering under smaller power consumption. Especially for the Ca3Co4O9 powder, densification during sintering was also accelerated by this modified PECS process.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

1997-01-01

Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (<50 m.sup.2 /gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, J.L.; Tran, T.D.; Feikert, J.H.; Mayer, S.T.

1997-06-10

Fabrication is described for conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive deionization, and waste treatment. Electrodes fabricated from low surface area (<50 m{sup 2}/gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon composites with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to high surface area carbons, fuel cell electrodes can be produced. 1 fig.

Water Treatment Using Plasma Discharge with Variation of Electrode Materials

NASA Astrophysics Data System (ADS)

Chanan, N.; Kusumandari; Saraswati, T. E.

2018-03-01

This research studied water treatment using plasma discharge. Plasma generated in this study produced active species that played a role in organic compound decomposition. The plasma reactor consisted of two needle electrodes made from stainless steel, tungsten, aluminium and grafit. It placed approximately 2 mm above the solution and connected with high-AC voltage. A solution of methylene blue used as an organic solution model. Plasma treatment times were 2, 4, 6, 8 and 10 min. The absorbance, temperature and pH of the solution were measured before and after treatment using various electrodes. The best electrode used in plasma discharging for methylene blue absorbance reduction was the graphite electrode, which provided the highest degradation efficiency of 98% at 6 min of treatment time.

High performance 1.2 Ah Si-alloy/Graphite|LiNi0.5Mn0.3Co0.2O2 prototype Li-ion battery

NASA Astrophysics Data System (ADS)

Marinaro, Mario; Yoon, Dong-hwan; Gabrielli, Giulio; Stegmaier, Petra; Figgemeier, Egbert; Spurk, Paul C.; Nelis, Daniël; Schmidt, Gregory; Chauveau, Jerome; Axmann, Peter; Wohlfahrt-Mehrens, Margret

2017-07-01

The study reports on realization and electrochemical testing of prototype Si-alloy/Graphite|LiNi0.5Mn0.3Co0.2O2 batteries. Water soluble polyacrylic acid (PAA), used as the only binder at the anode side, demonstrates excellent dispersant and binding properties. Sedimentation tests and rheological measurements show remarkable stability and mostly a thinning behavior of the non-Newtonian type of slurry. The cathode is processed in N-Methylpyrrolidone based slurry using polyvinylidene fluoride (PVDF) as the binding agent. The electronic conductivities of the manufactured Si-alloy/Graphite and LiNi0.5Mn0.3Co0.2O2 electrodes are evaluated. Furthermore, the cathode and anode electrochemical behavior is initially studied in half-cells, and subsequently in full Li-ion stacked prototype soft pouch-cells (1.22 Ah). It is demonstrated that the manufactured prototype cells can sustain about 290 charge/discharge galvanostatic cycles before the retained capacity drops below 80%. Cell aging is monitored using Electrochemical Impedance Spectroscopy (EIS), whereas post-mortem SEM analysis of electrodes cross-section is used to shed light on the causes of performance degradation of the cells.

In Situ Raman Microscopy of a Single Graphite Microflake Electrode in a Li(+)-containing Electrolyte

NASA Technical Reports Server (NTRS)

Shi, Qing-Fang; Dokko, Kaoru; Scherson, Daniel A.

2003-01-01

Highly detailed Raman spectra from a single KS-44 graphite microflake electrode as a function of the applied potential have been collected in situ using a Raman microscope and a sealed spectroelectrochemical cell isolated from the laboratory environment. Correlations were found between the Raman spectral features and the various Li(+) intercalation stages while recording in real time Raman spectra during a linear potential scan from 0.7 down ca. 0.0V vs Li/Li(+) at a rate of 0.1 mV/s in a 1M LiClO4 solution in a 1:l (by volume) ethylene carbonate (EC):diethyl carbonate (DEC) mixture. In particular, clearly defined isosbestic points were observed for data collected in the potential range where the transition between dilute phase 1 and phase 4 of lithiated graphite is known to occur, i.e. 0.157 < E < 0.215 vs Li/Li(+). Statistical analysis of the spectroscopic data within this region made it possible to determine independently the fraction of each of the two phases present as a function of potential without relying on coulometric information and then predict, based on the proposed stoichiometry for the transition, a spectrally-derived voltammetric feature.

