共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Trenczek-Zajac M. Radecka A. Brudnik S. Bourgeois L. Imhoff 《Journal of power sources》2009,194(1):93-103
Incorporation of oxygen into TiN lattice results in formation of titanium oxynitrides, TiOxNy that have become particularly interesting for photocatalytic applications. Elaboration as well as characterization of TiN and in situ oxygen-doped thin films is the subject of this paper. Thin films, 250-320 nm in thickness, have been deposited by dc-pulsed magnetron reactive sputtering from Ti target under controllable gas flows of Ar, N2 and O2. Optical monitoring of Ti plasma emission line at λ = 500 nm has been implemented in order to stabilize the sputtering rate. Scanning electron microscopy (SEM), X-ray diffraction in grazing incidence (GIXRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), optical spectrophotometry and four-point probe electrical resistivity measurements have been performed in order to follow evolution of film physical parameters as a function of the oxygen flow rate ηO2 at which the films were deposited. The relationship between ηO2 expressed in standard cubic centimetres per minute, sccm and the nitrogen/oxygen content in thin films has been established by means of the analysis of the XPS spectra. GIXRD studies indicate that incorporation of oxygen results in a progressive loss of preferential orientation in 〈1 1 1〉 direction, a change in the grain size from 16 nm for TiN to about 3 nm for films deposited at ηO2=1.32 sccm and a decrease in the lattice constant. A systematic shift of all X-ray diffraction (XRD) lines towards higher diffraction angles is consistent with substitution of oxygen for nitrogen. Micro-Raman investigations indicate amorphisation of thin films upon oxidation. Binding energies determined from fitting of the XPS results concerning the N1s and Ti2p lines give evidence of the presence of TiOxNy compound. Red-shift of the plasma reflectance edge upon TiN oxidation is correlated with a decreased carrier concentration. Metal-semiconductor transition can be expected on the basis of the electrical conductivity decrease and development of the fundamental absorption across the forbidden band of TiO2 upon increase in the oxygen flow rate. Additional absorption feature in the visible range, being a consequence of coexistence of free-electron and interband absorption within almost the same spectral range (λ = 400-600 nm) seems to be very promising for photocatalytic applications of titanium oxynitride thin films. 相似文献
2.
Carbon black and titanium dioxide supported iron tetraphenylporphyrin (FeTPP/TiO2/C) catalysts for oxygen reduction reaction (ORR) were prepared by sol-gel and precipitation methods followed by a heat-treatment at temperatures of 400-1000 °C. The FeTPP/C and TiO2/C were also studied for comparison. The FeTPP/TiO2/C pyrolyzed at 700 °C exhibits significantly improved stability while maintaining high activity towards ORR in comparison with the FeTPP/C counterpart. The electrochemical study combined with XRD, XPS, and SEM/EDX analyses revealed that the appropriate dispersion of TiO2 on the surface of FeTPP/TiO2/C catalysts, which depending on heat-treatment temperature, plays a crucial role in determining the activity and stability of catalysts. 相似文献
3.
Cubic titanium dioxide photoanode for dye-sensitized solar cells 总被引:1,自引:0,他引:1
Jinho ChaeMisook Kang 《Journal of power sources》2011,196(8):4143-4151
Following from the recently evolved concept of significantly improving the photovoltaic efficiency in dye-sensitized solar cells (DSSCs) by reducing the loss of electrons on the spherical surface of titanium dioxide, this study examines the synthesis of cubic TiO2 with a special morphology to overcome this electron loss and investigates its application to DSSCs. Cubic TiO2 is synthesized by an advanced rapid hydrothermal method, with the addition of an amine species additive. Transmission electron microscopy (TEM) images confirm the cubic shape of the TiO2 particles with a diameter less than 5-10 nm. Using N719 dye under illumination with 100 mW cm−2 simulated sunlight, the application of cubic TiO2 to DSSCs affords an energy conversion efficiency of approximately 9.77% (4.0-μm thick TiO2 film), which is considerably enhanced compared with that achieved using a commercial, spherical TiO2. Electrostatic force microscopy (EFM) and impedance analyses reveal that the electrons are transferred more rapidly to the surface of a cubic TiO2 film than on a spherical TiO2 film. 相似文献
4.
