An aqueous, organic dye derivatized SnO 2 /TiO 2 core/shell photoanode

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

Wee, Kyung-Ryang; Sherman, Benjamin D.; Brennaman, M. Kyle

2016-01-01

Visible light driven water splitting in a dye-sensitized photoelectrochemical cell (DSPEC) based on a phosphonic acid-derivatized donor–π–acceptor (D–π–A) organic dye (P–A–π–D) is described with the dye anchored to an FTO|SnO 2/TiO 2core/shell photoanode in a pH 7 phosphate buffer solution.

Locally placed nanoscale gold islands film within a TiO2 photoanode for enhanced plasmon light absorption in dye sensitized solar cells.

PubMed

Kim, Taeheon; Kumaresan, Yogeenth; Cho, Sung Jun; Lee, Chang-Lyoul; Lee, Heon; Jung, Gun Young

2016-01-01

As metal nanostructures demonstrated extraordinary plasmon resonance, their optical characteristics have widely been investigated in photo-electronic applications. However, there has been no clear demonstration on the location effect of plasmonic metal layer within the photoanode on both optical characteristics and photovoltaic performances. In this research, the gold (Au) nano-islands (NIs) film was embedded at different positions within the TiO 2 nanoparticulate photoanode in dye-sensitized solar cells (DSSC) to check the effect of plasmon resonance location on the device performance; at the top, in the middle, at the bottom of the TiO 2 photoanode, and also at all the three positions. The Au NIs were fabricated by annealing a Au thin film at 550 °C. The DSSC having the Au NIs-embedded TiO 2 photoanode exhibited an increase in short circuit currents (J sc ) and power conversion efficiency (PCE) owing to the plasmon resonance absorption. Thus, the PCE was increased from 5.92% (reference: only TiO 2 photoanode) to 6.52% when the Au NIs film was solely positioned at the bottom, in the middle or at the top of TiO 2 film. When the Au NIs films were placed at all the three positions, the J sc was increased by 16% compared to the reference cell, and consequently the PCE was further increased to 7.01%.

Natural dye sensitizer from cassava (Manihot utilissima) leaves extract and its adsorption onto TiO2 photo-anode

NASA Astrophysics Data System (ADS)

Nurlela; Wibowo, R.; Gunlazuardi, J.

2017-04-01

Interaction between TiO2 and dyes sensitizer have been studied. The chlorophyll presents in the crude leave extract (CLE-dye) from cassava (Manihot utilissima) was immobilized on to the photo-anode, consists of TiO2 supported by fluor doped Tin oxide (SnO2-F) Glass. The TiO2 was prepared by Rapid Breakdown Anodization (RBA) method then immobilized on to glass coated by SnO2-F using doctor blade technique, to give CLE-dye/TiO2/SnO2-F/Glass photo-anode. The prepared photo-anode was characterized by UV-Vis-DRS, FTIR, XRD, SEM, electrochemical and spectro-electrochemical systems. In this study, the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy level of the CLE-dye were empirically determined by cyclic voltammetry method, while spectro-electro-chemistry method was used to determine the coefficient of degradation and formation of the dyes, and diffusion coefficient of the hole recombination as well. Good anchoring between TiO2 with dye extracts (CLE-dye) can be seen from value of dye LUMO energy level (-4.26 eV), which is approaching the conduction band of TiO2 (-4.3 eV). The coefficient of degradation and formation of the CLE-dye showed a quasi reversible and diffusion coefficient hole recombination values were small, indicated that it is quite suitable as a sensitizer in a dyes sensitized solar cell.

Synthesis of two-dimensional nanowall of Cu-Doped TiO2 and its application as photoanode in DSSCs

NASA Astrophysics Data System (ADS)

Dahlan, Dahyunir; Md Saad, Siti Khatijah; Berli, Ade Usra; Bajili, Abdil; Umar, Akrajas Ali

2017-07-01

Two-dimensional nanowall of Cu-doped TiO2 (CuTNW) has been prepared in this work to study the role of Cu doping on its photoactivity properties and its photovoltaic performance as photoanode in a dye-sensitized solar cell (DSSC). TiO2 nanowall with five Cu ion doping, i.e. 6.25, 12.5, 25.0, 50.0 and 100.0 mM, were prepared via a liquid-phase deposition method using ammoniumhexafluorotitanate and hexamethylenetetramine as the reagents with a growth temperature of 90 °C. The X-Ray Diffraction (XRD), X-ray energy dispersion (EDX) and diffuse optical reflectance spectroscopy analysis results confirmed the successfulness of the Cu doping process in the TiO2 nanowall and effective modification on the photoactivity of the TiO2 nanowall. We found that the power conversion efficiency of the DSSC utilizing TiO2 nanowall as photoanode can be enhanced up to 2 times, i.e. from 0.2% to 0.44%, when the TiO2 nanowall doped with Cu ion. The nanostructure preparation, device fabrication and the mechanism for the device performance enhancement will be discussed.

Protecting hydrogenation-generated oxygen vacancies in BiVO4 photoanode for enhanced water oxidation with conformal ultrathin amorphous TiO2 layer

NASA Astrophysics Data System (ADS)

Zhang, Yang; Zhang, Xintong; Wang, Dan; Wan, Fangxu; Liu, Yichun

2017-05-01

Introducing appropriate amount of oxygen vacancies by hydrogenation treatment is a simple and efficient way to improve the photoelectrochemical performance of nanostructured oxide photoanodes. However, the hydrogenation effect is often not durable due to the gradual healing of oxygen vacancies at or close to surface of photoanodes. Herein, we tackled the problem by conformal coating the hydrogenated nanoporous BiVO4 (H-BiVO4) photoanode with an ultrathin layer of amorphous TiO2. Photoelectrochemical measurements showed that a 4 nm-thick TiO2 layer could significantly improve the stability of H-BiVO4 photoanode for repeated working test, with negligible influence on the initial photocurrent compared to the uncoated one. Mott-Schottky and linear sweep voltammetry measurements showed that donor density and photocurrent density of the H-BiVO4 electrode almost decayed to the values of pristine BiVO4 electrode after 3 h test, while the amorphous TiO2-coated electrode only degraded by 6% and 5% of the initial values respectively in the same period. The investigation thus suggested that the amorphous TiO2 layer did protect the oxygen vacancies in H-BiVO4 photoanode by isolating these oxygen vacancies from environmental oxygen, while at the same time not impeding the interfacial charge transfer to water molecules due to its leaky nature.

Toward Eco-Friendly and Highly Efficient Solar Water Splitting Using In2S3/Anatase/Rutile TiO2 Dual-Staggered-Heterojunction Nanodendrite Array Photoanode.

PubMed

Yang, Jih-Sheng; Wu, Jih-Jen

2018-01-31

The TiO 2 -based heterojunction nanodendrite (ND) array composed of anatase nanoparticles (ANPs) on the surface of the rutile ND (RND) array is selected as the model photoanode to demonstrate the strategies toward eco-friendly and efficient solar water splitting using neutral electrolyte and seawater. Compared with the performances in alkaline electrolyte, a non-negligible potential drop across the electrolyte as well as impeded charge injection and charge separation is monitored in the ANP/RND array photoanode with neutral electrolyte, which are, respectively, ascribed to the series resistance of neutral electrolyte, the fundamentally pH-dependent water oxidation mechanism on TiO 2 surface, as well as the less band bending at the interface of TiO 2 and neutral electrolyte. Accordingly, a TiO 2 -based dual-staggered heterojunction ND array photoanode is further designed in this work to overcome the issue of less band bending with the neutral electrolyte. The improvement of charge separation efficiency is realized by the deposition of a transparent In 2 S 3 layer on the ANP/RND array photoanode for constructing additional staggered heterojunction. Under illumination of AM 1.5G (100 mW cm -2 ), the improved photocurrent densities acquired both in neutral electrolyte and seawater at 1.23 V vs reversible hydrogen electrode (RHE), which approach the theoretical value for rutile TiO 2 , are demonstrated in the dual-staggered-heterojunction ND array photoanode. Faradaic efficiencies of ∼95 and ∼32% for solar water oxidation in neutral electrolyte and solar seawater oxidation for 2 h are acquired at 1.23 V vs RHE, respectively.

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

NASA Astrophysics Data System (ADS)

Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

2013-12-01

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

PubMed Central

2013-01-01

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors.

PubMed

Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

2013-12-26

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

Fabrication of transparent TiO2 nanotube-based photoanodes for CdS/CdTe quantum co-sensitized solar cells

NASA Astrophysics Data System (ADS)

Gualdrón-Reyes, A. F.; Cárdenas-Arenas, A.; Martínez, C. A.; Kouznetsov, V. V.; Meléndez, A. M.

2017-01-01

In order to fabricate a solar cell, ordered TiO2 nanotube (TNT) arrays were prepared by double anodization. TNT arrays with variable lengths were obtained by changing the duration of the anodizing process of up to 3h. TNT membranes were transferred to indium tin oxide substrates and attached with a B-TiO2 sol. TNT photoanode with the best photoelectrochemical performance was sensitized with CdS by SILAR method. On other hand, CdTe quantum dots prepared via colloidal synthesis were deposited on TNT photoanodes for 2h, 4h and 6h. In addition, TNT/CdS was loaded with CdTe quantum dots for 4 h. Morphology and chemical modification of TiO2 were characterized by FESEM and XPS, while their photoelectrochemical performance was measured by open-circuit photopotential and photovoltammetry under visible light. TiO2 nanotubes grown during 2.5h showed the highest photocurrent due to presence of Ti3+ donor states by N and F co-doping, increasing the number of photogenerated electrons transported to back collector. TNT/CdS/CdTe photoanode reach the highest conversion efficiency under AM 1.5G simulated solar illumination.

Enhanced Efficiency of Dye-Sensitized Solar Cells with Mesoporous-Macroporous TiO2 Photoanode Obtained Using ZnO Template

NASA Astrophysics Data System (ADS)

Pham, Trang T. T.; Mathews, Nripan; Lam, Yeng-Ming; Mhaisalkar, Subodh

2017-06-01

Improved light harvesting efficiency can be achieved by enhancing the optical properties of the titanium dioxide (TiO2) photoanode in dye-sensitized solar cells (DSSCs), leading to higher power conversion efficiency. By incorporating submicrometer cavities in TiO2 mesoporous film, using zinc oxide (ZnO) particles as a template, a bimodal pore size structure has been created, called a mesoporous-macroporous nanostructure. This photoanode structure consists of 20-nm TiO2 nanoparticles with two kinds of pores with size of 20 nm (mesopores) and 500 nm (macropores). Energy-dispersive x-ray spectroscopy and x-ray diffraction studies showed no trace of ZnO in the TiO2 after removal by TiCl4 treatment. Higher diffuse transmittance of this film compared with the standard transparent photoanode provides evidence of improved light scattering. When employed in a device, the incident-photon-to-current efficiency of ZnO-assisted devices showed enhancement at longer wavelengths, corresponding to the Mie light scattering effect with the macropores as scattering centers. This resulted in overall higher power conversion efficiency of the DSSC. In this work, a nonvolatile gel ionic liquid was used as the electrolyte to also demonstrate the benefit of this structure in combination with a viscous electrolyte and its promising application to prolong the stability of DSSCs.

Hyperbranched TiO2-CdS nano-heterostructures for highly efficient photoelectrochemical photoanodes.

PubMed

Mezzetti, Alessandro; Balandeh, Mehrdad; Luo, Jingshan; Bellani, Sebastiano; Tacca, Alessandra; Divitini, Giorgio; Cheng, Chuanwei; Ducati, Caterina; Meda, Laura; Fan, Hongjin; Di Fonzo, Fabio

2018-08-17

Quasi-1D-hyperbranched TiO 2 nanostructures are grown via pulsed laser deposition and sensitized with thin layers of CdS to act as a highly efficient photoelectrochemical photoanode. The device properties are systematically investigated by optimizing the height of TiO 2 scaffold structure and thickness of the CdS sensitizing layer, achieving photocurrent values up to 6.6 mA cm -2 and reaching saturation with applied biases as low as 0.35 V RHE . The high internal conversion efficiency of these devices is to be found in the efficient charge generation and injection of the thin CdS photoactive film and in the enhanced charge transport properties of the hyperbranched TiO 2 scaffold. Hence, the proposed device represents a promising architecture for heterostructures capable of achieving high solar-to-hydrogen efficiency.

Effect of Germanium on the TiO2 Photoanode for Dye Sensitized Solar Cell Applications. A Potential Sintering Aid

NASA Astrophysics Data System (ADS)

Ahmad, M. S.; Pandey, AK; Rahim, N. A.

2018-05-01

Anatase titanium-germanium (TiO2-Ge) nanocomposite has been prepared by using colloidal suspension process and investigated for photoanode to be used in dye sensitized solar cell. Ge possesses lower band gap energy compared to TiO2 and has the capability to absorb infrared region of solar spectrum. Its remarkable absorption and good electron transfer ability due to lower band gap energy makes it a potential candidate material in the field of DSSCs to counter important disadvantages such as high probability of electron recombination reactions and absorption of small region (UV region) of solar spectrum. Another advantage is its low sintering temperature which proved to be an added advantage to increase inter-particle contact which in turn leads to improved electron transfer. Scanning electron microscopy (SEM), uv-vis spectroscopy and electron impedance spectroscopy (EIS) have been employed to evaluate the effect of Ge on TiO2photoanode.

Ni-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

2018-06-01

Photoelectrochemical (PEC) water splitting hydrogen production provides a promising way for sustainable development. In this work, we prepared Ni-doped TiO2 (Ti-Ni-O) nanotubes through anodizing different Ti-Ni alloys and further annealing them at elevated temperatures, and reported their PEC water splitting performance. It was found that Ni doping could improve light absorption and facilitate separation of photo-excited electron-hole pair. The nanotubes fabricated on Ti-1 wt.% Ni alloy and annealed at 550 °C exhibited better PEC water splitting performance than those on Ti-10 wt.% Ni alloy. The photoconversion efficiency was 0.67%, which was 3.35 times the photoconversion efficiency of undoped TiO2. It demonstrated that it was feasible to fabricate high-performance Ti-Ni-O nanotubes on Ti-Ni alloys and used as photoanode for improving PEC water splitting.

Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte

NASA Astrophysics Data System (ADS)

Sabari Girisun, T. C.; Jeganathan, C.; Pavithra, N.; Anandan, S.

2018-02-01

Photoanodes made of highly oriented TiO2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current-voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (Jsc = 5.99 mA cm-2, Voc = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO2 NRs (8 μm, 254 nm).

Optimizing the photochemical conversion of UV-vis light of silver-nanoparticles decorated TiO2 nanotubes based photoanodes

NASA Astrophysics Data System (ADS)

Gaidi, M.; Trabelsi, K.; Hajjaji, A.; Chourou, M. L.; Alhazaa, A. N.; Bessais, B.; El Khakani, M. A.

2018-01-01

Homogeneous decoration of TiO2 nanotubes (NTs) by Ag metallic nanoparticles (NPs) was carried out by a relatively simple photoreduction process. This Ag-NPs decoration was found to improve the photoconversion efficiency of the TiO2-NTs based photoanodes. The x-ray photoelectron spectroscopy and x-ray diffraction analyses confirmed that all the Ag-NPs are metallic and the underlying TiO2-NTs crystallize in the anatase phase after their annealing at 400 °C, respectively. Transmission electron microscopy observations have confirmed the effective decoration of the TiO2-NTs’ surface by Ag-NPs, and allowed to measure the average Ag-NPs size, which was found to increase linearly from (4 ± 2) nm to (16 ± 4) nm when the photoreduction time is increased from 5 to 20 min. The diffuse reflectivity of the Ag-NPs decorated TiO2-NTs was found to decrease significantly as compared to the undecorated TiO2-NTs. Interestingly, the Ag-NPs decorated TiO2-NTs exhibited a significantly enhanced photochemical response, under visible radiation, with regards to the undecorated NTs. This enhancement was found to reach its maximum for the TiO2-NTs decorated with Ag-NPs having the optimal average diameter of ˜8.5 nm. The maximum photoconversion efficiency of Ag-NPs decorated TiO2-NTs was about two times greater than for the undecorated ones. This improved photo-electro-chemical response is believed to be associated with the additional absorption of visible light of Ag-NPs through the localized surface plasmon resonance phenomenon. This interpretation is supported by the fact that the photoluminescence intensity of the Ag-NPs decorated TiO2-NTs was found to decrease significantly as compared to undecorated NTs, due to charge carriers trapping in the Ag NPs. This demonstrates that Ag-NPs decoration promotes photogenerated charges separation in the TiO2-NTs, increasing thereby their capacity for current photogeneration. The surface decoration of TiO2 NTs by noble metals NPs is expected to

Optimizing the photochemical conversion of UV-vis light of silver-nanoparticles decorated TiO2 nanotubes based photoanodes.

PubMed

Gaidi, M; Trabelsi, K; Hajjaji, A; Chourou, M L; Alhazaa, A N; Bessais, B; El Khakani, M A

2018-01-05

Homogeneous decoration of TiO 2 nanotubes (NTs) by Ag metallic nanoparticles (NPs) was carried out by a relatively simple photoreduction process. This Ag-NPs decoration was found to improve the photoconversion efficiency of the TiO 2 -NTs based photoanodes. The x-ray photoelectron spectroscopy and x-ray diffraction analyses confirmed that all the Ag-NPs are metallic and the underlying TiO 2 -NTs crystallize in the anatase phase after their annealing at 400 °C, respectively. Transmission electron microscopy observations have confirmed the effective decoration of the TiO 2 -NTs' surface by Ag-NPs, and allowed to measure the average Ag-NPs size, which was found to increase linearly from (4 ± 2) nm to (16 ± 4) nm when the photoreduction time is increased from 5 to 20 min. The diffuse reflectivity of the Ag-NPs decorated TiO 2 -NTs was found to decrease significantly as compared to the undecorated TiO 2 -NTs. Interestingly, the Ag-NPs decorated TiO 2 -NTs exhibited a significantly enhanced photochemical response, under visible radiation, with regards to the undecorated NTs. This enhancement was found to reach its maximum for the TiO 2 -NTs decorated with Ag-NPs having the optimal average diameter of ∼8.5 nm. The maximum photoconversion efficiency of Ag-NPs decorated TiO 2 -NTs was about two times greater than for the undecorated ones. This improved photo-electro-chemical response is believed to be associated with the additional absorption of visible light of Ag-NPs through the localized surface plasmon resonance phenomenon. This interpretation is supported by the fact that the photoluminescence intensity of the Ag-NPs decorated TiO 2 -NTs was found to decrease significantly as compared to undecorated NTs, due to charge carriers trapping in the Ag NPs. This demonstrates that Ag-NPs decoration promotes photogenerated charges separation in the TiO 2 -NTs, increasing thereby their capacity for current photogeneration. The surface decoration of TiO 2 NTs by noble

Hybrid TiO2/ZnO and TiO2/Al plasmon impregnated ZnO nanocomposite photoanodes for DSSCs: synthesis and characterisation

NASA Astrophysics Data System (ADS)

Pugazhendhi, K.; D’Almeida, Steven; Naveen Kumar, P.; Sahaya Selva Mary, J.; Tenkyong, Tenzin; Sharmila, D. J.; J, Madhavan; Merline Shyla, J.

2018-04-01

The proposed work reports the synthesis and characterisation of novel and hybrid nanocomposites TiO2/ZnO and TiO2/Al plasmon impregnated ZnO, prepared using sol-gel method. X-Ray Diffraction analysis confirmed the crystalline nature of the nanocomposites with high degree of purity and the crystallite size was found to be 22 nm (TiO2/ZnO) and 21 nm (TiO2/Al-ZnO) using Scherrer’s formula. The surface chemistry, elemental compositions and purity were investigated and established using Energy Dispersive X-ray Analysis. The specific surface area of TiO2/ZnO was observed to be 23 m2 g‑1 whereas on comparison, a slight decrease was observed in the case of TiO2/Al-ZnO to 19 m2 g‑1 from Brunauer–Emmett–Teller analysis and in addition, both the samples were identified to be mesoporous in nature. The vibrational assignments were observed using Fourier Transform Infra-Red spectroscopy and results confirmed the existence of TiO2, ZnO and Al groups. The electrical response of the nanocomposites to the incident radiation with applied electric field was examined using Field Dependent Dark and Photo conductivity studies. The observed measurements revealed that the photocurrent values are greater than the dark currents which confirmed the photoconductive nature of the nanocomposites. While both the prepared nanocomposites qualify as good candidates for usage as efficient photoanodes for DSSCs, TiO2/Al-ZnO indicates a slight edge over the other.

Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte.

PubMed

Girisun, T C Sabari; Jeganathan, C; Pavithra, N; Anandan, S

2018-01-23

Photoanodes made of highly oriented TiO 2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO 2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO 2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current-voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (J sc  = 5.99 mA cm -2 , V oc  = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO 2 NRs (8 μm, 254 nm).

Photoinduced deposition of gold nanoparticles on TiO2-WO3 nanotube films as efficient photoanodes for solar water splitting

NASA Astrophysics Data System (ADS)

Momeni, Mohamad Mohsen; Ghayeb, Yousef

2016-06-01

Gold-modified TiO2-WO3 nanotubes with different amounts of gold were obtained by two methods; photoassisted deposition and one-step electrochemical anodizing method. The morphology, crystallinity and elemental composition were studied by FE-SEM, XRD and EDX. The photoelectrochemical performance was examined under Xe light illumination in 1 M NaOH electrolyte. Characterization of the as-prepared TiO2-WO3 samples indicated that sodium tungstate concentration in anodizing solution significantly influenced the morphology and photoelectrochemical activity of fabricated films. Also, photoelectrochemical characterizations show that the photocatalytic activity of Au/TiO2-WO3 nanotubes was improved as compared with that of bare TiO2-WO3 nanotubes. The experimental results showed that the photocatalytic activities of Au/TiO2-WO3 were significantly affected by the amount of Au nanoparticles. The amount of gold nanoparticles was effectively controlled by time of photoreduction of the chloroauric acid solution. These new photoanodes showed enhanced high photocurrent density with good stability and are a highly promising photoanodes for photocatalytic hydrogen production.

TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment

PubMed Central

2016-01-01

Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE. PMID:27163032

Application of immobilized nanotubular TiO(2) electrode for photocatalytic hydrogen evolution: reduction of hexavalent chromium (Cr(VI)) in water.

PubMed

Yoon, Jaekyung; Shim, Eunjung; Bae, Sanghyun; Joo, Hyunku

2009-01-30

In this study, immobilized TiO(2) electrode is applied to reduce toxic Cr(VI) to non-toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powder TiO(2), a novel technique of immobilization based on anodization was applied and investigated under various experimental conditions. The anodization was performed at 20V-5 degrees C for 45min with 0.5% hydrofluoric acid, and then the anodized samples were annealed under oxygen stream in the range 450-850 degrees C. Based on the results of the experiments, the photocatalytic Cr(VI) reduction was favorable in acidic conditions, with approximately 98% of the Cr(VI) being reduced within 2h at pH 3. Among the samples tested under same anodizing condition, the nanotubular TiO(2) annealed at 450 and 550 degrees C showed highest reduction efficiencies of Cr(VI). In addition, the surface characterizations (zeta potential, XRD, and SEM) of these samples proved that the Cr(VI) reduction efficiency was higher under acidic conditions and at a lower annealing temperature. From this research, it was concluded that the anodized TiO(2) has the potential to be a useful technology for environmental remediation as well as photocatalytic hydrogen production from water.

Efficiency enhancement of dye-sensitized solar cells by use of ZrO2-doped TiO2 nanofibers photoanode.

PubMed

Mohamed, Ibrahim M A; Dao, Van-Duong; Barakat, Nasser A M; Yasin, Ahmed S; Yousef, Ahmed; Choi, Ho-Suk

2016-08-15

Due to the good stability and convenient optical properties, TiO2 nanostructures still the prominent photoanode materials in the Dye Sensitized Solar Cells (DSCs). However, the well-known low bandgap energy and weak adsorption affinity for the dye distinctly constrain the wide application. This work discusses the impact of Zr-doping and nanofibrous morphology on the performance and physicochemical properties of TiO2. Zr-doped TiO2 nanofibers (NFs), with various zirconia content (0, 0.5, 1, 1.5 and 2wt%) were prepared by calcination of electrospun mats composed of polyvinyl acetate, titanium isopropoxyl and zirconium n-propoxyl. For all formulations, the results have shown that the prepared materials are continuous, randomly oriented, and good morphology nanofibers. The average diameter decreased from 353.85nm to 210.78nm after calcination without a considerable influence on the nanofibrous structure regardless the zirconia content. XRD result shows that there is no Rutile nor Brookite phases in the obtained material and the average crystallite size of the sample is affected by the presence of Zr-doping and changed from 23.01nm to 37.63nm for TiO2 and Zr-doped TiO2, respectively. Optical studies have shown Zr-doped TiO2 NFs have more absorbance in the visible region than that of pristine TiO2 NFs; the maximum absorbance is corresponding to the NFs having 1wt% zirconia. The improved spectra of Zr-doped TiO2 in the visible region is attributed to the heterostructure composition resulting from Zr-doping. The absorption bandgaps were calculated using Tauc model as 3.202 and 3.217 for pristine and Zr (1wt%)-doped TiO2 NFs, respectively. Furthermore, in Dye-sensitized Solar Cells, utilizing Zr (1wt%)-doped TiO2 nanofibers achieved higher efficiency of 4.51% compared to the 1.61% obtained from the pristine TiO2 NFs. Copyright © 2016 Elsevier Inc. All rights reserved.

Eosin-Y sensitized core-shell TiO2-ZnO nano-structured photoanodes for dye-sensitized solar cell applications.

PubMed

Manikandan, V S; Palai, Akshaya K; Mohanty, Smita; Nayak, Sanjay K

2018-06-01

In the current investigation, TiO 2 and TiO 2 -ZnO (core-shell) spherical nanoparticles were synthesized by simple combined hydrolysis and refluxing method. A TiO 2 core nanomaterial on the shell material of ZnO was synthesized by utilizing variable ratios of ZnO. The structural characterization of TiO 2 -ZnO core/shell nanoparticles were done by XRD analysis. The spherical structured morphology of the TiO 2 -ZnO has been confirmed through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies. The UV-visible spectra of TiO 2 -ZnO nanostructures were also compared with the pristine TiO 2 to investigate the shift of wavelength. The TiO 2 -ZnO core/shell nanoparticles at the interface efficiently collect the photogenarated electrons from ZnO and also ZnO act a barrier for reduced charge recombination of electrolyte and dye-nanoparticles interface. This combination improved the light absorption which induced the charge transfer ability and dye loading capacity of core-shell nanoparticles. An enhancement in the short circuit current (J sc ) from 1.67 mA/cm 2 to 2.1 mA/cm 2 has been observed for TiO 2 -ZnObased photoanode (with platinum free counter electrode), promises an improvement in the energy conversion efficiency by 57% in comparison with that of the DSSCs based on the pristine TiO 2 . Henceforth, TiO 2 -ZnO photoelectrode in ZnO will effectively act as barrier at the interface of TiO 2 -ZnO and TiO 2 , ensuring the potential for DSSC application. Copyright © 2018 Elsevier B.V. All rights reserved.

In-situ co-doping of sputter-deposited TiO2:WN films for the development of photoanodes intended for visible-light electro-photocatalytic degradation of emerging pollutants

NASA Astrophysics Data System (ADS)

Delegan, N.; Pandiyan, R.; Komtchou, S.; Dirany, A.; Drogui, P.; El Khakani, M. A.

2018-05-01

We report on the magnetron sputtering deposition of in-situ codoped TiO2:WN films intended for electro-photocatalytic (EPC) applications under solar irradiation. By varying the RF-magnetron sputtering deposition parameters, we were able to tune the in-situ incorporation of both N and W dopants in the TiO2 films over a wide concentration range (i.e., 0-9 at. % for N and 0-3 at. % for W). X-ray photoelectron spectroscopy analysis revealed that both dopants are mostly of a substitutional nature. The analysis of the UV-Vis transmission spectra of the films confirmed that the optical bandgap of both TiO2:N and TiO2:WN films can be significantly narrowed (from 3.2 eV for undoped-TiO2 down to ˜2.3 eV for the doped ones) by tuning their dopant concentrations. We were thus able to pinpoint an optimal window for both dopants (N and W) where the TiO2:WN films exhibit the narrowest bandgap. Moreover, the optimal codoping conditions greatly reduce the recombination defect state density compared to the monodoped TiO2:N films. These electronically passivated TiO2:WN films are shown to be highly effective for the EPC degradation of atrazine (pesticide pollutant) under sunlight irradiation (93% atrazine degraded after only 30 min of EPC treatment). Indeed, the optimally codoped TiO2:WN photoanodes were found to be more efficient than both the undoped-TiO2 and equally photosensitized TiO2:N photoanodes (by ˜70% and ˜25%, respectively) under AM1.5 irradiation.

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells.

PubMed

Lim, Su Pei; Lim, Yee Seng; Pandikumar, Alagarsamy; Lim, Hong Ngee; Ng, Yun Hau; Ramaraj, Ramasamy; Bien, Daniel Chia Sheng; Abou-Zied, Osama K; Huang, Nay Ming

2017-01-04

In the present investigation, gold-silver@titania (Au-Ag@TiO 2 ) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au-Ag incorporated TiO 2 photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO 2 photoanode (2.22%) under full sunlight illumination (100 mW cm -2 , AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au-Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO 2 was found to be Au 75 -Ag 25 . This was reflected in the femtosecond transient absorption dynamics in which the electron-phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO 2 /Au 75 :Ag 25 , compared to 2.38 ps for free Au and 4.02 ps for TiO 2 /Au 100 :Ag 0 . The slower dynamics indicates a more efficient electron-hole separation in TiO 2 /Au 75 :Ag 25 that is attributed to the formation of a Schottky barrier at the interface between TiO 2 and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au-Ag@TiO 2 plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs.

The effect of the DSSC photoanode area based on TiO2/Ag on the conversion efficiency of solar energy into electrical energy

NASA Astrophysics Data System (ADS)

Ibrayev, N.; Serikov, T.; Zavgorodniy, A.; Sadykova, A.

2018-01-01

A module based on dye-sensitized solar cells with Ag/TiO2 structure was developed. It is shown that the addition of the core-shell structure to the semiconductor film of titanium dioxide, where the nanoparticle Ag serves as the core, and the TiO2 is shell, increases the coefficient of solar energy conversion into electrical energy. The effect of the photoanode area on the efficiency of conversion of solar energy into electrical energy is studied. It is shown that the density of the photocurrent decreases with increasing of the photoanode area, which leads to a drop in the efficiency of solar cells.

Preparation of Pd-loaded La-doped TiO2 nanotubes and investigation of their photocatalytic activity under visible light

NASA Astrophysics Data System (ADS)

Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Wang, Xiaodong; Yang, Jianjun

2013-11-01

Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO2. However, in our former research, we found that calcination of TAN to anatase TiO2 would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La2O3) to keep the nanotubular morphology of TiO2, and obtained the anatase TiO2 nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO2 by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N2 adsorption-desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation ( λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO2 nanotubes improved effectively compared with that of La-doped TiO2 and pure TiO2.

High-speed growth of TiO2 nanotube arrays with gradient pore diameter and ultrathin tube wall under high-field anodization

NASA Astrophysics Data System (ADS)

Yuan, Xiaoliang; Zheng, Maojun; Ma, Li; Shen, Wenzhong

2010-10-01

Highly ordered TiO2 nanotubular arrays have been prepared by two-step anodization under high field. The high anodizing current densities lead to a high-speed film growth (0.40-1.00 µm min - 1), which is nearly 16 times faster than traditional fabrication of TiO2 at low field. It was found that an annealing process of Ti foil is an effective approach to get a monodisperse and double-pass TiO2 nanotubular layer with a gradient pore diameter and ultrathin tube wall (nearly 10 nm). A higher anodic voltage and longer anodization time are beneficial to the formation of ultrathin tube walls. This approach is simple and cost-effective in fabricating high-quality ordered TiO2 nanotubular arrays for practical applications.

High-speed growth of TiO2 nanotube arrays with gradient pore diameter and ultrathin tube wall under high-field anodization.

PubMed

Yuan, Xiaoliang; Zheng, Maojun; Ma, Li; Shen, Wenzhong

2010-10-08

Highly ordered TiO(2) nanotubular arrays have been prepared by two-step anodization under high field. The high anodizing current densities lead to a high-speed film growth (0.40-1.00 microm min(-1)), which is nearly 16 times faster than traditional fabrication of TiO(2) at low field. It was found that an annealing process of Ti foil is an effective approach to get a monodisperse and double-pass TiO(2) nanotubular layer with a gradient pore diameter and ultrathin tube wall (nearly 10 nm). A higher anodic voltage and longer anodization time are beneficial to the formation of ultrathin tube walls. This approach is simple and cost-effective in fabricating high-quality ordered TiO(2) nanotubular arrays for practical applications.

Double-side illuminated titania nanotubes for high volume hydrogen generation by water splitting

NASA Astrophysics Data System (ADS)

Mohapatra, Susanta K.; Mahajan, Vishal K.; Misra, Mano

2007-11-01

A sonoelectrochemical anodization method is proposed to synthesize TiO2 nanotubular arrays on both sides of a titanium foil (TiO2/Ti/TiO2). Highly ordered TiO2 nanotubular arrays of 16 cm2 area with uniform surface distribution can be obtained using this anodization procedure. These double-sided TiO2/Ti/TiO2 materials are used as both photoanode (carbon-doped titania nanotubes) and cathode (Pt nanoparticles dispersed on TiO2 nanotubes; PtTiO2/Ti/PtTiO2) in a specially designed photoelectrochemical cell to generate hydrogen by water splitting at a rate of 38 ml h-1. The nanomaterials are characterized by FESEM, HRTEM, STEM, EDS, FFT, SAED and XPS techniques. The present approach can be used for large-scale hydrogen generation using renewable energy sources.

A detailed study on the working mechanism of a heteropoly acid modified TiO2 photoanode for efficient dye-sensitized solar cells.

PubMed

Jiang, Yanxia; Yang, Yulin; Qiang, Liangsheng; Fan, Ruiqing; Li, Liang; Ye, Tengling; Na, Yong; Shi, Yan; Luan, Tianzhu

2015-03-14

A novel heteropolyacid (HPA) K6SiW11O39Ni(H2O)·xH2O (SiW11Ni) modified TiO2 has been successfully synthesized and introduced into the photoanode of dye-sensitized solar cells (DSSCs). The performance of the cell with the HPA-modified photoanode (SiW11Ni/TiO2), mixed with P25 powder in the ratio of 2 : 8, is better than the cell with a pristine P25 photoanode. An increase of 31% in the photocurrent and 22% improvement in the conversion efficiency are obtained. The effect of the heteropolyacid was well studied by UV-vis spectroscopy, spectro-electrochemical spectroscopy, dark current, intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy, open-circuit voltage decay and electrochemical impedance spectroscopy. The results show that the interfacial layer modified by SiW11Ni can enhance the injection and transport of electrons, and then retard the recombination of electrons, which results in a longer electron lifetime. What's more, the introduction of SiW11Ni can simultaneously broaden the absorption in the visible region, eventually leading to an efficient increase in energy conversion efficiency.

Improved performance of CdSe/CdS/PbS co-sensitized solar cell with double-layered TiO2 films as photoanode

NASA Astrophysics Data System (ADS)

Zhang, Xiaolong; Lin, Yu; Wu, Jihuai; Jing, Jing; Fang, Biaopeng

2017-07-01

Improving the photovoltaic performance of CdSe/CdS/PbS co-sensitized double-layered TiO2 solar cells is reported. Double-layered TiO2 films with TiO2 microspheres as the light blocking layers were prepared. PbS, CdS and CdSe quantum dots (QDs) were assembled onto TiO2 photoanodes by simple successive ionic layer absorption and reaction (SILAR) to fabricate CdSe/CdS/PbS co-sensitized solar cells. An improved power conversion efficiency (PCE) of 5.11% was achieved for CdSe/CdS/PbS co-sensitized solar cells at one sun illumination (AM 1.5 G, 100 mW cm-2), which had an improvement of 22.6% over that of the CdSe/CdS co-sensitized solar cells (4.17%). This enhancement is mainly attributed to their better ability of the absorption of solar light with the existence of PbS QDs, the reduction of charge recombination of the excited electron and longer lifetime of electrons, which have been proved with the photovoltaic studies and electrochemical impedance spectroscopy (EIS).

Low-temperature crystallization of anodized TiO2 nanotubes at the solid-gas interface and their photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Liu, Jing; Liu, Zhaoyue; Zhang, Tierui; Zhai, Jin; Jiang, Lei

2013-06-01

TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common thermal annealing at the same temperature but at atmospheric pressure, the hydrothermal route improves the photocurrent density of TiO2 nanotubes by ~10 times in KOH electrolyte. The duration of the hydrothermal reaction has a substantial effect on the photoelectrochemical properties of TiO2 nanotubes, which is ascribed to the synergetic effect between the crystallization and structural evolution. Electron donors can further suppress the charge recombination in the low-temperature crystallized TiO2 nanotubes and boost the photocurrent density by ~120%.TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common

3D FTO/FTO-Nanocrystal/TiO2 Composite Inverse Opal Photoanode for Efficient Photoelectrochemical Water Splitting.

PubMed

Wang, Zhiwei; Li, Xianglin; Ling, Han; Tan, Chiew Kei; Yeo, Loo Pin; Grimsdale, Andrew Clive; Tok, Alfred Iing Yoong

2018-05-01

A 3D fluorine-doped SnO 2 (FTO)/FTO-nanocrystal (NC)/TiO 2 inverse opal (IO) structure is designed and fabricated as a new "host and guest" type of composite photoanode for efficient photoelectrochemical (PEC) water splitting. In this novel photoanode design, the highly conductive and porous FTO/FTO-NC IO acts as the "host" skeleton, which provides direct pathways for faster electron transport, while the conformally coated TiO 2 layer acts as the "guest" absorber layer. The unique composite IO structure is fabricated through self-assembly of colloidal spheres template, a hydrothermal method and atomic layer deposition (ALD). Owing to its large surface area and efficient charge collection, the FTO/FTO-NC/TiO 2 composite IO photoanode shows excellent photocatalytic properties for PEC water splitting. With optimized dimensions of the SnO 2 nanocrystals and the thickness of the ALD TiO 2 absorber layers, the 3D FTO/FTO-NC/TiO 2 composite IO photoanode yields a photocurrent density of 1.0 mA cm -2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5 illumination, which is four times higher than that of the FTO/TiO 2 IO reference photoanode. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bi-component semiconductor oxide photoanodes for the photoelectrocatalytic oxidation of organic solutes and vapours: a short review with emphasis to TiO2-WO3 photoanodes.