Secondary-electron-emission losses in multistage depressed collectors and traveling-wave-tube efficiency improvements with carbon collector electrode surfaces

NASA Technical Reports Server (NTRS)

Ramins, P.; Ebihara, B. T.

1986-01-01

Secondary-electron-emission losses in multistage depressed collectors (MDC's) and their effects on overall traveling-wave-tube (TWT) efficiency were investigated. Two representative TWT's and several computer-modeled MDC's were used. The experimental techniques provide the measurement of both the TWT overall and the collector efficiencies. The TWT-MDC performance was optimized and measured over a wide range of operating conditions, with geometrically identical collectors, which utilized different electrode surface materials. Comparisons of the performance of copper electrodes to that of various forms of carbon, including pyrolytic and iisotropic graphites, were stressed. The results indicate that: (1) a significant improvement in the TWT overall efficiency was obtained in all cases by the use of carbon, rather than copper electrodes, and (2) that the extent of this efficiency enhancement depended on the characteristics of the TWT, the TWT operating point, the MDC design, and collector voltages. Ion textured graphite was found to be particularly effective in minimizing the secondary-electron-emission losses. Experimental and analytical results, however, indicate that it is at least as important to provide a maximum amount of electrostatic suppression of secondary electrons by proper MDC design. Such suppression, which is obtained by ensuring that a substantial suppressing electric field exists over the regions of the electrodes where most of the current is incident, was found to be very effective. Experimental results indicate that, with proper MDC design and the use of electrode surfaces with low secondary-electron yield, degradation of the collector efficiency can be limited to a few percent.

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

Engineering and Optimization of Silicon-Iron-Manganese Nanoalloy Electrode for Enhanced Lithium-Ion Battery

NASA Astrophysics Data System (ADS)

Alaboina, Pankaj K.; Cho, Jong-Soo; Cho, Sung-Jin

2017-10-01

The electrochemical performance of a battery is considered to be primarily dependent on the electrode material. However, engineering and optimization of electrodes also play a crucial role, and the same electrode material can be designed to offer significantly improved batteries. In this work, Si-Fe-Mn nanomaterial alloy (Si/alloy) and graphite composite electrodes were densified at different calendering conditions of 3, 5, and 8 tons, and its influence on electrode porosity, electrolyte wettability, and long-term cycling was investigated. The active material loading was maintained very high ( 2 mg cm-2) to implement electrode engineering close to commercial loading scales. The densification was optimized to balance between the electrode thickness and wettability to enable the best electrochemical properties of the Si/alloy anodes. In this case, engineering and optimizing the Si/alloy composite electrodes to 3 ton calendering (electrode densification from 0.39 to 0.48 g cm-3) showed enhanced cycling stability with a high capacity retention of 100% over 100 cycles. [Figure not available: see fulltext.

Conductive ink containing thermally exfoliated graphite oxide and method a conductive circuit using the same

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

2011-01-01

A conductive ink containing a conductive polymer, wherein the conductive polymer contains at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, and it use in a method for making a conductive circuit.

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.

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.

Electron cyclotron resonance plasma reactor for production of carbon stripper foil

NASA Astrophysics Data System (ADS)

Faith Romero, Camille; Kanamori, Keita; Kinsho, Michikazu; Yoshimoto, Masahiro; Wada, Motoi

2018-01-01

A graphite antenna for the production of carbon-containing hydrogen plasmas is being developed to prepare impurity-free charge exchange foils for high-energy synchrotrons. Microwave power at 2.45 GHz frequency drives a coaxial structure antenna with a 12-mm-diameter central graphite cylinder and a tapered surrounding cylinder serving as the ground electrode. The antenna was placed in a linear magnetic field to investigate how it performs under an electron cyclotron resonance (ECR) condition. A clear resonance phenomenon was observed in plasma luminosity, microwave power absorption, and microwave power reflection when the induction current used to produce a linear magnetic field was changed. The antenna realized the best microwave coupling to the plasma with the ECR zone formed 5 mm from the end of the center electrode. The antenna realized stable operation for more than 5 h with 100 W input microwave power and with operating hydrogen pressure from 0.5 to 50 Pa.