Influence of Cr on structural and optical properties of TiO2:Cr nanopowders prepared by flame spray synthesis 总被引:1,自引:0,他引:1
A. Trenczek-Zajac M. Jasinski M. Rekas K. Zakrzewska A. Heel K. Kowalski 《Journal of power sources》2009,194(1):104-111
Influence of chromium incorporation on structural and optical properties of titanium dioxide nanopowders obtained by flame spray synthesis, FSS is studied by means of: X-ray diffraction, XRD; Raman spectroscopy; transmission electron spectroscopy, TEM; photoelectron spectroscopy, XPS and optical spectrophotometry over the ultraviolet, UV and visible range of the light spectrum from 250 nm to 2200 nm. The specific surface area, SSA, of the powders has been adjusted from 48 m2/g for TiO2 + 0.1at.% Cr to 177 m2/g for TiO2 + 15 at.% Cr which is accompanied by a decrease in the anatase grain size from 21 nm to 5 nm. The anatase-to-rutile ratio changes with Cr3+ concentration but there is no evidence of precipitation of chromium oxides or chromium titanates. Incorporation of Cr3+ into TiO2 lattice, as proved by XPS, is found to affect the electronic structure of TiO2, as indicated by the optical spectrophotometry. The impurity band is formed within the forbidden band gap of titanium dioxide which results in the additional absorption within the visible range of the light spectrum. The general aim of this work is to improve the visible light absorption and hence the efficiency of photocatalytic decomposition of organic contaminants. 相似文献
5.
This research coats a commercial TiO2 nanoparticle Degussa P25 with good roundness and size uniformity on an indium tin oxide (ITO) glass substrate and to be photoelectrical electrode by electrophoresis deposition. It combined with dye N719, electrolyte I-/ and counter-electrode of Pt layer to produce dye-sensitized solar cells (DSSCs). Through the electrophoretic technique, a multilayer film of an appropriate thickness is deposited in the suspension containing TiO2 nanoparticles and isopropanol. In this process, electric current, voltage, and the number of deposition cycles are well controlled to obtain a single TiO2 film of around 3.3 μm thick. Stacking is then performed to obtain a multilayer-typed TiO2 film of around 12 μm thick. As the sintering temperature reaches 400 °C, the prepared multilayer TiO2 film with a good compactness can increase the dye adsorption capability of the thin film and enhance its adsorption percentage. In addition, the heat treatment will transfer a portion of the rutile crystalline into the anatase crystalline, resulting in better material properties for DSSCs application. DSSCs produced are exposed to metal halide lamp and their energy conversion efficiency is measured. The I-V curve of the produced DSSCs shows that it has an excellent energy conversion efficiency of 6.9%. 相似文献
6.
M. Gustavsson H. Ekström P. Hanarp L. Eurenius G. Lindbergh E. Olsson B. Kasemo 《Journal of power sources》2007
Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3–6 μg cm−2). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nafion increases the performance compared to a Pt film deposited directly on Nafion. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nafion and in addition, substantial proton conduction through the thin TiO2 layer. It is also shown that deposition order and the film thickness affects the performance. 相似文献
7.
Sreenivasan Koliyat Parayil Harrison S. Kibombo Chia-Ming Wu Rui Peng Jonas Baltrusaitis Ranjit T. Koodali 《International Journal of Hydrogen Energy》2012
We report a green and facile approach for the preparation of carbon-modified (C-modified) TiO2 composite materials by hydrothermal synthesis followed by pyrolytic treatment. The resultant materials were characterized by powder X-ray diffraction (XRD), nitrogen physisorption studies, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). The photocatalytic performances of these materials were evaluated by calculating the amount of hydrogen evolved from the decomposition of water under solar simulated irradiation conditions. An improvement was achieved from no H2 evolution at all with the bare TiO2, to an evolution of 0.21 mL g−1 h−1 from a composite material modified with an optimum carbon loading of 3.62%. These results suggested that the interaction of carbon with predominantly rutile form of TiO2 can promote shallow trapping of photogenerated electrons in the oxygen vacancies. This phenomenon consequently enhances the photocatalytic activity by minimizing charge carrier recombination, a characteristic demonstrated by fluorescence quenching of the TiO2 emission. 相似文献
8.