PubMed

Georgieva, J; Valova, E; Armyanov, S; Philippidis, N; Poulios, I; Sotiropoulos, S

2012-04-15

The use of binary semiconductor oxide anodes for the photoelectrocatalytic oxidation of organic species (both in solution and gas phase) is reviewed. In the first part of the review, the principle of electrically assisted photocatalysis is presented, the preparation methods for the most common semiconductor oxide catalysts are briefly mentioned, while the advantages of appropriately chosen semiconductor combinations for efficient UV and visible (vis) light utilization are highlighted. The second part of the review focuses on the discussion of TiO(2)-WO(3) photoanodes (among the most studied bi-component semiconductor oxide systems) and in particular on coatings prepared by electrodeposition/electrosynthesis or powder mixtures (the focus of the authors' research during recent years). Studies concerning the microscopic, spectroscopic and photoelectrochemical characterization of the catalysts are presented and examples of photoanode activity towards typical dissolved organic contaminants as well as organic vapours are given. Particular emphasis is paid to: (a) The dependence of photoactivity on catalyst morphology and composition and (b) the possibility of carrying out photoelectrochemistry in all-solid cells, thus opening up the opportunity for photoelectrocatalytic air treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Understanding charge transfer dynamics in QDs-TiO2 nanorod array photoanodes for solar fuel generation

NASA Astrophysics Data System (ADS)

Li, Jiangtian; McClure, Joshua P.; Fu, Richard; Jiang, Rongzhong; Chu, Deryn

2018-01-01

Harvesting light to drive water splitting for hydrogen generation is an attractive approach to satisfy the urgent energy demands. The design and fabrication of photoelectrode materials that are able to harvest sunlight is an important scientific undertaking. In this study, a two-quantum-dot (QD) layer is developed to decorate one-dimensional TiO2 nanorod arrays, which are subsequently utilized as photoanodes to harvest the wide-spectrum sunlight for water splitting. The QD-coated TiO2 nanorod arrays extend the light absorption range from the UV into the visible region yielding increased solar-to-hydrogen efficiencies. Transient photocurrent decay measurements demonstrate that the multi-layer CdSe-CdS QDs deposited onto the TiO2 nanorod arrays result in a stepwise band alignment that not only improves the hole extraction but also facilitates electron injection from the QDs to TiO2 rods. Moreover, the multi-heterojunction photoanode introduces interfacial states that act as recombination centers to trap the photogenerated electrons.

Enhancement of Energy Conversion Efficiency for Dye Sensitized Solar Cell Using Zinc Oxide Photoanode

NASA Astrophysics Data System (ADS)

Jamalullail, N.; Smohamad, I.; Nnorizan, M.; Mahmed, N.

2018-06-01

Dye sensitized solar cell (DSSC) is a third generation solar cell that is well known for its low cost, simple fabrication process and promised reasonable energy conversion efficiency. Basic structure of DSSC is composed of photoanode, dye sensitizer, electrolyte that is sandwiched together in between two transparent conductive oxide (TCO) glasses. Each of the components in the DSSC contributes important role that affect the energy conversion efficiency. In this research, the commonly used titanium dioxide (TiO2) photoanode has previously reported to have high recombination rate and low electron mobility which caused efficiency loss had been compared with the zinc oxide (ZnO) photoanode with high electron mobility (155 cm2V-1s-1). Both of these photoanodes had been deposited through doctor blade technique. The electrical performance of the laboratory based DSSCs were tested using solar cell simulator and demonstrated that ZnO is a better photoanode compared to TiO2 with the energy conversion efficiency of 0.34% and 0.29% respectively. Nanorods shape morphology was observed in ZnO photoanode with average particle size of 41.60 nm and average crystallite size of 19.13 nm. This research proved that the energy conversion efficiency of conventional TiO2 based photoanode can be improved using ZnO material.

Morphological study of electrophoretically deposited TiO2 film for DSSC application

NASA Astrophysics Data System (ADS)

Patel, Alkesh B.; Patel, K. D.; Soni, S. S.; Sonigara, K. K.

2018-05-01

In the immerging field of eco-friendly and low cost photovoltaic devices, dye sensitized solar cell (DSSC) [1] has been investigated as promising alternative to the conventional silicon-based solar cells. In the DSSC device, photoanode is crucial component that take charge of holding sensitizer on it and inject the electrons from the sensitizer to current collector. Nanoporous TiO2 is the most relevant candidate for the preparation of photoanode in DSSCs. Surface properties, morphology, porosity and thickness of TiO2 film as well as preparation technique determine the performance of device. In the present work we have report the study of an effect of nanoporous anatase titanium dioxide (TiO2) film thickness on DSSC performance. Photoanode TiO2 (P25) film was deposited on conducting substrate by electrophoresis technique (EPD) and film thickness was controlled during deposition by applying different current density for a constant time interval. Thickness and surface morphology of prepared films was studied by SEM and transmittance analysis. The same set of photoanode was utilized in DSSC devices using metal free organic dye sensitizer to evaluate the photovoltaic performance. Devices were characterized through Current-Voltage (I-V) characteristic, electrochemical impedance spectroscopy (EIS) and open circuit voltage decay curves. Dependency of device performance corresponding to TiO2 film thickness is investigated through the lifetime kinetics of electron charge transfer mechanism trough impedance fitting. It is concluded that appropriate thickness along with uniformity and porosity are required to align the dye molecules to respond efficiently the incident light photons.

Investigating the performance of nitrogen-doped graphene photoanode in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Joseph, Easter; Singh, Balbir Singh Mahinder; Mohamed, Norani Muti; Kait, Chong Fai; Saheed, Mohamed Shuaib Mohamed; Khatani, Mehboob

2016-11-01

In this paper, the atmospheric pressure chemical vapor deposition (AP-CVD) is used to synthesize graphene on a copper substrate by utilizing methane as a precursor and N-doped graphene (NDG) in the presence of ammonia. The performance of pure titanium dioxide (TiO2), TiO2/graphene, and TiO2/NDG as photoanodes in dye-sensitized solar cell (DSSC) were compared. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed flakes of few layers with an interrupted layer in both graphene and NDG. DSSC consist of TiO2/NDG photoanode exhibits a better enhancement due to the high conductivity of donor N in graphene which enhances the electron transportation across nanoporous TiO2.

Boosting Photovoltaic Performance of Dye-Sensitized Solar Cells Using Silver Nanoparticle-Decorated N,S-Co-Doped-TiO2 Photoanode

PubMed Central

Lim, Su Pei; Pandikumar, Alagarsamy; Lim, Hong Ngee; Ramaraj, Ramasamy; Huang, Nay Ming

2015-01-01

A silver nanoparticle-decorated N,S-co-doped TiO2 nanocomposite was successfully prepared and used as an efficient photoanode in high-performance dye-sensitized solar cells (DSSCs) with N719 dye. The DSSCs assembled with the N,S-TiO2@Ag-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 8.22%, which was better than that of a DSSC photoanode composed of unmodified TiO2 (2.57%) under full sunlight illumination (100 mWcm−2, AM 1.5 G). This enhanced efficiency was mainly attributed to the reduced band gap energy, improved interfacial charge transfer, and retarded charge recombination process. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with N,S-TiO2 was found to be 20 wt%. Because of the enhanced solar energy conversion efficiency of the N,S-TiO2@Ag nanocomposite, it should be considered as a potential photoanode for high-performance DSSCs. PMID:26146362

Titanium mesh supported TiO2 nanowire arrays/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles novel composites for flexible dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, Wenwu; Zhang, Huanyu; Wang, Hui-gang; Zhang, Mei; Guo, Min

2017-11-01

Ti-mesh supported TiO2 nanowire arrays (NWAs)/upconversion luminescence Er3+-Yb3+ codoped TiO2 nanoparticles (UC-EY-TiO2 NPs) composite structured photoanodes for fully flexible dye sensitized solar cells (DSSCs) were firstly constructed via a hydrothermal and spin coating process. UV-vis-NIR absorption spectra of the TiO2 NWAs/UC-EY-TiO2 NPs composites exhibited strong absorption around near infrared (NIR) 980 nm. The composites excited by 980 nm NIR laser could emit upconversion fluorescence at 489, 526, 549 and 658 nm, which expanded the spectral response range and sunlight capturing capability of formed flexible DSSCs. Moreover, the TiO2 NWAs/UC-EY-TiO2 NPs was coated with an Nb2O5 thin layer to further suppress electron recombination losses. The complete flexible DSSCs based on Nb2O5 coated TiO2 NWAs/2.0 mol% Er3+-1.0 mol% Yb3+ codoped TiO2 NPs photoanode and Pt/ITO-PEN counter electrode exhibited an enhanced photon to current conversion efficiency of 8.10%, a 68% improvement compared to TiO2 NWAs/undoped TiO2 NPs based DSSCs (4.82%).

Extremely enhanced photovoltaic properties of dye-sensitized solar cells by sintering mesoporous TiO2 photoanodes with crystalline titania chelated by acetic acid

NASA Astrophysics Data System (ADS)

Liu, Bo-Tau; Chou, Ya-Hui; Liu, Jin-Yan

2016-04-01

The study presents a significant improvement on the performance of dye-sensitized solar cells (DSSCs) through incorporating the crystalline titania chelated by acetic acid (TAc) into the mesoporous TiO2 photoanodes. The effects of TAc on the blocking layer, mesoporous TiO2 layer, and post-treatment have been investigated. The TAc blocking layer displays compact construction, revealing superior response time and resistance to suppress dark current compared to the blocking layer made from titanium(IV) isopropoxide (TTIP). The power conversion efficiency of DSSCs with the TAc treatment can reach as high as 10.49%, which is much higher than that of pristine DSSCs (5.67%) and that of DSSCs treated by TTIP (7.86%). We find that the TAc incorporation can lead to the decrease of charge transfer resistance and the increase of dye adsorption. The result may be attributed to the fact that the TAc possesses high crystallinity, exposed (101) planes, and acid groups chelated on surface, which are favorable for dye attachment and strong bonding at the FTO/TiO2 and the TiO2/TiO2 interfaces, These improvements result in the remarkable increase of photocurrent and thereby that of power conversion efficiency.

Enhanced photoelectrical performance of dye-sensitized solar cells with double-layer TiO2 on perovskite SrTiO3 substrate

NASA Astrophysics Data System (ADS)

Liu, Qiuhong; Sun, Qiong; Zhang, Min; Li, Yang; Zhao, Mei; Dong, Lifeng

2016-04-01

In this research, perovskite SrTiO3 particles are synthesized by a hydrothermal method, and TiO2 with a double-layer structure is grown on the SrTiO3 surface by a hydrolysis-condensation process. Structural characterizations reveal that TiO2 comprises of two phases: anatase film at the bottom and single-crystal rutile nanorods grown along the [110] direction on top. The TiO2-SrTiO3 composite film is investigated as photoanode material for dye-sensitized solar cells. In comparison with pure TiO2 and SrTiO3, the composite photoanode shows a much better performance in photoelectric conversion efficiency (1.35 %), which is about 2 and 100 times as efficient as pure TiO2 and SrTiO3, respectively. This indicates that the composite structure can facilitate charge carrier transfer and reduce electron-hole recombination to enhance photoelectrical properties of TiO2-based photoanode materials.

Quantum dot sensitized solar cell based on TiO2/CdS/Ag2S heterostructure

NASA Astrophysics Data System (ADS)

Pawar, Sachin A.; Patil, Dipali S.; Kim, Jin Hyeok; Patil, Pramod S.; Shin, Jae Cheol

2017-04-01

Quantum dot sensitized solar cell (QDSSC) is fabricated based on a stepwise band structure of TiO2/CdS/Ag2S to improve the photoconversion efficiency of TiO2/CdS system by incorporating a low band gap Ag2S QDs. Vertically aligned TiO2 nanorods assembly is prepared by a simple hydrothermal technique. The formation of CdS and Ag2S QDs over TiO2 nanorods assembly as a photoanode is carried out by successive ionic layer adsorption and reaction (SILAR) technique. The synthesized electrode materials are characterized by XRD, XPS, field emission scanning electron microscopy (FE-SEM), Optical, solar cell and electrochemical performances. The results designate that the QDs of CdS and Ag2S have efficiently covered exterior surfaces of TiO2 nanorods assembly. A cautious evaluation between TiO2/CdS and TiO2/CdS/Ag2S sensitized cells tells that CdS and Ag2S synergetically helps to enhance the light harvesting ability. Under AM 1.5G illumination, the photoanodes show an improved power conversion efficiency of 1.87%, in an aqueous polysulfide electrolyte with short-circuit photocurrent density of 7.03 mA cm-2 which is four fold higher than that of a TiO2/CdS system.

TiO2 hierarchical porous film constructed by ultrastable foams as photoanode for quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Du, Xing; He, Xuan; Zhao, Lei; Chen, Hui; Li, Weixin; Fang, Wei; Zhang, Wanqiu; Wang, Junjie; Chen, Huan

2016-11-01

It reported a novel and simple method for the first time to prepare TiO2 hierarchical porous film (THPF) using ultrastable foams as a soft template to construct porous structures. Moreover, dodecanol as one foam component was creatively used as solvent during the synthesis of CdSe quantum dots (QDs) to decrease reaction temperature and simplify precipitation process. The result showed that hierarchical pores in scale of microns introduced by foams were regarded to benefit for high coverage and unimodal distribution of QDs on the surface of THPF to increase the efficiencies of light-harvesting, charge-collection and charge-transfer. The increased efficiencies caused an enhancement in quantum efficiency of the cell and thus remarkably increased the short circuit current density (Jsc). In addition, the decrease of charge recombination resulted in the increase of the open circuit voltage (Voc) as well. The QDSSC based on THPF exhibited about 2-fold higher power conversion efficiency (η = 2.20%, Jsc = 13.82 mA cm-2, Voc = 0.572 V) than that of TiO2 nanoparticles film (TNF) (η = 1.06%, Jsc = 6.70 mA cm-2, Voc = 0.505 V). It provided a basis to use foams both as soft template and carrier to realize simultaneously construction and in-situ sensitization of photoanode in further work.

Nanographite-TiO2 photoanode for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Sharma, S. S.; Sharma, Khushboo; Sharma, Vinay

2016-05-01

Nanographite-TiO2 (NG-TiO2) composite was successfully synthesized by the hydrothermal method and its performance as the photoanode for dye-sensitized solar cells (DSSCs) was investigated. Environmental Scanning electron microscope (E-SEM) micrographs show the uniform distribution of TiO2 nanoflowers deposited over nanographite sheets. The average performance characteristics of the assembled cell in terms of short-ciruit current density (JSC), open circuit voltage (VOC), fill factor (FF) and photoelectric conversion efficiency (η) were measured.

Band edge movement and structural modifications in transition metal doped TiO2 nanocrystals for the application of DSSC

NASA Astrophysics Data System (ADS)

Patle, L. B.; Huse, V. R.; Chaudhari, A. L.

2017-10-01

Nanocrystalline undoped and transition metal ion doped (TM:Cu2+, Mn2+ and Fe3+) TiO2 nanoparticles, with 1 mol% were synthesized by a simple and cost effective modified co-precipitation method at room temperature and were successfully used as photoanode for dye sensitized solar cell (DSSC). The effect of transition metal ions into TiO2 nano crystalline powder has been systematically investigated using x-ray diffraction (XRD), UV-Vis spectroscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDX). The results of XRD confirm nanocrystalline anatase tetragonal structure of prepared undoped and TM doped TiO2 semiconductor. The influence of doping on band edge movement has been estimated using UV-visible spectroscopy. The SEM results indicate that microscopic effect of doping on morphology of the TiO2. The peaks of EDX signify incorporation of transition metal cations into TiO2 lattice. The effect of doping on flat band potential was estimated using interpolation on Mott-Schottky plot. The performances of DSSCs of undoped and doped TiO2 photoelectrodes were investigated under light illumination. In comparison with undoped and (Cu2+, Fe3+) doped TiO2 photoanodes we found that incorporation of Mn2+ into TiO2 exhibits improvement in photoconversion efficiency (η). There is increase in photoconversion efficiency of DSSCs with Mn2+ doped TiO2 by 6% as compared to that of undoped TiO2 photoanode.

Probing interfacial energetics and charge transfer kinetics in semiconductor nanocomposites: New insights into heterostructured TiO 2/BiVO 4 photoanodes

DOE PAGES

Hess, Lucas H.; Cooper, Jason K.; Loiudice, Anna; ...

2017-02-28

Heterostructured nanocomposites offer promise for creating systems exhibiting functional properties that exceed those of the isolated components. For solar energy conversion, such combinations of semiconducting nanomaterials can be used to direct charge transfer along pathways that reduce recombination and promote efficient charge extraction. However, interfacial energetics and associated kinetic pathways often differ significantly from predictions derived from the characteristics of pure component materials, particularly at the nanoscale. Here, the emergent properties of TiO 2/BiVO 4 nanocomposite photoanodes are explored using a combination of X-ray and optical spectroscopies, together with photoelectrochemical (PEC) characterization. Application of these methods to both the puremore » components and the fully assembled nanocomposites reveals unpredicted interfacial energetic alignment, which promotes ultrafast injection of electrons from BiVO 4 into TiO 2. Physical charge separation yields extremely long-lived photoexcited states and correspondingly enhanced photoelectrochemical functionality. This work highlights the importance of probing emergent interfacial energetic alignment and kinetic processes for understanding mechanisms of solar energy conversion in complex nanocomposites.« less

Facile synthesis of GO@SnO2/TiO2 nanofibers and their behavior in photovoltaics.

PubMed

Mohamed, Ibrahim M A; Dao, Van-Duong; Yasin, Ahmed S; Choi, Ho-Suk; Khalil, KhalilAbdelrazek; Barakat, Nasser A M

2017-03-15

Chemical doping is a widely-used strategy to improve the performance of TiO 2 for the dye-sensitized solar cells (DSCs). However, the effect of two efficient dopants has been rarely investigated. We present the synthesis of GO@SnO 2 /TiO 2 nanofibers (NFs) by a facile method using electrospinning and hydrothermal processes. The synthesized NFs are described in terms of morphology, crystallinity and chemistry through FESEM, TEM, HR-TEM, XRD, EDX, XPS, FT-IR and Raman spectra. As the results, the axial ratio and the average diameter of NFs decreased after the hydrothermal treatment and calcination process, respectively. The prepared Titania-based nanofibers have 81.82% anatase and 18.18% rutile-structure. The developed materials are applied as working electrodes of DSCs. The photovoltaic performances showed that the efficiency of the device employed GO@SnO 2 /TiO 2 photoanode gave 5.41%, which was higher than those of cells fabricated with SnO 2 /TiO 2 NFs (3.41%) and GO@TiO 2 NFs (4.52%) photoanodes. The photovoltaic parameters such as J sc , V oc , FF and R ct are calculated and found to be 11.19mAcm -2 , 0.72V, 0.67 and 9.26Ω, respectively. The high photovoltaic response of DSC based of GO@SnO 2 /TiO 2 NFs may be attributed to the large surface area of the NFs, and the low electron recombination. Furthermore, the start-stop switches of the cell devices with the developed photoanode affirmed the stability and photovoltaic performance of the cell. Copyright © 2016 Elsevier Inc. All rights reserved.

ZnO Photoanode Effect on the Efficiency Performance of Organic Based Dye Sensitized Solar Cell

NASA Astrophysics Data System (ADS)

Mohamad, I. S.; Ismail, S. S.; Norizan, M. N.; Murad, S. A. Z.; Abdullah, M. M. A.

2017-06-01

Dye sensitized solar cell has been emerged as one of the most promising candidates for photovoltaics applications in good quality of their low manufacturing cost and impressive conversion energy. Titanium dioxide (TiO2) which is used as photoanode in the market has the advantage of wide bandgap energy but low in electron mobility (∼10 cm2/(V.s)). Ruthenium in the other hand, as the dye sensitizer is a rare noble metal and harmful to human health. Thus, this article reveals the performance of photo-to-electric conversion efficiency with the usage of Zinc Oxide as photoanode with higher electron mobility (155 cm2/(V.s)) compared to TiO2 utilizing three natural fruit dyes of Prunus domestica, Magnifera indica and Citrus limon. ZnO and TiO2 photoanodes were fabricated using sol gel and dr blade method respectively. The morphology of the photoanodes were characterized using Scanning Electron Microscope and the efficiency of the complete DSSC with all different fruit dyes were characterized using Semiconductor Parametric Analyzer. The different property of electron mobility photoanodes effect in DSSC proved to give better performance with the photoconversion efficiency of 3.082% using ZnO with Prunus domestica dye. This article also reveals that pH indicator does not affect the selection and the performance of DSSC.

Mesoporous TiO2 Bragg Stack Templated by Graft Copolymer for Dye-sensitized Solar Cells

PubMed Central

Park, Jung Tae; Chi, Won Seok; Kim, Sang Jin; Lee, Daeyeon; Kim, Jong Hak

2014-01-01

Organized mesoporous TiO2 Bragg stacks (om-TiO2 BS) consisting of alternating high and low refractive index organized mesoporous TiO2 (om-TiO2) films were prepared to enhance dye loading, light harvesting, electron transport, and electrolyte pore-infiltration in dye-sensitized solar cells (DSSCs). The om-TiO2 films were synthesized via a sol-gel reaction using amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, i.e., PVC-g-POEM as templates. To generate high and low index films, the refractive index of om-TiO2 film was tuned by controlling the grafting ratio of PVC-g-POEM via atomic transfer radical polymerization (ATRP). A polymerized ionic liquid (PIL)-based DSSC fabricated with a 1.2-μm-thick om-TiO2 BS-based photoanode exhibited an efficiency of 4.3%, which is much higher than that of conventional DSSCs with a nanocrystalline TiO2 layer (nc-TiO2 layer) (1.7%). A PIL-based DSSC with a heterostructured photoanode consisting of 400-nm-thick organized mesoporous TiO2 interfacial (om-TiO2 IF) layer, 7-μm-thick nc-TiO2, and 1.2-μm-thick om-TiO2 BS as the bottom, middle and top layers, respectively, exhibited an excellent efficiency of 7.5%, which is much higher than that of nanocrystaline TiO2 photoanode (3.5%). PMID:24980936

Incorporating TiO2 nanotubes with a peptide of D-amino K122-4 (D) for enhanced mechanical and photocatalytic properties

NASA Astrophysics Data System (ADS)

Guo, L. Q.; Hu, Y. W.; Yu, B.; Davis, E.; Irvin, R.; Yan, X. G.; Li, D. Y.

2016-02-01

Titanium dioxide (TiO2) nanotubes are promising for a wide variety of potential applications in energy, biomedical and environmental sectors. However, their low mechanical strength and wide band gap limit their widespread technological use. This article reports our recent efforts to increase the mechanical strength of TiO2 nanotubes with lowered band gap by immobilizing a peptide of D-amino K122-4 (D) onto the nanotubes. Topographies and chemical compositions of the peptide-coated and uncoated TiO2 nanotubular arrays were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). Properties of the peptide-coated and uncoated TiO2 nanotubular arrays, including hardness, elastic modulus, electron work function and photocurrent, were evaluated using micromechanical probe, Kelvin Probe and electrochemical system. Effect of the peptide on surface conductivity was also investigated through current mapping and I-V curve analysis with conductive atomic force microscopy. It is demonstrated that the peptide coating simultaneously enhances the mechanical strength, photocatalytic and electrical properties of TiO2 nanotubes.

Initial formation behaviour of polypyrrole on single crystal TiO2 through photo-electrochemical reaction.

PubMed

Kawakita, Jin; Weitzel, Matthias

2011-04-01

Hybrid materials of the organic and inorganic semiconductors have a potential to show the better performance in the charge separation at the junction upon the photovoltaic action by the presence of the space charge layer in the inorganic semiconductor. In this study, the photo-anodic polymerization was selected as a fabrication method for the hybrid materials composed of TiO2 and polypyrrole on the basis of some advantages of this method. For the process control of the photo-anodic polymerization, it is important to elucidate the formation and growth mechanisms of the organic polymer. In this study, a flat sheet of single-crystal TiO2 was used as a well-defined surface for preparation of the organic polymer of pyrrole. Photo-anodic polarization behaviour was clarified and polypyrrole was prepared on TiO2. The formation process, especially the initial step was revealed by observation of polypyrrole with atomic force microscope (AFM) and statistical interpretation of the morphology of polypyrrole in the nano-scopic level. The formation process of polypyrrole on the TiO2 surface was summarized; (1) adsorption of precursors, (2) localized formation and growth of polypyrrole under the photo-illumination, and (3) homogenous growth of polypyrrole with the external current application under the photo-illumination.

Symbiotic organism search algorithm for simulation of J- V characteristics and optimizing internal parameters of DSSC developed using electrospun TiO2 nanofibers

NASA Astrophysics Data System (ADS)

Vinoth, S.; Kanimozhi, G.; Kumar, Harish; Srinadhu, E. S.; Satyanarayana, N.

2017-12-01

In the present investigation, the recently developed, simple, robust, and powerful metaheuristic symbiotic organism search (SOS) algorithm was used for simulation of J- V characteristics and optimizing the internal parameters of the dye-sensitized solar cells (DSSCs) fabricated using electrospun 1-D mesoporous TiO2 nanofibers as photoanode. The efficiency ( η = 5.80 %) of the DSSC made up of TiO2 nanofibers as photoanode is found to be ˜ 21.59% higher compared to the efficiency ( η = 4.77 %) of the DSSC made up of TiO2 nanoparticles as photoanode. The observed high efficiency can be attributed to high dye loading as well as high electron transport in the mesoporous 1-D TiO2 nanofibers. Further, the validity and advantage of SOS algorithm are verified by simulating J- V characteristics of DSSC with Lambert-W function.

Designing nanostructured one-dimensional TiO2 nanotube and TiO2 nanoparticle multilayer composite film as photoanode in dye-sensitized solar cells to increase the charge collection efficiency

NASA Astrophysics Data System (ADS)

Akilavasan, Jeganathan; Al-Jassim, Maufick; Bandara, Jayasundera

2015-01-01

A photoanode consisting of hydrothermally synthesized TiO2 nanotubes (TNT) and TiO2 nanoparticles (TNP) was designed for efficient charge collection in dye-sensitized solar cells. TNT and TNP films were fabricated on a conductive glass substrate by using electrophoretic deposition and doctor-blade methods, respectively. The TNP, TNT, and TNT/TNP bi-layer electrodes exhibit solar cell efficiencies of 5.3, 7.4, and 9.2%, respectively. Solar cell performance results indicate a higher short-circuit current density (Jsc) for the TNT/TNP bi-layer electrode when compared to a TNT or TNP electrode alone. The open-circuit voltages (Voc) of TNT/TNP and TNT electrodes are comparable while the Voc of TNP electrode is inferior to that of the TNT/TNP electrode. Fill factors of TNT/TNP, TNT, and TNP electrodes also exhibit similar behaviors. The enhanced efficiency of the TNT/TNP bi-layer electrode is found to be mainly due to the enhancement of charge collection efficiency, which is confirmed by the charge transport parameters measured by electrochemical impedance spectroscopy (EIS). EIS analyses also revealed that the TNT/TNP incurs smaller charge transport resistances and longer electron life times when compared to those of TNT or TNP electrodes alone. It was demonstrated that the TNT/TNP bi-layer electrode can possess the advantages of both rapid electron transport rate and a high light scattering effect.

Tunable photovoltaic performance of preferentially oriented rutile TiO₂ nanorod photoanodes based dye sensitized solar cells with quasi-state electrolyte.

PubMed

T C, Sabari Girisun; C, Jeganathan; N, Pavithra; Anandan, Sambandam

2017-12-20

Photoanodes made of highly oriented TiO2 nanorod arrays with different aspect ratios were synthesized via one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in XRD pattern (2θ=63o, (0 0 2)). FESEM image evidence the growth of an array of nanorods having different geometry with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the nanorods increased with reaction time as 4 hours (1.98 μm, 121 nm, 15.32), 8 hours (4 μm, 185 nm, 22.70), 12 hours (5.6 μm, 242 nm, 27.24) and 16 hours (8 μm, 254 nm, 38.02) respectively. Unlike conventional Dye-Sensitized Solar Cell (DSSC) with a liquid electrolyte, DSSC were fabricated here using 1D rutile TiO2 nanorods based photoanodes, N719 dye and quasi-state electrolyte. The charge transport properties were investigated from current-voltage curves and fitted using one-diode model. Interestingly photovoltaic performance of DSSCs increased exponentially with the length of the nanorod and is attributed to the higher surface to volume ratio, more dye anchoring, and channelized electron transport. Higher photovoltaic performance (Jsc=5.99 mA/cm2, Voc=750 mV, η=3.08%) was observed with photoanodes (16 hours) made of densely packed longest TiO2 nanorods (8 µm, 254 nm). © 2017 IOP Publishing Ltd.

Cold sprayed WO3 and TiO2 electrodes for photoelectrochemical water and methanol oxidation in renewable energy applications.

PubMed

Haisch, Christoph; Schneider, Jenny; Fleisch, Manuel; Gutzmann, Henning; Klassen, Thomas; Bahnemann, Detlef W

2017-10-03

Films prepared by cold spray have potential applications as photoanodes in electrochemical water splitting and waste water purification. In the present study cold sprayed photoelectrodes produced with WO 3 (active under visible light illumination) and TiO 2 (active under UV illumination) on titanium metal substrates were investigated as photoanodes for the oxidation of water and methanol, respectively. Methanol was chosen as organic model pollutant in acidic electrolytes. Main advantages of the cold sprayed photoelectrodes are the improved metal-semiconductor junctions and the superior mechanical stability. Additionally, the cold spray method can be utilized as a large-scale electrode fabrication technique for photoelectrochemical applications. Incident photon to current efficiencies reveal that cold sprayed TiO 2 /WO 3 photoanodes exhibit the best photoelectrochemical properties with regard to the water and methanol oxidation reactions in comparison with the benchmark photocatalyst Aeroxide TiO 2 P25 due to more efficient harvesting of the total solar light irradiation related to their smaller band gap energies.

Fabrication and Characterization of Nanoporous Niobia, and Nanotubular Tantala, Titania and Zirconia via Anodization

PubMed Central

Minagar, Sepideh; Berndt, Christopher C.; Wen, Cuie

2015-01-01

Valve metals such as titanium (Ti), zirconium (Zr), niobium (Nb) and tantalum (Ta) that confer a stable oxide layer on their surfaces are commonly used as implant materials or alloying elements for titanium-based implants, due to their exceptional high corrosion resistance and excellent biocompatibility. The aim of this study was to investigate the bioactivity of the nanostructures of tantala (Ta2O5), niobia (Nb2O5), zirconia (ZrO2) and titania (TiO2) in accordance to their roughness and wettability. Therefore, four kinds of metal oxide nanoporous and nanotubular Ta2O5, Nb2O5, ZrO2 and TiO2 were fabricated via anodization. The nanosize distribution, morphology and the physical and chemical properties of the nanolayers and their surface energies and bioactivities were investigated using SEM-EDS, X-ray diffraction (XRD) analysis and 3D profilometer. It was found that the nanoporous Ta2O5 exhibited an irregular porous structure, high roughness and high surface energy as compared to bare tantalum metal; and exhibited the most superior bioactivity after annealing among the four kinds of nanoporous structures. The nanoporous Nb2O5 showed a uniform porous structure and low roughness, but no bioactivity before annealing. Overall, the nanoporous and nanotubular layers of Ta2O5, Nb2O5, ZrO2 and TiO2 demonstrated promising potential for enhanced bioactivity to improve their biomedical application alone or to improve the usage in other biocompatible metal implants. PMID:25837724

Rational design of a tripartite-layered TiO2 photoelectrode: a candidate for enhanced power conversion efficiency in dye sensitized solar cells.

PubMed

Khan, Javid; Gu, Jiuwang; He, Shiman; Li, Xiaohui; Ahmed, Gulzar; Liu, Zhongwu; Akhtar, Muhammad Nadeem; Mai, Wenjie; Wu, Mingmei

2017-07-20

A tri-layered photoelectrode for dye-sensitized solar cells (DSSCs) is assembled using single crystal hollow TiO 2 nanoparticles (HTNPs), sub-micro hollow TiO 2 mesospheres (SHTMSs) and hierarchical TiO 2 microspheres (HTMSs). The bottom layer composed of single crystal hollow TiO 2 nanoparticles serves to absorb dye molecules, harvest light due to its hollow structure and keep a better mechanical contact with FTO conducting glass; the middle layer consisting of sub-micro hollow mesospheres works as a multifunctional layer due to its high dye adsorption ability, strong light trapping and scattering ability and slow recombination rates; and the top layer consisting of hierarchical microspheres enhances light scattering. The DSSCs made of photoanodes with a tripartite-layer structure (Film 4) show a superior photoconversion efficiency (PCE) of 9.24%, which is 7.4% higher than a single layered photoanode composed of HTNPs (Film 1: 8.90%), 4.6% higher than a double layer-based electrode consisting of HTNPs and SHTMSs (Film 2: 9.03%) and 2.6% higher than a double layer-based electrode made of HTNPs and HTMSs (Film 3: 9.11%). The significant improvements in the PCE for tri-layered TiO 2 photoanodes are mainly because of the combined effects of their higher light scattering ability, long electron lifetime, fast electron transport rate, efficient charge collection and a considerable surface area with high dye-loading capability. This study confirms that the facile tri-layered photoanode is an interesting structure for high-efficiency DSSCs.

Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

PubMed Central

Selopal, Gurpreet Singh; Wu, Hui-Ping; Lu, Jianfeng; Chang, Yu-Cheng; Wang, Mingkui; Vomiero, Alberto; Concina, Isabella; Diau, Eric Wei-Guang

2016-01-01

We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction. PMID:26738698

Highly Ordered TiO2 Microcones with High Rate Performance for Enhanced Lithium-Ion Storage.

PubMed

Rhee, Oonhee; Lee, Gibaek; Choi, Jinsub

2016-06-15

The perpendicularly oriented anatase TiO2 microcones for Li-ion battery application were synthesized via anodization of a Ti foil in aqueous HF + H3PO4 solution. The TiO2 microcones exhibited a high active surface area with a hollow core depending on applied voltage and reaction time, confirmed by SEM, XRD and TEM with EDS mapping. Li insertion/desertion into TiO2 microcones was evaluated for the first time in half-cell configuration in terms of various current density and long-term cyclability. The electrochemical experiments demonstrated that the as-prepared TiO2 microcones as anode material exhibited 3 times higher capacity as compared with TiO2 nanotubular structures, excellent rate performance (0.054 mAhcm(-2) even at 50 C) and reliable capacity retention during 500 cycles, which was attributed to facile diffusion of Li-ions induced in hollow anatase TiO2 microcones structure with multilayered nanofragment.

Calculation of DSSC parameters based on ZnO nanorod/TiO2 mesoporous photoanode

NASA Astrophysics Data System (ADS)

Safriani, L.; Nurrida, A.; Mulyana, C.; Susilawati, T.; Bahtiar, A.; Aprilia, A.

2017-07-01

Photoanode of dye sensitized solar cell (DSSC) plays an important role as electron transport media to accept photogenerated electron from excited state of dye. There are several physical properties that are required from photoanode of DSSC. It should be highly transparent, have large surface area, has a conduction band lower than LUMO of dye molecule, has high charge carrier mobility and finally has a good stability in redox electrolyte process. In this work, DSSC with structure FTO/ZnO nanorod/TiO2 mesoporous/Ru-dye/gel electrolyte/ Pt/FTO has been fabricated. In order to modified the structures of photoanode, ZnO nanorod was grown on aluminium doped ZnO seed layer by variation concentration of Al (0 wt%, 0.5 wt% and 1.0 wt%). Zinc nitrate hexahydrate and hexamethylenetetramine used as raw materials for ZnO nanorod growth solution and deposited by self-assembly methods on FTO/Al doped ZnO seed layer. It is then followed by deposition of titania (TiO2) paste by screen printing methods. DSSC parameters i.e. ideally factor (n), series resistance (RS ), and shunt resistance (RSH ) was derived from current density-voltage (I-V) curve using the simplify equation of ideal diode model. The influences of ZnO photoanode structures to the solar cell performance will be completely discussed.

The influence of anatase-rutile mixed phase and ZnO blocking layer on dye-sensitized solar cells based on TiO2nanofiberphotoanodes

PubMed Central

2013-01-01

High performance is expected in dye-sensitized solar cells (DSSCs) that utilize one-dimensional (1-D) TiO2 nanostructures owing to the effective electron transport. However, due to the low dye adsorption, mainly because of their smooth surfaces, 1-D TiO2 DSSCs show relatively lower efficiencies than nanoparticle-based ones. Herein, we demonstrate a very simple approach using thick TiO2 electrospun nanofiber films as photoanodes to obtain high conversion efficiency. To improve the performance of the DSCCs, anatase-rutile mixed-phase TiO2 nanofibers are achieved by increasing sintering temperature above 500°C, and very thin ZnO films are deposited by atomic layer deposition (ALD) method as blocking layers. With approximately 40-μm-thick mixed-phase (approximately 15.6 wt.% rutile) TiO2 nanofiber as photoanode and 15-nm-thick compact ZnO film as a blocking layer in DSSC, the photoelectric conversion efficiency and short-circuit current are measured as 8.01% and 17.3 mA cm−2, respectively. Intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy measurements reveal that extremely large electron diffusion length is the key point to support the usage of thick TiO2 nanofibers as photoanodes with very thin ZnO blocking layers to obtain high photocurrents and high conversion efficiencies. PMID:23286741

Design of an efficient photoanode for dye-sensitized solar cells using electrospun one-dimensional GO/N-doped nanocomposite SnO2/TiO2

NASA Astrophysics Data System (ADS)

Mohamed, Ibrahim M. A.; Dao, Van-Duong; Yasin, Ahmed S.; Barakat, Nasser A. M.; Choi, Ho-Suk

2017-04-01

This study presents the combination of N, graphene oxide (GO) and SnO2 as efficient dopants into TiO2 nanofibers (NFs) photoanode substrate for highly efficient dye-sensitized solar cells (DSCs). The developed NFs are synthesized by electrospinning and hydrothermal processes and characterized by FESEM, TEM, XPS, FT-IR, Raman and EDX-studies. The formation of short NFs is confirmed through FESEM and TEM measurements. As the results, the major crystal structure of TiO2 in the prepared NFs has anatase (85.23%) and rutile-structure (14.67%). XPS and EDX studies affirm that the material has Ti, O, Sn, N and C elements. In addition, FT-IR and Raman spectra give an indication about the GO-content. Typically, the DSC based on the novel NFs shows 6.18% efficiency. The Jsc, Voc, FF and Rct are estimated and found to be 10.32 mA cm-2, 0.825 V, 0.73 and 21.66 Ω, respectively. The high-power efficiency is contributed by three reasons. The first one is the high dye-loading (2.16 × 10-7 mol cm-2). The second reason is the enhanced charge transfer and decreasing of the electrons/holes recombination through formation of wide band-gap oxide (3.246 eV). Finally, the third one is GO-doping which may create new routes for the electron transfer in working electrode layer.

Photoelectric performance of TiO2 nanotube array photoelectrodes sensitized with CdS0.54Se0.46 quantum dots

NASA Astrophysics Data System (ADS)

Gakhar, Ruchi; Smith, York R.; Misra, Mano; Chidambaram, Dev

2015-11-01

The photoelectrochemical performance of CdSSe quantum dots tethered to a framework of vertically oriented titania (TiO2) nanotubes was studied. The TiO2/CdSSe framework demonstrated improved charge transfer due to its unique band edge structure, thus validating the higher photocurrent generation. The composite film led to an 11-fold enhancement in comparison to the control TiO2 film, implying that the ternary quantum dots and the nanotubular structure of TiO2 work in tandem to promote charge separation and favorably impact photoelectrochemical performance. Further, the results also suggest that structural and optoelectronic properties of TiO2 films are significantly affected by the thicknesses of the CdSSe layer.

An Alternative to Annealing TiO2 Nanotubes for Morphology Preservation: Atmospheric Pressure Plasma Jet Treatment.

PubMed

Seo, Sang-Hee; Uhm, Soo-Hyuk; Kwon, Jae-Sung; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2015-03-01

Titanium oxide nanotube layer formed by plasma electrolytic oxidation (PEO) is known to be excellent in biomaterial applications. However, the annealing process which is commonly performed on the TiO2 nanotubes cause defects in the nanotubular structure. The purpose of this work was to apply a non-thermal atmospheric pressure plasma jet on diameter-controlled TiO2 nanotubes to mimic the effects of annealing while maintaining the tubular structure for use as biomaterial. Diameter-controlled nanotube samples fabricated by plasma electrolytic oxidation were dried and prepared under three different conditions: untreated, annealed at 450 °C for 1 h in air with a heating rate of 10 °C/min, and treated with an air-based non-thermal atmospheric pressure plasma jet for 5 minutes. The contact angle measurement was investigated to confirm the enhanced hydrophilicity of the TiO2 nanotubes. The chemical composition of the surface was studied using X-ray photoelectron spectroscopy, and the morphology of TiO2 nanotubes was examined by field emission scanning electron microscopy. For the viability of the cell, the attachment of the osteoblastic cell line MC3T3-E1 was determined using the water-soluble tetrazolium salt assay. We found that there are no morphological changes in the TiO2 nanotubular structure after the plasma treatment. Also, we investigated a change in the chemical composition and enhanced hydrophilicity which result in improved cell behavior. The results of this study indicated that the non-thermal atmospheric pressure plasma jet results in osteoblast functionality that is comparable to annealed samples while maintaining the tubular structure of the TiO2 nanotubes. Therefore, this study concluded that the use of a non-thermal atmospheric pressure plasma jet on nanotube surfaces may replace the annealing process following plasma electrolytic oxidation.

The effect of silver nanoparticles/graphene-coupled TiO2 beads photocatalyst on the photoconversion efficiency of photoelectrochemical hydrogen production

NASA Astrophysics Data System (ADS)

Ke, Chun-Ren; Guo, Jyun-Sheng; Su, Yen-Hsun; Ting, Jyh-Ming

2016-10-01

In this work, a novel configuration of the photoelectrochemical hydrogen production device is demonstrated. It is based on TiO2 beads as the primary photoanode material with the addition of a heterostructure of silver nanoparticles/graphene. The heterostructure not only caters to a great improvement in light harvesting efficiency (LHE) but also enhances the charge collection efficiency. For LHE, the optimized cell based on TiO2 beads/Ag/graphene shows a 47% gain as compared to the cell having a photoanode of commercial P25 TiO2 powders. For the charge collection efficiency, there is a pronounced improvement of an impressive value of 856%. The reason for the improvement in light absorption is attributed to either the light scattering of TiO2 beads or the surface plasmonic resonance on the Ag nanoparticles/graphene. The photoconversion efficiency (PCE) of the resulting cells is also presented and discussed. The PCE of the TiO2 beads/Ag/graphene cell is approximately 2.5 times than that of pure P25 cell.

Depth elemental characterization of 1D self-aligned TiO2 nanotubes using calibrated radio frequency glow discharge optical emission spectroscopy (GDOES)

NASA Astrophysics Data System (ADS)

Mohajernia, Shiva; Mazare, Anca; Hwang, Imgon; Gaiaschi, Sofia; Chapon, Patrick; Hildebrand, Helga; Schmuki, Patrik

2018-06-01

In this work we study the depth composition of anodic TiO2 nanotube layers. We use elemental depth profiling with Glow Discharge Optical Emission Spectroscopy and calibrate the results of this technique with X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). We establish optimized sputtering conditions for nanotubular structures using the pulsed RF mode, which causes minimized structural damage during the depth profiling of the nanotubular structures. This allows to obtain calibrated sputter rates that account for the nanotubular "porous" morphology. Most importantly, sputter-artifact free compositional profiles of these high aspect ratio 3D structures are obtained, as well as, in combination with SEM, elegant depth sectional imaging.

Improved utilization of photogenerated charge using fluorine-doped TiO(2) hollow spheres scattering layer in dye-sensitized solar cells.

PubMed

Song, Junling; Yang, Hong Bin; Wang, Xiu; Khoo, Si Yun; Wong, C C; Liu, Xue-Wei; Li, Chang Ming

2012-07-25

We demonstrate a strategy to improve utilization of photogenerated charge in dye-sensitized solar cells (DSSCs) with fluorine-doped TiO2 hollow spheres as the scattering layer, which improves the fill factor from 69.4% to 74.1% and in turn results in an overall efficiency of photoanode increased by 13% (from 5.62% to 6.31%) in comparison with the control device using undoped TiO2 hollow spheres. It is proposed that the fluorine-doping improves the charge transfer and inhibition of charge recombination to enhance the utilization of the photogenerated charge in the photoanode.

Exploring Step‐by‐Step Assembly of Nanoparticle:Cytochrome Biohybrid Photoanodes

PubMed Central

Hwang, Ee Taek; Orchard, Katherine L.; Hojo, Daisuke; Beton, Joseph; Lockwood, Colin W. J.; Adschiri, Tadafumi

2017-01-01

Abstract Coupling light‐harvesting semiconducting nanoparticles (NPs) with redox enzymes has been shown to create artificial photosynthetic systems that hold promise for the synthesis of solar fuels. High quantum yields require efficient electron transfer from the nanoparticle to the redox protein, a property that can be difficult to control. Here, we have compared binding and electron transfer between dye‐sensitized TiO2 nanocrystals or CdS quantum dots and two decaheme cytochromes on photoanodes. The effect of NP surface chemistry was assessed by preparing NPs capped with amine or carboxylic acid functionalities. For the TiO2 nanocrystals, binding to the cytochromes was optimal when capped with a carboxylic acid ligand, whereas for the CdS QDs, better adhesion was observed for amine capped ligand shells. When using TiO2 nanocrystals, dye‐sensitized with a phosphonated bipyridine Ru(II) dye, photocurrents are observed that are dependent on the redox state of the decaheme, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the decaheme conduit. In contrast, when CdS NPs are used, photocurrents are not dependent on the redox state of the decaheme, consistent with a model in which electron transfer from CdS to the photoanode bypasses the decaheme protein. These results illustrate that although the organic shell of NPs nanoparticles crucially affects coupling with proteinaceous material, the coupling can be difficult to predict or engineer. PMID:28920010

TiO2 film decorated with highly dispersed polyoxometalate nanoparticles synthesized by micelle directed method for the efficiency enhancement of dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

He, Lifei; Chen, Li; Zhao, Yue; Chen, Weilin; Shan, Chunhui; Su, Zhongmin; Wang, Enbo

2016-10-01

In this work, two kinds of polyoxometalate (POM) nanoparticles with controlled shapes and structures were synthesized by micelle directed method and then composited with TiO2 via calcination to remove the surfactants owing to the excellent electronic storage and transmission ability of POM, finally obtaining two kinds of TiO2 composites with highly dispersed and small-sized POM nanoparticles (∼1 nm). The TiO2 composites were then induced into the photoanodes of dye-sensitized (N719) solar cells (DSSCs). The separation of electron-holes becomes more favorable due to the nanostructure and high dispersion of POM which provide more active sites than pure POM tending to agglomeration. The TiO2 composite photoanodes finally yielded the power conversion efficiency (PCE) of 8.4% and 8.2%, respectively, which were 42% and 39% higher than the pristine TiO2 based anodes. In addition, the mechanisms of POM in DSSC are proposed.

Influence of immersion cycles during n-β-Bi2O3 sensitization on the photoelectrochemical behaviour of N-F-codoped TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Hoyos, Lina J.; Rivera, Diego F.; Gualdrón-Reyes, Andrés F.; Ospina, Rogelio; Rodríguez-Pereira, Jhonatan; Ropero-Vega, Jose L.; Niño-Gómez, Martha E.

2017-11-01

Sensitization of TiO2 nanotube (TNT)-based photoanodes with narrow-band gap semiconductors is an important alternative to improving the photoelectrochemical properties of the material. However, the interaction between the sensitizer and TNT is not understood deeply enough to relate charge carrier transport into the composite photoanode with its photoactivity. In this contribution, we studied the photoelectrochemical behaviour of N-F-self codoped TiO2 nanotubes (N-F-TNTs) that were grown by anodization of titanium plates and sensitized with β-Bi2O3 by immersing the TNTs into a Bi2O3 sol solution by dip-coating. The number of immersion cycles was varied. The as-fabricated photoanodes were characterized by FESEM, GIXRD, DRS and XPS, while their photoelectrochemical and semiconducting properties were investigated by photovoltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis in 0.1 M HClO4. The photoelectrocatalytic activity of the composite photoanodes was evaluated for glycerol oxidation under acidic and alkaline conditions. The N-F-TNTs exhibit a well-oriented structure after β-Bi2O3 deposition. The presence of substitutions of both N and F, identified by XPS, indicates the self-doping of the TNTs during anodization. The visible-light harvesting of the N-F-TNT photoanode was enhanced after three -immersion cycles during β-Bi2O3 sensitization, establishing an adequate n-n heterojunction at the N-F-TNT/Bi2O3 interface. In addition, bismuth migration from the sensitizer to the TNT lattice was promoted during thermal treatment, forming Bi-N-F-tridoping of TNT (Bi-N-F-TNT). The suitable band alignment between TNT and β-Bi2O3 and incorporation of the Bi3+ energy levels into TiO2 facilitate charge carrier separation and electron transport throughout the cell. Nevertheless, increasing the number of immersion cycles over three creates an excess of Bi3+ species at the N-F-TNT/β-Bi2O3 interface, producing an energetic barrier that hinders electron

Progress in nanostructured photoanodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, Xueyang; Fang, Jian; Liu, Yong; Lin, Tong

2016-09-01

Solar cells represent a principal energy technology to convert light into electricity. Commercial solar cells are at present predominately produced by single- or multi-crystalline silicon wafers. The main drawback to silicon-based solar cells, however, is high material and manufacturing costs. Dye-sensitized solar cells (DSSCs) have attracted much attention during recent years because of the low production cost and other advantages. The photoanode (working electrode) plays a key role in determining the performance of DSSCs. In particular, nanostructured photoanodes with a large surface area, high electron transfer efficiency, and low electron recombination facilitate to prepare DSSCs with high energy conversion efficiency. In this review article, we summarize recent progress in the development of novel photoanodes for DSSCs. Effect of semiconductor material (e.g. TiO2, ZnO, SnO2, N2O5, and nano carbon), preparation, morphology and structure (e.g. nanoparticles, nanorods, nanofibers, nanotubes, fiber/particle composites, and hierarchical structure) on photovoltaic performance of DSSCs is described. The possibility of replacing silicon-based solar cells with DSSCs is discussed.

The TiO2 Hierarchical Structure with Nanosheet Spheres for Improved Photoelectric Performance in Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Yin, Xin; Guan, Yingli; Song, Lixin; Xie, Xueyao; Du, Pingfan; Xiong, Jie

2018-04-01

A bi-layer photoanode is successfully fabricated for dye-sensitized solar cells (DSSCs) composed of P25/TiO2 nanorod (P25/TNR) as the underlayer and TiO2 nanosheet spheres (TNSs) as the light-scattering layer. Notably, the P25-TNR provides multiple functions, including more dye loading, more efficient charge transport and a lower electron recombination rate for the photoanode. Besides, the unique structure of TNS can significantly improve the light-harvesting capacity, boosting the light-harvesting efficiency. Therefore, an enhanced short-circuit current and power conversion efficiency of 18.04 mA cm-2 and 5.99%, respectively, were achieved for the P25/TNR-TNS-based DSSC, which was better than that of the P25-TNS-based (15.17 mA cm-2, 5.36%) and bare TNS-based (11.43 mA cm-2, 4.14%) DSSCs. This indicates that this bi-layer structure effectively combines the advantages of the one-dimensional (1D) nanostructure and three-dimensional (3D) hierarchical structure. In short, this work demonstrates the possibility of fabricating desirable photoanodes for high-performance DSSCs by rational design of nanostructures and effective combination of multi-functional components.

Efficient light harvesting with micropatterned 3D pyramidal photoanodes in dye-sensitized solar cells.

PubMed

Wooh, Sanghyuk; Yoon, Hyunsik; Jung, Jae-Hyun; Lee, Yong-Gun; Koh, Jai Hyun; Lee, Byoungho; Kang, Yong Soo; Char, Kookheon

2013-06-11

3D TiO2 photoanodes in dye-sensitized solar cells (DSCs) are fabricated by the soft lithographic technique for efficient light trapping. An extended strategy to the construction of randomized pyramid structure is developed by the conventional wet-etching of a silicon wafer for low-cost fabrication. Moreover, the futher enhancement of light absorption resulting in photocurrent increase is achieved by combining the 3D photoanode with a conventional scattering layer. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Electromagnetic Field Enhancement of TiO2 Nanotube Electrodes.

PubMed

Öner, Ibrahim Halil; Querebillo, Christine Joy; David, Christin; Gernert, Ulrich; Walter, Carsten; Driess, Matthias; Leimkühler, Silke; Ly, Khoa Hoang; Weidinger, Inez M

2018-06-11

We present the fabrication of TiO 2 nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface-enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochrome b 5 were observed upon covalent immobilization of the protein matrix on the TiO 2 surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 °C. For the first time, such high values are reported for non-directly surface-interacting probes, for which the involvement of charge-transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

TiO2-Photoanode-Assisted Direct-Solar-Energy Harvesting and Storage in a Solar-Powered Redox Cell Using Halides as Active Materials.

PubMed

Zhang, Shun; Chen, Chen; Zhou, Yangen; Qian, Yumin; Ye, Jing; Xiong, Shiyun; Zhao, Yu; Zhang, Xiaohong

2018-06-27

The rapid deployment of renewable energy is resulting in significant energy security, climate change mitigation, and economic benefits. We demonstrate here the direct solar-energy harvesting and storage in a rechargeable solar-powered redox cell, which can be charged solely by solar irradiation. The cell follows a conventional redox-flow cell design with one integrated TiO 2 photoanode in the cathode side. Direct charging of the cell by solar irradiation results in the conversion of solar energy in to chemical energy. Whereas discharging the cell leads to the release of chemical energy in the form of electricity. The cell integrates energy conversion and storage processes in a single device, making the solar energy directly and efficiently dispatchable. When using redox couples of Br 2 /Br - and I 3 - /I - in the cathode side and anode side, respectively, the cell can be directly charged upon solar irradiation, yielding a discharge potential of 0.5 V with good round-trip efficiencies. This design is expected to be a potential alternative toward the development of affordable, inexhaustible, and clean solar-energy technologies.

Strong efficiency improvement in dye-sensitized solar cells by novel multi-dimensional TiO2 photoelectrode

NASA Astrophysics Data System (ADS)

Zhao, Fengyang; Ma, Rong; Jiang, Yongjian

2018-03-01

Titanium dioxide (TiO2) based dye-sensitized solar cells (DSSCs) often exhibit superior power conversion performance. Here we report a DSSC with novel hierarchical TiO2 composite structure (TCS) composed of anatase TiO2 micro-spheres and rutile TiO2 nanobelt framework by hydrothermal approach for high-performance. As photoanode, the TCS based DSSC shows a strong efficiency enhancement by 58% compared with Degussa TiO2 (P25)-DSSC (4.33%). The excellent performance is mainly attribute to its special multi-dimensional structures of TiO2: much active sites of 0D nanoparticle with exposed excellent {001} facet, special electronic transmission channel of 1D nanobelt, good dye adsorption capacity of 2D nanosheet and high light scattering ability of 3D micro-spheres. The novel multi-dimensional TCS materials will open up a new avenue to the electronic devices fields.

Rational design of anatase TiO2 architecture with hierarchical nanotubes and hollow microspheres for high-performance dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Gu, Jiuwang; Khan, Javid; Chai, Zhisheng; Yuan, Yufei; Yu, Xiang; Liu, Pengyi; Wu, Mingmei; Mai, Wenjie

2016-01-01

Large surface area, sufficient light-harvesting and superior electron transport property are the major factors for an ideal photoanode of dye-sensitized solar cells (DSSCs), which requires rational design of the nanoarchitectures and smart integration of state-of-the-art technologies. In this work, a 3D anatase TiO2 architecture consisting of vertically aligned 1D hierarchical TiO2 nanotubes (NTs) with ultra-dense branches (HTNTs, bottom layer) and 0D hollow TiO2 microspheres with rough surface (HTS, top layer) is first successfully constructed on transparent conductive fluorine-doped tin oxide glass through a series of facile processes. When used as photoanodes, the DSSCs achieve a very large short-current density of 19.46 mA cm-2 and a high overall power conversion efficiency of 8.38%. The remarkable photovoltaic performance is predominantly ascribed to the enhanced charge transport capacity of the NTs (function as the electron highway), the large surface area of the branches (act as the electron branch lines), the pronounced light harvesting efficiency of the HTS (serve as the light scattering centers), and the engineered intimate interfaces between all of them (minimize the recombination effect). Our work demonstrates a possibility of fabricating superior photoanodes for high-performance DSSCs by rational design of nanoarchitectures and smart integration of multi-functional components.

Deliberate Design of TiO2 Nanostructures towards Superior Photovoltaic Cells.

PubMed

Sun, Ziqi; Liao, Ting; Sheng, Liyuan; Kou, Liangzhi; Kim, Jung Ho; Dou, Shi Xue

2016-08-01

TiO2 nanostructures are being sought after as flexibly utilizable building blocks for the fabrication of the mesoporous thin-film photoelectrodes that are the heart of the third-generation photovoltaic devices, such as dye-sensitized solar cells (DSSCs), quantum-dot-sensitized solar cells (QDSSCs), and the recently promoted perovskite-type solar cells. Here, we report deliberate tailoring of TiO2 nanostructures for superior photovoltaic cells. Morphology engineering of TiO2 nanostructures is realized by designing synthetic protocols in which the precursor hydrolysis, crystal growth, and oligomer self-organization are precisely controlled. TiO2 nanostructures in forms varying from isolated nanocubes, nanorods, and cross-linked nanorods to complex hierarchical structures and shape-defined mesoporous micro-/nanostructures were successfully synthesized. The photoanodes made from the shape-defined mesoporous TiO2 microspheres and nanospindles presented superior performances, owing to the well-defined overall shapes and the inner ordered nanochannels, which allow not only a high amount of dye uptake, but also improved visible-light absorption. This study provides a new way to seek an optimal synthetic protocol to meet the required functionality of the nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrothermal synthesis of TiO2-ZnO-graphene nanocomposite towards photocatalytic and photovoltaic applications

NASA Astrophysics Data System (ADS)

Gayathri, S.; Jayabal, P.; Ramakrishnan, V.

2015-06-01

Titanium dioxide (TiO2) - Zinc oxide (ZnO) - Graphene (G) nanocomposite was successfully synthesized through facile hydrothermal method. The X-ray diffraction (XRD) pattern and the micro-Raman spectroscopic technique revealed the formation of TiO2-ZnO-Graphene (TZG) nanocomposite. The ZnO and TiO2 nanoparticles decorated graphene sheets were clearly noticeable in the Field Emission Scanning Electron Micrograph (FE-SEM). The UV-Visible absorption spectra clearly indicated that the formation of TZG nanocomposite enriched the absorption in the visible region. Hence, the prepared nanocomposite can be used as photocatalyst to remove organic dyes from water and as photoanode in the fabrication of dye sensitized solar cells (DSSCs).

Atomic Layer Deposition Al2O3 Coatings Significantly Improve Thermal, Chemical, and Mechanical Stability of Anodic TiO2 Nanotube Layers

PubMed Central

2017-01-01

We report on a very significant enhancement of the thermal, chemical, and mechanical stability of self-organized TiO2 nanotubes layers, provided by thin Al2O3 coatings of different thicknesses prepared by atomic layer deposition (ALD). TiO2 nanotube layers coated with Al2O3 coatings exhibit significantly improved thermal stability as illustrated by the preservation of the nanotubular structure upon annealing treatment at high temperatures (870 °C). In addition, a high anatase content is preserved in the nanotube layers against expectation of the total rutile conversion at such a high temperature. Hardness of the resulting nanotube layers is investigated by nanoindentation measurements and shows strongly improved values compared to uncoated counterparts. Finally, it is demonstrated that Al2O3 coatings guarantee unprecedented chemical stability of TiO2 nanotube layers in harsh environments of concentrated H3PO4 solutions. PMID:28291942

Hyperbranched quasi-1D TiO2 nanostructure for hybrid organic-inorganic solar cells.

PubMed

Ghadirzadeh, Ali; Passoni, Luca; Grancini, Giulia; Terraneo, Giancarlo; Li Bassi, Andrea; Petrozza, Annamaria; Di Fonzo, Fabio

2015-04-15

The performance of hybrid solar cells is strongly affected by the device morphology. In this work, we demonstrate a poly(3-hexylthiophene-2,5-diyl)/TiO2 hybrid solar cell where the TiO2 photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of poly(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure.

Developing the photovoltaic performance of dye-sensitized solar cells (DSSCs) using a SnO2-doped graphene oxide hybrid nanocomposite as a photo-anode

NASA Astrophysics Data System (ADS)

Sasikumar, Ragu; Chen, Tse-Wei; Chen, Shen-Ming; Rwei, Syang-Peng; Ramaraj, Sayee Kannan

2018-05-01

Tin(IV) oxide nanoparticles (SnO2 NPs) doped on the surface of graphene oxide (GO) sheets for application in Dye-Sensitized Solar Cells (DSSCs). The effective incorporation of SnO2 on the surface of GO sheets were confirmed by powder X-ray diffraction (PXRD), Fourier transform infra-red spectroscopy (FT-IR), thermogravimetric analysis (TGA), electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. The morphology of the GO/SnO2 hybrid nanocomposite was confirmed by field emission scanning electron microscopy (FE-SEM) analysis. This current study involvement with the effect of different photo-anodes such as GO, SnO2, and GO/SnO2 hybrid nanocomposite on the power conversion efficiency (PCE) of the triiodide electrolyte based DSSCs. Remarkably, GO/SnO2 hybrid nanocomposite based photo-anode for DSSC observed PCE of 8.3% and it is about 12% higher than that of un-doped TiO2 photo-anode. The equivalent short-circuit photocurrent density (Jsc) of 16.67 mA cm-2, open circuit voltage (Voc) of 0.77 V, and fill factor (FF) of 0.65 respectively. The achieved results propose that the hybrid nanocomposite is an appropriate photo-anodic material for DSSCs applications.

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals.

PubMed

Mao, Xiaoli; Zhou, Ru; Zhang, Shouwei; Ding, Liping; Wan, Lei; Qin, Shengxian; Chen, Zhesheng; Xu, Jinzhang; Miao, Shiding

2016-01-13

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs.

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals

PubMed Central

Mao, Xiaoli; Zhou, Ru; Zhang, Shouwei; Ding, Liping; Wan, Lei; Qin, Shengxian; Chen, Zhesheng; Xu, Jinzhang; Miao, Shiding

2016-01-01

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs. PMID:26758941

Significant enhancement of power conversion efficiency for dye sensitized solar cell using 1D/3D network nanostructures as photoanodes

PubMed Central

Wang, Hao; Wang, Baoyuan; Yu, Jichao; Hu, Yunxia; Xia, Chen; Zhang, Jun; Liu, Rong

2015-01-01

The single–crystalline TiO2 nanorod arrays with rutile phase have attracted much attention in the dye sensitized solar cells (DSSCs) applications because of their superior chemical stability, better electron transport properties, higher refractive index and low production cost. However, it suffers from a low surface area as compared with TiO2 nanoparticle films. In order to enlarge the surface area of TiO2 nanorod arrays, the 1D nanorods/3D nanotubes sample was synthesized using a facile two-step hydrothermal process involving hydrothermal growth 1D/3D nanorods and followed by post-etching treatment. In such bi-layer structure, the oriented TiO2 nanorods layer could provide direct pathway for fast electron transportation, and the 3D nanotubes layer offers a higher surface area for dye loading, therefore, the 1D nanorods/3D nanotubes photoanode exhibited faster electron transport and higher surface area than either 1D or 3D nanostructures alone, and an highest efficiency of 7.68% was achieved for the DSSCs based on 1D nanorods/3D nanotubes photoanode with further TiCl4 treatment. PMID:25800933

A thermal study on the structural changes of bimetallic ZrO2-modified TiO2 nanotubes synthesized using supercritical CO2.

PubMed

Lucky, R A; Charpentier, P A

2009-05-13

In this study the thermal behavior of bimetallic ZrO(2)-TiO(2) (10/90 mol/mol) nanotubes are discussed which were synthesized via a sol-gel process in supercritical carbon dioxide (scCO(2)). The effects of calcination temperature on the morphology, phase structure, mean crystallite size, specific surface area and pore volume of the nanotubes were investigated by using a variety of physiochemical techniques. We report that SEM and TEM images showed that the nanotubular structure was preserved at up to 800 degrees C calcination temperature. When exposed to higher temperatures (900-1000 degrees C) the ZrO(2)-TiO(2) tubes deformed and the crystallites fused together, forming larger crystallites, and a bimetallic ZrTiO(4) species was detected. These results were further examined using TGA, FTIR, XRD and HRTEM analysis. The BET textural properties demonstrated that the presence of a small amount of Zr in the TiO(2) matrix inhibited the grain growth, stabilized the anatase phase and increased the thermal stability.

Enhanced photovoltaic performance of dye-sensitized solar cells based on nickel oxide supported on nitrogen-doped graphene nanocomposite as a photoanode.

PubMed

Ranganathan, Palraj; Sasikumar, Ragu; Chen, Shen-Ming; Rwei, Syang-Peng; Sireesha, Pedaballi

2017-10-15

We applied the nitrogen-doped graphene@nickel oxide (NGE/NiO) nanocomposite doped TiO 2 as a photo-anode for dye-sensitized solar cells (DSSCs) on fluorine-doped tin oxide (FTO) substrates by screen printing method. Power conversion efficiency (PCE) of 9.75% was achieved for this DSSCs device, which is greater than that of DSSCs devices using GO/TiO 2 , and NiO/TiO 2 based photo-anodes (PCE=8.55, and 9.11%). Also, the fill factor (FF) of the DSSCs devices using the NGE/NiO/TiO 2 nanocomposite photo-anode was better than that of other photo-anodes. The NGE/NiO/TiO 2 short-circuit photocurrent density (J sc ) of 19.04mAcm -2 , open circuit voltage (V oc ) of 0.76V, fill factor (FF) of 0.67 and dye absorption rate 0.21×10 -6 molcm -2 . The obtained results suggest that as-prepared NGE/NiO/TiO 2 nanocomposite is suitable photo-anode for DSSCs application. Copyright © 2017 Elsevier Inc. All rights reserved.

Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation

NASA Astrophysics Data System (ADS)

Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

2016-05-01

TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

NASA Astrophysics Data System (ADS)

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-02-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

PubMed Central

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-01-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

Enhanced photovoltaic performance of a quantum dot-sensitized solar cell using a Nb-doped TiO2 electrode.

PubMed

Jiang, Lei; You, Ting; Deng, Wei-Qiao

2013-10-18

In this work Nb-doped anatase TiO2 nanocrystals are used as the photoanode of quantum-dot-sensitized solar cells. A solar cell with CdS/CdSe quantum dots co-sensitized 2.5 mol% Nb-doped anatase TiO2 nanocrystals can achieve a photovoltaic conversion efficiency of 3.3%, which is almost twice as high as the 1.7% obtained by a cell based on undoped TiO2 nanocrystals. The incident photon-to-current conversion efficiency can reach as high as 91%, which is a record for all quantum-dot-sensitized solar cells. Detailed analysis shows that such an enhancement is due to improved lifetime and diffusion length of electrons in the solar cell.

Kinetics of Photoelectrochemical Oxidation of Methanol on Hematite Photoanodes

PubMed Central

2017-01-01

The kinetics of photoelectrochemical (PEC) oxidation of methanol, as a model organic substrate, on α-Fe2O3 photoanodes are studied using photoinduced absorption spectroscopy and transient photocurrent measurements. Methanol is oxidized on α-Fe2O3 to formaldehyde with near unity Faradaic efficiency. A rate law analysis under quasi-steady-state conditions of PEC methanol oxidation indicates that rate of reaction is second order in the density of surface holes on hematite and independent of the applied potential. Analogous data on anatase TiO2 photoanodes indicate similar second-order kinetics for methanol oxidation with a second-order rate constant 2 orders of magnitude higher than that on α-Fe2O3. Kinetic isotope effect studies determine that the rate constant for methanol oxidation on α-Fe2O3 is retarded ∼20-fold by H/D substitution. Employing these data, we propose a mechanism for methanol oxidation under 1 sun irradiation on these metal oxide surfaces and discuss the implications for the efficient PEC methanol oxidation to formaldehyde and concomitant hydrogen evolution. PMID:28735533

Facile fabrication of Si-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical hydrogen generation

NASA Astrophysics Data System (ADS)

Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

2018-04-01

Photoelectrochemical (PEC) water splitting based doping modified one dimensional (1D) titanium dioxide (TiO2) nanostructures provide an efficient method for hydrogen generation. Here we first successfully fabricated 1D Si-doped TiO2 (Ti-Si-O) nanotube arrays through anodizing Ti-Si alloys with different Si amount, and reported the PEC properties for water splitting. The Ti-Si-O nanotube arrays fabricated on Ti-5 wt.% Si alloy and annealed at 600 °C possess higher PEC activity, yielding a higher photocurrent density of 0.83 mA/cm2 at 0 V vs. Ag/AgCl. The maximum photoconversion efficiency was 0.54%, which was 2.7 times the photoconversion efficiency of undoped TiO2.

Immobilization of Ag nanoparticles/FGF-2 on a modified titanium implant surface and improved human gingival fibroblasts behavior.

PubMed

Ma, Qianli; Mei, Shenglin; Ji, Kun; Zhang, Yumei; Chu, Paul K

2011-08-01

The objective of this study was to form a rapid and firm soft tissue sealing around dental implants that resists bacterial invasion. We present a novel approach to modify Ti surface by immobilizing Ag nanoparticles/FGF-2 compound bioactive factors onto a titania nanotubular surface. The titanium samples were anodized to form vertically organized TiO(2) nanotube arrays and Ag nanoparticles were electrodeposited onto the nanotubular surface, on which FGF-2 was immobilized with repeated lyophilization. A uniform distribution of Ag nanoparticles/FGF-2 was observed on the TiO(2) nanotubular surface. The L929 cell line was used for cytotoxicity assessment. Human gingival fibroblasts (HGFs) were cultured on the modified surface for cytocompatibility determination. The Ag/FGF-2 immobilized samples displayed excellent cytocompatibility, negligible cytotoxicity, and enhanced HGF functions such as cell attachment, proliferation, and ECM-related gene expression. The Ag nanoparticles also exhibit some bioactivity. In conclusion, this modified TiO(2) nanotubular surface has a large potential for use in dental implant abutment. Copyright © 2011 Wiley Periodicals, Inc.

Performance optimization of dye-sensitized solar cells by multilayer gradient scattering architecture of TiO2 microspheres.

PubMed

Li, Mingyue; Li, Meiya; Liu, Xiaolian; Bai, Lihua; Luoshan, Mengdai; Lei, Wen; Wang, Zhen; Zhu, Yongdan; Zhao, Xingzhong

2017-01-20

TiO 2 microspheres (TMSs) with unique hierarchical structure and unusual high specific surface area are synthesized and incorporated into a photoanode in various TMS multilayer gradient architectures to form novel photoanodes and dye-sensitized solar cells (DSSCs). Significant influences of these architectures on the photoelectric properties of DSSCs are obtained. The DSSC with the optimal TMS gradient-ascent architecture of M036 has the largest amounts of dye absorption, strongest light absorption, longest electron lifetime and lowest electron recombination, and thus exhibits the maximum short circuit current density (J sc ) of 16.49 mA cm -2 and photoelectric conversion efficiency (η) of 7.01%, notably higher than those of conventional DSSCs by 21% and 22%, respectively. These notable improvements in the properties of DSSCs can be attributed to the TMS gradient-ascent architecture of M036 which can most effectively increase dye absorption and localize incident light within the photoanode by the light scattering of TMSs, and thus utilize the incident light thoroughly. This study provides an optimized and universal configuration for the scattering microspheres incorporated in the hybrid photoanode, which can significantly improve the performance of DSSCs.

Quantum Dot Sensitized Solar Cells Based on TiO2/AgInS2

NASA Astrophysics Data System (ADS)

Pawar, Sachin A.; Jeong, Jae Pil; Patil, Dipali S.; More, Vivek M.; Lee, Rochelle S.; Shin, Jae Cheol; Choi, Won Jun

2018-05-01

Quantum dot heterojunctions with type-II band alignment can efficiently separate photogenerated electron-hole pairs and, hence, are useful for solar cell studies. In this study, a quantum dot sensitized solar cell (QDSSC) made of TiO2/AgInS2 is achieved to boost the photoconversion efficiency for the TiO2-based system by varying the AgInS2 layer's thickness. The TiO2 nanorods array film is prepared by using a simple hydrothermal technique. The formation of a AgInS2 QD-sensitized TiO2-nanorod photoelectrode is carried out by successive ionic layer adsorption and reaction (SILAR) technique. The effect of the QD layer on the performance of the solar cell is studied by varying the SILAR cycles of the QD coating. The synthesized electrode materials are characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy and solar cell performances. The results indicate that the nanocrystals have effectively covered the outer surfaces of the TiO2 nanorods. The interfacial structure of quantum dots (QDs)/TiO2 is also investigated, and the growth interface is verified. A careful comparison between TiO2/AgInS2 sensitized cells reveals that the trasfer of electrons and hole proceeds efficiently, the recombination is suppressed for the optimum thickness of the QD layer and light from the entire visible spectrum is utilised. Under AM 1.5G illumination, a high photocurrent of 1.36 mAcm-2 with an improved power conversion efficiency of 0.48% is obtained. The solar cell properties of our photoanodes suggest that the TiO2 nanorod array films co-sensitized by AgInS2 nanoclusters have potential applications in solar cells.

Wettability, structural and optical properties investigation of TiO{sub 2} nanotubular arrays

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

Zalnezhad, E., E-mail: erfan@hanyang.ac.kr; Maleki, E.; Banihashemian, S.M.

2016-06-15

Graphical abstract: FESEM images of the TiO 2 nanotube layers formed at 0.5 wt% NH4F/ glycerol. - Highlights: • Structural property investigation of TiO{sub 2} nanotube. • Evaluation of wettability of TiO{sub 2} nanotube. • Study on optical properties of TiO{sub 2} nanotube. • The effect of anatase phase on optical and wettability properties of TiO{sub 2.} - Abstract: In this study, the effect of microstructural evolution of TiO{sub 2} nanotubular arrays on wettability and optical properties was investigated. Pure titanium was deposited on silica glass by PVD magnetron sputtering technique. The Ti coated substrates were anodized in an electrolytemore » containing NH{sub 4}F/glycerol. The structures of the ordered anodic TiO{sub 2} nanotubes (ATNs) as long as 175 nm were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The result shows a sharp peak in the optical absorbance spectra around the band gap energy, 3.49–3.42 eV for annealed and non-annealed respectively. The thermal process induced growth of the grain size, which influence on the density of particles and the index of refraction. Furthermore, the wettability tests' result displays that the contact angle of intact substrate (θ = 74.7°) was decreased to 31.4° and 17.4° after anodization for amorphous and heat treated (450 °C) ANTs coated substrate, respectively.« less

Callindra haematocephata and Peltophorum pterocarpum flowers as natural sensitizers for TiO2 thin film based dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Maurya, Ishwar Chandra; Neetu; Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

2016-10-01

We have studied the performance of dye-sensitized solar cells employing natural dye extracted from the flowers Callindra haematocephata and Peltophorum pterocarpum as sensitizers for TiO2 photoanode. The extracts have shown appreciable absorption in the visible region. FTIR studies indicated the presence of anthocyanins and β-carotene in the flowers of C. haematocephata and P. pterocarpum respectively. The extracts were anchored on TiO2 film deposited on transparent conductive glass (FTO) which were used as photoanode. The dye coated TiO2 film electrode, Pt counter electrode and electrolyte (I-3) assembled into a cell module was illuminated by a light source with intensity 100 mW/cm2 to measure the photoelectric conversion efficiency of the DSSCs. From the J-V characteristic curves of cells, the parameters related to the solar cell performance were determined. The conversion efficiency of the DSSC employing natural dye extract from the flower C. haematocephata and P. pterocarpumwere was found as 0.06% and 0.04%, with open-circuit voltage (VOC) of 370 mV & 400 mV, short-circuit current density (JSC) of 0.25 mA/cm2 & 0.15 mA/cm2, fill factor (FF) of 0.70 & 0.71 and Pmax of 65 & 45 μW cm-2 respectively. The extract of the flower C. haematocephata exhibited better photosensitization action compared to the flower of P. pterocarpum.

Heterojunction Fe2O3-SnO2 Nanostructured Photoanode for Efficient Photoelectrochemical Water Splitting

NASA Astrophysics Data System (ADS)

Han, Hyun Soo; Shin, Sun; Noh, Jun Hong; Cho, In Sun; Hong, Kug Sun

2014-04-01

Hierarchically organized nanostructures were fabricated by growing SnO2 nanoparticles on a fluorine-doped tin oxide/glass substrate via a laser ablation method. Cauliflower-like clusters consisting of agglomerated nanoparticles were deposited and aligned with respect to the substrate with a large internal surface area and open channels of pores. The morphological changes of SnO2 nanostructured films were investigated as a function of the oxygen working pressure in the range of 100-500 mTorr. A nanostructured scaffold prepared at an oxygen working pressure of 100 mTorr exhibited the best photoelectrochemical (PEC) performance. A Ti:Fe2O3-SnO2 nanostructured photoanode showed the photocurrent that was 34% larger than that of a Ti:Fe2O3 flat photoanode when the amount of Ti:Fe2O3 sensitizer was identical for the two photoanodes. The larger surface area and longer electron lifetime of the Ti:Fe2O3-SnO2 nanostructured photoanode explains its improved PEC performance.

Solvothermal Synthesis of Hierarchical TiO2 Microstructures with High Crystallinity and Superior Light Scattering for High-Performance Dye-Sensitized Solar Cells.

PubMed

Li, Zhao-Qian; Mo, Li-E; Chen, Wang-Chao; Shi, Xiao-Qiang; Wang, Ning; Hu, Lin-Hua; Hayat, Tasawar; Alsaedi, Ahmed; Dai, Song-Yuan

2017-09-20

In this article, hierarchical TiO 2 microstructures (HM-TiO 2 ) were synthesized by a simple solvothermal method adopting tetra-n-butyl titanate as the titanium source in a mixed solvent composed of N,N-dimethylformamide and acetic acid. Due to the high crystallinity and superior light-scattering ability, the resultant HM-TiO 2 are advantageous as photoanodes for dye-sensitized solar cells. When assembled to the entire photovoltaic device with C101 dye as a sensitizer, the pure HM-TiO 2 -based solar cells showed an ultrahigh photovoltage up to 0.853 V. Finally, by employing the as-obtained HM-TiO 2 as the scattering layer and optimizing the architecture of dye-sensitized solar cells, both higher photovoltage and incident photon-to-electron conversion efficiency value were harvested with respect to TiO 2 nanoparticles-based dye-sensitized solar cells, resulting in a high power conversion efficiency of 9.79%. This work provides a promising strategy to develop photoanode materials with outstanding photoelectric conversion performance.