Kun-Mu Lee Wei-Hao Chiu Yung-Liang Tung Kuo-Chuan Ho 《Solar Energy Materials & Solar Cells》2009,93(11):2003-2007
The ionic conductivities and performances of dye-sensitized solar cells (DSSCs) of gel polymer electrolytes (GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent ((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO2 electrode not only reduced dye aggregation, but also reacted with the cross-linkers in the GPE at the TiO2/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of JSC significantly increased from 7.72 to 10.00 mA cm−2. In addition, in order to reduce the ionic diffusion resistance within the TiO2 electrode, incorporation of monodispersed PMMA in the TiO2 paste was considered. With the optimal weight ratio of PMMA/TiO2 (w/w=3.75), the TiO2 electrode exhibited larger pores (ca. 350 nm) uniformly distributed after sintering at 500 °C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100 mW cm−2, an improvement of ca. 55%. 相似文献
9.
Iron oxide n-Fe2O3 nanowire photoelectrodes were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, Jp. The optimized electric oven-made n-Fe2O3 nanowire photoelectrodes showed photocurrent densities of 1.46 mA cm−2 at measured potential of 0.1 V/SCE at illumination intensity of 100 mW cm−2 from a Solar simulator with a global AM 1.5 filter. For the optimized carbon modified (CM)-n-TiO2 synthesized by thermal flame oxidation the photocurrent density for water splitting was found to increase by two fold to 3.0 mA cm−2 measured at the same measured potential and the illumination intensity. The carbon modified (CM)-n-Fe2O3 electrode showed a shift of the open circuit potential by −100 mV/SCE compared to undoped n-Fe2O3 nanowires. A maximum photoconversion efficiency of 2.3% at applied potential of 0.5 V/Eaoc was found for CM-n-Fe2O3 compared to 1.69% for n-Fe2O3 nanowires at higher applied potential of 0.7 V/Eaoc. These CM-n- Fe2O3 and n- Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). 相似文献
10.
The Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) cathode for solid oxide fuel cell has been prepared by glycine–nitrate combustion process. Crystal structure and chemical state of BSCF have been studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD pattern indicates that a single cubic perovskite phase of BSCF oxide is successfully obtained after calcination at 850 °C for 2 h. XPS results show there exists a little amount of SrCO3 in the surface of BSCF. Co2p spectra indicate that some Co3+ ions have changed into Co4+ ions to maintain the electrical neutrality. O1s spectra present that adsorbed oxygen species appear in the surface BSCF oxide. 相似文献
11.
Zhenbiao Dong Yiqiang Cai Ke Zhang Zhong Chu Sheng Han Zhenyu Li 《International Journal of Hydrogen Energy》2021,46(5):3554-3564
Self-doping of oxygen vacancies (VO) states into TiO2-based nanotubes was an efficient way for improving photoelectrochemical (PEC) water splitting properties. Here we induced oxygen vacancies into Si-doped TiO2 (Ti–Si–O) nanotubes on Ti–Si alloy via a facile electrochemical surface reduction, and applied it for PEC water splitting. Systematic studies revealed that the self-doped oxygen vacancies not only promoted optical absorption of the doped nanotubes but also enhanced separation-transport processes of the photo-generated charge carriers, and thus resulted in improved PEC water splitting properties. The VO/Ti–Si–O co-doping system exhibited a higher photocurrent density of 1.63 mA/cm2 at 0 V vs. Ag/AgCl. Corresponding solar-to-hydrogen efficiency could reach 0.81%, which was about 5.4 times that of undoped TiO2. It's believed that elements doping and oxygen vacancies self-doping synergistic strategy employed in this work, may provide theoretical and practical significance for designing and fabricating efficient TiO2-based nanostructures photoanodes in PEC water splitting for boosted solar-to-hydrogen conversion. 相似文献
12.