Controllable Synthesis of TiO2@Fe2O3 Core-Shell Nanotube Arrays with Double-Wall Coating as Superb Lithium-Ion Battery Anodes

PubMed Central

Zhong, Yan; Ma, Yifan; Guo, Qiubo; Liu, Jiaqi; Wang, Yadong; Yang, Mei; Xia, Hui

2017-01-01

Highlighted by the safe operation and stable performances, titanium oxides (TiO2) are deemed as promising candidates for next generation lithium-ion batteries (LIBs). However, the pervasively low capacity is casting shadow on desirable electrochemical behaviors and obscuring their practical applications. In this work, we reported a unique template-assisted and two-step atomic layer deposition (ALD) method to achieve TiO2@Fe2O3 core-shell nanotube arrays with hollow interior and double-wall coating. The as-prepared architecture combines both merits of the high specific capacity of Fe2O3 and structural stability of TiO2 backbone. Owing to the nanotubular structural advantages integrating facile strain relaxation as well as rapid ion and electron transport, the TiO2@Fe2O3 nanotube arrays with a high mass loading of Fe2O3 attained desirable capacity of ~520 mA h g−1, exhibiting both good rate capability under uprated current density of 10 A g−1 and especially enhanced cycle stability (~450 mA h g−1 after 600 cycles), outclassing most reported TiO2@metal oxide composites. The results not only provide a new avenue for hybrid core-shell nanotube formation, but also offer an insight for rational design of advanced electrode materials for LIBs. PMID:28098237

Hierarchically mesostructured porous TiO2 hollow nanofibers for high performance glucose biosensing.

PubMed

Guo, Qiaohui; Liu, Lijuan; Zhang, Man; Hou, Haoqing; Song, Yonghai; Wang, Huadong; Zhong, Baoying; Wang, Li

2017-06-15

Effective immobilization of enzymes on an electrode surface is of great importance for biosensor development, but it still remains challenging because enzymes tend to denaturation and/or form close-packed structures. In this work, a free-standing TiO 2 hollow nanofibers (HNF-TiO 2 ) was successfully prepared by a simple and scalable electrospun nanofiber film template-assisted sol-gel method, and was further explored for glucose oxidase (GOD) immobilization and biosensing. This porous and nanotubular HNF-TiO 2 provides a well-defined hierarchical nanostructure for GOD loading, and the fine TiO 2 nanocrystals facilitate direct electron transfer from GOD to the electrode, also the strong interaction between GOD and HNF-TiO 2 greatly enhances the stability of the biosensor. The as-prepared glucose biosensors show good sensing performances both in O 2 -free and O 2 -containing conditions with good sensitivity, satisfactory selectivity, long-term stability and sound reliability. The novel textile formation, porous and hierarchically mesostructured nature of HNF-TiO 2 with excellent analytical performances make it a superior platform for the construction of high-performance glucose biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

The tailored inner space of TiO2 electrodes via a 30 second wet etching process: high efficiency solid-state perovskite solar cells.

PubMed

Kwon, Jeong; Kim, Sung June; Park, Jong Hyoek

2015-06-28

We fabricated a perovskite solar cell with enhanced device efficiency based on the tailored inner space of the TiO2 electrode by utilizing a very short chemical etching process. It was found that the mesoporous TiO2 photoanode treated with a HF solution exhibited remarkably enhanced power conversion efficiencies under simulated AM 1.5G one sun illumination. The controlled inner space and morphology of the etched TiO2 electrode provide an optimized space for perovskite sensitizers and infiltration of a hole transport layer without sacrificing its original electron transport ability, which resulted in higher JSC, FF and VOC values. This simple platform provides new opportunities for tailoring the microstructure of the TiO2 electrode and has great potential in various optoelectronic devices utilizing metal oxide nanostructures.

Application of nitrogen-doped TiO2 nano-tubes in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tran, Vy Anh; Truong, Trieu Thinh; Phan, Thu Anh Pham; Nguyen, Trang Ngoc; Huynh, Tuan Van; Agresti, Antonio; Pescetelli, Sara; Le, Tien Khoa; Di Carlo, Aldo; Lund, Torben; Le, So-Nhu; Nguyen, Phuong Tuyet

2017-03-01

Our research aimed to improve the overall energy conversion efficiency of DSCs by applying nitrogen-doped TiO2 nano-tubes (N-TNT) for the preparation of DSCs photo-anodes. The none-doped TiO2 nano-tubes (TNTs) were synthesized by alkaline hydrothermal treatment of Degussa P25 TiO2 particles in 10 M NaOH. The nano-tubes were N-doped by reflux in various concentrations of NH4NO3. The effects of nitrogen doping on the structure, morphology, and crystallography of N-TNT were analyzed by transmission electron microscopy (TEM), infrared spectroscopy (IR), Raman spectroscopy, and X-ray photoelectron spectra (XPS). DSCs fabricated with doped N-TNT and TNT was characterized by J-V measurements. Results showed that nitrogen doping significantly enhanced the efficiency of N-TNT cells, reaching the optimum value (η = 7.36%) with 2 M nitrogen dopant, compared to η = 4.75% of TNT cells. The high efficiency of the N-TNT cells was attributed to increased current density due to the reduction of dark current in the DSCs.

Ag plasmonic nanostructures and a novel gel electrolyte in a high efficiency TiO2/CdS solar cell.

PubMed

Kumar, P Naresh; Deepa, Melepurath; Srivastava, Avanish Kumar

2015-04-21

A novel photoanode architecture with plasmonic silver (Ag) nanostructures embedded in titania (TiO2), which served as the wide band gap semiconducting support and CdS quantum dots (QDs), as light absorbers, is presented. Ag nanostructures were prepared by a polyol method and are comprised of clumps of nanorods, 15-35 nm wide, interspersed with globular nanoparticles and they were characterized by a face centered cubic lattice. Optimization of Ag nanostructures was achieved on the basis of a superior power conversion efficiency (PCE) obtained for the cell with a Ag/TiO2/CdS electrode encompassing a mixed morphology of Ag nano-rods and particles, relative to analogous cells with either Ag nanoparticles or Ag nanorods. Interfacial charge transfer kinetics was unraveled by fluorescence quenching and lifetime studies. Ag nanostructures improve the light harvesting ability of the TiO2/CdS photoanode via (a) plasmonic and scattering effects, which induce both near- and far-field enhancements which translate to higher photocurrent densities and (b) charging effects, whereby, photoexcited electron transfer from TiO2 to Ag is facilitated by Fermi level equilibration. Owing to the spectacular ability of Ag nanostructures to increase light absorption, a greatly increased PCE of 4.27% and a maximum external quantum efficiency of 55% (at 440 nm) was achieved for the cell based on Ag/TiO2/CdS, greater by 42 and 66%, respectively, compared to the TiO2/CdS based cell. In addition, the liquid S(2-) electrolyte was replaced by a S(2-) gel containing fumed silica, and the redox potential, conductivity and p-type conduction of the two were deduced to be comparable. Although the gel based cells showed diminished solar cell performances compared to their liquid counterparts, nonetheless, the Ag/TiO2/CdS electrode continued to outperform the TiO2/CdS electrode. Our studies demonstrate that Ag nanostructures effectively capture a significant chunk of the electromagnetic spectrum and aid QD

Silver doped TiO2 nano crystallites for dye-sensitized solar cell (DSSC) applications

NASA Astrophysics Data System (ADS)

Sakthivel, T.; Ashok Kumar, K.; Ramanathan, Rajajeyaganthan; Senthilselvan, J.; Jagannathan, K.

2017-12-01

This communication deals with the synthesis of Ag doped TiO2 nanoparticles with different doping concentrations prepared by reduction method for the possible usage of photo anode material in DSSC. The prepared nanoparticles are characterized by x-ray diffraction to study their structural properties which confirms the formation of mixed anatase-rutile crystalline phases. The particulate size, shape and surface morphology are examined using FESEM which indicates agglomerated nanostructures with the average particle size of 20-25 nm. The UV-visible absorption spectra showed enhanced absorption in the visible range in accordance with the doping concentration of Ag with a red shift in their absorption edge. The interfacial charge transport phenomena of the DSSCs are determined by electrochemical impedance spectroscopy (EIS) and the corresponding efficiencies are calculated using J-V curve. In the present work, the UV active TiO2 and Ag doped TiO2 nanoparticles are employed as photoanode for the fabrication of DSSCs based on N3 dye and maximum power conversion efficiency of 1.544% is realized.

Rapid fabrication of mesoporous TiO2 thin films by pulsed fibre laser for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hadi, Aseel; Alhabradi, Mansour; Chen, Qian; Liu, Hong; Guo, Wei; Curioni, Michele; Cernik, Robert; Liu, Zhu

2018-01-01

In this paper we demonstrate for the first time that a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds can be applied to generate mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass in ambient atmosphere, by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles, without thermally damaging the ITO layer and the glass substrate. The fabrication of the mesoporous TiO2 thin films was achieved by stationary laser beam irradiation of 1 min. The dye sensitized solar cell (DSSC) with the laser-sintered TiO2 photoanode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 μm compared with 2.99% for the furnace-sintered. Electrochemical impedance spectroscopy studies revealed that the laser sintering under the optimised condition effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. The use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future.

Influence of size and shape of sub-micrometer light scattering centers in ZnO-assisted TiO2 photoanode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Pham, Trang T. T.; Mathews, Nripan; Lam, Yeng-Ming; Mhaisalkar, Subodh

2018-03-01

Sub-micrometer cavities have been incorporated in the TiO2 photoanode of dye-sensitized solar cell to enhance its optical property with light scattering effect. These are large pores of several hundred nanometers in size and scatter incident light due to the difference refraction index between the scattering center and the surrounding materials, according to Mie theory. The pores are created using polystyrene (PS) or zinc oxide (ZnO) templates reported previously which resulted in ellipsoidal and spherical shapes, respectively. The effect of size and shape of scattering center was modeled using a numerical analysis finite-difference time-domain (FDTD). The scattering cross-section was not affected significantly with different shapes if the total displacement volume of the scattering center is comparable. Experiments were carried out to evaluate the optical property with varying size of ZnO templates. Photovoltaic effect of dye-sensitized solar cells made from these ZnO-assisted films were investigated with incident-photon-to-current efficiency to understand the effect of scattering center size on the enhancement of absorption. With 380 nm macropores incorporated, the power conversion efficiency has increased by 11% mostly thanks to the improved current density, while 170 nm and 500 nm macropores samples did not have increment in sufficiently wide range of absorbing wavelengths.

Activity of vancomycin release from bioinspired coatings of hydroxyapatite or TiO2 nanotubes.

PubMed

Ionita, Daniela; Bajenaru-Georgescu, Daniela; Totea, Georgeta; Mazare, Anca; Schmuki, Patrik; Demetrescu, Ioana

2017-01-30

Herein we investigate the efficiency of various biomimetic coatings for localized drug delivery, using vancomycin as key therapeutic drug, which is a widely used antibiotic for the treatment of strong infections caused by positive Gram bacteria. We evaluate classical hydroxyapatite and biomimetic hydroxyapatite-collagen coatings obtained by electrochemical deposition as well as TiO 2 nanotubes arrays obtained by electrochemical anodization. Surface morphology, compositional and structural data confirm the incorporation of vancomycin into the layers and drug release profiles for vancomycin evaluate their release ability. Namely, hydroxyapatite coatings lead to a ≈92% vancomycin release after 30h and hydroxyapatite-collagen to 85%, while the TiO 2 nanotubes layers lead to 78% release. The antibacterial effect of such drug loaded coatings is evaluated against S. aureus (Gram-positive bacteria). Our study shows that the vancomycin incorporated hydroxyapatite coatings lead to a faster release, while the nanotubular coatings may lead to longer time release and additionally both types of coatings ensure a good antibacterial inhibition. Copyright © 2016 Elsevier B.V. All rights reserved.

Characteristics and anticorrosion performance of Fe-doped TiO2 films by liquid phase deposition method

NASA Astrophysics Data System (ADS)

Liu, Yu; Xu, Chao; Feng, ZuDe

2014-09-01

Fe-doped TiO2 thin films were fabricated by liquid phase deposition (LPD) method, using Fe(III) nitrate as both Fe element source and fluoride scavenger instead of commonly-used boric acid (H3BO3). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectrum were employed to examine the effects of Fe element on morphology, structure and optical characteristics of TiO2 films. The as-prepared films were served as photoanode applied to photogenerated cathodic protection of SUS304 stainless steel (304SS). It was observed that the photoelectrochemical properties of the as-prepared films were enhanced with the addition of Fe element compared to the undoped TiO2 film. The highest photoactivity was achieved for Ti13Fe (Fe/Ti = 3 molar ratio) film prepared in precursor bath containing 0.02 M TiF4 + 0.06 M Fe(NO3)3 under white-light illumination. The effective anticorrosion behaviors can be attributed to the Fe element incorporation which decreases the probability of photogenerated charge-carrier recombination and extends the light response range of Fe-doped TiO2 films appeared to visible-light region.

Synthesis of LaVO4/TiO2 heterojunction nanotubes by sol-gel coupled with hydrothermal method for photocatalytic air purification.

PubMed

Zou, Xuejun; Li, Xinyong; Zhao, Qidong; Liu, Shaomin

2012-10-01

With the aim of improving the effective utilization of visible light, the LaVO(4)/TiO(2) heterojunction nanotubes were fabricated by sol-gel coupled with hydrothermal method. The photocatalytic ability was demonstrated through catalytic removal of gaseous toluene species. The nanotube samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface photovoltage (SPV), Raman spectra and N(2) adsorption-desorption measurements. The characterization results showed that the samples with high specific surface areas were of typical nanotubular morphology, which would lead to the high separation and transfer efficiency of photo induced electron-hole pairs. The as-prepared nanotubes exhibited high photocatalytic activity in decomposing toluene species under visible light irradiation with fine photochemical stability. The enhanced photocatalytic performance of LaVO(4)/TiO(2) nanotubes might be attributed to the matching band potentials, the interconnected heterojunction of LaVO(4) versus TiO(2), and the large specific surface areas of nanotubes. Copyright © 2012 Elsevier Inc. All rights reserved.

Piper Ornatum and Piper Betle as Organic Dyes for TiO2 and SnO2 Dye Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Hayat, Azwar; Putra, A. Erwin E.; Amaliyah, Novriany; Hayase, Shuzi; Pandey, Shyam. S.

2018-03-01

Dye sensitized solar cell (DSSC) mimics the principle of natural photosynthesis are now currently investigated due to low manufacturing cost as compared to silicon based solar cells. In this report, we utilized Piper ornatum (PO) and Piper betle (PB) as sensitizer to fabricate low cost DSSCs. We compared the photovoltaic performance of both sensitizers with Titanium dioxide (TiO2) and Tin dioxide (SnO2) semiconductors. The results show that PO and PB dyes have higher Short circuit current (Jsc) when applied in SnO2 compared to standard TiO2 photo-anode film even though the Open circuit voltage (Voc) was hampered on SnO2 device. In conclusion, from the result, higher electron injections can be achieved by choosing appropriate semiconductors with band gap that match with dyes energy level as one of strategy for further low cost solar cell.

Revelation of rutile phase by Raman scattering for enhanced photoelectrochemical performance of hydrothermally-grown anatase TiO2 film

NASA Astrophysics Data System (ADS)

Cho, Hsun-Wei; Liao, Kuo-Lun; Yang, Jih-Sheng; Wu, Jih-Jen

2018-05-01

Photoelectrochemical (PEC) performances of the anatase TiO2 films hydrothermally grown on the seeded fluorine-doped tin oxide (FTO) substrates are examined in this work. Structural characterizations of the TiO2 films were conducted using Raman scattering spectroscopy. Although there is no obvious rutile peak appearing, an asymmetrical peak centered at ∼399 cm-1 was observed in the Raman spectra of the TiO2 films deposited either on the low-temperature-formed seed layers or with low concentrations of Ti precursor. The asymmetrical Raman shift can be deconvoluted into the B1g mode of anatase and Eg mode of rutile TiO2 peaks centered at ∼399 cm-1 and ∼447 cm-1, respectively. Therefore, a minute quantity of rutile phase was inspected in the anatase film using Raman scattering spectroscopy. With the same light harvesting ability, we found that the PEC performance of the anatase TiO2 film was significantly enhanced as the minute quantity of rutile phase existing in the film. It is ascribed to the formation of the anatase/rutile heterojunction which is beneficial to the charge separation in the photoanode.

TiO2 Nanostructure Synthesized by Sol-Gel for Dye Sensitized Solar Cells as Renewable Energy Source

NASA Astrophysics Data System (ADS)

Ramelan, A. H.; Wahyuningsih, S.; Saputro, S.; Supriyanto, E.; Hanif, Q. A.

2017-02-01

The use of renewable materials as a constituent of a smart alternative energy such as the use of natural dyes for light harvesting needs to be developed. Synthesis of anatase titanium dioxide (TiO2) and fabrication Dye-Sensitized Solar Cell (DSSC) using dye-based of anthocyanin from purple sweet potato (Ipomoea batatas L.) as a photosensitizer had been done. Synthesis TiO2 through sol-gel process with the addition of triblock copolymer Pluronic F127 template was controlled at pH 3 whereas calcination was carried out at a temperature of 500 °C, 550 °C and 600 °C. The obtained TiO2 were analyzed by XRD, SAA, and SEM. The conclusion is anatase TiO2 obtained until annealing up to 600 °C. Self-assembly Pluronic F127 triblock copolymer capable of restraining the growth of TiO2 crystals. Retention growth of TiO2 mesoporous produces material character that can be used as builders photoanode DSSC with natural sensitizer anthocyanin from purple sweet potatoes. Based on the analysis of X-ray diffraction patterns and surface area analyser, the higher the calcination temperature the greater the size of the anatase crystals is obtained, however, the smaller its surface area. Purple sweet potato anthocyanin’s dyed on to TiO2 was obtained a good enough performance for DSSC’s and gain the optimum performance from DSSC’s system built with mesoporous TiO2 annealed 550 °C using flavylium form anthocyanin.

Incorporation of indium in TiO2-based photoanodes for enhancing the photovoltaic conversion efficiency of dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Beula, R. Jeba; Devadason, Suganthi; Vidhya, B.

2018-06-01

Sol-gel-assisted spin-coating method was used to prepare TiO2 photoelectrodes doped with four different concentrations of indium 0.025, 0.05, 0.075 and 0.1 M. The crystalline phase and average crystallite size of the pure- and indium-doped TiO2 films were found using X-ray diffractometer. Raman analysis was performed for the pure- and In-doped TiO2 films to confirm the structure of anatase phase. UV-visible and photoluminescence spectrophotometer were used to analyze the optical properties of the films. A shift towards a lower wavelength in the absorption spectrum and widening of band gap were noted for the doped TiO2 films. Reduction in the peak intensity was observed in the PL spectra to indicate the inhibiting action of electron-hole recombination. A maximum (2.71%) light to current efficiency is noted for the dye-sensitized solar cells (DSSC) fabricated based on 0.025M In-doped TiO2 electrode.

Synthesis of polycarbonate-r-polyethylene glycol copolymer for templated synthesis of mesoporous TiO2 films.

PubMed

Patel, Rajkumar; Kim, Jinkyu; Lee, Chang Soo; Kim, Jong Hak

2014-12-01

We synthesized a novel polycarbonate Z-r-polyethylene glycol (PCZ-r-PEG) copolymer by solution polycondensation. Successful synthesis of PCZ-r-PEG copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), and transmission electron microscopy (TEM). PCZ-r-PEG copolymer was used as a structure-directing agent for fabrication of mesoporous thin film containing a titanium dioxide (TiO2) layer. To control the porosity of the resultant inorganic layer, the ratio of titanium(IV) isopropoxide (TTIP) to PCZ-r-PEG copolymer was varied. The structure and porosity of the resulting mesoporous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Mesoporous TiO2 films fabricated on an F-doped tin oxide (FTO) surface were used as photoanodes for quasi-solid-state dye-sensitized solar cells (qssDSSCs). The highest efficiency achieved was 3.3% at 100 mW/cm2 for a film thickness of 750 nm, which is high considering the thickness of TiO2 film, indicating the importance of the structure-directing agent.

Cellulose nanofiber-templated three-dimension TiO 2 hierarchical nanowire network for photoelectrochemical photoanode

Treesearch

Zhaodong Li; Chunhua Yao; Fei Wang; Zhiyong Cai; Xudong Wang

2014-01-01

Three dimensional (3D) nanostructures with extremely large porosity possess a great promise for the development of high-performance energy harvesting storage devices. In this paper, we developed a high-density 3D TiO2 fiber-nanorod (NR) heterostructure for photoelectrochemical (PEC) water splitting. The hierarchical structure was synthesized on a...

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility

NASA Astrophysics Data System (ADS)

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J.

2014-07-01

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

PubMed

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J

2014-08-07

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

g-C3N4 modified TiO2 nanosheets with enhanced photoelectric conversion efficiency in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Xu, Jian; Wang, Guanxi; Fan, Jiajie; Liu, Baoshun; Cao, Shaowen; Yu, Jiaguo

2015-01-01

Dye-sensitized solar cells (DSSCs) were fabricated by using g-C3N4 modified TiO2 nanosheets (CTS) as photoanode materials in this research. A thin layer of g-C3N4 was coated on the surface of TiO2 nanosheets by simply heating the mixture of TiO2 nanosheets and urea, which led to the formation of TiO2@g-C3N4 nanosheet heterostructure. The experimental results showed that the photoelectric conversion efficiency of DSSCs was obviously improved after modified by g-C3N4. The measurements of I-V characteristic indicated that the introduction of g-C3N4 could increase both the open circuit voltage and short-circuit photocurrent density. Along with the analysis of electrochemical impedance spectroscopy, it is considered that the thin layer of g-C3N4 can act as the blocking layer for electron backward recombination with electrolyte, which can be used as the functional material to increase the DSSC performance.

Hierarchical porous photoanode based on acid boric catalyzed sol for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Maleki, Khatereh; Abdizadeh, Hossein; Golobostanfard, Mohammad Reza; Adelfar, Razieh

2017-02-01

The hierarchical porous photoanode of the dye sensitized solar cell (DSSC) is synthesized through non-aqueous sol-gel method based on H3BO3 as an acid catalyst and the efficiencies of the fabricated DSSC based on these photoanodes are compared. The sol parameters of 0.17 M, water mole ratio of 4.5, acid mole ratio of 0.45, and solvent type of ethanol are introduced as optimum parameters for photoanode formation without any detectable cracks. The optimized hierarchical photoanode mainly contains anatase phase with slight shift toward higher angles, confirming the doping of boron into titania structure. Moreover, the porous structure involves two ranges of average pore sizes of 20 and 635 nm. The diffuse reflectance spectroscopy (DRS) shows the proper scattering and blueshift in band gap. The paste parameters of solid:liquid, TiO2:ethyl cellulose, and terpineol:ethanol equal to 11:89, 3.5:7.5, and 25:64, respectively, are assigned as optimized parameters for this novel paste. The photovoltaic properties of short circuit current density, open circuit voltage, fill factor, and efficiency of 5.89 mA/cm2, 703 mV, 0.7, and 2.91% are obtained for the optimized sample, respectively. The relatively higher short circuit current of the main sample compared to other samples is mainly due to higher dye adsorption in this sample corresponding to its higher surface area and presumably higher charge transfer confirmed by low RS and Rct in electrochemical impedance spectroscopy data. Boric acid as a catalyst in titania sol not only forms hierarchical porous structure, but also dopes the titania lattice, which results in appreciated performance in this device.

A strategy of combining SILAR with solvothermal process for In2S3 sensitized quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Yang, Peizhi; Tang, Qunwei; Ji, Chenming; Wang, Haobo

2015-12-01

Pursuit of an efficient strategy for quantum dot-sensitized photoanode has been a persistent objective for enhancing photovoltaic performances of quantum dot-sensitized solar cell (QDSC). We present here the fabrication of the indium sulfide (In2S3) quantum dot-sensitized titanium dioxide (TiO2) photoanode by combining successive ionic layer adsorption and reaction (SILAR) with solvothermal processes. The resultant QDSC consists of an In2S3 sensitized TiO2 photoanode, a liquid polysulfide electrolyte, and a Co0.85Se counter electrode. The optimized QDSC with photoanode prepared with the help of a SILAR method at 20 deposition cycles and solvothermal method yields a maximum power conversion efficiency of 1.39%.

Dual functional reduced graphene oxide as photoanode and counter electrode in dye-sensitized solar cells and its exceptional efficiency enhancement

NASA Astrophysics Data System (ADS)

Jumeri, F. A.; Lim, H. N.; Zainal, Z.; Huang, N. M.; Pandikumar, A.; Lim, S. P.

2015-10-01

The dual functionalities of reduced graphene oxide (rGO) as photoanode and counter electrode in dye-sensitized solar cells (DSSCs) is explored. A titanium dioxide (TiO2) film is deposited on an indium tin oxide (ITO) glass using an in-house aerosol-assisted chemical vapor deposition method. Graphene oxide (GO) is then introduced onto the TiO2-ITO substrate, and the GO layer is successively thermally treated to rGO. The TiO2-rGO film is used as a compact layer for the photoanode of the DSSC. A layer of zinc oxide-silver (ZnO-Ag) is introduced on top of the compact layer as an active material. Its highly porous flower-shaped morphology is advantageous for the adsorption of dye. The in-situ electrochemical polymerization method used for the fabrication of polypyrrole incorporated with rGO and p-toluenesulfonate (pTS) (Ppy-rGO-pTS) on an ITO glass is used as a counter electrode for the DSSC. The DSSC assembled with the Ppy-rGO-1.0pTS counter electrode exhibites an enhanced conversion efficiency of 1.99% under solar illumination, which is better than that using conventional Pt as a counter electrode (0.08%). This is attributed to the increased contact area between the Ppy-rGO-pTS counter electrode and electrolyte, which subsequently improves the conductivity and high electrocatalytic activities of the Ppy-rGO-pTS counter electrode.

Enhancement of the performance of cadmium sulfide quantum dot solar cells using a platinum-polyaniline counter electrode and a silver nanoparticle-sensitized photoanode

NASA Astrophysics Data System (ADS)

Nourolahi, Hamzeh; Bolorizadeh, Mohammadagha A.; Dorri, Navid; Behjat, Abbas

2017-07-01

A metal-polymer nanocomposite of platinum-polyaniline (Pt/PANI) was deposited on fluorine-doped tin oxide glass substrates to function as a counter electrode for polysulfide redox reactions in cadmium sulfide quantum dot-sensitized solar cells. In addition, front-side illuminated photoelectrodes were sensitized by silver (Ag) nanoparticles (NPs) as an interfacial layer between a transparent conducting oxide substrate and a TiO2 layer. This configuration, i.e., both the Pt/PANI counter electrode and the Ag NPs in the photoanode, leads to 1.92% in the power-conversion efficiency (PCE) of the fabricated cells. A PCE enhancement of around 21% was obtained for the Ag NPs-sensitized photoanodes, as compared with the Ag NPs-free one. The improved performance can be attributed to the easier transport of excited electrons and the inhibition of charge recombination due to the application of an Ag NPs layer. Electrochemical impedance spectroscopy measurements showed that once Ag NPs are incorporated in a photoanode, electron transport time decreases in the photoanode structure.

Photo-electrochemical properties of graphene wrapped hierarchically branched nanostructures obtained through hydrothermally transformed TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Rambabu, Y.; Jaiswal, Manu; Roy, Somnath C.

2017-10-01

Hierarchically structured nanomaterials play an important role in both light absorption and separation of photo-generated charges. In the present study, hierarchically branched TiO2 nanostructures (HB-MLNTs) are obtained through hydrothermal transformation of electrochemically anodized TiO2 multi-leg nanotubes (MLNT) arrays. Photo-anodes based on HB-MLNTs demonstrated 5 fold increase in applied bias to photo-conversion efficiency (%ABPE) over that of TiO2 MLNTs without branches. Further, such nanostructures are wrapped with reduced graphene oxide (rGO) films to enhance the charge separation, which resulted in ∼6.5 times enhancement in %ABPE over that of bare MLNTs. We estimated charge transport (η tr) and charge transfer (η ct) efficiencies by analyzing the photo-current data. The ultra-fine nano branches grown on the MLNTs are effective in increasing light absorption through multiple scattering and improving charge transport/transfer efficiencies by enlarging semiconductor/electrolyte interface area. The charge transfer resistance, interfacial capacitance and electron decay time have been estimated through electrochemical impedance measurements which correlate with the results obtained from photocurrent measurements.

Ultrafast recombination dynamics in dye-sensitized SnO 2/TiO 2 core/shell films

DOE PAGES

Gish, Melissa K.; Lapides, Alexander M.; Brennaman, M. Kyle; ...

2016-12-02

In dye-sensitized photoelectrosynthesis cells (DSPECs), molecular chromophores and catalysts are integrated on a semiconductor surface to perform water oxidation or CO 2 reduction after a series of light-induced electron transfer events. Unfortunately, recombination of the charge separated state (CSS) is competitive with productive catalysis. To overcome this major obstacle, implementation of photoanodic core/shell films within these devices improve electrochemical behavior and slow recombination through the introduction of an energetic barrier between the semiconductor core and oxidized species on the surface. In this study, interfacial dynamics are investigated in SnO 2/TiO 2 core/shell films derivatized with a Ru(II)-polypyridyl chromophore ([RuII(bpy)2(4,4'-(PO 3Hmore » 2) 2bpy)] 2+, RuP) using transient absorption methods. Electron injection from the chromophore into the TiO 2 shell occurs within a few picoseconds after photoexcitation. Loss of the oxidized dye through recombination occurs across time scales spanning 10 orders of magnitude. The majority (60%) of charge recombination events occur shortly after injection (τ = 220 ps), while a small fraction (≤20%) of the oxidized chromophores persists for milliseconds. The lifetime of long-lived CSS depends exponentially on shell thickness, suggesting that the injected electrons reside in the SnO 2 core and must tunnel through the TiO 2 shell to recombine with oxidized dyes. While the core/shell architecture extends the lifetime in a small fraction of the CSS, making water oxidation possible, the subnanosecond recombination process has profound implications for the overall efficiencies of DSPECs.« less

Chalcogenide Sensitized Carbon Based TiO2 Nanomaterial For Solar Driven Applications

NASA Astrophysics Data System (ADS)

Pathak, Pawan

sensitized photoanode using the one pot method. Finally, the charge transportation effect of carbon allotropes has been studied. For this we assembled TiO2 conductive carbon chalcogenide nanocomposite system. Surface and elemental characterization using electron microscopy, EDX (energy dispersive x-ray) and x-ray diffraction pattern, provide the insights into the assembly of the nanostructure. Optical absorbance, Photo chronometry, Linear sweep voltammetry, and electrochemical impedance analysis have been used to provide opto-electronic performance of the material. We have studied the loading effect of various carbon allotropes, [fullerene (C 60), reduced graphene oxide (RGO), carbon nanotubes (CNTs), and graphene quantum dots (GQDs)], loading effect of chalcogenide, and effect of nitrogen doping on the carbon allotropes to optimize the performance of the heterostructure. This dissertation is expected to impact the materials synthesis strategies and assemble the nanostructures used in composite electrode driven applications in the area of photo electrochemistry, PV, solar-fuels, and other associated topics of energy storage and sensing.

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

NASA Astrophysics Data System (ADS)

Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

2014-12-01

Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

Efficient PbS/CdS co-sensitized solar cells based on TiO2 nanorod arrays

PubMed Central

2013-01-01

Narrow bandgap PbS nanoparticles, which may expand the light absorption range to the near-infrared region, were deposited on TiO2 nanorod arrays by successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The thicknesses of PbS nanoparticles were optimized to enhance the photovoltaic performance of PbS QDSCs. A uniform CdS layer was directly coated on previously grown PbS-TiO2 photoanode to protect the PbS from the chemical attack of polysulfide electrolytes. A remarkable short-circuit photocurrent density (approximately 10.4 mA/cm2) for PbS/CdS co-sensitized solar cell was recorded while the photocurrent density of only PbS-sensitized solar cells was lower than 3 mA/cm2. The power conversion efficiency of the PbS/CdS co-sensitized solar cell reached 1.3%, which was beyond the arithmetic addition of the efficiencies of single constituents (PbS and CdS). These results indicate that the synergistic combination of PbS with CdS may provide a stable and effective sensitizer for practical solar cell applications. PMID:23394609

Heterostructured TiO2/NiTiO3 Nanorod Arrays for Inorganic Sensitized Solar Cells with Significantly Enhanced Photovoltaic Performance and Stability.

PubMed

Li, Yue-Ying; Wang, Jian-Gan; Sun, Huan-Huan; Wei, Bingqing

2018-04-11

Organic dyes used in the conventional dye-sensitized solar cells (DSSCs) suffer from poor light stability and high cost. In this work, we demonstrate a new inorganic sensitized solar cell based on ordered one-dimensional semiconductor nanorod arrays of TiO 2 /NiTiO 3 (NTO) heterostructures prepared via a facile two-step hydrothermal approach. The semiconductor heterostructure arrays are highly desirable and promising for DSSCs because of their direct charge transport capability and slow charge recombination rate. The low-cost NTO inorganic semiconductor possesses an appropriate band gap that matches well with TiO 2 , which behaves like a "dye" to enable efficient light harvesting and fast electron-hole separation. The solar cells constructed by the ordered TiO 2 /NTO heterostructure photoanodes show a significantly improved power conversion efficiency, high fill factor, and more promising, outstanding life stability. The present work will open up an avenue to design heterostructured inorganics for high-performance solar cells.

Improved electron transfer and plasmonic effect in dye-sensitized solar cells with bi-functional Nb-doped TiO2/Ag ternary nanostructures.

PubMed

Park, Jung Tae; Chi, Won Seok; Jeon, Harim; Kim, Jong Hak

2014-03-07

TiO2 nanoparticles are surface-modified via atom transfer radical polymerization (ATRP) with a hydrophilic poly(oxyethylene)methacrylate (POEM), which can coordinate to the Ag precursor, i.e. silver trifluoromethanesulfonate (AgCF3SO3). Following the reduction of Ag ions, a Nb2O5 doping process and calcination at 450 °C, bi-functional Nb-doped TiO2/Ag ternary nanostructures are generated. The resulting nanostructures are characterized by energy-filtering transmission electron microscopy (EF-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy. The dye-sensitized solar cell (DSSC) based on the Nb-doped TiO2/Ag nanostructure photoanode with a polymerized ionic liquid (PIL) as the solid polymer electrolyte shows an overall energy conversion efficiency (η) of 6.9%, which is much higher than those of neat TiO2 (4.7%) and Nb-doped TiO2 (5.4%). The enhancement of η is mostly due to the increase of current density, attributed to the improved electron transfer properties including electron injection, collection, and plasmonic effects without the negative effects of charge recombination or problems with corrosion. These properties are supported by intensity modulated photocurrent/voltage spectroscopy (IMPS/IMVS) and incident photon-to-electron conversion efficiency (IPCE) measurements.

Combined Embedding of N/F-Doping and CaCO3 Surface Modification in the TiO2 Photoanode for Dye-Sensitized Solar Cells.

PubMed

Park, Su Kyung; Yun, Tae Kwan; Bae, Jae Young

2016-03-01

N/F-doping and CaCO3 surface modification was carried out in TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect of the N/F doped TiO2 and the CaCO3 coating showed a great increase of the short-circuit current (J(sc)), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 7.00% of a commercial TiO2 photoelectrode to 7.90% of an uncoated N/F-doped electrode, and to 9.09% of a N/F-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N/F-doped TiO2 nanoparticles generate more photo-excited electrons, as supported by measured UV-Vis diffuse reflectance spectra. A successive CaCO3 surface modification then forms a barrier on the surface of the N/F-doped TiO2 particles; the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

Silver nanoparticles-incorporated Nb2O5 surface passivation layer for efficiency enhancement in dye-sensitized solar cells.

PubMed

Suresh, S; Unni, Gautam E; Satyanarayana, M; Sreekumaran Nair, A; Mahadevan Pillai, V P

2018-08-15

Guiding and capturing photons at the nanoscale by means of metal nanoparticles and interfacial engineering for preventing back-electron transfer are well documented techniques for performance enhancement in excitonic solar cells. Drifting from the conventional route, we propose a simple one-step process to integrate both metal nanoparticles and surface passivation layer in the porous photoanode matrix of a dye-sensitized solar cell. Silver nanoparticles and Nb 2 O 5 surface passivation layer are simultaneously deposited on the surface of a highly porous nanocrystalline TiO 2 photoanode, facilitating an absorption enhancement in the 465 nm and 570 nm wavelength region and a reduction in back-electron transfer in the fabricated dye-sensitized solar cells together. The TiO 2 photoanodes were prepared by spray pyrolysis deposition method from a colloidal solution of TiO 2 nanoparticles. An impressive 43% enhancement in device performance was accomplished in photoanodes having an Ag-incorporated Nb 2 O 5 passivation layer as against a cell without Ag nanoparticles. By introducing this idea, we were able to record two benefits - the metal nanoparticles function as the absorption enhancement agent, and the Nb 2 O 5 layer as surface passivation for TiO 2 nanoparticles and as an energy barrier layer for preventing back-electron transfer - in a single step. Copyright © 2018 Elsevier Inc. All rights reserved.

Synthesis, characterization and application of Co doped TiO2 multilayer thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.

2018-06-01

To use the visible portion of solar light, 2% cobalt doped TiO2 (Co: TiO2) multilayer thin films having 1, 2, 3 and 4 stacked layers have been deposited on FTO substrates using spray pyrolysis technique. XRD results show that 1 and 2 layers of films have anatase phase. Brookite phase has been appeared at the 3 and 4 layered films. The average grain size of 1, 2, 3 and 4 layers of films are 14.4, 23.5, 29.7 and 33.6 nm respectively. UV-Vis results show that 4th layer film has high absorption in the visible region. The calculated Eg of 1, 2, 3 and 4 layers is 3.54, 3.42, 3.30 and 3.03 eV respectively. The calculated average sheet resistivity of 1, 2, 3 and 4 layers of films is 7.68 × 104, 4.54 × 104, 8.85 × 103 and 7.95 × 102 (ohm-m) respectively, according to four point probe technique. Solar simulator results show that highest solar conversion efficiency (5.6%) has been obtained by using 3 stacked layers photoanode. This new structure in the form of stack layers provides a way to improve the efficiency of optoelectronic devices.

Development of a TiO2 modified optical fiber electrode and its incorporation into a photoelectrochemical reactor for wastewater treatment.

PubMed

Esquivel, K; Arriaga, L G; Rodríguez, F J; Martínez, L; Godínez, Luis A

2009-08-01

Electrochemical advanced oxidation processes (EAOPs) are used to chemically burn non biodegradable complex organic compounds that are present in polluted effluents. A common approach involves the use of TiO2 semiconductor substrates as either photocatalytic or photoelectrocatalytic materials in reactors that produce a powerful oxidant (hydroxyl radical) that reacts with pollutant species. In this context, the purpose of this work is to develop a new TiO2 based photoanode using an optic fiber support. The novel arrangement of a TiO2 layer positioned on top of a surface modified optical fiber substrate, allowed the construction of a photoelectrochemical reactor that works on the basis of an internally illuminated approach. In this way, a semi-conductive optical fiber modified surface was prepared using 30 microm thickness SnO2:Sb films on which the photoactive TiO2 layer was electrophoretically deposited. UV light transmission experiments were conducted to evaluate the transmittance along the optical fiber covered with SnO2:Sb and TiO2 showing that 43% of UV light reached the optical fiber tip. With different illumination configurations (external or internal), it was possible to get an increase in the amount of photo-generated H(2)O(2) close to 50% as compared to different types of TiO2 films. Finally, the electro-Fenton photoelectrocatalytic Oxidation process studied in this work was able to achieve total color removal of Azo orange II dye (15 mg L(-1)) and a 57% removal of total organic carbon (TOC) within 60 min of degradation time.

Multifunctional Ag-decorated porous TiO2 nanofibers in dye-sensitized solar cells: efficient light harvesting, light scattering, and electrolyte contact.

PubMed

Hwang, Sun Hye; Song, Hee; Lee, Jungsup; Jang, Jyongsik

2014-09-26

Designing the photoanode structure in dye-sensitized solar cells (DSSCs) is vital to realizing enhanced power conversion efficiency (PCE). Herein, novel multifunctional silver-decorated porous titanium dioxide nanofibers (Ag/pTiO2 NFs) made by simple electrospinning, etching, and chemical reduction processes are introduced. The Ag/pTiO2 NFs with a high surface area of 163 m(2)  g(-1) provided sufficient dye adsorption for light harvesting. Moreover, the approximately 200 nm diameter and rough surface of the Ag/pTiO2 NFs offered enough light scattering, and the enlarged interpores among the NFs in the photoanode also permitted electrolyte circulation. Ag nanoparticles (NPs) were well dispersed on the surface of the TiO2 NFs, which prevented aggregation of the Ag NPs after calcination. Furthermore, a localized surface plasmon resonance effect by the Ag NPs served to increase the light absorption at visible wavelengths. The surface area and amount of Ag NPs was optimized. The PCE of pTiO2 NF-based DSSCs was 27 % higher (from 6.2 to 7.9 %) than for pure TiO2 NFs, whereas the PCE of Ag/pTiO2 NF-based DSSCs increased by about 12 % (from 7.9 to 8.8 %). Thus, the PCE of the multifunctional pTiO2 NFs was improved by 42 %, that is, from 6.2 to 8.8 %. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO2 photoanodes

PubMed Central

Basu, Kaustubh; Benetti, Daniele; Zhao, Haiguang; Jin, Lei; Vetrone, Fiorenzo; Vomiero, Alberto; Rosei, Federico

2016-01-01

We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO2) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiOx or TiCl4 precursor solutions to create a blocking layer before tape casting the SnO2 mesoporous anode. In addition, SnO2 photoelectrodes were treated with the same precursor solutions to deposit a TiO2 passivating layer covering the SnO2 particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl4 treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO2 anode by titania can play a major role in maximizing the photo conversion efficiency. PMID:26988622

Chromatic Titanium Photoanode for Dye-Sensitized Solar Cells under Rear Illumination.

PubMed

Huang, Chih-Hsiang; Chen, Yu-Wen; Chen, Chih-Ming

2018-01-24

Titanium (Ti) has high potential in many practical applications such as biomedicine, architecture, aviation, and energy. In this study, we demonstrate an innovative application of dye-sensitized solar cells (DSSCs) based on Ti photoanodes that can be integrated into the roof engineering of large-scale architectures. A chromatic Ti foil produced by anodizing oxidation (coloring) technology is an attractive roof material for large-scale architecture, showing a colorful appearance due to the formation of a reflective TiO 2 thin layer on both surfaces of Ti. The DSSC is fabricated on the backside of the chromatic Ti foil using the Ti foil as the working electrode, and this roof-DSSC hybrid configuration can be designed as an energy harvesting device for indoor artificial lighting. Our results show that the facet-textured TiO 2 layer on the chromatic Ti foil not only improves the optical reflectance for better light utilization but also effectively suppresses the charge recombination for better electron collection. The power conversion efficiency of the roof-DSSC hybrid system is improved by 30-40% with a main contribution from an improvement of short-circuit current density under standard 1 sun and dim-light (600-1000 lx) illumination.

Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

NASA Astrophysics Data System (ADS)

Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

2018-03-01

Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

Effect of the LHCII pigment-protein complex aggregation on photovoltaic properties of sensitized TiO2 solar cells.

PubMed

Yang, Yiqun; Jankowiak, Ryszard; Lin, Chen; Pawlak, Krzysztof; Reus, Michael; Holzwarth, Alfred R; Li, Jun

2014-10-14

A modified dye-sensitized solar cell consisting of a thin TiO2 barrier layer sensitized with natural trimeric light-harvesting complex II (LHCII) from spinach was used as a biomimetic model to study the effects of LHCII aggregation on the photovoltaic properties. The aggregation of individual trimers induced molecular reorganization, which dramatically increased the photocurrent. The morphology of small- and large-size LHCII aggregates deposited on a surface was confirmed by atomic force microscopy. Enhanced LHCII immobilization was accomplished via electrostatic interaction with amine-functionalized photoanodes. The photocurrent responses of the assembled solar cells under illumination at three characteristic wavelength bands in the UV-Vis absorption spectra of LHCII solutions confirmed that a significant photocurrent was generated by LHCII photosensitizers. The enhanced photocurrent by large aggregated LHCII is shown to correlate with the quenching in the far-red fluorescence deriving from chlorophyll-chlorophyll charge transfer states that are effectively coupled with the TiO2 surface and thus inject electrons into the TiO2 conduction band. The large aggregated LHCII with more chlorophyll-chlorophyll charge transfer states is a much better sensitizer since it injects electrons more efficiently into the conduction band of TiO2 than the small aggregated LHCII mostly consisting of unquenched chlorophyll excited state. The assembled solar cells demonstrated remarkable stability in both aqueous buffer and acetonitrile electrolytes over 30 days.

Interfacial Engineering of Nanoporous Architectures in Ga2O3 Film toward Self-Aligned Tubular Nanostructure with an Enhanced Photocatalytic Activity on Water Splitting.

PubMed

Shrestha, Nabeen K; Bui, Hoa Thi; Lee, Taegweon; Noh, Yong-Young

2018-04-17

The present work demonstrates the formation of self-aligned nanoporous architecture of gallium oxide by anodization of gallium metal film controlled at -15 °C in aqueous electrolyte consisting of phosphoric acid. SEM examination of the anodized film reveals that by adding ethylene glycol to the electrolyte and optimizing the ratio of phosphoric acid and water, chemical etching at the oxide/electrolyte interfaces can be controlled, leading to the formation of aligned nanotubular oxide structures with closed bottom. XPS analysis confirms the chemical composition of the oxide film as Ga 2 O 3 . Further, XRD and SAED examination reveals that the as-synthesized nanotubular structure is amorphous, and can be crystallized to β-Ga 2 O 3 phase by annealing the film at 600 °C. The nanotubular structured film, when used as photoanode for photoelectrochemical splitting of water, achieved a higher photocurrent of about two folds than that of the nanoporous film, demonstrating the rewarding effect of the nanotubular structure. In addition, the work also demonstrates the formation of highly organized nonporous Ga 2 O 3 structure on a nonconducting glass substrate coated with thin film of Ga-metal, highlighting that the current approach can be extended for the formation of self-organized nanoporous Ga 2 O 3 thin film even on nonconducting flexible substrates.

One-Step Formation of WO3-Loaded TiO2 Nanotubes Composite Film for High Photocatalytic Performance

PubMed Central

Lee, Wai Hong; Lai, Chin Wei; Abd Hamid, Sharifah Bee

2015-01-01

High aspect ratio of WO3-loaded TiO2 nanotube arrays have been successfully synthesized using the electrochemical anodization method in an ethylene glycol electrolyte containing 0.5 wt% ammonium fluoride in a range of applied voltage of 10–40 V for 30 min. The novelty of this research works in the one-step formation of WO3-loaded TiO2 nanotube arrays composite film by using tungsten as the cathode material instead of the conventionally used platinum electrode. As compared with platinum, tungsten metal has lower stability, forming dissolved ions (W6+) in the electrolyte. The W6+ ions then move towards the titanium foil and form a coherent deposit on titanium foil. By controlling the oxidation rate and chemical dissolution rate of TiO2 during the electrochemical anodization, the nanotubular structure of TiO2 film could be achieved. In the present study, nanotube arrays were characterized using FESEM, EDAX, XRD, as well as Raman spectroscopy. Based on the results obtained, nanotube arrays with average pore diameter of up to 74 nm and length of 1.6 µm were produced. EDAX confirmed the presence of tungsten element within the nanotube arrays which varied in content from 1.06 at% to 3.29 at%. The photocatalytic activity of the nanotube arrays was then investigated using methyl orange degradation under TUV 96W UV-B Germicidal light irradiation. The nanotube with the highest aspect ratio, geometric surface area factor and at% of tungsten exhibited the highest photocatalytic activity due to more photo-induced electron-hole pairs generated by the larger surface area and because WO3 improves charge separation, reduces charge carrier recombination and increases charge carrier lifetime via accumulation of electrons and holes in the two different metal oxide semiconductor components.

Enhanced photoelectrochemical water splitting of BiVO4 photonic crystal photoanode by decorating with MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Nan, Feng; Cai, Tianyi; Ju, Sheng; Fang, Liang

2018-04-01

Bismuth vanadate (BiVO4) has been considered as one of the promising Photoelectrochemical (PEC) photoanode materials. However, the performances remain poorly rated due to inefficient carrier separation, short carrier diffusion length, and sluggish water oxidation kinetics. Herein, a photoanode consisting of MoS2 nanosheet coating on the three-dimensional ordered BiVO4 inverse opal is fabricated by a facile combination of nanosphere lithography and hydrothermal methods. By taking advantage of the photonic crystal and two-dimensional material, the optimized MoS2/BiVO4 inverse opal photoanode exhibits a 560% improvement of the photocurrent density and threefold enhancement of the incident photon-to-current efficiency than that of the pristine BiVO4 film photoanode. Systematic studies reveal that the excellent PEC activity should be attributed to enhanced light harvesting and charge separation efficiency.

Metal TiO2 Nanotube Layers for the Treatment of Dental Implant Infections.

PubMed

Roguska, Agata; Belcarz, Anna; Zalewska, Justyna; Hołdyński, Marcin; Andrzejczuk, Mariusz; Pisarek, Marcin; Ginalska, Grazyna

2018-05-23

Titanium oxide nanotube layers with silver and zinc nanoparticles are attracting increasing attention in the design of bone and dental implants due to their antimicrobial potential and their ability to control host cell adhesion, growth, and differentiation. However, recent reports indicate that the etiology of dental infections is more complex than has been previously considered. Therefore, the antimicrobial potential of dental implants should be evaluated against at least several different microorganisms cooperating in human mouth colonization. In this study, Ag and Zn nanoparticles incorporated into titanium oxide nanotubular layers were studied with regard to how they affect Candida albicans, Candida parapsilosis, and Streptococcus mutans. Layers of titanium oxide nanotubes with an average diameter of 110 nm were fabricated by electrochemical anodization, annealed at 650 °C, and modified with approx. 5 wt % Ag or Zn nanoparticles. The surfaces were examined with the scanning electron microscopy-energy dispersive X-ray analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy techniques and subjected to evaluation of microbial-killing and microbial adhesion-inhibiting potency. In a 1.5 h long adhesion test, the samples were found more effective toward yeast strains than toward S. mutans. In a release-killing test, the microorganisms were almost completely eliminated by the samples, either within 3 h of contact (for S. mutans) or 24 h of contact (for both yeast strains). Although further improvement is advisable, it seems that Ag and Zn nanoparticles incorporated into TiO 2 nanotubular surfaces provide a powerful tool for reducing the incidence of bone implant infections. Their high bidirectional activity (against both Candida species and S. mutans) makes the layers tested particularly promising for the design of dental implants.

Enhancing the photoelectrochemical response of TiO2 nanotubes through their nanodecoration by pulsed-laser-deposited Ag nanoparticles

NASA Astrophysics Data System (ADS)

Trabelsi, K.; Hajjaji, A.; Gaidi, M.; Bessais, B.; El Khakani, M. A.

2017-08-01

We report on the pulsed laser deposition (PLD) based nanodecoration of titanium dioxide (TiO2) nanotube arrays (NTAs) by Ag nanoparticles (NPs). We focus here on the investigation of the effect of the number of laser ablation pulses (NLP) of the silver target on both the average size of the Ag-NPs and the photoelectrochemical conversion efficiency of the Ag-NP decorated TiO2-NT based photoanodes. By varying the NLP, we were able to not only control the size of the PLD-deposited Ag nanoparticles from 20 to ˜50 nm, but also to increase concomitantly the surface coverage of the TiO2 NTAs by Ag-NPs. The red-shifting of the surface plasmon resonance peak of the PLD-deposited Ag-NPs deposited onto quartz substrates confirmed the increase of their size as the NLP is increased from 500 to 10 000. By investigating the photo-electrochemical properties of Ag-NP decorated TiO2-NTAs, by means of linear sweep cyclic voltammetry under UV-Vis illumination, we found that the generated photocurrent is sensitive to the size of the Ag-NPs and reaches a maximum value at NLP =500 (i.e.,; Ag-NP size of ˜20 nm). For NLP = 500, the photoconversion efficiency of the Ag-NP decorated TiO2-NTAs is shown to reach a maximum of 4.5% (at 0.5 V vs Ag/AgCl). The photocurrent enhancement of Ag-NP decorated TiO2-NTAs is believed to result from the additional light harvesting enabled by the ability of Ag-NPs to absorb visible irradiation caused by various localized surface plasmon resonances, which in turn depend on the size and interdistance of the Ag nanoparticles.

TiO2/PbS/ZnS heterostructure for panchromatic quantum dot sensitized solar cells synthesized by wet chemical route

NASA Astrophysics Data System (ADS)

Bhat, T. S.; Mali, S. S.; Sheikh, A. D.; Korade, S. D.; Pawar, K. K.; Hong, C. K.; Kim, J. H.; Patil, P. S.

2017-11-01

So far we developed the efficient photoelectrodes which can harness the UV as well as the visible regime of the solar spectrum effectively. In order to exploit a maximum portion of solar spectrum, it is necessary to study the synergistic effect of a photoelectrode comprising UV and visible radiations absorbing materials. Present research work highlights the efforts to study the synchronized effect of TiO2 and PbS on the power conversion efficiency of quantum dot sensitized solar cell (QDSSC). A cascade structure of TiO2/PbS/ZnS QDSSC is achieved to enhance the photoconversion efficiency of TiO2/PbS system by incorporating a surface passivation layer of ZnS which avoids the recombination of charge carriers. A QDSSC is fabricated using a simple and cost-effective technique such as hydrothermally grown TiO2 nanorod arrays decorated with PbS and ZnS using successive ionic layer adsorption and reaction (SILAR) method. Synthesized electrode materials are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), High resolution-transmission electron microscopy (TEM), STEM-EDS mapping, optical and solar cell performances. Phase formation of TiO2, PbS and ZnS get confirmed from the XPS study. FE-SEM images of the photoelectrode show uniform coverage of PbS QDs onto the TiO2 nanorods which increases with increasing number of SILAR cycles. The ZnS layer not only improves the charge transport but also reduces the photocorrosion of lead chalcogenides in the presence of a liquid electrolyte. Finally, the photoelectrochemical (PEC) study is carried out using an optimized photoanode comprising TiO2/PbS/ZnS assembly. Under AM 1.5G illumination the TiO2/PbS/ZnS QDSSC photoelectrode shows 4.08 mA/cm2 short circuit current density in a polysulfide electrolyte which is higher than that of a bare TiO2 nanorod array.

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode.

PubMed

Mehraeen, Shayan; Taşdemir, Adnan; Gürsel, Selmiye Alkan; Yürüm, Alp

2018-06-22

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO 2 to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO 2 -B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g -1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO 2 have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li + and increases the electronic conductivity of the anode.

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode

NASA Astrophysics Data System (ADS)

Mehraeen, Shayan; Taşdemir, Adnan; Alkan Gürsel, Selmiye; Yürüm, Alp

2018-06-01

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO2 to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO2-B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g‑1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO2 have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li+ and increases the electronic conductivity of the anode.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

PubMed Central

Maijenburg, A. Wouter; Rodijk, Eddy J.B.; Maas, Michiel G.; ten Elshof, Johan E.

2014-01-01

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution. PMID:24837535

Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

2015-04-01

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

Bimodal porous TiO2 structures templated by graft copolymer/homopolymer blend for dye-sensitized solar cells with polymer electrolyte

NASA Astrophysics Data System (ADS)

Kim, Jin Kyu; Lee, Chang Soo; Lee, Sang-Yup; Cho, Hyung Hee; Kim, Jong Hak

2016-12-01

Bimodal porous TiO2 (BP-TiO2) with large surface area, high porosity, good interconnectivity, and excellent light-scattering ability are synthesized via a facile one-step method using a self-assembled blend template consisting of an amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) graft copolymer and a hydrophobic poly(vinyl chloride) (PVC) homopolymer. The hydrophilically surface-modified TiO2 nanoparticles selectively interact with the hydrophilic POEM chains, while the addition of the PVC homopolymer increases the hydrophobic domain size, resulting in the formation of dual pores (i.e., macropores and mesopores). The sizes and numbers of macropores can easily be controlled by changing the molecular weight and amount of the PVC homopolymer. The polymer electrolyte dye-sensitized solar cells (DSSCs) fabricated with BP-TiO2 photoanodes exhibited energy conversion efficiencies of up to 7.6% at 100 mW cm-2, which is much higher than those of mesoporous TiO2 (5.8%) with PVC-g-POEM only and conventional nanocrystalline TiO2 (4.9%) with commercial Dyesol paste. The enhanced energy conversion efficiencies mostly resulted from the light-scattering effects of the macropores, which increased the light-harvesting efficiencies. The improved light-harvesting and photovoltaic performances of the DSSCs were characterized by UV-vis spectroscopy, incident photon-to-current conversion efficiency analysis, electrochemical impedance spectroscopy, intensity-modulated photocurrent spectroscopy, and intensity-modulated photovoltage spectroscopy.

Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

PubMed

Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

2014-02-01

One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Coated α-Fe2O3 Photoanode Synthesized by a Facile Anodic Electrodeposition for Highly Efficient Water Oxidation

NASA Astrophysics Data System (ADS)

Zhang, Honglei; Li, Longzhu; Liu, Changhai; Wang, Wenchang; Liang, Penghua; Mitsuzak, Naotoshi; Chen, Zhidong

2018-05-01

This work provides a facile anodic electrodeposition method for synthesizing carbon coated α-Fe2O3 photoanode followed by annealing treatment with argon atmosphere. Compared with bare hematite photoanode, the carbon coated α-Fe2O3 photoanodes annealed at lower temperature (Fe2O3/C-L) and higher temperature (Fe2O3/C-H) have higher photocurrent density as 0.3 and 0.5 mA cm-2 (at 1.23 V vs. RHE), respectively. The excellent PEC performance is attributed to the synergistic reaction of carbon and vacancy oxygen. The morphology and properties of the sample were characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV-Vis spectra, X-ray diffractometry, X-ray photoelectron spectra, and photoelectrical measurements.

Improved electron density through hetero-junction binary sensitized TiO2/ CdTe / D719 system as photoanode for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Pandey, A. K.; Ahmad, Muhammad Shakeel; Alizadeh, Mahdi; Rahim, Nasrudin Abd

2018-07-01

The combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv-vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs.

Protected, back-illuminated silicon photocathodes or photoanodes for water splitting tandem stacks (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vesborg, Peter C.; Bae, Dowon; Seger, Brian J.; Chorkendorff, Ib; Hansen, Ole; Pedersen, Thomas; Mei, Bastian; Frydendal, Rasmus

2016-10-01

Silicon is a promising contender in the race for low-bandgap absorbers for use in a solar driven monolithic water splitting cell (PEC). However, given its role as the low-bandgap material the silicon must sit behind the corresponding high-bandgap material and as such, it will be exposed to (red) light from the dry back-side - not from the wet front side, where the electrochemistry takes place.[1,2] Depending on the configuration of the selective contacts (junctions) this may lead to compromises between high absorption and low recombination.[2,3] We discuss the tradeoffs and compare modeling results to measurements. Regardless of configuration, the wet surface of the silicon is prone to passivation or corrosion and must therefore be carefully protected in service in order to remain active. We demonstrate the use of TiO2 as an effective protection layer for both photoanodes and photocathodes in acid electrolyte [4] and NiCoOx for photoanodes in alkaline electrolyte. [3] References: [1]: B. Seger et alia, Energ. Environ. Sci., 7 (8), 2397-2413 (2014), DOI:10.1039/c4ee01335b [2]: D. Bae et alia, Energ. Environ. Sci., 8 (2), 650-660 (2015), DOI: 10.1039/c4ee03723e [3]: D. Bae et alia, submitted, (2016) [4]: B. Mei et alia, J. Phys. Chem. C., 119 (27), 15019-15027 (2015), DOI: 10.1021/acs.jpcc.5b04407

Effect of Cyclic Precalcification of Nanotubular TiO2 Layer on the Bioactivity of Titanium Implant

PubMed Central

Park, Il Song; Yang, Eun Jin; Bae, Tae Sung

2013-01-01

The objective of this study is to investigate the effect of cyclic precalcification treatment to impart bioactive properties for titanium implants. Before precalcification, the titanium implants were subjected to blasting using hydroxyapatite (HAp), a resorbable blasting medium (RBM treated), and anodized using an electrolyte containing glycerol, H2O, and NH4F. Precalcification treatment was performed by two different methods, namely, continuous immersion treatment (CIT) and alternate immersion treatment (AIT). In CIT, the RBM treated and anodized titanium implants were immersed in 0.05 M NaH2PO4 solution at 80°C and saturated Ca(OH)2 solution at 100°C for 20 min, whereas during AIT, they were immersed alternatively in both solutions for 1 min for 20 cycles. Anodizing of the titanium implants enables the formation of self-organized TiO2 nanotubes. Cyclic precalcification treatment imparts a better bioactive property and enables an increase in activation level of the titanium implants. The removal torque values of the RBM treated, CIT treated, and AIT treated titanium implants are 10.8 ± 3.7 Ncm, 17.5 ± 3.5 Ncm, and 28.1 ± 2.4 Ncm, respectively. The findings of the study indicate the cyclic precalcification in an effective surface treatment method that would help accelerate osseointegration and impart bioactive property of titanium implants. PMID:24069596

Dye sensitized solar cell applications of CdTiO3-TiO2 composite thin films deposited from single molecular complex

NASA Astrophysics Data System (ADS)

Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

2015-10-01

A heterobimetallic complex [Cd2Ti4(μ-O)6(TFA)8(THF)6]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO3-TiO2 composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO3-TiO2 composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application.

Final Report

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

Chidambaram, Dev; Misra, Mano; Heske, Clemens

2014-12-21

The objectives included: Develop high efficiency metal oxide nanotubular array photo-anodes for generating hydrogen by water splitting; Develop density functional theory to understand the effect of the morphology of the nanotubes on the photo-electrochemical (PEC) properties of the photo-anodes; Develop kinetics and formation mechanism of the metal oxide nanotubes under different synthesis conditions; Develop combinatorial approach to prepare hybrid photo-anodes having multiple hetero-atoms incorporation in a single photo anode; Improve the durability of the material; and Scale up the laboratory demonstration to production unit.

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

PubMed

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

2014-06-17

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

Morphology-controlled cactus-like branched anatase TiO2 arrays with high light-harvesting efficiency for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wu, Wu-Qiang; Rao, Hua-Shang; Feng, Hao-Lin; Guo, Xin-Dong; Su, Cheng-Yong; Kuang, Dai-Bin

2014-08-01

The present work establishes a facile process for one-step hydrothermal growth of vertically aligned anatase cactus-like branched TiO2 (CBT) arrays on a transparent conducting oxide (TCO) substrate. Various CBT morphologies are obtained by adjusting the potassium titanium oxide oxalate (PTO) reactant concentration (from 0.05 M to 0.15 M) and this yields a morphologically-controllable branched TiO2 arrays geometry. The CBT arrays consist of a vertically oriented nanowire (NW) or nanosheet (NS) stem and a host of short nanorod (NR) branches. The hierarchical CBT arrays demonstrate their excellent candidatures as photoanodes, which are capable of exhibiting high light-harvesting efficiency in dye-sensitized solar cells (DSSCs). Consequently, DSSCs based on 7 μm long optimized CBT arrays (0.05 M PTO), which are assembled with high density and high aspect-ratio NR branches, exhibit an impressive power conversion efficiency of 6.43% under AM 1.5G one sun illumination. The high performance can be attributed to the prominent light-harvesting efficiency, resulting from larger surface area and superior light-scattering capability.

TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

NASA Astrophysics Data System (ADS)

Ghalamboran, Milad; Saedi, Yasin

2016-03-01

The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

BiVO4 Photoanode with Exposed (040) Facets for Enhanced Photoelectrochemical Performance

NASA Astrophysics Data System (ADS)

Xia, Ligang; Li, Jinhua; Bai, Jing; Li, Linsen; Chen, Shuai; Zhou, Baoxue

2018-03-01

A BiVO4 photoanode with exposed (040) facets was prepared to enhance its photoelectrochemical performance. The exposure of the (040) crystal planes of the BiVO4 film was induced by adding NaCl to the precursor solution. The as-prepared BiVO4 photoanode exhibits higher solar-light absorption and charge-separation efficiency compared to those of an anode prepared without adding NaCl. To our knowledge, the photocurrent density (1.26 mA cm-2 at 1.23 V vs. RHE) of as-prepared BiVO4 photoanode is the highest according to the reports for bare BiVO4 films under simulated AM1.5G solar light, and the incident photon-to-current conversion efficiency is above 35% at 400 nm. The photoelectrochemical (PEC) water-splitting performance was also dramatically improved with a hydrogen evolution rate of 9.11 μmol cm-2 h-1, which is five times compared with the BiVO4 photoanode prepared without NaCl (1.82 μmol cm-2 h-1). Intensity-modulated photocurrent spectroscopy and transient photocurrent measurements show a higher charge-carrier-transfer rate for this photoanode. These results demonstrate a promising approach for the development of high-performance BiVO4 photoanodes which can be used for efficient PEC water splitting and degradation of organic pollutants. [Figure not available: see fulltext.

Influence of Au and TiO2 structures on hydrogen dissociation over TiO2/Au(100)

NASA Astrophysics Data System (ADS)

Nakamura, I.; Mantoku, H.; Furukawa, T.; Takahashi, A.; Fujitani, T.

2012-11-01

We performed H2-D2 exchange reactions over TiOx/Au(100) and compared the observed reaction kinetics with those reported for TiOx/Au(111) in order to clarify the influence of the Au and TiO2 structures on dissociation of H2 molecules. Low energy electron diffraction observations showed that the TiO2 produced on Au(100) was disordered, in contrast to the comparatively ordered TiO2 structure formed on Au(111). The activation energies and the turnover frequencies for HD formation over TiO2/Au(100) agreed well with those for TiO2/Au(111), clearly indicating that the hydrogen dissociation sites created over TiO2/Au(100) were the perimeter interface between stoichiometric TiO2 and Au, as was previously concluded for TiO2/Au(111). We concluded that the creation of active sites for hydrogen dissociation was independent of the Au and TiO2 structures consisting perimeter interface, and that local bonds that formed between Au and O atoms of stoichiometric TiO2 were essential for the creation of active sites.

High-efficiency p-n junction oxide photoelectrodes for photoelectrochemical water splitting.

PubMed

Liu, Zhifeng; Yan, Lu

2016-11-16

Development of all oxide p-n junctions makes a significant advancement in photoelectrode catalysis functional materials. In this article, we report the preparation of TiO 2 nanorod (NR)/Cu 2 O photoanodes via a simple hydrothermal method followed by an electrochemical deposition process. This facile synthesis route can simultaneously achieve uniform TiO 2 NR/Cu 2 O composite nanostructures and obtain varied amounts of Cu 2 O by controlling the deposition time. The photocurrent density of TiO 2 NR/Cu 2 O heterojunction photoanodes enhanced the photocatalytic activity with a photocurrent density of 5.25 mA cm -2 at 1.23 V versus RHE compared to pristine TiO 2 NR photoanodes under the same conditions. It is demonstrated that the presence of Cu 2 O has played an important role in expanding the spectral response region and reducing the photogenerated charge recombination rate. More importantly, the results provide new insights into the performance of all oxide p-n junctions as photoanodes for PEC water splitting.

Enhanced performance of dye-sensitized solar cell using Bi2Te3 nanotube/ZnO nanoparticle composite photoanode by the synergistic effect of photovoltaic and thermoelectric conversion

NASA Astrophysics Data System (ADS)

Dou, Yuanyao; Wu, Fang; Fang, Liang; Liu, Gaobin; Mao, Caiying; Wan, Kai; Zhou, Miao

2016-03-01

Ultralong and highly crystalline rhombohedral Bi2Te3 nanotubes were fabricated by a two-step solution phase reaction. A novel photoanode architecture has been fabricated by embedding 0-2.5 wt.% Bi2Te3 nanotubes into ZnO nanoparticles. The photocurrent density-voltage (J-V) characteristics reveal that the dye sensitized solar cells (DSSCs) with Bi2Te3/ZnO composite photoanode exhibit significantly enhanced photovoltaic performance. Notably, the DSSC incorporating 1.5 wt.% Bi2Te3 in the ZnO photoanode demonstrates an energy conversion efficiency (η) of 4.27%, which is 44.3% higher than that of the bare ZnO photoanode. The electrochemical impedance spectroscopy (EIS) analysis shows that the Bi2Te3 nanotubes can provide a direct pathway for electron transportation, prolong the lifetime of electrons, suppress the charge recombination and improve the electron collection efficiency. The thermoelectric effect analysis indicates that with the increase of irradiation time, Bi2Te3/ZnO composite photoanode could convert both heat and photon energies to electrical energy simultaneously and slow down the decline of η. The calculated electron density (ns) further proves that the increment of short-circuit current density (Jsc) is attributed to Seebeck effect in the composite photoanode. These results suggest that compositing 1D thermoelectric nano-materials in photoanode is a promising route to improve the performance of DSSCs.

Magnetic and optical effects in TiO2 based dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Kannan U., M.; Jammalamadaka, S. Narayana

2018-04-01

We report on the magnetic effects on the solar cell efficiency of TiO2 based dye sensitized solar cells (DSSC). The strong spin orbit coupling of rare earth Ho3+ ions introduced by the addition of Ho2O3 into the photoanode resulted in a 28% enhancement in the power conversion efficiency of DSSC. Such an enhancement in the efficiency may be attributed to the improved lifetime of photo generated excitons as a result of the accelerated intersystem crossing phenomenon. This observation is supported by our photoluminescence (PL) measurements where we could observe a decrease in the photo emission intensity with the addition of Ho2O3. In addition, we have used a low magnetic field of 100 Oe to further enhance the overall efficiency to 5.6%, which in turn proves that the Lorentz force plays a significant role in magnetic field controlled charge transport in DSSC. Finally, we have carried out a transfer matrix model based theoretical simulation for studying the optical properties of the multilayer device stack.

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance.

PubMed

Ding, Hao; Lv, Jindian; Wu, Huaping; Chai, Guozhong; Liu, Aiping

2018-01-01

A 'sandwich'-structured TiO 2 NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO 2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy 'antennas' to trap the local-field light near the TiO 2 NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO 2 NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO 2 NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices.

Enhanced light trapping and high charge transmission capacities of novel structures for efficient photoelectrochemical water splitting.

PubMed

Mu, Jianglong; Miao, Hui; Liu, Enzhou; Feng, Juan; Teng, Feng; Zhang, Dekai; Kou, Yumeng; Jin, Yanping; Fan, Jun; Hu, Xiaoyun

2018-06-13

Excellent PEC efficiency, good reusability and the super stability of trap-like SnS2/TiO2 nanotube arrays (NTs)-based photoanodes are reported. Specifically, the SnS2/TiO2-180 °C (ST-180) photoanode exhibited the highest photocurrent density (1.05 mA cm-2) and an optimal η (0.73%) at 0.5 V (vs. SCE) under simulated light irradiation (AM 1.5G), which are 4.6 and 3.8 times higher than those of pure TiO2 NTs (0.23 mA cm-2 and 0.19%). The IPCE values of ST-180 can reach 21.5% (365 nm) and 13.8% (420 nm), which are much higher than those of pure TiO2 NTs (10.6% at 365 nm and 0.8% at 420 nm). The APCE values of the pure TiO2 NTs photoelectrode are 12.8% (365 nm) and 1.1% (420 nm), while the ST-180 values are 22.3% and 14.2%, respectively. Furthermore, the generation rates of H2 and O2 for the ST-180 photoanode are 47.2 and 23.1 μmol cm-2 h-1 at 0.5 V under AM 1.5G, corresponding to faradaic efficiencies of around 80.1% and 78.3%, respectively. In short, the high-efficiency PEC water splitting performance of this SnS2/TiO2 photoanode results from the enhanced light harvesting ability of the trap-like SnS2 structure, accelerated carrier transportation properties of TiO2 NTs, and effective carrier separation of the type-II heterojunction structure. This work may offer a combinatorial strategy for the preparation of heterojunction structures with high PEC performance and can be a model structure for similar photoanode materials.

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

PubMed

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

High Throughput Discovery of Solar Fuels Photoanodes in the CuO-V 2 O 5 System

DOE PAGES

Zhou, Lan; Yan, Qimin; Shinde, Aniketa; ...

2015-08-26

Solar photoelectrochemical generation of fuel is a promising energy technology yet the lack of an efficient, robust photoanode remains a primary materials challenge in the development and deployment of solar fuels generators. Metal oxides comprise the most promising class of photoanode materials, but no known material meets the demanding requirements of low band gap energy, photoelectrocatalysis of the oxygen evolution reaction, and stability under highly oxidizing conditions. Here, we report the identification of new photoelectroactive materials through a strategic combination of combinatorial materials synthesis, high-throughput photoelectrochemistry, optical spectroscopy, and detailed electronic structure calculations. We identify 4 photoelectrocatalyst phases - α-Cumore » 2V 2O 7, β-Cu 2V 2O 7, γ-Cu 3V 2O 8, and Cu 11V 6O 26 - with band gap energy at or below 2 eV. The photoelectrochemical properties and 30-minute stability of these copper vanadate phases are demonstrated in 3 different aqueous electrolytes (pH 7, pH 9, and pH 13), with select combinations of phase and electrolyte exhibiting unprecedented photoelectrocatalytic stability for metal oxides with sub-2 eV band gap. Through integration of experimental and theoretical techniques, we determine new structure-property relationships and establish CuO-V 2O 5 as the most prominent composition system for OER photoelectrocatalysts, providing crucial information for materials genomes initiatives and paving the way for continued development of solar fuels photoanodes.« less

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance

PubMed Central

Lv, Jindian; Wu, Huaping; Chai, Guozhong; Liu, Aiping

2018-01-01

A ‘sandwich'-structured TiO2NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy ‘antennas' to trap the local-field light near the TiO2NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO2NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO2NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices. PMID:29410838

Dye- and quantum dot-sensitized solar cells based on nanostructured wide-bandgap semiconductors via an integrated experimental and modeling study

NASA Astrophysics Data System (ADS)

Xin, Xukai

Dye-sensitized solar cells (DSSCs) and quantum dot-sensitized solar cells (QDSSCs) are two promising alternative, cost-effective concepts for solar-to-electric energy conversion that have been offered to challenge conventional Si solar cells over the past decade. The configuration of a DSSC or a QDSSC consists of sintered TiO2 nanoparticle films, ruthenium-based dyes or quantum dots (QDs) (i.e., sensitizers), and electrolytes. Upon the absorption of photons, the dyes or QDs generate excitons (i.e., electron-hole pairs). Subsequently, the electrons inject into the TiO2 photoanode to generate photocurrent; scavenged by a redox couple, holes transport to the cathode. The overall power conversion efficiency (PCE) of a DSSC or QDSSC is dictated by the light harvest efficiency, quantum yield for charge injection, and charge collection efficiency at the electrodes. The goal of our research is to understand the fundamental physics and performance of DSSCs and QDSSCs with improved PCE at the low cost based on rational engineering of TiO2 nanostructures, sensitizers, and electrodes through an integrated experimental and modeling study. In this presentation, I will discuss three aspects that I have accomplished over the last several years. (1) Effects of surface treatment and structural modification of photoanode on the performance of DSSCs. First, our research indicates that the surface treatment with both TiCl4 and oxygen plasma yields the most efficient dye-sensitized TiO2-nanoparticle solar cells. A maximum PCE is achieved with a 21 microm thick TiO2 film; the PCE further increases to 8.35% after TiCl4 and O 2 plasma treatments, compared to the untreated TiO2 ( PCE = 3.86%). Second, we used a layer of TiO2 nanoparticle film coated on the FTO glass, and a bilayer of TiO2nanoparticle/freestanding TiO2 nanotube film deposited on the FTO glass as photoanodes. The J˜V parameter analysis acquired by equivalent circuit model simulation reveals that nanotubular structures are

Effect of photoanode thickness on electrochemical performance of dye sensitized solar cell

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

Khatani, Mehboob, E-mail: mkhatani@hotmail.com; Hamid, Nor Hisham, E-mail: hishmid@petronas.com.my; Sahmer, Ahmed Zahrin, E-mail: azclement@yahoo.com

2015-07-22

The thickness of photoanode is crucial as it adsorbed a large amount of dye molecules that provide electrons for generation of electricity in dye sensitized solar cell (DSC). Thus, in order to realize the practical application of DSC, study on various thickness of photoanode need to be carried out to analyze its effect on the electrochemical behavior of dye sensitized solar cell. To enhance the conversion efficiency, an additional layer of TiO{sub 2} using TiCl{sub 4} treatment was deposited prior to the deposition of the photoanode (active area of 1cm{sup 2}) with the thickness of 6, 12, 18, 24, andmore » 30 µm on fluorine doped tin oxide (FTO) glass substrate. The resulting photoanode after the soak in N719 dye for more than 12hrs were used to be assembled in a test cell in combination with liquid electrolyte and counter electrode. The fabricated cells were characterized by solar simulator, ultraviolet-visible spectroscopy (UV-VIS), and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) was used to approximate the thickness of photoanode. An optimum power conversion efficiency of 4.54% was obtained for the cell fabricated with 18 µm photoanode thickness. This is attributed to the reduced resistance related to electron transport in the TiO{sub 2}/dye/electrolyte interface as proven by the EIS result. This led to the reduction of internal resistance, the increase in the electron life time and the improvement in the conversion efficiency.« less

Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

NASA Astrophysics Data System (ADS)

Lin, Wensheng; Zheng, Jiaxian; Yan, Lianghong; Zhang, Xinxiang

2018-03-01

Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.

NiO nanoparticles anchored on P-doped α-Fe2O3 nanoarrays: an efficient hole extraction p-n heterojunction photoanode for water oxidation.

PubMed

Li, Feng; Li, Jing; Zhang, Jie; Gao, Lili; Long, Xuefeng; Hu, Yiping; Li, Shuwen; Jin, Jun; Ma, Jiantai

2018-05-16

The photoelectrochemical (PEC) water splitting efficiency of hematite-based photoanode is still far from the theoretical value due to its poor surface reaction kinetics and high density of surface trapping states. To solve these drawbacks, a photoanode consisting of NiO nanoparticles anchored on a gradient P-doped α-Fe2O3 nanorod (NR) array (NiO/P-α-Fe2O3) was fabricated to achieve optimal light absorption and charge separation, and rapid surface reaction kinetic. Specifically, the photoanode with the NR arrays structure allowed high mass transport rate to be achieved while the P-doping effectively decreased surface trapping sites and improved the electrical conductivity of α-Fe2O3. Furthermore, the p-n junction formed between the NiO and P-α-Fe2O3 can further improve the PEC performance due to the efficient hole extraction property and water oxidization catalytic activity of NiO. Consequently, the NiO/P-α-Fe2O3 NR photoanode produced a high photocurrent density of 2.08 mA cm-2 at 1.23V vs. RHE and a 110 mV cathodic shift of the onset potential. This rational design of structure offers a new perspective in exploring high performance PEC photoanodes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoniobia modification of CdS photoanode for an efficient and stable photoelectrochemical cell.

PubMed

Pareek, Alka; Paik, Pradip; Borse, Pramod H

2014-12-30

Herein we report the surface modification of a CdS film by niobia nanoparticles via thioglycerol as an organic linker and thus fabricate an efficient and a stable photoanode for a photoelectrochemical (PEC) cell. We have synthesized three differenly sized (∼3, ∼6 ,and ∼9 nm) niobia nanoparticles by a hydrothermal synthesis approach and have further investigated the particle-size-dependent PEC performance of the nanoparticle-modified CdS photoanode. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirm the formation of Nb2O5 nanoparticles that are prepared via decomposition of the niobium peroxo complex during the hydrothermal reaction and reveal the presence of surface OH(-) groups over niobia nanoparticles that impart a high catalytic property to a material. The nano-Nb2O5-modified photoanode displayed a 23-fold higher power conversion efficiency compared to that of CdS. This modified structure increases the open circuit voltage (OCV) from 0.65 to 0.77 V, which is attributed to the nano-Nb2O5-induced surface passivation effect over bare CdS. Linking of nanoparticles on the CdS surface improves the photocorrosion stability of the CdS photoanode for even longer than 4 h in contrast to the tens of minutes for the base CdS surface. The uniform coverage of the CdS photoanode surface by niobia nanoparticles is thus found to be the controlling parameter for achieving a higher PEC performance and stability of the photoanode. This finding directed us to design an improved CdS photoanode for efficient and prolonged PEC hydrogen generation from a PEC cell.

Nanotubular surface modification of metallic implants via electrochemical anodization technique.

PubMed

Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

2014-01-01

Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility.

Nanotubular surface modification of metallic implants via electrochemical anodization technique

PubMed Central

Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

2014-01-01

Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility. PMID:25258532

Zinc Tantalum Oxynitride (ZnTaO2N) Photoanode Modified with Cobalt Phosphate Layers for the Photoelectrochemical Oxidation of Alkali Water

PubMed Central

T. Weller, Mark

2018-01-01

Photoanodes fabricated by the electrophoretic deposition of a thermally prepared zinc tantalum oxynitride (ZnTaO2N) catalyst onto indium tin oxide (ITO) substrates show photoactivation for the oxygen evolution reaction (OER) in alkaline solutions. The photoactivity of the OER is further boosted by the photodeposition of cobalt phosphate (CoPi) layers onto the surface of the ZnTaO2N photoanodes. Structural, morphological, and photoelectrochemical (PEC) properties of the modified ZnTaO2N photoanodes are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible (UV−Vis) diffuse reflectance spectroscopy, and electrochemical techniques. The presence of the CoPi layer significantly improved the PEC performance of water oxidation in an alkaline sulphate solution. The photocurrent-voltage behavior of the CoPi-modified ZnTaO2N anodes was improved, with the influence being more prominent at lower oxidation potentials. A stable photocurrent density of about 2.3 mA·cm−2 at 1.23 V vs. RHE was attained upon visible light illumination. Relative to the ZnTaO2N photoanodes, an almost three-fold photocurrent increase was achieved at the CoPi/ZnTaO2N photoelectrode. Perovskite-based oxynitrides are modified using an oxygen-evolution co-catalyst of CoPi, and provide a new dimension for enhancing the photoactivity of oxygen evolution in solar-assisted water-splitting reactions. PMID:29346306

Preparation of brookite TiO2 nanoparticles with small sizes and the improved photovoltaic performance of brookite-based dye-sensitized solar cells.

PubMed

Xu, Jinlei; Wu, Shufang; Jin, Jingpeng; Peng, Tianyou

2016-11-10

Brookite TiO 2 nanoparticles with small sizes (hereafter denoted as BTP particles) were synthesized through the hydrothermal treatment of TiCl 4 solution with Pb(NO 3 ) 2 as an additive. The obtained BTP particles have a large specific surface area (∼122.2 m 2 g -1 ) and relatively uniform particle sizes (∼10 nm) with the coexistence of a small quantity of nanorods with a length of ∼100 nm. When used as a photoanode material for dye-sensitized solar cells (DSSCs), the BTP particles show a much higher dye-loading content than the brookite TiO 2 quasi nanocubes (denoted as BTN particles) with a mean size of ∼50 nm and a specific surface area of ∼34.2 m 2 g -1 that were prepared through a similar hydrothermal process but without the addition of Pb(NO 3 ) 2 . The fabricated BTP film-based solar cell with an optimized film thickness gives a conversion efficiency up to 6.36% with a 74% improvement when compared to the BTN film-based one (3.65%) under AM 1.5G one sun irradiation, while the corresponding bilayer brookite-based solar cell by using brookite TiO 2 submicrometer particles as an overlayer of the BTP film displays a significantly enhanced efficiency of 7.64%. Both of them exceed the current record (5.97%) for the conversion efficiency of pure brookite-based DSSCs reported in the literature. The present results not only demonstrate a really simple synthesis of brookite TiO 2 nanoparticles with both high phase purity and a large surface area, but also offer an efficient approach to improve the photovoltaic performance of brookite-based solar cells by offsetting brookite's inherent shortages such as lower dye-loading and poor conductivity as compared to anatase.

Nanoparticulate hollow TiO2 fibers as light scatterers in dye-sensitized solar cells: layer-by-layer self-assembly parameters and mechanism.

PubMed

Rahman, Masoud; Tajabadi, Fariba; Shooshtari, Leyla; Taghavinia, Nima

2011-04-04

Hollow structures show both light scattering and light trapping, which makes them promising for dye-sensitized solar cell (DSSC) applications. In this work, nanoparticulate hollow TiO(2) fibers are prepared by layer-by-layer (LbL) self-assembly deposition of TiO(2) nanoparticles on natural cellulose fibers as template, followed by thermal removal of the template. The effect of LbL parameters such as the type and molecular weight of polyelectrolyte, number of dip cycles, and the TiO(2) dispersion (amorphous or crystalline sol) are investigated. LbL deposition with weak polyelectrolytes (polyethylenimine, PEI) gives greater nanoparticle deposition yield compared to strong polyelectrolytes (poly(diallyldimethylammonium chloride), PDDA). Decreasing the molecular weight of the polyelectrolyte results in more deposition of nanoparticles in each dip cycle with narrower pore size distribution. Fibers prepared by the deposition of crystalline TiO(2) nanoparticles show higher surface area and higher pore volume than amorphous nanoparticles. Scattering coefficients and backscattering properties of fibers are investigated and compared with those of commercial P25 nanoparticles. Composite P25-fiber films are electrophoretically deposited and employed as the photoanode in DSSC. Photoelectrochemical measurements showed an increase of around 50% in conversion efficiency. By employing the intensity-modulated photovoltage and photocurrent spectroscopy methods, it is shown that the performance improvement due to addition of fibers is mostly due to the increase in light-harvesting efficiency. The high surface area due to the nanoparticulate structure and strong light harvesting due to the hollow structure make these fibers promising scatterers in DSSCs. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photovoltaic studies of Dye Sensitized Solar cells Fabricated from Microwave Exposed Photo anodes

NASA Astrophysics Data System (ADS)

Ramachandran, Anju; Sreekala, C. O.; Sreelatha, K. S.; Jinchu, I.

2018-02-01

The configuration of Dye Sensitized solar cells (DSSC), consists of sintered nanoparticle titanium dioxide film, dyes, electrolyte and counter electrodes. Upon the absorption of photons by the dye molecules, excitons are generated, subsequently electrons are injected into the TiO2 photoanode. Afterward the electrons injected into the TiO2 photoanode, to produce photocurrent, scavenged by redox couple, and the hole transport to the photo cathode. The power conversion efficiency of the device depends on the amount of dye adsorbed by the photoanode. This paper explores in enhancing the efficiency of the device by controlled microwave exposure. With same exposure time, the photoanode is exposed at three different frequencies. SEM analysis is carried out to find the porosity of the photoanode on exposure. Current density is found to have an effect on microwave exposure.

Synergistic effects between TiO2 and carbon nanotubes (CNTs) in a TiO2/CNTs system under visible light irradiation.

PubMed

Wu, Chung-Hsin; Kuo, Chao-Yin; Chen, Shih-Ting

2013-01-01

This study synthesized a TiO2/carbon nanotubes (CNTs) composite via the sol-gel method. The surface characteristics of the TiO2/CNTs composite were determined by X-ray diffraction, transmission electron microscopy, specific surface area analyser, ultraviolent (UV)-vis spectroscopy, X-ray photoelectron spectroscopy and Raman spectrometer. The photocatalytic activity ofthe TiO2/CNTs composite was evaluated by decolourizing C.I. Reactive Red 2 (RR2) under visible light irradiation. Furthermore, the effects of calcination temperature, pH, RR2 concentration, and the TiO2/CNTs composite dosage on RR2 decolourization were determined simultaneously. The optimal calcination temperature to generate TiO2 and the TiO2/CNTs composite was 673 K, as the percentage of anatase crystallization at this temperature was highest. The specific surface area of the TiO2/CNTs composite and TiO2 were 45 and 42 m2/g, respectively. The band gap of TiO2 and the TiO2/CNTs composite was 2.97 and 2.71 eV by UV-vis measurements, respectively. Experimental data indicate that the Ti-O-C bond formed in the TiO2/CNTs composite. The RR2 decolourization rates can be approximated by pseudo-first-order kinetics; moreover, only the TiO2/CNTs composite had photocatalytic activity under visible light irradiation. At pH 7, the RR2 decolourization rate constant of 0.5, 1 and 2 g/L TiO2/CNTs addition was 0.005, 0.0015, and 0.0047 min(-1), respectively. Decolourization rate increased as pH and the RR2 concentration decreased. The CNTs functioned as electron acceptors, promoting separation of photoinduced electron-hole pairs to retard their recombination; thus, photocatalytic activity of the TiO2/CNTs composite exceeded that of TiO2.

Interface Engineering through Atomic Layer Deposition towards Highly Improved Performance of Dye-Sensitized Solar Cells

PubMed Central

Lu, Hao; Tian, Wei; Guo, Jun; Li, Liang

2015-01-01

A composite photoanode comprising ultralong ZnO nanobelts and TiO2 nanoparticles was prepared and its performance in dye-sensitized solar cells (DSSCs) was optimized and compared to the photoanode consisting of conventional TiO2 nanoparticles. The ultralong ZnO nanobelts were synthesized in high yield by a facile solution approach at 90 oC followed by annealing at 500 oC. The effect of the ratio of ZnO nanobelts to TiO2 nanoparticles on the light scattering, specific surface area, and interface recombination were investigated. An optimum amount of ZnO nanobelts enhanced the photon-conversion efficiency by 61.4% compared to that of the conventional TiO2 nanoparticles. To further reduce the recombination rate and increase the carrier lifetime, Atomic Layer Deposition (ALD) technique was utilized to coat a continuous TiO2 film surrounding the ZnO nanobelts and TiO2 nanoparticles, functioning as a barrier-free access of all electrons to conductive electrodes. This ALD treatment improved the interface contact within the whole photoanode system, finally leading to significant enhancement (137%) in the conversion efficiency of DSSCs. PMID:26238737

Phase transformation synthesis of TiO2/CdS heterojunction film with high visible-light photoelectrochemical activity

NASA Astrophysics Data System (ADS)

Liu, Canjun; Yang, Yahui; Li, Jie; Chen, Shu

2018-06-01

CdS/TiO2 heterojunction film used as a photoanode has attracted much attention in the past few years due to its good visible light photocatalytic activity. However, CdS/TiO2 films prepared by conventional methods (successive ionic layer adsorption and reaction, chemical bath deposition and electrodeposition) show numerous grain boundaries in the CdS layer and an imperfect contact at the heterojunction interface. In this study, we designed a phase transformation method to fabricate CdS/TiO2 nanorod heterojunction films. The characterization results showed that the CdS layer with fewer grain boundaries was conformally coated on the TiO2 nanorod surface and the formation mechanism has been explained in this manuscript. Moreover, the prepared CdS/TiO2 films show a high photocatalytic activity and the photocurrent density is as high as 9.65 mA cm‑2 at 0.80 V versus RHE. It may be attributed to fewer grain boundaries and a compact heterojunction contact, which can effectively improve charge separation and transportation.

Effect of TiO2 on the Gas Sensing Features of TiO2/PANi Nanocomposites

PubMed Central

Huyen, Duong Ngoc; Tung, Nguyen Trong; Thien, Nguyen Duc; Thanh, Le Hai

2011-01-01

A nanocomposite of titanium dioxide (TiO2) and polyaniline (PANi) was synthesized by in-situ chemical polymerization using aniline (ANi) monomer and TiCl4 as precursors. SEM pictures show that the nanocomposite was created in the form of long PANi chains decorated with TiO2 nanoparticles. FTIR, Raman and UV-Vis spectra reveal that the PANi component undergoes an electronic structure modification as a result of the TiO2 and PANi interaction. The electrical resistor of the nanocomposite is highly sensitive to oxygen and NH3 gas, accounting for the physical adsorption of these gases. A nanocomposite with around 55% TiO2 shows an oxygen sensitivity of 600–700%, 20–25 times higher than that of neat PANi. The n-p contacts between TiO2 nanoparticles and PANi matrix give rise to variety of shallow donors and acceptor levels in the PANi band gap which enhance the physical adsorption of gas molecules. PMID:22319389

Preparation of Carbon Nanotube/TiO2 Mesoporous Hybrid Photoanode with Iron Pyrite (FeS2) Thin Films Counter Electrodes for Dye-Sensitized Solar Cell

PubMed Central

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Ozer, Oguz Can; Asgin, Mansur; Cebeci, Hulya; Urk, Deniz; Mucur, Selin Pravadili

2016-01-01

Multi-walled carbon nanotube (MWCNT)/TiO2 mesoporous networks can be employed as a new alternative photoanode in dye-sensitized solar cells (DSSCs). By using the MWCNT/TiO2 mesoporous as photoanodes in DSSC, we demonstrate that the MWCNT/TiO2 mesoporous photoanode is promising alternative to standard FTO/TiO2 mesoporous based DSSC due to larger specific surface area and high electrochemical activity. We also show that iron pyrite (FeS2) thin films can be used as an efficient counter electrode (CE), an alternative to the conventional high cost Pt based CE. We are able to synthesis FeS2 nanostructures utilizing a very cheap and easy hydrothermal growth route. MWCNT/TiO2 mesoporous based DSSCs with FeS2 CE achieved a high solar conversion efficiency of 7.27% under 100 mW cm−2 (AM 1.5G 1-Sun) simulated solar irradiance which is considerably (slightly) higher than that of A-CNT/TiO2 mesoporous based DSSCs with Pt CE. Outstanding performance of the FeS2 CE makes it a very promising choice among the various CE materials used in the conventional DSSC and it is expected to be used more often to achieve higher photon-to-electron conversion efficiencies. PMID:27243374

Enhanced conversion efficiency of dye-sensitized solar cells using a CNT-incorporated TiO{sub 2} slurry-based photoanode

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

Cai, Jiaoping; Chen, Zexiang, E-mail: zxchen@uestc.edu.cn; Li, Jun

2015-02-15

A new titanium dioxide (TiO{sub 2}) slurry formulation is herein reported for the fabrication of TiO{sub 2} photoanode for use in dye-sensitized solar cells (DSSCs). The prepared TiO{sub 2} photoanode featured a highly uniform mesoporous structure with well-dispersed TiO{sub 2} nanoparticles. The energy conversion efficiency of the resulting TiO{sub 2} slurry-based DSSC was ∼63% higher than that achieved by a DSSC prepared using a commercial TiO{sub 2} slurry. Subsequently, the incorporation of acid-treated multi-walled carbon nanotubes (CNTs) into the TiO{sub 2} slurry was examined. More specifically, the effect of varying the concentration of the CNTs in this slurry on themore » performance of the resulting DSSCs was studied. The chemical state of the CNTs-incorporated TiO{sub 2} photoanode was investigated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A high energy conversion efficiency of 6.23% was obtained at an optimum CNT concentration of ∼0.06 wt.%. The obtained efficiency corresponds to a 63% enhancement when compared with that obtained from a DSSC based on a commercial TiO{sub 2} slurry. The higher efficiency was attributed to the improvement in the collection and transport of excited electrons in the presence of the CNTs.« less

Visible-light responsive photocatalytic fuel cell based on WO(3)/W photoanode and Cu(2)O/Cu photocathode for simultaneous wastewater treatment and electricity generation.

PubMed

Chen, Quanpeng; Li, Jinhua; Li, Xuejin; Huang, Ke; Zhou, Baoxue; Cai, Weimin; Shangguan, Wenfeng

2012-10-16

A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO(3)/W photoanode and Cu(2)O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO(3)/W photoanode is higher than that of Cu(2)O/Cu photocathode. An interior bias can be produced based on which the electrons of WO(3)/W photoanode can transfer from the external circuit to combine with the holes of Cu(2)O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO(3)/W photoanode and electrons of Cu(2)O/Cu photocathode. Organic compounds can be decomposed by the holes of WO(3)/W photoanode due to its high oxidation power (+3.1-3.2 V(NHE)). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.

Nanotubular Toughening Inclusions

NASA Technical Reports Server (NTRS)

Park, Cheol (Inventor); Working, Dennis C. (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

2017-01-01

Conventional toughening agents are typically rubbery materials or small molecular weight molecules, which mostly sacrifice the intrinsic properties of a matrix such as modulus, strength, and thermal stability as side effects. On the other hand, high modulus inclusions tend to reinforce elastic modulus very efficiently, but not the strength very well. For example, mechanical reinforcement with inorganic inclusions often degrades the composite toughness, encountering a frequent catastrophic brittle failure triggered by minute chips and cracks. Thus, toughening generally conflicts with mechanical reinforcement. Carbon nanotubes have been used as efficient reinforcing agents in various applications due to their combination of extraordinary mechanical, electrical, and thermal properties. Moreover, nanotubes can elongate more than 20% without yielding or breaking, and absorb significant amounts of energy during deformation, which enables them to also be an efficient toughening agent, as well as excellent reinforcing inclusion. Accordingly, an improved toughening method is provided by incorporating nanotubular inclusions into a host matrix, such as thermoset and thermoplastic polymers or ceramics without detrimental effects on the intrinsic physical properties of the matrix.

Nanotubular Toughening Inclusions

NASA Technical Reports Server (NTRS)

Park, Cheol (Inventor); Working, Dennis C. (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

2015-01-01

Conventional toughening agents are typically rubbery materials or small molecular weight molecules, which mostly sacrifice the intrinsic properties of a matrix such as modulus, strength, and thermal stability as side effects. On the other hand, high modulus inclusions tend to reinforce elastic modulus very efficiently, but not the strength very well. For example, mechanical reinforcement with inorganic inclusions often degrades the composite toughness, encountering a frequent catastrophic brittle failure triggered by minute chips and cracks. Thus, toughening generally conflicts with mechanical reinforcement. Carbon nanotubes have been used as efficient reinforcing agents in various applications due to their combination of extraordinary mechanical, electrical, and thermal properties. Moreover, nanotubes can elongate more than 20% without yielding or breaking, and absorb significant amounts of energy during deformation, which enables them to also be an efficient toughening agent, as well as excellent reinforcing inclusion. Accordingly, an improved toughening method is provided by incorporating nanotubular inclusions into a host matrix, such as thermoset and thermoplastic polymers or ceramics without detrimental effects on the matrix's intrinsic physical properties.

Photocatalytic activity of TiO2/Nb2O5/PANI and TiO2/Nb2O5/RGO as new nanocomposites for degradation of organic pollutants.

PubMed

Zarrin, Saviz; Heshmatpour, Felora

2018-06-05

In this study, highly active titanium dioxide modified by niobium oxide (Nb 2 O 5 ), polymer (PANI) and reduced graphene oxide (RGO) were successfully prepared. The morphology, structure, surface area and light absorption properties of the present nanocomposites for removal of methylene blue (MB) and methyl orange (MO) were investigated and compared with those of TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. The characterization techniques such as XRD, FT-IR, UV-vis, SEM, EDX, BET and TEM were employed in order to identify the nanocomposites. Also, photocatalytic properties of TiO 2 /Nb 2 O 5 /PANI and TiO 2 /Nb 2 O 5 /RGO nanocomposites under visible light irradiation were studied. In this way, the obtained results were compared to each other and also compared to TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. In this context, the chemical oxygen demand (COD) removal follows the photodegradation in observed performance. The results indicate that reduced TiO 2 /Nb 2 O 5 nanocomposite is effectively modified by graphene oxide to give TiO 2 /Nb 2 O 5 /RGO composite. The TiO 2 /Nb 2 O 5 /RGO exhibits significantly higher photocatalytic activity in degradation of organic dyes under visible light rather than that of TiO 2 /Nb 2 O 5 /PANI, TiO 2 /Nb 2 O 5 and pure TiO 2 . Copyright © 2018 Elsevier B.V. All rights reserved.

A Synergistic Effect of Surfactant and ZrO2 Underlayer on Photocurrent Enhancement and Cathodic Shift of Nanoporous Fe2O3 Photoanode

PubMed Central

Shinde, Pravin S.; Lee, Su Yong; Choi, Sun Hee; Lee, Hyun Hwi; Ryu, Jungho; Jang, Jum Suk

2016-01-01

Augmenting the donor density and nanostructure engineering are the crucial points to improve solar water oxidation performance of hematite (α-Fe2O3). This work addresses the sluggish water oxidation reaction associated with hematite photoanode by tweaking its internal porosity. The porous hematite photoanodes are fabricated by a novel synthetic strategy via pulse reverse electrodeposition (PRED) method that involves incorporation of a cationic CTAB surfactant in a sulfate electrolyte and spin-coated ZrO2 underlayer (UL) on FTO. CTAB is found to be beneficial in promoting the film growth rate during PRED. Incorporation of Zr4+ ions from ZrO2 UL and Sn4+ ions from FTO into the Fe2O3 lattice via solid-state diffusion reaction during pertinent annihilation of surfactant molecules at 800 °C produced internally porous hematite films with improved carrier concentration. The porous hematite demonstrated a sustained photocurrent enhancement and a significant cathodic shift of 130 mV relative to the planar hematite under standard illumination conditions (AM 1.5G) in 1 M NaOH electrolyte. The absorption, electrochemical impedance spectroscopy and Mott-Schottky analyses revealed that the ZrO2 UL and CTAB not only increased the carrier density and light harvesting but also accelerated the surface oxidation reaction kinetics, synergistically boosting the performance of internally porous hematite photoanodes. PMID:27577967

A Synergistic Effect of Surfactant and ZrO2 Underlayer on Photocurrent Enhancement and Cathodic Shift of Nanoporous Fe2O3 Photoanode.

PubMed

Shinde, Pravin S; Lee, Su Yong; Choi, Sun Hee; Lee, Hyun Hwi; Ryu, Jungho; Jang, Jum Suk

2016-08-31

Augmenting the donor density and nanostructure engineering are the crucial points to improve solar water oxidation performance of hematite (α-Fe2O3). This work addresses the sluggish water oxidation reaction associated with hematite photoanode by tweaking its internal porosity. The porous hematite photoanodes are fabricated by a novel synthetic strategy via pulse reverse electrodeposition (PRED) method that involves incorporation of a cationic CTAB surfactant in a sulfate electrolyte and spin-coated ZrO2 underlayer (UL) on FTO. CTAB is found to be beneficial in promoting the film growth rate during PRED. Incorporation of Zr(4+) ions from ZrO2 UL and Sn(4+) ions from FTO into the Fe2O3 lattice via solid-state diffusion reaction during pertinent annihilation of surfactant molecules at 800 °C produced internally porous hematite films with improved carrier concentration. The porous hematite demonstrated a sustained photocurrent enhancement and a significant cathodic shift of 130 mV relative to the planar hematite under standard illumination conditions (AM 1.5G) in 1 M NaOH electrolyte. The absorption, electrochemical impedance spectroscopy and Mott-Schottky analyses revealed that the ZrO2 UL and CTAB not only increased the carrier density and light harvesting but also accelerated the surface oxidation reaction kinetics, synergistically boosting the performance of internally porous hematite photoanodes.

A Synergistic Effect of Surfactant and ZrO2 Underlayer on Photocurrent Enhancement and Cathodic Shift of Nanoporous Fe2O3 Photoanode

NASA Astrophysics Data System (ADS)

Shinde, Pravin S.; Lee, Su Yong; Choi, Sun Hee; Lee, Hyun Hwi; Ryu, Jungho; Jang, Jum Suk

2016-08-01

Augmenting the donor density and nanostructure engineering are the crucial points to improve solar water oxidation performance of hematite (α-Fe2O3). This work addresses the sluggish water oxidation reaction associated with hematite photoanode by tweaking its internal porosity. The porous hematite photoanodes are fabricated by a novel synthetic strategy via pulse reverse electrodeposition (PRED) method that involves incorporation of a cationic CTAB surfactant in a sulfate electrolyte and spin-coated ZrO2 underlayer (UL) on FTO. CTAB is found to be beneficial in promoting the film growth rate during PRED. Incorporation of Zr4+ ions from ZrO2 UL and Sn4+ ions from FTO into the Fe2O3 lattice via solid-state diffusion reaction during pertinent annihilation of surfactant molecules at 800 °C produced internally porous hematite films with improved carrier concentration. The porous hematite demonstrated a sustained photocurrent enhancement and a significant cathodic shift of 130 mV relative to the planar hematite under standard illumination conditions (AM 1.5G) in 1 M NaOH electrolyte. The absorption, electrochemical impedance spectroscopy and Mott-Schottky analyses revealed that the ZrO2 UL and CTAB not only increased the carrier density and light harvesting but also accelerated the surface oxidation reaction kinetics, synergistically boosting the performance of internally porous hematite photoanodes.

Study of concentration-dependent cobalt ion doping of TiO2 and TiO(2-x)Nx at the nanoscale.

PubMed

Gole, James L; Prokes, Sharka M; Glembocki, O J; Wang, Junwei; Qiu, Xiaofeng; Burda, Clemens

2010-07-01

Experiments with a porous sol-gel generated TiO(2) nanocolloid and its corresponding oxynitride TiO(2-x)N(x) are carried out to evaluate those transformations which accompany additional doping with transition metals. In this study, doping with cobalt (Co(ii)) ions is evaluated using a combination of core level and VB-photoelectron and optical spectroscopy, complementing data obtained from Raman spectroscopy. Raman spectroscopy suggests that cobalt doping of porous sol-gel generated anatase TiO(2) and nitridated TiO(2-x)N(x) introduces a spinel-like structure into the TiO(2) and TiO(2-x)N(x) lattices. TEM and XPS data complemented by valence band-photoelectron spectra demonstrate that metallic cobalt clusters are not formed even at high doping levels. As evidenced by Raman spectroscopy, the creation of a spinel-like structure is commensurate with the room temperature conversion of the oxide and its oxynitride from the anatase to the rutile form. The onset of this kinetically driven process correlates with the formation of spinel sites within the TiO(2) and TiO(2-x)N(x) particles. Despite their visible light absorption, the photocatalytic activity of these cobalt seeded systems is diminished relative to the oxynitride TiO(2-x)N(x).

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

NASA Astrophysics Data System (ADS)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented

TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: A comparative study of photo catalysis on acid red 88

NASA Astrophysics Data System (ADS)

Balachandran, K.; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P.

2014-07-01

A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6 h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m2/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4 h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

S-TiO2/S-reduced graphene oxide for enhanced photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Elbakkay, Mohamed H.; El Rouby, Waleed M. A.; El-Dek, S. I.; Farghali, Ahmed A.

2018-05-01

Sulfur-doped titanium oxide on the surface of sulfur-doped reduced graphene oxide nanocomposites (S-TiO2/S-RGO) were successfully synthesized for the first time through a simple low cost solvothermal reaction process. The sulfur doping was detected in both TiO2 matrix and carbon framework structure of reduced graphene oxide using X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX). Cross-sectional AFM analysis of S-RGO nanosheets reveals a thickness of 0.51 nm which is much thinner than those previously reported of heteroatom doped-RGO, confirming the single-layer feature. When the as-prepared (S-TiO2/S-RGO) nanocomposites are utilized as photoanodes for photoelectrochemical (PEC) water splitting, they exhibited an enhanced photoelectrochemical performance and long-term stability. The photocurrent density of S-TiO2/S-RGO(0.2) photoanode revealed 3.36 mA/cm2 at 1 V vs Ag/AgCl which is considered 3 times compared to bare synthesized TiO2. This improvement in the photocurrent density was attributed to the increased separation rate of photogenerated electrons and holes and efficient visible light harvesting as a result of the successful combination of the S-TiO2 and the S-RGO in the same nanocomposite photoanode. This promising result presents a new approach for the synthesis of high-efficient future metal-free photoelectrocatalysts.

Zinc-aluminum oxide solid solution nanosheets obtained by pyrolysis of layered double hydroxide as the photoanodes for dye-sensitized solar cells.

PubMed

Xu, Zhiyuan; Shi, Jingjing; Haroone, Muhammad Sohail; Chen, Wenpeng; Zheng, Shufang; Lu, Jun

2018-04-01

Due to the superiority of metal-doped ZnO compared to TiO 2 , the Zn-M (M = Al 3+ , Ga 3+ , Cr 3+ , Ti 4+ , Ce 4+ ) mixed metal oxide solid solutions have been extensively studied for photocatalytic and photovoltaic applications. In this work, a systematic research has proceeded for the preparation of a zinc-aluminum oxide semiconductor as a photoanode for the dye-sensitized solar cells (DSSCs) by a simple pyrolysis route with the Zn-Al layered double hydroxide (LDH) as a precursor. The Zn-Al oxide solid solution has been applied for DSSCs as an electron acceptor, which is used to study the influence of different Al content and sintering temperature on the device efficiency. Finally, the Zn-Al oxide solid solution with calcination temperature 600 °C and Al 27 at.% content exhibits the best performance. The photoelectric efficiency improved 100 times when the Al 3+ content decreased from 44 to 27 at.%. The Zn x Al y O solid solution show a reasonable efficiency as photoanode materials in DSSCs, with the best preliminary performance reported so far, and shows its potential application for the photovoltaic devices. Copyright © 2018 Elsevier Inc. All rights reserved.

Effects of TiO2 and TiC Nanofillers on the Performance of Dye Sensitized Solar Cells Based on the Polymer Gel Electrolyte of a Cobalt Redox System.

PubMed

Venkatesan, Shanmuganathan; Liu, I-Ping; Chen, Li-Tung; Hou, Yi-Chen; Li, Chiao-Wei; Lee, Yuh-Lang

2016-09-21

Polymer gel electrolytes (PGEs) of cobalt redox system are prepared for dye sensitized solar cell (DSSC) applications. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is used as a gelator of an acetonitrile (ACN) liquid electrolyte containing tris(2,2'-bipyridine)cobalt(II/III) redox couple. Titanium dioxide (TiO2) and titanium carbide (TiC) nanoparticles are utilized as nanofillers (NFs) of this PGE, and the effects of the two NFs on the conductivity of the PGEs, charge-transfer resistances at the electrode/PGE interface, and the performance of the gel-state DSSCs are studied and compared. The results show that the presence of TiC NFs significantly increases the conductivity of the PGE and decreases the charge-transfer resistance at the Pt counter-electrode (CE)/PGE interface. Therefore, the gel-state DSSC utilizing TiC NFs can achieve a conversion efficiency (6.29%) comparable to its liquid counterpart (6.30%), and, furthermore, the cell efficiency can retain 94% of its initial value after a 1000 h stability test at 50 °C. On the contrary, introduction of TiO2 NFs in the PGE causes a decrease of cell performances. It shows that the presence of TiO2 NFs increases the charge-transfer resistance at the Pt CE/PGE interface, induces the charge recombination at the photoanode/PGE interface, and, furthermore, causes a dye desorption in a long-term-stability test. These results are different from those reported for the iodide redox system and are ascribed to a specific attractive interaction between TiO2 and cobalt redox ions.

Photocatalysis effect of nanometer TiO2 and TiO2-coated ceramic plate on Hepatitis B virus.

PubMed

Zan, Ling; Fa, Wenjun; Peng, Tianyou; Gong, Zhen-Kui

2007-02-01

The photocatalysis effect of nanometer TiO2 particles and TiO2-coated ceramic plate on Hepatitis B virus surface antigen (HBsAg) was investigated. The ELISA (enzyme-linked immunosorbent assay) standard method was used to assess the efficiency of TiO2 material to destroy the HBsAg. The research has shown that the suspension of TiO2 (0.5g/L) can destroy most of the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.6mW/cm(2) at 365nm wavelength, or under the sunlight irradiation for a few hours. TiO2-coated ceramic plates can also destroy the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.05mW/cm(2) at 365nm wavelength or under the room daylight for a few hours.

TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: a comparative study of photo catalysis on acid red 88.

PubMed

Balachandran, K; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P

2014-07-15

A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m(2)/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88. Copyright © 2014 Elsevier B.V. All rights reserved.

Formation of anodic TiO2 nanotube arrays in NaOH added fluoride-ethylene glycol electrolyte for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Tan, Wai Kian; Kawamura, Go; Matsuda, Atsunori; Lockman, Zainovia

2017-07-01

TiO2 nanotube (TNT) arrays were formed by anodizing titanium foil in fluoride-ethylene glycol (EG) electrolyte added to it either water (H2O) or sodium hydroxide (NaOH) as oxidant. In NaOH added fluoride-EG electrolyte, 10 µm long TNT arrays were formed compared to 5 μm long nanotubes in H2O added fluoride-EG electrolyte. When NaOH was added to EG, the electrolyte pH was 9. As the pH of the electrolyte was rather high, surface etching of the nanotubes was reduced resulting in tubes with longer length. Moreover, the addition of NaOH into fluoride-EG resulted in the crystallization of anatase in the as-made TNT arrays. Annealing obviously improved the crystallinity of the oxide. The TNT arrays were then used as a photoanode in a dye-sensitized solar cell (DSSC). A photoconversion efficiency of 2.4 % was recorded with photocurrent of 6.9 mA/cm2.

Photoelectrochemical studies of InGaN/GaN MQW photoanodes

NASA Astrophysics Data System (ADS)

Butson, Joshua; Reddy Narangari, Parvathala; Krishna Karuturi, Siva; Yew, Rowena; Lysevych, Mykhaylo; Tan, Hark Hoe; Jagadish, Chennupati

2018-01-01

The research interest in photoelectrochemical (PEC) water splitting is ever growing due to its potential to contribute towards clean and portable energy. However, the lack of low energy band gap materials with high photocorrosion resistance is the primary setback inhibiting this technology from commercialisation. The ternary alloy InGaN shows promise to meet the photoelectrode material requirements due to its high chemical stability and band gap tunability. The band gap of InGaN can be modulated from the UV to IR regions by adjusting the In concentration so as to absorb the maximum portion of the solar spectrum. This paper reports on the influence of In concentration on the PEC properties of planar and nanopillar (NP) InGaN/GaN multi-quantum well (MQW) photoanodes, where NPs were fabricated using a top-down approach. Results show that changing the In concentration, while having a minor effect on the PEC performance of planar MQWs, has an enormous impact on the PEC performance of NP MQWs, with large variations in the photocurrent density observed. Planar photoanodes containing MQWs generate marginally lower photocurrents compared to photoanodes without MQWs when illuminated with sunlight. NP MQWs with 30% In generated the highest photocurrent density of 1.6 mA cm-2, 4 times greater than that of its planar counterpart and 1.8 times greater than that of the NP photoanode with no MQWs. The InGaN/GaN MQWs also slightly influenced the onset potential of both the planar and NP photoanodes. Micro-photoluminescence, diffuse reflectance spectroscopy and IPCE measurements are used to explain these results.

Superior photoelectrochemical properties of ZnO nanorods/poly(3-hexylthiophene) hybrid photoanodes

NASA Astrophysics Data System (ADS)

Majumder, T.; Hmar, J. J. L.; Dhar, S.; Mondal, S. P.

2017-06-01

Photoelectrochemical properties of ZnO nanorods (ZnO NRs) and poly(3-hexylthiophene) (P3HT) polymer hybrid photoanodes have been studied. The hybrid photoanodes demonstrated higher photoconversion efficiency, incident photon to current conversion efficiency (IPCE) and lower interfacial resistance compared to pristine ZnO nanorods and P3HT based electrodes. The origin of superior photoelectrochemical properties of ZnO/P3HT photoanodes has been explained using carrier transport mechanism at semiconductor/electrolyte junction. The stability of ZnO NRs/P3HT photoanode has been demonstrated.

Pure rotational spectra of TiO and TiO2 in VY Canis Majoris

NASA Astrophysics Data System (ADS)

Kamiński, T.; Gottlieb, C. A.; Menten, K. M.; Patel, N. A.; Young, K. H.; Brünken, S.; Müller, H. S. P.; McCarthy, M. C.; Winters, J. M.; Decin, L.

2013-03-01

We report the first detection of pure rotational transitions of TiO and TiO2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational temperature, Trot, of about 250 K was derived for TiO2. Although Trot was not well constrained for TiO, it is likely somewhat higher than that of TiO2. The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow. Based on observations carried out with the Submillimeter Array and IRAM Plateau de Bure Interferometer.Plateau de Bure data (FITS file) is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/551/A113

High-resolution photoelectron spectroscopy of TiO3H2-: Probing the TiO2- + H2O dissociative adduct

NASA Astrophysics Data System (ADS)

DeVine, Jessalyn A.; Abou Taka, Ali; Babin, Mark C.; Weichman, Marissa L.; Hratchian, Hrant P.; Neumark, Daniel M.

2018-06-01

Slow electron velocity-map imaging spectroscopy of cryogenically cooled TiO3H2- anions is used to probe the simplest titania/water reaction, TiO20/- + H2O. The resultant spectra show vibrationally resolved structure assigned to detachment from the cis-dihydroxide TiO(OH)2- geometry based on density functional theory calculations, demonstrating that for the reaction of the anionic TiO2- monomer with a single water molecule, the dissociative adduct (where the water is split) is energetically preferred over a molecularly adsorbed geometry. This work represents a significant improvement in resolution over previous measurements, yielding an electron affinity of 1.2529(4) eV as well as several vibrational frequencies for neutral TiO(OH)2. The energy resolution of the current results combined with photoelectron angular distributions reveals Herzberg-Teller coupling-induced transitions to Franck-Condon forbidden vibrational levels of the neutral ground state. A comparison to the previously measured spectrum of bare TiO2- indicates that reaction with water stabilizes neutral TiO2 more than the anion, providing insight into the fundamental chemical interactions between titania and water.

Fabrication of ZnO/SnO2 hierarchical structures as the composite photoanodes for efficient CdS/CdSe co-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lin, Yibing; Lin, Yu; Wu, Jihuai; Zhang, Xiaolong; Fang, Biaopeng

2017-03-01

The composite photoanodes based on the ZnO/SnO2 hierarchical structures with high photoelectricity properties have been successfully synthesized, and used in the CdS and CdSe quantum dots co-sensitized solar cells (QDSSCs). In this experiment, the ZnO/SnO2 nanoparticles (ZS-NP) and hierarchical nanosheets-based microflowers (ZS-MF) were prepared by the one-step hydrothermal route and the morphologies of the products were controlled by the solvent variation. An improved power conversion efficiency of 4.98% was achieved for the cell based on the ZS-MF composite photoanodes, which showed an increase of 21.8% compared to the ZS-NP photoanodes (4.09%). This result is mainly connected to the unique superiority of the three-dimensional hierarchical microflower nanostructures for light scattering and quantum dots loading, which is responsible for the increase of photocurrent values and eventual PCE.

Optimization of the photoelectrocatalytic oxidation of landfill leachate using copper and nitrate co-doped TiO2 (Ti) by response surface methodology

PubMed Central

Zhou, Shaoqi; Feng, Xinbin

2017-01-01

In this paper, a statistically-based experimental design with response surface methodology (RSM) was employed to examine the effects of functional conditions on the photoelectrocatalytic oxidation of landfill leachate using a Cu/N co-doped TiO2 (Ti) electrode. The experimental design method was applied to response surface modeling and the optimization of the operational parameters of the photoelectro-catalytic degradation of landfill leachate using TiO2 as a photo-anode. The variables considered were the initial chemical oxygen demand (COD) concentration, pH and the potential bias. Two dependent parameters were either directly measured or calculated as responses: chemical oxygen demand (COD) removal and total organic carbon (TOC) removal. The results of this investigation reveal that the optimum conditions are an initial pH of 10.0, 4377.98mgL-1 initial COD concentration and 25.0 V of potential bias. The model predictions and the test data were in satisfactory agreement. COD and TOC removals of 67% and 82.5%, respectively, were demonstrated. Under the optimal conditions, GC/MS showed 73 organic micro-pollutants in the raw landfill leachate which included hydrocarbons, aromatic compounds and esters. After the landfill leachate treatment processes, 38 organic micro-pollutants disappeared completely in the photoelectrocatalytic process. PMID:28671943

TiO2 Nanoparticles Are Phototoxic to Marine Phytoplankton

PubMed Central

Miller, Robert J.; Bennett, Samuel; Keller, Arturo A.; Pease, Scott; Lenihan, Hunter S.

2012-01-01

Nanoparticulate titanium dioxide (TiO2) is highly photoactive, and its function as a photocatalyst drives much of the application demand for TiO2. Because TiO2 generates reactive oxygen species (ROS) when exposed to ultraviolet radiation (UVR), nanoparticulate TiO2 has been used in antibacterial coatings and wastewater disinfection, and has been investigated as an anti-cancer agent. Oxidative stress mediated by photoactive TiO2 is the likely mechanism of its toxicity, and experiments demonstrating cytotoxicity of TiO2 have used exposure to strong artificial sources of ultraviolet radiation (UVR). In vivo tests of TiO2 toxicity with aquatic organisms have typically shown low toxicity, and results across studies have been variable. No work has demonstrated that photoactivity causes environmental toxicity of TiO2 under natural levels of UVR. Here we show that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO2 nanoparticles to marine phytoplankton, the most important primary producers on Earth. No effect of TiO2 on phytoplankton was found in treatments where UV light was blocked. Under low intensity UVR, ROS in seawater increased with increasing nano-TiO2 concentration. These increases may lead to increased overall oxidative stress in seawater contaminated by TiO2, and cause decreased resiliency of marine ecosystems. Phototoxicity must be considered when evaluating environmental impacts of nanomaterials, many of which are photoactive. PMID:22276179

Enhanced Dispersion of TiO2 Nanoparticles in a TiO2/PEDOT:PSS Hybrid Nanocomposite via Plasma-Liquid Interactions

NASA Astrophysics Data System (ADS)

Liu, Yazi; Sun, Dan; Askari, Sadegh; Patel, Jenish; Macias-Montero, Manuel; Mitra, Somak; Zhang, Richao; Lin, Wen-Feng; Mariotti, Davide; Maguire, Paul

2015-10-01

A facile method to synthesize a TiO2/PEDOT:PSS hybrid nanocomposite material in aqueous solution through direct current (DC) plasma processing at atmospheric pressure and room temperature has been demonstrated. The dispersion of the TiO2 nanoparticles is enhanced and TiO2/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. Increased electrical conductivity was observed for the plasma treated TiO2/PEDOT:PSS nanocomposite. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma treated TiO2 nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are proposed to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer binding.

ZnO Hierarchical Nanostructure Photoanode in a CdS Quantum Dot-Sensitized Solar Cell

PubMed Central

Liu, Huan; Zhang, Gengmin; Sun, Wentao; Shen, Ziyong; Shi, Mingji

2015-01-01

A hierarchical array of ZnO nanocones covered with ZnO nanospikes was hydrothermally fabricated and employed as the photoanode in a CdS quantum dot-sensitized solar cell (QDSSC). This QDSSC outperformed the QDSSC based on a simple ZnO nanocone photoanode in all the four principal photovoltaic parameters. Using the hierarchical photoanode dramatically increased the short circuit current density and also slightly raised the open circuit voltage and the fill factor. As a result, the conversion efficiency of the QDSSC based on the hierarchical photoanode was more than twice that of the QDSSC based on the simple ZnO nanocone photoanode. This improvement is attributable to both the enlarged specific area of the photoanode and the reduction in the recombination of the photoexcited electrons. PMID:26379268

Oxygen vacancy induces self-doping effect and metalloid LSPR in non-stoichiometric tungsten suboxide synergistically contributing to the enhanced photoelectrocatalytic performance of WO3-x/TiO2-x heterojunction.

PubMed

Huang, Weicheng; Wang, Jinxin; Bian, Lang; Zhao, Chaoyue; Liu, Danqing; Guo, Chongshen; Yang, Bin; Cao, Wenwu

2018-06-27

A WO3-x/TiO2-x nanotube array (NTA) heterojunction photoanode was strategically designed to improve photoelectrocatalytic (PEC) performance by establishing a synergistic vacancy-induced self-doping effect and localized surface plasmon resonance (LSPR) effect of metalloid non-stoichiometric tungsten suboxide. The WO3-x/TiO2-x NTA heterojunction photoanode was synthesized through a successive process of anodic oxidation to form TiO2 nanotube arrays, magnetron sputtering to deposit metalloid WO3-x, and post-hydrogen reduction to engender oxygen vacancy in TiO2-x as well as crystallization. On the merits of such a synergistic effect, WO3-x/TiO2-x shows higher light-harvesting ability, stronger photocurrent response, and resultant improved photoelectrocatalytic performance than the contrast of WO3-x/TiO2, WO3/TiO2 and TiO2, confirming the importance of oxygen vacancies in improving PEC performance. Theoretical calculation based on density functional theory was applied to investigate the electronic structural features of samples and reveal how the oxygen vacancy determines the optical property. The carrier density tuning mechanism and charge transfer model were considered to be associated with the synergistic effect of self-doping and metalloid LSPR effect in the WO3-x/TiO2-x NTA.

Growth of a sea urchin-like rutile TiO2 hierarchical microsphere film on Ti foil for a quasi-solid-state dye-sensitized solar cell.

PubMed

Ri, Jin Hyok; Wu, Shufang; Jin, Jingpeng; Peng, Tianyou

2017-11-30

A sea urchin-like rutile TiO 2 microsphere (RMS) film was fabricated on Ti foil via a hydrothermal process. The resulting rutile TiO 2 hierarchical microspheres with a diameter of 5-6 μm are composed of nanorods with a diameter of ∼200 nm and a length of 1-2 μm. The sea urchin-like hierarchical structure leads to the Ti foil-based RMS film possessing much better light-scattering capability in the visible region than the bare Ti foil. By using it as an underlayer of a nanosized anatase TiO 2 film (bTPP3) derived from a commercially available paste (TPP3), the corresponding bilayer Ti foil-based quasi-solid-state dye-sensitized solar cell (DSSC) only gives a conversion efficiency of 4.05%, much lower than the single bTPP3 film-based one on Ti foil (5.97%). By spin-coating a diluted TPP3 paste (sTPP3) on the RMS film prior to scraping the bTPP3 film, the resulting RMS/sTPP3/bTPP3 film-based DSSC achieves a significantly enhanced efficiency (7.27%). The electrochemical impedance spectra (EIS) show that the RMS/sTPP3/bTPP3 film possesses better electron transport capability and longer electron lifetime than the bTPP3 film. This work not only provides the first example of directly growing rutile TiO 2 hierarchically structured microsphere film on Ti foil suitable for replacing the rigid, heavy and expensive transparent conductive oxide (TCO) glass substrate to serve as a light-scattering underlayer of Ti foil-based quasi-solid-state DSSCs, but also paves a new route to develop Ti foil-based flexible DSSCs with high efficiency, low cost and a wide application field through optimizing the composition and structure of the photoanode.

Hetero-Orientation Epitaxial Growth of TiO2 Splats on Polycrystalline TiO2 Substrate

NASA Astrophysics Data System (ADS)

Chen, Lin; Yang, Guan-Jun

2018-05-01

In the present study, the effect of titania (TiO2) substrate grain size and orientation on the epitaxial growth of TiO2 splat was investigated. Interestingly, the splat presented comparable grain size with that of substrate, indicating the hereditary feature of grain size. In addition, hetero- and homo-orientation epitaxial growth was observed at deposition temperatures below 400 °C and above 500 °C, respectively. The preferential growth of high-energy (001) face was also observed at low deposition temperatures (≤ 400 °C), which was found to result from dynamic nonequilibrium effect during the thermal spray deposition. Moreover, thermal spray deposition paves the way for a new approach to prepare high-energy (001) facets of TiO2 crystals.

Comparison study on photocatalytic oxidation of pharmaceuticals by TiO2-Fe and TiO2-reduced graphene oxide nanocomposites immobilized on optical fibers.

PubMed

Lin, Lu; Wang, Huiyao; Jiang, Wenbin; Mkaouar, Ahmed Radhi; Xu, Pei

2017-07-05

Incorporating reduced graphene oxide (rGO) or Fe 3+ ions in TiO 2 photocatalyst could enhance photocatalytic degradation of organic contaminants in aqueous solutions. This study characterized the photocatalytic activities of TiO 2 -Fe and TiO 2 -rGO nanocomposites immobilized on optical fibers synthesized by polymer assisted hydrothermal deposition method. The photocatalysts presented a mixture phase of anatase and rutile in the TiO 2 -rGO and TiO 2 -Fe nanocomposites. Doping Fe into TiO 2 particles (2.40eV) could reduce more band gap energy than incorporating rGO (2.85eV), thereby enhancing utilization efficiency of visible light. Incorporating Fe and rGO in TiO 2 decreased significantly the intensity of TiO 2 photoluminescence signals and enhanced the separation rate of photo-induced charge carriers. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO 2 -rGO exhibited higher photocatalytic activity for the degradation of pharmaceuticals under UV irradiation, while TiO 2 -Fe demonstrated more suitable for visible light oxidation. The results suggested that the enhanced photocatalytic performance of TiO 2 -rGO could be attributed to reduced recombination rate of photoexcited electrons-hole pairs, but for TiO 2 -Fe nanocomposite, narrower band gap would contribute to increased photocatalytic activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Hetero-type dual photoanodes for unbiased solar water splitting with extended light harvesting.

PubMed

Kim, Jin Hyun; Jang, Ji-Wook; Jo, Yim Hyun; Abdi, Fatwa F; Lee, Young Hye; van de Krol, Roel; Lee, Jae Sung

2016-12-14

Metal oxide semiconductors are promising photoelectrode materials for solar water splitting due to their robustness in aqueous solutions and low cost. Yet, their solar-to-hydrogen conversion efficiencies are still not high enough for practical applications. Here we present a strategy to enhance the efficiency of metal oxides, hetero-type dual photoelectrodes, in which two photoanodes of different bandgaps are connected in parallel for extended light harvesting. Thus, a photoelectrochemical device made of modified BiVO 4 and α-Fe 2 O 3 as dual photoanodes utilizes visible light up to 610 nm for water splitting, and shows stable photocurrents of 7.0±0.2 mA cm -2 at 1.23 V RHE under 1 sun irradiation. A tandem cell composed with the dual photoanodes-silicon solar cell demonstrates unbiased water splitting efficiency of 7.7%. These results and concept represent a significant step forward en route to the goal of >10% efficiency required for practical solar hydrogen production.

Discovery and Characterization of a Pourbaix-Stable, 1.8 eV Direct Gap Bismuth Manganate Photoanode

DOE PAGES

Newhouse, Paul F.; Reyes-Lillo, Sebastian E.; Li, Guo; ...

2017-11-13

Solar-driven oxygen evolution is a critical technology for renewably synthesizing hydrogen- and carbon-containing fuels in solar fuel generators. New photoanode materials are needed to meet efficiency and stability requirements, motivating materials explorations for semiconductors with (i) band-gap energy in the visible spectrum and (ii) stable operation in aqueous electrolyte at the electrochemical potential needed to evolve oxygen from water. Motivated by the oxygen evolution competency of many Mn-based oxides, the existence of several Bi-containing ternary oxide photoanode materials, and the variety of known oxide materials combining these elements with Sm, we explore the Bi-Mn-Sm oxide system for new photoanodes. Throughmore » the use of a ferri/ferrocyanide redox couple in high-throughput screening, BiMn 2O 5 and its alloy with Sm are identified as photoanode materials with a near-ideal optical band gap of 1.8 eV. Using density functional theory-based calculations of the mullite Bi 3+ Mn 3+ Mn 4+O 5 phase, we identify electronic analogues to the well-known BiVO 4 photoanode and demonstrate excellent Pourbaix stability above the oxygen evolution Nernstian potential from pH 4.5 to 15. Lastly, our suite of experimental and computational characterization indicates that BiMn 2O 5 is a complex oxide with the necessary optical and chemical properties to be an efficient, stable solar fuel photoanode.« less

Discovery and Characterization of a Pourbaix-Stable, 1.8 eV Direct Gap Bismuth Manganate Photoanode

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

Newhouse, Paul F.; Reyes-Lillo, Sebastian E.; Li, Guo

Solar-driven oxygen evolution is a critical technology for renewably synthesizing hydrogen- and carbon-containing fuels in solar fuel generators. New photoanode materials are needed to meet efficiency and stability requirements, motivating materials explorations for semiconductors with (i) band-gap energy in the visible spectrum and (ii) stable operation in aqueous electrolyte at the electrochemical potential needed to evolve oxygen from water. Motivated by the oxygen evolution competency of many Mn-based oxides, the existence of several Bi-containing ternary oxide photoanode materials, and the variety of known oxide materials combining these elements with Sm, we explore the Bi-Mn-Sm oxide system for new photoanodes. Throughmore » the use of a ferri/ferrocyanide redox couple in high-throughput screening, BiMn 2O 5 and its alloy with Sm are identified as photoanode materials with a near-ideal optical band gap of 1.8 eV. Using density functional theory-based calculations of the mullite Bi 3+ Mn 3+ Mn 4+O 5 phase, we identify electronic analogues to the well-known BiVO 4 photoanode and demonstrate excellent Pourbaix stability above the oxygen evolution Nernstian potential from pH 4.5 to 15. Lastly, our suite of experimental and computational characterization indicates that BiMn 2O 5 is a complex oxide with the necessary optical and chemical properties to be an efficient, stable solar fuel photoanode.« less

Effect of dye extracting solvents and sensitization time on photovoltaic performance of natural dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hossain, Md. Khalid; Pervez, M. Firoz; Mia, M. N. H.; Mortuza, A. A.; Rahaman, M. S.; Karim, M. R.; Islam, Jahid M. M.; Ahmed, Farid; Khan, Mubarak A.

In this study, natural dye sensitizer based solar cells were successfully fabricated and photovoltaic performance was measured. Sensitizer (turmeric) sources, dye extraction process, and photoanode sensitization time of the fabricated cells were analyzed and optimized. Dry turmeric, verdant turmeric, and powder turmeric were used as dye sources. Five distinct types of solvents were used for extraction of natural dye from turmeric. Dyes were characterized by UV-Vis spectrophotometric analysis. The extracted turmeric dye was used as a sensitizer in the dye sensitized solar cell's (DSSC) photoanode assembly. Nano-crystalline TiO2 was used as a film coating semiconductor material of the photoanode. TiO2 films on ITO glass substrate were prepared by simple doctor blade technique. The influence of the different parameters VOC, JSC, power density, FF, and η% on the photovoltaic characteristics of DSSCs was analyzed. The best energy conversion performance was obtained for 2 h adsorption time of dye on TiO2 nano-porous surface with ethanol extracted dye from dry turmeric.

Exchange of TiO2 nanoparticles between streams and streambeds.

PubMed

Boncagni, Natalia Ticiana; Otaegui, Justo Manuel; Warner, Evelyn; Curran, Trisha; Ren, Jianhong; de Cortalezzi, Maria Marta Fidalgo

2009-10-15

The expanding use of manufactured nanoparticles has increased the potential for their release into the natural environment. Particularly, TiO2 nanoparticles pose significant exposure risk to humans and other living species due to their extensive use in a wide range of fields. To better understand the environmental and health risks associated with the release of TiO2 nanoparticles, knowledge on their fate and transport is needed. This study evaluates the transport of two different TiO2 nanoparticles: one commercially available (P25 TiO2 and the other synthesized at a lab scale (synthesized TiO2). Laboratory flume, column, and batch experiments were conducted to investigate the processes dominating the transport of TiO2 nanoparticles between streams and streambeds and to characterize the properties of these nanoparticles under different physicochemical conditions. Results show that the synthesized TiO2 was more stable compared to the P25 TiO2, which underwent significant aggregation under the same experimental conditions. As a result, P25 TiO2 deposited at a faster rate than the synthesized TiO2 in the streambed. Both types of TiO2 nanoparticles deposited in the streambed were easily released when the stream velocity was increased. The aggregation and deposition of P25 TiO2 were highly dependent on pH. A process-based colloid exchange model was applied to interpret the observed transport behavior of the TiO2 nanoparticles.

MoSe2 modified TiO2 nanotube arrays with superior photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Zhang, Yaping; Zhu, Haifeng; Yu, Lianqing; He, Jiandong; Huang, Chengxing

2018-04-01

TiO2 nanotube arrays (TNTs) are first prepared by anodization Ti foils in ethylene glycol electrolyte. Then, MoSe2 deposites electrochemically on TNTs. The as-synthesized MoSe2/TiO2 composite has a much higher photocurrent density of 1.07 mA cm‑2 at 0 V than pure TNTs of 0.38 mA cm‑2, which suggests that the MoSe2/TiO2 composite film has optimum photoelectrocatalysis properties. The electron transport resistances of the MoSe2/TiO2 decreases to half of pure TiO2, at 295.6 ohm/cm2. Both photocurrent-time and Mott-Schottky plots indicate MoSe2 a p-type semiconductor characteristics. MoSe2/TiO2 composite can achieve a maximum 5 orders of magnitude enhancement in carrier density (4.650 × 1027 cm‑3) than that of pure TiO2 arrays. It can be attributed to p-n heterojunction formed between MoSe2 and TiO2, and the composite can be potentially applied in photoelectrochemical, photocatalysis fields.

Plasmon enhanced water splitting mediated by hybrid bimetallic Au-Ag core-shell nanostructures.

PubMed

Erwin, William R; Coppola, Andrew; Zarick, Holly F; Arora, Poorva; Miller, Kevin J; Bardhan, Rizia

2014-11-07

In this work, we employed wet chemically synthesized bimetallic Au-Ag core-shell nanostructures (Au-AgNSs) to enhance the photocurrent density of mesoporous TiO2 for water splitting and we compared the results with monometallic Au nanoparticles (AuNPs). While Au-AgNSs incorporated photoanodes give rise to 14× enhancement in incident photon to charge carrier efficiency, AuNPs embedded photoanodes result in 6× enhancement. By varying nanoparticle concentration in the photoanodes, we observed ∼245× less Au-AgNSs are required relative to AuNPs to generate similar photocurrent enhancement for solar fuel conversion. Power-dependent measurements of Au-AgNSs and AuNPs showed a first order dependence to incident light intensity, relative to half-order dependence for TiO2 only photoanodes. This indicated that plasmonic nanostructures enhance charge carriers formed on the surface of the TiO2 which effectively participate in photochemical reactions. Our experiments and simulations suggest the enhanced near-field, far-field, and multipolar resonances of Au-AgNSs facilitating broadband absorption of solar radiation collectively gives rise to their superior performance in water splitting.

Labeling TiO2 nanoparticles with dyes for optical fluorescence microscopy and determination of TiO2-DNA nanoconjugate stability.

PubMed

Thurn, Kenneth T; Paunesku, Tatjana; Wu, Aiguo; Brown, Eric M B; Lai, Barry; Vogt, Stefan; Maser, Jörg; Aslam, Mohammed; Dravid, Vinayak; Bergan, Raymond; Woloschak, Gayle E

2009-06-01

Visualization of nanoparticles without intrinsic optical fluorescence properties is a significant problem when performing intracellular studies. Such is the case with titanium dioxide (TiO2) nanoparticles. These nanoparticles, when electronically linked to single-stranded DNA oligonucleotides, have been proposed to be used both as gene knockout devices and as possible tumor imaging agents. By interacting with complementary target sequences in living cells, these photoinducible TiO2-DNA nanoconjugates have the potential to cleave intracellular genomic DNA in a sequence specific and inducible manner. The nanoconjugates also become detectable by magnetic resonance imaging with the addition of gadolinium Gd(III) contrast agents. Herein two approaches for labeling TiO2 nanoparticles and TiO2-DNA nanoconjugates with optically fluorescent agents are described. This permits direct quantification of fluorescently labeled TiO2 nanoparticle uptake in a large population of living cells (>10(4) cells). X-ray fluorescence microscopy (XFM) is combined with fluorescent microscopy to determine the relative intracellular stability of the nanoconjugates and used to quantify intracellular nanoparticles. Imaging the DNA component of the TiO2-DNA nanoconjugate by fluorescent confocal microscopy within the same cell shows an overlap with the titanium signal as mapped by XFM. This strongly implies the intracellular integrity of the TiO2-DNA nanoconjugates in malignant cells.

Photoanode Thickness Optimization and Impedance Spectroscopic Analysis of Dye-Sensitized Solar Cells based on a Carbazole-Containing Ruthenium Dye

NASA Astrophysics Data System (ADS)

Choi, Jongwan; Kim, Felix Sunjoo

2018-03-01

We studied the influence of photoanode thickness on the photovoltaic characteristics and impedance responses of the dye-sensitized solar cells based on a ruthenium dye containing a hexyloxyl-substituted carbazole unit (Ru-HCz). As the thickness of photoanode increases from 4.2 μm to 14.8 μm, the dye-loading amount and the efficiency increase. The device with thicker photoanode shows a decrease in the efficiency due to the higher probability of recombination of electron-hole pairs before charge extraction. We also analyzed the electron-transfer and recombination characteristics as a function of photoanode thickness through detailed electrochemical impedance spectroscopy analysis.

Trade-off between Zr Passivation and Sn Doping on Hematite Nanorod Photoanodes for Efficient Solar Water Oxidation: Effects of a ZrO2 Underlayer and FTO Deformation.

PubMed

Subramanian, Arunprabaharan; Annamalai, Alagappan; Lee, Hyun Hwi; Choi, Sun Hee; Ryu, Jungho; Park, Jung Hee; Jang, Jum Suk

2016-08-03

Herein we report the influence of a ZrO2 underlayer on the PEC (photoelectrochemical) behavior of hematite nanorod photoanodes for efficient solar water splitting. Particular attention was given to the cathodic shift in onset potential and photocurrent enhancement. Akaganite (β-FeOOH) nanorods were grown on ZrO2-coated FTO (fluorine-doped tin oxide) substrates. Sintering at 800 °C transformed akaganite to the hematite (α-Fe2O3) phase and induced Sn diffusion into the crystal structure of hematite nanorods from the FTO substrates and surface migration, shallow doping of Zr atoms from the ZrO2 underlayer. The ZrO2 underlayer-treated photoanode showed better water oxidation performance compared to the pristine (α-Fe2O3) photoanode. A cathodic shift in the onset potential and photocurrent enhancement was achieved by surface passivation and shallow doping of Zr from the ZrO2 underlayer, along with Sn doping from the FTO substrate to the crystal lattice of hematite nanorods. The Zr based hematite nanorod photoanode achieved 1 mA/cm(2) at 1.23 VRHE with a low turn-on voltage of 0.80 VRHE. Sn doping and Zr passivation, as well as shallow doping, were confirmed by XPS, Iph, and M-S plot analyses. Electrochemical impedance spectroscopy revealed that the presence of a ZrO2 underlayer decreased the deformation of FTO substrate, improved electron transfer at the hematite/FTO interface and increased charge-transfer resistance at the electrolyte/hematite interface. This is the first systematic investigation of the effects of Zr passivation, shallow doping, and Sn doping on hematite nanorod photoanodes through application of a ZrO2 underlayer on the FTO substrate.

Charge transfer between biogenic jarosite derived Fe3+and TiO2 enhances visible light photocatalytic activity of TiO2.

PubMed

Chowdhury, Mahabubur; Shoko, Sipiwe; Cummings, Fransciuos; Fester, Veruscha; Ojumu, Tunde Victor

2017-04-01

In this work, we have shown that mining waste derived Fe 3+ can be used to enhance the photocatalytic activity of TiO 2 . This will allow us to harness a waste product from the mines, and utilize it to enhance TiO 2 photocatalytic waste water treatment efficiency. An organic linker mediated route was utilized to create a composite of TiO 2 and biogenic jarosite. Evidence of FeOTi bonding in the TiO 2 /jarosite composite was apparent from the FTIR, EFTEM, EELS and ELNEFS analysis. The as prepared material showed enhanced photocatalytic activity compared to pristine TiO 2 , biogenic jarosite and mechanically mixed sample of jarosite and TiO 2 under both simulated and natural solar irradiation. The prepared material can reduce the electrical energy consumption by 4 times compared to pristine P25 for degradation of organic pollutant in water. The material also showed good recyclability. Results obtained from sedimentation experiments showed that the larger sized jarosite material provided the surface to TiO 2 nanoparticles, which increases the settling rate of the materials. This allowed simple and efficient recovery of the catalyst from the reaction system after completion of photocatalysis. Enhanced photocatalytic activity of the composite material was due to effective charge transfer between TiO 2 and jarosite derived Fe 3+ as was shown from the EELS and ELNEFS. Generation of OH was supported by photoluminesence (PL) experiments. Copyright © 2016. Published by Elsevier B.V.

Properties of TiO2 thin films and a study of the TiO2-GaAs interface

NASA Technical Reports Server (NTRS)

Chen, C. Y.; Littlejohn, M. A.

1977-01-01

Titanium dioxide (TiO2) films prepared by chemical vapor deposition were investigated in this study for the purpose of the application in the GaAs metal-insulator-semiconductor field-effect transistor. The degree of crystallization increases with the deposition temperature. The current-voltage study, utilizing an Al-TiO2-Al MIM structure, reveals that the d-c conduction through the TiO2 film is dominated by the bulk-limited Poole-Frenkel emission mechanism. The dependence of the resistivity of the TiO2 films on the deposition environment is also shown. The results of the capacitance-voltage study indicate that an inversion layer in an n-type substrate can be achieved in the MIS capacitor if the TiO2 films are deposited at a temperature higher than 275 C. A process of low temperature deposition followed by the pattern definition and a higher temperature annealing is suggested for device fabrications. A model, based on the assumption that the surface state densities are continuously distributed in energy within the forbidden band gap, is proposed to interpret the lack of an inversion layer in the Al-TiO2-GaAs MIS structure with the TiO2 films deposited at 200 C.

Stabilization of n-type semiconductors to photoanodic dissolution by competitive electron transfer processes

NASA Technical Reports Server (NTRS)

Wrighton, M. S.; Bocarsly, A. B.; Bolts, J. M.; Ellis, A. B.; Legg, K. D.

1977-01-01

The behavior of n-type CdX (X = S, Se, Te) and GaP, GaAs, and InP in alkaline electrolytes containing X(--) and X sub n(--) ions is reviewed. Of the 18 combinations of electrode and electrolyte, 12 alliances are completely stable to photoanodic dissolution of the n-type photoanode. In each case the oxidation of the chalcogenide species at the photoanode is reversed at the cathode to complete an electrochemical cycle involving no net chemical change. The best system in terms of light-to-electric energy conversion seems to be the CdTe-based cell employing the Te(--)/Te2(--) electrolyte, with roughly 10% efficiency at an output voltage of 0.35 V for monochromatic 633 nm input optical energy at about 25 mW/sq cm.

A comparative study between titania and zirconia as material for scattering layer in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Nursam, N. M.; Hidayat, J.; Shobih; Rosa, E. S.; Pranoto, L. M.

2018-04-01

The photoanode of dye-sensitized solar cells (DSSC) is typically composed of nanocrystalline titania (TiO2) layer that has been sensitized with light-absorbing dye molecules. Large portion of the light, however, could not be efficiently absorbed due to some physical reasons, such as TiO2 crystal size (typically 10-25 nm) that makes the photoanode remains partially transparent to the visible region in the solar spectrum. One of the ways to improve the light harvesting efficiency in DSSC could be achieved by employing an additional scattering layer over the TiO2 electron transport material. In this contribution, we evaluate the effect of light scattering properties on the performance of DSSC. Specifically, the light scattering properties provided from two different scattering materials, i.e. additional TiO2 scattering layer and zirconia (ZrO2) scattering layer, were compared. Both layers were deposited using screen printing technique under the same condition on top of 8 µm thick TiO2 photoanode layer. All samples subsequently received the same thermal annealing treatment at 500 °C and sensitized with ruthenium-based synthetic dyes. Our results revealed that the thickness of the scattering layer for both TiO2 and ZrO2 had a significant effect on the solar cell performance. The best photoconversion efficiency was achieved by samples that were coated with one screen-printing cycle, giving an overall efficiency of 3.50 % and 4.02% for TiO2 and ZrO2, respectively.

Highly uniform and vertically aligned SnO2 nanochannel arrays for photovoltaic applications

NASA Astrophysics Data System (ADS)

Kim, Jae-Yup; Kang, Jin Soo; Shin, Junyoung; Kim, Jin; Han, Seung-Joo; Park, Jongwoo; Min, Yo-Sep; Ko, Min Jae; Sung, Yung-Eun

2015-04-01

Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO2 nanochannel arrays. Building on this breakthrough, we first demonstrate the photovoltaic application of these vertically aligned SnO2 nanochannel arrays. These vertically aligned arrays were directly and successfully applied in quasi-solid state dye-sensitized solar cells (DSSCs) as photoanodes, yielding reasonable conversion efficiency under back-side illumination. In addition, a significantly short process time (330 s) for achieving the optimal thickness (7.0 μm) and direct utilization of the anodized electrodes enable a simple, rapid and low-cost fabrication process. Furthermore, a TiO2 shell layer was coated on the SnO2 nanochannel arrays by the atomic layer deposition (ALD) process for enhancement of dye-loading and prolonging the electron lifetime in the DSSC. Owing to the presence of the ALD TiO2 layer, the short-circuit photocurrent density (Jsc) and conversion efficiency were increased by 20% and 19%, respectively, compared to those of the DSSC without the ALD TiO2 layer. This study provides valuable insight into the development of efficient SnO2-based photoanodes for photovoltaic application by a simple and rapid fabrication process.Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process

The presence of Ti(II) centers in doped nanoscale TiO2 and TiO2-xNx

NASA Astrophysics Data System (ADS)

Mikulas, Tanya; Fang, Zongtang; Gole, James L.; White, Mark G.; Dixon, David A.

2012-06-01

Unusual trends are observed in the Ti (2s, 2p) XPS spectra of Fe(II) doped TiO2 and TiO2-xNx. The binding energy of Ti (2s, 2p) initially decreases with increasing Fe(II) concentration, as expected, but increases at higher Fe(II) doping levels. Density functional theory is used to analyze the results. The observed VB-XPS and core level XPS spectra are consistent with the facile charge transfer sequence Ti(IV) + Fe(II) → Ti(III) + Fe(III) followed by Ti(III) + Fe(II) → Ti(II) + Fe(III). The formed Ti(II) sites may be relevant to nanoparticle catalysis on TiO2 surfaces.

Photocatalytic TiO2 nanoparticles enhanced polymer antimicrobial coating

NASA Astrophysics Data System (ADS)

Wei, Xiaojin; Yang, Zhendi; Tay, See Leng; Gao, Wei

2014-01-01

Copper (Cu) containing coatings can provide sustainable protection against microbial contamination. However, metallic Cu coatings have not been widely used due to the relatively high cost, poor corrosion resistance, and low compatibility with non-metal substrates. Titanium dioxide (TiO2) possesses antibacterial functions by its photocatalytic properties which can destroy bacteria or suppress their reproduction. TiO2 also has the function of improving the mechanical properties through particle dispersion strengthening. We have recently developed an innovative polymer based coating system containing fine particles of Cu and TiO2 nanoparticles. These polymer based coatings simultaneously display excellent antimicrobial and good mechanical properties. The results showed that the addition of TiO2 has improved the antimicrobial property under sunlight, which provides extended applications in outdoor environment. The elimination of 106 bacterial by contacting the coatings without TiO2 needs 5 h, while contacting with the Cu/TiO2- 1 wt.% TiO2 took only 2 h to kill the same amount of bacteria. The coatings also presented enhanced hardness and wear resistance after adding TiO2. The width of wear track decreased from 270 μm of the Cu-polymer coating to 206 μm of Cu/TiO2-polymer coatings with 10 wt.% TiO2. Synchrotron Infrared Microscopy was used to in-situ and in-vivo study the bacteria killing process at the molecular level. The real-time chemical images of bacterial activities showed that the bacterial cell membranes were damaged by the Cu and TiO2 containing coatings

Influence of the surface chemistry on TiO2 - TiO2 nanocontact forces as measured by an UHV-AFM

NASA Astrophysics Data System (ADS)

Kunze, Christian; Giner, Ignacio; Torun, Boray; Grundmeier, Guido

2014-03-01

Particle-wall contact forces between a TiO2 film coated AFM tip and TiO2(1 1 0) single crystal surfaces were analyzed by means of UHV-AFM. As a reference system an octadecylphosphonic acid monolayer covered TiO2(1 1 0) surface was studied. The defect chemistry of the TiO2 substrate was modified by Ar ion bombardment, water dosing at 3 × 10-6 Pa and an annealing step at 473 K which resulted in a varying density of Ti(III) states. The observed contact forces are correlated to the surface defect density and are discussed in terms of the change in the electronic structure and its influence on the Hamaker constant.

In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation.

PubMed

Zhang, Yong-Gang; Ma, Li-Li; Li, Jia-Lin; Yu, Ying

2007-09-01

TiO2/Cu2O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO2/Cu2O composite films with different ratio of TiO2 and Cu2O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO2/Cu2O composite film with the presence of FeSO4 and EDTA is much higher than that for the similar system with only TiO2 and Cu2O film respectively. Without the presence of FeSO4 and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO2/Cu2O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of Ti02 in the composite, and the second significant factor is the concentration of FeSO4. During the degradation of methylene blue under visible light, TiO2/Cu2O composite film generates H202, and Fenton regent is formed with Fe2+ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO2/Cu2O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO2/Cu2O composite under visible light are transferred from the conduction band of Cu2O to that of Ti02. The formed intermediate state of Ti 3+ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO/Cu2O composite film. Additionally, the accumulated electrons in the conduction band of TiO2 are transferred to oxygen on the TiO2 surface for the formation of O2- or O2(2-), which combines with H+ to form H2O2. The evolved H202 with FeSO4 and EDTA forms Fenton reagentto degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO2/Cu2O composite film does not need to

Two-step electrodeposition to fabricate the p-n heterojunction of a Cu2O/BiVO4 photoanode for the enhancement of photoelectrochemical water splitting.

PubMed

Bai, Shouli; Liu, Jingchao; Cui, Meng; Luo, Ruixian; He, Jing; Chen, Aifan

2018-05-15

A Cu2O/BiVO4 p-n heterojunction based photoanode in photoelectrochemical (PEC) water splitting is fabricated by a two-step electrodeposition method on an FTO substrate followed by annealing treatment. The structures and properties of the samples are characterized by XRD, FESEM, HRTEM, XPS and UV-visible spectra. The photoelectrochemical activity of the photoanode in water oxidation has been investigated and measured in a three electrode quartz cell system; the obtained maximum photocurrent density of 1.72 mA cm-2 at 1.23 V vs. RHE is 4.5 times higher than that of pristine BiVO4 thin films (∼0.38 mA cm-2). The heterojunction based photoanode also exhibits a tremendous cathodic shift of the onset potential (∼420 mV) and enhancement in the IPCE value by more than 4-fold. The enhanced photoelectrochemical properties of the Cu2O/BiVO4 photoelectrode are attributed to the efficient separation of the photoexcited electron-hole pairs caused by the inner electronic field (IEF) of the p-n heterojunction.

Formation of artificial pores in nano-TiO2 photo-electrode films using acetylene-black for high-efficiency, dye-sensitized solar cells

PubMed Central

Cho, Tae-Yeon; Han, Chi-Whan; Jun, Yongseok; Yoon, Soon-Gil

2013-01-01

Acetylene-black paste without a light scattering layer was applied to meso-porous TiO2 photo-electrode films with a crystalline framework, a low residual carbon, and a tunable morphological pore size. The thermal-treated TiO2 photo-electrode films had an increased acetylene-black concentration with an increase in artificial pores and a decrease in residual carbon. The performance of dye-sensitized solar cells (DSSCs) was enhanced by the use of the TiO2 photo-anode pastes at various acetylene-black concentrations. The photo-conversion efficiency of the DSSCs using TiO2 photo-electrode films with 1.5 wt% acetylene-black was enhanced from 7.98 (no acetylene-black) to 9.75% without the integration of a light- scattering layer. PMID:23511122

Sol-gel TiO2 films as NO2 gas sensors

NASA Astrophysics Data System (ADS)

Georgieva, V.; Gadjanova, V.; Grechnikov, A.; Donkov, N.; Sendova-Vassileva, M.; Stefanov, P.; Kirilov, R.

2014-05-01

TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (ΔF) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

A TiO2 abundance map for the northern maria

NASA Technical Reports Server (NTRS)

Johnson, T. V.; Saunders, R. S.; Matson, D. L.; Mosher, J. A.

1977-01-01

A map of TiO2 abundance for most of the northern maria is presented. The telescopic data base used is the 0.38/0.56-micron ratio mosaic from Johnson et at. (1977). The titanium content has been estimated using the correlation established by Charette et al. (1974). The combination of observational, processing, and calibration errors indicates that the TiO2 map is accurate to + or - 2% (wt% TiO2) for high TiO2 content (more than 5%) and + or - 1% for low values of TiO2. Analysis of the lunar sample and telescopic data suggests strongly that the spectral parameter mapped is sensitive primarily to TiO2 abundance in the range 3-9% and does not correlate directly with iron content. It is suggested, however, that for the low TiO2 mare regions (less than 2-3% TiO2) there may be a relation between the spectral ratio and iron content and that some of the reddest mare areas in the Imbrium region may have low iron contents as well as low titanium abundances.

Photoelectrochemical Degradation of Organic Compounds Coupled with Molecular Hydrogen Generation Using Electrochromic TiO2 Nanotube Arrays.

PubMed

Koo, Min Seok; Cho, Kangwoo; Yoon, Jeyong; Choi, Wonyong

2017-06-06

Vertically aligned TiO 2 nanotube arrays (TNTs) were prepared by electrochemical anodization, and then cathodically polarized with dark blue coloration for the dual-functional photoelectrochemical water treatment of organic substrates degradation and accompanying H 2 generation. The resulting Blue-TNTs (inner diameter: ∼40 nm; length: ∼9 μm) showed negligible shift in X-ray diffraction pattern compared with the intact TNTs, but the X-ray photoelectron spectra indicated a partial reduction of Ti 4+ to Ti 3+ on the surface. The electrochemical analyses of Blue-TNTs revealed a marked enhancement in donor density and electrical conductivity by orders of magnitude. Degradations of test organic substrates on Blue-TNTs were compared with the intact TNTs in electrochemical (EC), photocatalytic (PC), and photoelectrochemical (PEC) conditions (potential bias: 1.64 V NHE ; λ > 320 nm). The degradation of 4-chlorophenol was greatly enhanced on Blue-TNTs particularly in PEC condition, whereas the PC activities of the Blue- and intact TNTs were similar. The potential bias of 1.64 V NHE did not induce any noticeable activity in EC condition. Similar trends were observed for the degradation of humic acid and fulvic acid, where main working oxidants were found to be the surface hydroxyl radical as confirmed by hydroxyl radical probe and scavenger tests. H 2 generation coupled with the organic degradation was observed only in PEC condition, where the H 2 generation rate with Blue-TNTs was more than doubled from that of intact TNTs. Such superior PEC activity was not observed when a common TiO 2 nanoparticle film was used as a photoanode. The enhanced electric conductivity of Blue-TNTs coupled with a proper band bending in PEC configuration seemed to induce a highly synergic enhancement.

SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

NASA Astrophysics Data System (ADS)

Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

2017-05-01

Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

Hydrogenated TiO2 nanotube arrays for supercapacitors.

PubMed

Lu, Xihong; Wang, Gongming; Zhai, Teng; Yu, Minghao; Gan, Jiayong; Tong, Yexiang; Li, Yat

2012-03-14

We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors. © 2012 American Chemical Society

Polyaniline as a new type of hole-transporting material to significantly increase the solar water splitting performance of BiVO4 photoanodes

NASA Astrophysics Data System (ADS)

Wang, Xiaojun; Ye, Kai-Hang; Yu, Xiang; Zhu, Jiaqian; Zhu, Yi; Zhang, Yuanming

2018-07-01

Polyaniline (PANI), with its low cost, chemical stability and high conductivity, is used as a hole transporting layer to fabricate NiOOH/PANI/BiVO4 (NPB) photoanode, of which the photoelectrochemical (PEC) water splitting performance is significantly enhanced. The remarkable water oxidation photocurrent of NPB photoanode achieves 3.31 mA cm-2 at 1.23 V vs. RHE under AM 1.5G solar light irradiation, which is greatly increased compared with that of pristine BiVO4 (0.89 mA cm-2 under the same condition). The maximal incident photon-to-current conversion efficiency achieves 83.3% at 430 nm at 1.23 V vs. RHE and the maximal applied bias photo-to-current efficiency reaches 1.20% at 0.68 V vs. RHE, which are nearly five and ten times higher than that of pristine BiVO4 photoanode, respectively. This NPB photoanode exhibits excellent stability with about 97.22% Faraday efficiency after PEC water splitting for 3 h. The exciting results demonstrate that PANI shows great potential as a hole-transporting layer for photoanode and NPB is an efficient and stable photoanode material with a great potential application in PEC water splitting. Overall, this work provides an excellent reference on designing and fabricating photoanode materials for the future.

Interface actions between TiO2 and porous diatomite on the structure and photocatalytic activity of TiO2-diatomite

NASA Astrophysics Data System (ADS)

Xia, Yue; Li, Fangfei; Jiang, Yinshan; Xia, Maosheng; Xue, Bing; Li, Yanjuan

2014-06-01

TiO2-diatomite photocatalysts were prepared by sol-gel process with various pre-modified diatomite. In order to obtain diatomite with different surface characteristics, two modification approaches including calcination and phosphoric acid treatment on the micro-structure of diatomite are introduced. The photocatalysts were characterized by XRD, XPS, nitrogen adsorption-desorption isotherms and micromorphology analysis. The results indicate that, compared with pure TiO2, the anatase-to-rutile phase transition temperature of TiO2 loaded on diatomite carrier is significantly increased to nearly 900 °C, depending on the different pretreatment method of diatomite. The photocatalytic activities of different samples were evaluated by their degradation rate of methyl orange (MO) dye under UV and visible-light irradiation. The samples prepared by phosphoric acid pretreatment method exhibit the highest photocatalytic activity. After 90 min of UV irradiation, about 90% of MO is decomposed by the best effective photocatalyst. And after 8 h visible-light irradiation, nearly 60% of MO is decomposed by the same sample. Further mechanism investigation reveals that the H3PO4 pretreatment process can obviously change the surface features of diatomite carrier, cause the formation of Si-O-Ti bond, increase the binding strength between TiO2 and diatomite, restrain crystal growth of loaded TiO2, and thus form thermal-stable mesoporous structure at the granular spaces. It helps to build micro-, meso- and macro-porous hierarchical porous structure in TiO2-diatomite, and improves the charge and mass transfer efficiency during catalyzing process, resulting in the significantly increased photocatalytic activity of TiO2-diatomite pretreated by phosphoric acid.

Beneficial effects of amino acid-functionalized graphene nanosheets incorporated in the photoanode material of dye-sensitized solar cells: A practical and theoretical study

NASA Astrophysics Data System (ADS)

Taki, Mahmood; Rezaei, Behzad; Fani, Najmeh; Borandeh, Sedigheh; Abdolmaleki, Amir; Ensafi, Ali A.

2017-05-01

In this research, covalently functionalized graphene oxide (GO) with some biocompatible amino acids were incorporated to the TiO2 film and employed as the photoanodes of dye-sensitized solar cells (DSSCs). Electrochemical analysis of the amino acids-functionalized graphene oxide (AFGs) confirmed that the attached amino acids could be acted as a reducing agent of the GO. The photovoltaic performance of the assembled DSSCs under illumination of simulated AM 1.5 sunlight (100 mW cm-2) showed an enhancement of about 4.1 and 1.8 fold for the solar cell assembled with the tyrosine-functionalized GO in relation to the control solar cells constructed with GO-TiO2 composite and blank TiO2 film, respectively. These results were in accordance with electron life time and transport time resulted from the open circuit voltage decay (OCVD), electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent spectroscopy (IMPS) analysis. The density functional theory (DFT) calculations exhibited a proper spacial arrangement for the tyrosine-GO structure that could improve electron transfer between the adjucent GO sheets. Density of electronic states (DOS) exhibited a gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels for the simulated AFG structures. This effect could facilitate the light adsorption process in near-IR region.

Thermoelectric Properties of Self Assembled TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 W/mK2 at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Targeted sonodynamic therapy using protein-modified TiO2 nanoparticles.

PubMed

Ninomiya, Kazuaki; Ogino, Chiaki; Oshima, Shuhei; Sonoke, Shiro; Kuroda, Shun-ichi; Shimizu, Nobuaki

2012-05-01

Our previous study suggested new sonodynamic therapy for cancer cells based on the delivery of titanium dioxide (TiO(2)) nanoparticles (NPs) modified with a protein specifically recognizing target cells and subsequent generation of hydroxyl radicals from TiO(2) NPs activated by external ultrasound irradiation (called TiO(2)/US treatment). The present study first examined the uptake behavior of TiO(2) NPs modified with pre-S1/S2 (model protein-recognizing hepatocytes) by HepG2 cells for 24h. It took 6h for sufficient uptake of the TiO(2) NPs by the cells. Next, the effect of the TiO(2)/US treatment on HepG2 cell growth was examined for 96 h after the 1 MHz ultrasound was irradiated (0.1 W/cm(2), 30s) to the cells which incorporated the TiO(2) NPs. Apoptosis was observed at 6h after the TiO(2)/US treatment. Although no apparent cell-injury was observed until 24h after the treatment, the viable cell concentration had deteriorated to 46% of the control at 96 h. Finally, the TiO(2)/US treatment was applied to a mouse xenograft model. The pre-S1/S2-immobilized TiO(2) (0.1mg) was directly injected into tumors, followed by 1 MHz ultrasound irradiation at 1.0 W/cm(2) for 60s. As a result of the treatment repeated five times within 13 days, tumor growth could be hampered up to 28 days compared with the control conditions. Copyright © 2011 Elsevier B.V. All rights reserved.

Thermoelectric Properties of Self Assemble TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 (mu)W/m sq K at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Photodecomposition of volatile organic compounds using TiO2 nanoparticles.

PubMed

Jwo, Ching-Song; Chang, Ho; Kao, Mu-Jnug; Lin, Chi-Hsiang

2007-06-01

This study examined the photodecomposition of volatile organic compounds (VOCs) using TiO2 catalyst fabricated by the Submerged Arc Nanoparticle Synthesis System (SANSS). TiO2 catalyst was employed to decompose volatile organic compounds and compare with Degussa-P25 TiO2 in terms of decomposition efficiency. In the electric discharge manufacturing process, a Ti bar, applied as the electrode, was melted and vaporized under high temperature. The vaporized Ti powders were then rapidly quenched under low-temperature and low-pressure conditions in deionized water, thus nucleating and forming nanocrystalline powders uniformly dispersed in the base solvent. The average diameter of the TiO2 nanoparticles was 20 nm. X-ray diffraction analysis confirmed that the nanoparticles in the deionized water were Anatase type TiO2. It was found that gaseous toluene exposed to UV irradiation produced intermediates that were even harder to decompose. After 60-min photocomposition, Degussa-P25 TiO2 reduced the concentration of gaseous toluene to 8.18% while the concentration after decomposition by SANSS TiO2 catalyst dropped to 0.35%. Under UV irradiation at 253.7 +/- 184.9 nm, TiO2 prepared by SANSS can produce strong chemical debonding energy, thus showing great efficiency, superior to that of Degussa-P25 TiO2, in decomposing gaseous toluene and its intermediates.

SiO2 and TiO2 nanoparticles synergistically trigger macrophage inflammatory responses.

PubMed

Tsugita, Misato; Morimoto, Nobuyuki; Nakayama, Masafumi

2017-04-11

Silicon dioxide (SiO 2 ) nanoparticles (NPs) and titanium dioxide (TiO 2 ) NPs are the most widely used inorganic nanomaterials. Although the individual toxicities of SiO 2 and TiO 2 NPs have been extensively studied, the combined toxicity of these NPs is much less understood. In this study, we observed unexpected and drastic activation of the caspase-1 inflammasome and production of IL-1β in mouse bone marrow-derived macrophages stimulated simultaneously with SiO 2 and TiO 2 NPs at concentrations at which these NPs individually do not cause macrophage activation. Consistent with this, marked lung inflammation was observed in mice treated intratracheally with both SiO 2 and TiO 2 NPs. In macrophages, SiO 2 NPs localized in lysosomes and TiO 2 NPs did not; while only TiO 2 NPs produced ROS, suggesting that these NPs induce distinct cellular damage leading to caspase-1 inflammasome activation. Intriguingly, dynamic light scattering measurements revealed that, although individual SiO 2 and TiO 2 NPs immediately aggregated to be micrometer size, the mixture of these NPs formed a stable and relatively monodisperse complex with a size of ~250 nm in the presence of divalent cations. Taken together, these results suggest that SiO 2 and TiO 2 NPs synergistically induce macrophage inflammatory responses and subsequent lung inflammation. Thus, we propose that it is important to assess the synergistic toxicity of various combinations of nanomaterials.

Synthesis of nanodimensional TiO2 thin films.

PubMed

Thakurdesai, Madhavi; Mohanty, T; John, J; Rao, T K Gundu; Raychaudhuri, Pratap; Bhattacharyya, V; Kanjilal, D

2008-08-01

Nanodimensional TiO2 has wide application in the field of photocatalysis, photovoltaic and photochromic devices. In present investigation TiO2 thin films deposited by pulsed laser deposition method are irradiated by 100 MeV Ag ion beam to achieve growth of nanophases. The nanostructure evolution is characterized by atomic force microscopy (AFM). The phases of TiO2 formed after irradiation are identified by glancing angle X-ray diffraction and Raman spectroscopy. The particle radius estimated by AFM varies from 10-13 nm. Anatase phase of TiO2 is formed after irradiation. The blue shift observed in UV-VIS absorption spectra indicates the nanostructure formation. The shape and size of nanoparticles formed due to high electronic excitation depend upon thickness of the film.

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

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

Petit, Sarah; Melissen, Sigismund T. A. G.; Duclaux, Loraine

We discuss here for the first time how to combine iron and titanium metal ions to achieve a high photo-electrochemical activity for TiO 2-based photo-anodes in water splitting devices. To do so, a wide range of photoelectrode materials with tailored Ti/Fe ratio and element vicinity were synthesized by using the versatility of aqueous sol–gel chemistry in combination with a microwave-assisted crystallization process. At low ferric concentrations, single phase TiO 2 anatase doped with various Fe amounts were prepared. Strikingly, at higher ferric concentrations, we observed the concomitant crystallization of two polymorphs of Fe 2TiO 5. The as-synthesized compounds were testedmore » as photoelectrode and compared with pure nanoparticles of TiO 2, Fe 2TiO 5 and α- or γ-Fe 2O 3 and with corresponding nanocomposites. When TiO 2 is slightly doped by Fe, the performance of this photo-electrode improves particularly in the low-bias region (< 1.0 V vs. reversible hydrogen electrode.) The photoanode exhibits a higher photocurrent than nanocomposite with TiO 2/Fe 2O 3 and FeTi 2O 5, and more cathodic onset potential. The former can be partly explained by a lower bandgap and a hole with a longer lifetime. For the latter, we propose that the nature of the heterojunction impacts charge carrier recombination. Here, the results presented herein not only answer whether iron and titanium should be combined in the same structure or into heterostructured systems, but also on the importance of the arrangement of ions in the structure to improve the performances of the photoanode.« less

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

DOE PAGES

Petit, Sarah; Melissen, Sigismund T. A. G.; Duclaux, Loraine; ...

2016-10-04

We discuss here for the first time how to combine iron and titanium metal ions to achieve a high photo-electrochemical activity for TiO 2-based photo-anodes in water splitting devices. To do so, a wide range of photoelectrode materials with tailored Ti/Fe ratio and element vicinity were synthesized by using the versatility of aqueous sol–gel chemistry in combination with a microwave-assisted crystallization process. At low ferric concentrations, single phase TiO 2 anatase doped with various Fe amounts were prepared. Strikingly, at higher ferric concentrations, we observed the concomitant crystallization of two polymorphs of Fe 2TiO 5. The as-synthesized compounds were testedmore » as photoelectrode and compared with pure nanoparticles of TiO 2, Fe 2TiO 5 and α- or γ-Fe 2O 3 and with corresponding nanocomposites. When TiO 2 is slightly doped by Fe, the performance of this photo-electrode improves particularly in the low-bias region (< 1.0 V vs. reversible hydrogen electrode.) The photoanode exhibits a higher photocurrent than nanocomposite with TiO 2/Fe 2O 3 and FeTi 2O 5, and more cathodic onset potential. The former can be partly explained by a lower bandgap and a hole with a longer lifetime. For the latter, we propose that the nature of the heterojunction impacts charge carrier recombination. Here, the results presented herein not only answer whether iron and titanium should be combined in the same structure or into heterostructured systems, but also on the importance of the arrangement of ions in the structure to improve the performances of the photoanode.« less

Plasmonic-resonance-based ternary composite complementary enhancement of the performance of dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Bai, Lihua; Li, Meiya; Liu, Xiaolian; Luoshan, Mengdai; Zhang, Feng; Guo, Kaimo; Zhu, Yongdan; Sun, Beilei; Zhao, Xingzhong

2016-10-01

Graphene (G), TiO2 fusiform nanorods (TiO2NRs) adsorbed with Au nanoparticles (AuNPs) are prepared and blended as multifunctional materials into TiO2 nanocrystalline film to form a novel ternary (G-TiO2NRs-Au) composite photoanode in dye-sensitized solar cells (DSSCs). The effects of G-TiO2NRs-Au on the properties of the photoanode and DSSC are investigated. Results show that, by blending G-TiO2NRs-Au, the light absorption and scattering of the photoanode are obviously improved, and the charge transfer resistance R2 and electron recombination are decreased, resulting in a significant enhancement in the short-circuit current density (J sc) and the photoelectric conversion efficiency (PCE) of the DSSCs. The maximum J sc of 17.66 mA cm-2 and PCE of 8.56% are obtained in the optimal G-TiO2NRs-Au-based DSSC, about 33.6% and 35.0% higher than that obtained in the conventional TiO2-based DSSC. This significant improvement in the performance of the DSSC can be attributed to the ternary composite complementary effects of multi-functions from the surface plasmon resonance of AuNPs, light scattering of TiO2NRs, and the improved dye loading and fast electron transmission channel from graphene. This study provides an effective way of ternary composite complementary enhancement of the J sc and PCE of the DSSCs.

Improved hydrogen storage properties of MgH2 catalyzed with TiO2

NASA Astrophysics Data System (ADS)

Jangir, Mukesh; Meena, Priyanka; Jain, I. P.

2018-05-01

In order to improve the hydrogenation properties of the MgH2, various concentration of rutile Titanium Oxide (TiO2) (X wt%= 5, 10, 15 wt %) is added to MgH2 by ball milling and the catalytic effect of TiO2 on hydriding/dehydriding properties of MgH2 has been investigated. Result shows that the TiO2 significantly reduced onset temperature of desorption. Onset temperature as low as 190 °C were observed for the MgH2-15 wt% TiO2 sample which is 60 °C and 160 °C lower than the as-milled and as-received MgH2. Fromm the Kissinger plot the activation energy of 15 wt% TiO2 added sample is calculated to be -75.48 KJ/mol. These results indicate that the hydrogenation properties of MgH2-TiO2 have been improved compared to the as-milled and as-received MgH2. Furthermore, XRD and XPS were performed to characterize the structural evolution upon milling and dehydrogenation.

Photo degradation of methyl orange by attapulgite-SnO2-TiO2 nanocomposites.

PubMed

Zhang, Lili; Lv, Fujian; Zhang, Weiguang; Li, Rongqing; Zhong, Hui; Zhao, Yijiang; Zhang, Yu; Wang, Xin

2009-11-15

Photocatalytic removal of methyl orange under ultraviolet radiation has been studied using attapulgite (ATT) composites, which were synthesized by depositing SnO(2)-TiO(2) hybrid oxides on the surface of ATT to form a composite photocatalyst (denoted ATT-SnO(2)-TiO(2)) using an in situ sol-gel technique. Results showed that SnO(2)-TiO(2) nanocomposite particles with average size of about 10nm were loaded successfully on to the surface of ATT fibers and were widely dispersed. Correspondingly, the photocatalytic activity of ATT was improved significantly by loading SnO(2)-TiO(2). The photoactivity of the composite photocatalyst decreased in the sequence ATT-SnO(2)-TiO(2)>ATT-SnO(2)>ATT-TiO(2)>ATT. In order to achieve the best photocatalyst, the molar ratio of SnO(2) and TiO(2) in the ATT-SnO(2)-TiO(2) composites was adjusted to give a series with proportions r=n(Ti)/(n(Ti)+n(Sn))=0.0, 0.25, 0.33, 0.50, 0.67, 0.75, 0.80, 0.82, 0.86, 1.0. Results indicated that the proportion of SnO(2) and TiO(2) had a critical effect on the photocatalytic activity, which increased as the content of TiO(2) increased to r0.82. The highest degradation rate of methyl orange was 99% within 30 min obtained by using ATT-SnO(2)-TiO(2) with r=0.82. The repeated use of the composite photocatalyst was also confirmed.

BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell.

PubMed

Baek, Ji Hyun; Kim, Byeong Jo; Han, Gill Sang; Hwang, Sung Won; Kim, Dong Rip; Cho, In Sun; Jung, Hyun Suk

2017-01-18

Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO 4 /WO 3 /SnO 2 triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO 2 film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO 3 deposition, leading to the formation of a double layer of dense WO 3 and a WO 3 /SnO 2 mixture at the bottom. Subsequently, a BiVO 4 nanoparticle film was deposited by spin coating. Importantly, the WO 3 /(WO 3 +SnO 2 ) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO 4 /WO 3 heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm 2 at 1.23 V vs RHE) compared to the previously reported BiVO 4 /WO 3 photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO x electrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).

TiO2-SnS2 nanocomposites: solar-active photocatalytic materials for water treatment.

PubMed

Kovacic, Marin; Kusic, Hrvoje; Fanetti, Mattia; Stangar, Urska Lavrencic; Valant, Matjaz; Dionysiou, Dionysios D; Bozic, Ana Loncaric

2017-08-01

The study is aimed at evaluating TiO 2 -SnS 2 composites as effective solar-active photocatalysts for water treatment. Two strategies for the preparation of TiO 2 -SnS 2 composites were examined: (i) in-situ chemical synthesis followed by immobilization on glass plates and (ii) binding of two components (TiO 2 and SnS 2 ) within the immobilization step. The as-prepared TiO 2 -SnS 2 composites and their sole components (TiO 2 or SnS 2 ) were inspected for composition, crystallinity, and morphology using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analyses. Diffuse reflectance spectroscopy (DRS) was used to determine band gaps of immobilized TiO 2 -SnS 2 and to establish the changes in comparison to respective sole components. The activity of immobilized TiO 2 -SnS 2 composites was tested for the removal of diclofenac (DCF) in aqueous solution under simulated solar irradiation and compared with that of single component photocatalysts. In situ chemical synthesis yielded materials of high crystallinity, while their morphology and composition strongly depended on synthesis conditions applied. TiO 2 -SnS 2 composites exhibited higher activity toward DCF removal and conversion in comparison to their sole components at acidic pH, while only in situ synthesized TiO 2 -SnS 2 composites showed higher activity at neutral pH.

Oriented epitaxial TiO2 nanowires for water splitting

NASA Astrophysics Data System (ADS)

Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

2017-06-01

Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

Photodegradation of Orange II by mesoporous TiO2.

PubMed

Kuang, Liyuan; Zhao, Yaping; Liu, Lu

2011-09-01

Mesoporous TiO(2) microspheres were prepared by a hydrothermal reaction and are characterized in this paper. Decoloration and mineralization during photodegradation of Orange II by mesoporous TiO(2) at different pH values, formation of sulfate, relative luminosity to luminous bacteria and recycling experiments of the catalyst were studied. The FTIR results further suggested that the novel mesoporous TiO(2) can not only decolor and mineralize dyes completely but also can be effectively reused several times. On the basis of the research, mesoporous TiO(2) would be a promising photocatalyst for practical use.

Metal oxide-encapsulated dye-sensitized photoanodes for dye-sensitized solar cells

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

Hupp, Joseph T.; Son, Ho-Jin

2016-01-12

Dye-sensitized semiconducting metal oxide films for photoanodes, photoanodes incorporating the films and DSCs incorporating the photoanodes are provided. Also provided are methods for making the dye sensitized semiconducting metal oxide films. The methods of making the films are based on the deposition of an encapsulating layer of a semiconducting metal oxide around the molecular anchoring groups of photosensitizing dye molecules adsorbed to a porous film of the semiconducting metal oxide. The encapsulating layer of semiconducting metal oxide is formed in such a way that it is not coated over the chromophores of the adsorbed dye molecules and, therefore, allows themore » dye molecules to remain electrochemically addressable.« less

Hierarchical TiO2/C nanocomposite monoliths with a robust scaffolding architecture, mesopore-macropore network and TiO2-C heterostructure for high-performance lithium ion batteries

NASA Astrophysics Data System (ADS)

Huang, Hai-Bo; Yang, Yue; Chen, Li-Hua; Wang, Yun; Huang, Shao-Zhuan; Tao, Jia-Wei; Ma, Xiao-Ting; Hasan, Tawfique; Li, Yu; Xu, Yan; Su, Bao-Lian

2016-05-01

Engineering hierarchical structures of electrode materials is a powerful strategy for optimizing the electrochemical performance of an anode material for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical TiO2/C nanocomposite monoliths by mediated mineralization and carbonization using bacterial cellulose (BC) as a scaffolding template as well as a carbon source. TiO2/C has a robust scaffolding architecture, a mesopore-macropore network and TiO2-C heterostructure. TiO2/C-500, obtained by calcination at 500 °C in nitrogen, contains an anatase TiO2-C heterostructure with a specific surface area of 66.5 m2 g-1. When evaluated as an anode material at 0.5 C, TiO2/C-500 exhibits a high and reversible lithium storage capacity of 188 mA h g-1, an excellent initial capacity of 283 mA h g-1, a long cycle life with a 94% coulombic efficiency preserved after 200 cycles, and a very low charge transfer resistance. The superior electrochemical performance of TiO2/C-500 is attributed to the synergistic effect of high electrical conductivity, anatase TiO2-C heterostructure, mesopore-macropore network and robust scaffolding architecture. The current material strategy affords a general approach for the design of complex inorganic nanocomposites with structural stability, and tunable and interconnected hierarchical porosity that may lead to the next generation of electrochemical supercapacitors with high energy efficiency and superior power density.Engineering hierarchical structures of electrode materials is a powerful strategy for optimizing the electrochemical performance of an anode material for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical TiO2/C nanocomposite monoliths by mediated mineralization and carbonization using bacterial cellulose (BC) as a scaffolding template as well as a carbon source. TiO2/C has a robust scaffolding architecture, a mesopore-macropore network and TiO2-C heterostructure. TiO2/C-500

First-Principles Modeling of Polaron Formation in TiO2 Polymorphs.

PubMed

Elmaslmane, A R; Watkins, M B; McKenna, K P

2018-06-21

We present a computationally efficient and predictive methodology for modeling the formation and properties of electron and hole polarons in solids. Through a nonempirical and self-consistent optimization of the fraction of Hartree-Fock exchange (α) in a hybrid functional, we ensure the generalized Koopmans' condition is satisfied and self-interaction error is minimized. The approach is applied to model polaron formation in known stable and metastable phases of TiO 2 including anatase, rutile, brookite, TiO 2 (H), TiO 2 (R), and TiO 2 (B). Electron polarons are predicted to form in rutile, TiO 2 (H), and TiO 2 (R) (with trapping energies ranging from -0.02 eV to -0.35 eV). In rutile the electron localizes on a single Ti ion, whereas in TiO 2 (H) and TiO 2 (R) the electron is distributed across two neighboring Ti sites. Hole polarons are predicted to form in anatase, brookite, TiO 2 (H), TiO 2 (R), and TiO 2 (B) (with trapping energies ranging from -0.16 eV to -0.52 eV). In anatase, brookite, and TiO 2 (B) holes localize on a single O ion, whereas in TiO 2 (H) and TiO 2 (R) holes can also be distributed across two O sites. We find that the optimized α has a degree of transferability across the phases, with α = 0.115 describing all phases well. We also note the approach yields accurate band gaps, with anatase, rutile, and brookite within six percent of experimental values. We conclude our study with a comparison of the alignment of polaron charge transition levels across the different phases. Since the approach we describe is only two to three times more expensive than a standard density functional theory calculation, it is ideally suited to model charge trapping at complex defects (such as surfaces and interfaces) in a range of materials relevant for technological applications but previously inaccessible to predictive modeling.

Ultrafine Ti4+ doped α-Fe2O3 nanorod array photoanodes with high charge separation efficiency for solar water splitting

NASA Astrophysics Data System (ADS)

Liu, Yilin; Liu, Jie; Luo, Wenjun; Wen, Xin; Liu, Xiaokang; Zou, Zhigang; Huang, Wei

2017-06-01

Hematite (α-Fe2O3) is a promising photoanode material for solar water splitting due to its suitable band gap, earth-abundance, excellent stability and non-toxicity. However, a short hole diffusion length limits its performance. A nanorod array structure can shorten hole transfer distance to photoelectrode/electrolyte interface and decrease recombination of photo-generated carriers. However, average diameters of all previously reported nanorods are over 50 nm, thus being too thick for holes to transfer to the interface. It is still a big challenge to prepare a Fe2O3 nanorod array photoelectrode with finer diameter. In this study, we prepare an ultrafine α-Fe2O3 nanorod array film with average diameter about 25 nm by calcining γ-FeOOH for the first time. The ultrafine nanorod array photoanode indicates much higher carrier separation efficiency and performance than a conventional nanorod array film.

Protecting the surface of a light absorber in a photoanode

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

Hu, Shu; Lewis, Nathan S.

A photoanode includes a passivation layer on a light absorber. The passivation layer is more resistant to corrosion than the light absorber. The photoanode includes a surface modifying layer that is location on the passivation layer such that the passivation layer is between the light absorber and the surface modifying layer. The surface modifying layer reduces a resistance of the passivation layer to conduction of holes out of the passivation layer.

High pressure synthesis of amorphous TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Li, Quanjun; Liu, Ran; Wang, Tianyi; Xu, Ke; Dong, Qing; Liu, Bo; Liu, Jing; Liu, Bingbing

2015-09-01

Amorphous TiO2 nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO2 nanotubes. The structural phase transitions of anatase TiO2 nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ˜20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO2 nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO2 phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B0 = 158 GPa) of the anatase TiO2 nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO2 nanotubes.

[Preparation and Photocatalytic Properties of Supported TiO2 Photocatalytic Material].

PubMed

Guo, Yu; Jin, Yu-jia; Wu, Hong-mei; Li, Dong-xin

2015-06-01

Titanium dioxide (TiO2) supported on spherical alumina substrate was prepared by using sol-gel method combined with dip-coating process. The surface morphology and structure of the synthesized samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) pattern. The results show that the morphology of the supported TiO2 composite material was obviously different from that of the original support. It reveals a layer formed by anatase TiO2 nanoparticles of 10-20 nm was deposited on the alumina substrate. Energy dispersive X-ray spectroscopy (EDX) analyses on the spherical alumina substrate and the resulting TiO2 composite catalyst were performed to determine the TiO2 loading content in the samples. It indicates that the TiO2 loading content on alumina substrate could be effectively increased by increasing the times of dip-coating alumina support in TiO2 sol. When dip-coating times increased to 5, the TiO2 loading content increased from 3.8 Wt. % to 15.7 Wt. %. In addition, the photocatalytic performances of the supported TiO2 materials prepared by different dip-coating times have been investigated by degrading methylene blue. It was found that the surface morphology of the supported TiO2 material was not only improved, but also the photocatalytic activity could be promoted significantly by increasing the dip-coating times. When the alumina substrate was dip-coated in TiO2 sol from 1 to 4 times, the degradation rate of methylene blue increased from 40% to 83.1%. However, after dip-coating the alumina support in TiO2 sol for 5 times, the degradation of methylene blue was only up to 85.6%. This indicates that the photocatalytic activity increased slowly when the TiO2 content in the supported catalyst was up to some extent. It is attributed to the continuous dip-coating resulted in less opportunities and weak intensity of illumination for the TiO2 nano-particles that under lower layer. The photocatalytic activity was relatively stable

Nano-engineering of p-n CuFeO2-ZnO heterojunction photoanode with improved light absorption and charge collection for photoelectrochemical water oxidation

NASA Astrophysics Data System (ADS)

Karmakar, Keshab; Sarkar, Ayan; Mandal, Kalyan; Gopal Khan, Gobinda

2017-08-01

The effective utilization of abundant visible solar light for photoelectrochemical water splitting is a green approach for energy harvesting, to reduce the enormous rise of carbon content in the atmosphere. Here, a novel efficient design strategy for p-n type nano-heterojunction photoanodes is demonstrated, with the goal of improving water splitting efficiency by growing low band gap p-CuFeO2 nanolayers on n-ZnO nanorods by an easy and scalable electrochemical route. The photoconversion efficiency of p-n CuFeO2/ZnO photoanodes is found to be ˜450% higher than that of pristine ZnO nanorod electrodes under visible solar light illumination (λ > 420 nm, intensity 10 mW cm-2). The p-n CuFeO2/ZnO nano-engineering not only boosts the visible light absorption but also resolves limitations regarding effective charge carrier separation and transportation due to interfacial band alignment. This photoanode also shows remarkably enhanced stability, where the formation of p-n nano-heterojunction enhances the easy migration of holes to the electrode/electrolyte interface, and of electrons to the counter electrode (Pt) for hydrogen generation. Therefore, this work demonstrates that p-n nano-engineering is a potential strategy to design light-harvesting electrodes for water splitting and clean energy generation.

Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications

NASA Astrophysics Data System (ADS)

Onozuka, Katsuhiro; Ding, Bin; Tsuge, Yosuke; Naka, Takayuki; Yamazaki, Michiyo; Sugi, Shinichiro; Ohno, Shingo; Yoshikawa, Masato; Shiratori, Seimei

2006-02-01

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO2 membranes as electrode materials. A thin TiO2 film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF4 aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO2 film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO2 membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO2 membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N'-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO2 film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO2 membranes. The efficiency of the fibrous TiO2 photoelectrode with the average membrane thickness of 3.9 µm has a maximum value of 4.14%.

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

PubMed

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

2012-09-26

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

Improved photoelectrical performance of graphene supported highly crystallized anatase TiO2

NASA Astrophysics Data System (ADS)

Zhang, Min; Sun, Qiong; Zhao, Mei; Li, Yang; Liu, Qiuhong; Dong, Lifeng

2015-08-01

In this study, titanium oxysulfate (TiOSO4) and graphene were used as titanium source and supporter, respectively, to synthesize anatase TiO2-graphene (TiO2-G) composite. Crystal structure, morphology, and composition of TiO2-G were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and thermogravimetric analysis. Both TiO2-G and blank TiO2 powders exhibit spindle-shaped structure with the long axis along [001]. Compared to unsupported TiO2, TiO2 nanoparticles uniformly formed on graphene surface. When fabricated into dye-sensitized solar cells, photoelectrical conversion efficiency of TiO2-G (2.3 %) was much higher than that of blank TiO2 (0.89 %) prepared at the same conditions. Moreover, high sintering temperature enhanced photoelectrical performance of the composite. When the temperature was increased from 450 to 600 °C, the efficiency was improved from 1.5 to 2.6 %. The findings above demonstrate that TiO2-G has great potential for applications in dye-sensitized solar cells.

Surface study and sensing activity of nanotubular indium trioxide to NH3, H2S, NO2 and CO environmental pollutants

NASA Astrophysics Data System (ADS)

Zamani, Mehdi

2016-02-01

Molecular and electronic structures of nanotubular indium trioxide were studied using B3LYP and CAM-B3LYP density functional methods. Three nanotube models including nanotubes with closed ends (CENT), one opened end (OOENT) and two opened ends (TOENT) were considered. The highest occupied molecular orbital (HOMO) of CENT is distributed over the entire nanotube; while it is distributed on the end cap of OOENT. In both CENT and OOENT, the distribution of the lowest unoccupied molecular orbital (LUMO) is on the end caps. HOMO and LUMO of TOENT are distributed on the center of nanotube. The sensing activity of OOENT to environmental pollutants was evaluated regarding the interaction of nanotube with NH3, H2S, NO2 and CO molecules. Adsorptions over different positions of OOENT are exothermic and the NH3 adsorption is thermodynamically more favorable. The selectivity of OOENT toward gaseous pollutants is investigated as NH3 > H2S > CO > NO2. Interaction of NO2 and CO over the closed end (end cap) of nanotube is preferred; while adsorption of NH3 and H2S on the opened end is more favorable.

The double peaks and symmetric path phenomena in the catalytic activity of Pd/Al2O3-TiO2 catalysts with different TiO2 contents

NASA Astrophysics Data System (ADS)

Zhang, Shen; Guo, Yuyu; Li, Xingying; Wu, Xu; Li, Zhe

2018-06-01

Physicochemical properties of Pd/Al2O3-TiO2 catalysts with different amounts of TiO2 contents were investigated by XRD, nitrogen adsorption-desorption, FTIR, NH3-TPD, H2-TPR and XPS techniques. Catalysts of different compositions were tested in the ethanol oxidation reaction to study the effects of TiO2 contents. Double peaks and symmetric path phenomena were observed at certain temperatures with the increase in TiO2 contents. The symmetric peak phenomena and the diverse activity fluctuations have been ascribed to the controlling factors such as temperature and compositions. With the increase in TiO2 content, the surface area, adsorbed oxygen contents and surface acid quantity decreased gradually. The large surface area and adsorbed oxygen contents were conducive to the performance, while increased acid amounts were not beneficial for ethanol oxidation. At 150 and 175 °C, Pd/AT(X1

Effect of TiO2, ZrO2, and TiO2-ZrO2 on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol

NASA Astrophysics Data System (ADS)

Xiao, Jie; Mao, Dongsen; Guo, Xiaoming; Yu, Jun

2015-05-01

The influence of TiO2, ZrO2, and TiO2-ZrO2 mixed oxide on the catalytic performance of CuO-ZnO catalyst in the methanol synthesis from CO2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N2 adsorption, XRD, reactive N2O adsorption, XPS, H2-TPR, H2-TPD, and CO2-TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO2 and H2. The results of catalytic test reveal that the additives increase both the CO2 conversion and methanol selectivity, and TiO2-ZrO2 mixed oxide is more effective than single components of TiO2 or ZrO2. Moreover, the activity of methanol synthesis is correlated directly with CO2 adsorption capacity over the catalysts.

Tandem Core–Shell Si–Ta 3N 5 Photoanodes for Photoelectrochemical Water Splitting

DOE PAGES

Narkeviciute, Ieva; Chakthranont, Pongkarn; Mackus, Adriaan J. M.; ...

2016-11-22

Here, nanostructured core–shell Si–Ta 3N 5 photoanodes were designed and synthesized to overcome charge transport limitations of Ta 3N 5 for photoelectrochemical water splitting. The core–shell devices were fabricated by atomic layer deposition of amorphous Ta 2O 5 onto nanostructured Si and subsequent nitridation to crystalline Ta 3N 5. Nanostructuring with a thin shell of Ta 3N 5 results in a 10-fold improvement in photocurrent compared to a planar device of the same thickness. In examining thickness dependence of the Ta 3N 5 shell from 10 to 70 nm, superior photocurrent and absorbed-photon-to-current efficiencies are obtained from the thinner Tamore » 3N 5 shells, indicating minority carrier diffusion lengths on the order of tens of nanometers. The fabrication of a heterostructure based on a semiconducting, n-type Si core produced a tandem photoanode with a photocurrent onset shifted to lower potentials by 200 mV. CoTiO x and NiO x water oxidation cocatalysts were deposited onto the Si–Ta 3N 5 to yield active photoanodes that with NiO x retained 50–60% of their maximum photocurrent after 24 h chronoamperometry experiments and are thus among the most stable Ta 3N 5 photoanodes reported to date.« less

Characterization of the thin layer photocatalysts TiO2 and V2O5- and Fe2O3- doped TiO2 prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Loc Luu, Cam; Nguyen, Quoc Tuan; Thoang Ho, Si; Nguyen, Tri

2013-09-01

The catalysts TiO2 and TiO2 doped with Fe and V were prepared using the sol-gel method. TiO2-modified samples were obtained in the form of a thick film on pyrex glass sticks and tubes and were used as catalysts in the gas phase photo-oxidation of p-xylene. The physico-chemical characteristics of the catalysts were determined using the methods of Brunauer-Emmett-Teller adsorption, x-ray diffraction, and infrared, ultraviolet and visible and Raman spectroscopies. The experimental results show that the introduction of V did not expand the region of light absorption, but slightly reduced the size of the TiO2 particles, and reduced the number of OH-groups, which should decrease the photocatalytic activity and efficiency of the obtained catalysts compared to those of pure TiO2. The Fe-doped TiO2 samples, in contrast, are characterized by an extension of the spectrum of photon absorption to the visible region with wavenumbers λ up to 464 nm and the values of their band gap energy decreased to lower quantities (up to 2.67 eV), therefore they should have higher catalytic activity and conversion efficiency of p-xylene in the visible region than the original sample. For these catalysts, a combined utilization of radiation by ultraviolet (λ = 365 nm) and visible (λ = 470 nm) light increased the activity and the yield in p-xylene conversion by a factor of around 2-3, as well as making these quantities more stable in comparison with those of TiO2-P25 Degussa.