In this paper, novel TiO2 submicro-rings were synthesized via potentiostatic anodization of titanium powder coated on transparent conducting oxide glass. The TiO2 submicro-rings film was characterized by SEM, XPS and 3D optical profiling. Accordingly, a possible growth mechanism of submicro-rings was discussed. The TiO2 submicro-rings based dye-sensitized solar cell (DSSC) with the film thickness of ca. 3.1 μm was assembled and a conversion efficiency of 1.36% was achieved under AM 1.5 illumination. The photoelectron transport properties of TiO2 submicro-rings based DSSC were also discussed according to the electron impedance spectroscopy. 相似文献
13.
Hirokazu Kitaura Akitoshi HayashiKiyoharu Tadanaga Masahiro Tatsumisago 《Journal of power sources》2009
The all-solid-state Li–In/Li4Ti5O12 cell using the 80Li2S·20P2S5 (mol%) solid electrolyte was assembled to investigate rate performances. It was difficult to obtain the stable performance at the charge current density of 3.8 mA cm−2 in the all-solid-state cell. In order to improve the rate performance, the pulverized Li4Ti5O12 particles were applied to the all-solid-state cell, which retained the reversible capacity of about 90 mAh g−1 at 3.8 mA cm−2. The 70Li2S·27P2S5·3P2O5 glass–ceramic, which exhibits the higher lithium ion conductivity than the 80Li2S·20P2S5 solid electrolyte, was also used. The Li–In/70Li2S·27P2S5·3P2O5 glass–ceramic/pulverized Li4Ti5O12 cell was charged at a current density higher than 3.8 mA cm−2 and showed the reversible capacity of about 30 mAh g−1 even at 10 mA cm−2 at room temperature. 相似文献
14.
A dense and crack-free La0.9Sr0.1Ga0.8Mg0.2O3 − δ thin film has been prepared by RF magnetron sputtering. The XRD, FESEM, XPS and four-probe technique are employed to characterize the La0.9Sr0.1Ga0.8Mg0.2O3 − δ film. Results show that after annealing at 1000 °C, the La0.9Sr0.1Ga0.8Mg0.2O3 − δ film presents a polycrystalline perovskite structure with grain size of 100–300 nm. XPS data show that both La and Ga are in their +3 state. Sr element has two chemical states which are related to Sr2+ in the perovskite lattice and SrO1 − δ suboxide. The O 1s spectrum also shows two chemical states which can be assigned to molecularly adsorbed O2 species and O2− in the lattice. The electrical conductivity reaches to 0.093 S cm−1 at 800 °C. The microstructure and conductivity analysis indicates that the La0.9Sr0.1Ga0.8Mg0.2O3 − δ thin film prepared by RF magnetron sputtering is suitable for intermediate temperature Solid oxide fuel cell. 相似文献
15.
Jang-Hee YoonDong-Min Kim Sang-Su YoonMi-Sook Won Yoon-Bo Shim 《Journal of power sources》2011,196(20):8874-8880
Conductive polymer precursors, including carboxylic acid, cyano groups, amino groups, 5,2′:5′,2″-terthiophene-3′-carboxylic acid (TTCA), 3′-cyano-5,2′:5′,2″-terthiophene (CTT), and 3′,4′-diamino-2,2′:5′,2″-terthiophene (DATT) are synthesized. Electrochemically polymerized films of the precursors on a nanocrystalline TiO2 layer are examined as photo sensitizers, and the cell performance is compared. The photovoltaic cells are assembled with a polymer-coated TiO2 layer treated with TiCl4 as an anode and a Pt layer as a cathode in a propionitrile solution containing an iodide ion-based redox electrolyte. The charge-transfer processes of polymer-dyed cells are studied using impedance spectroscopy. The polymer dyes on the TiO2 surfaces are characterized by scanning electron microscope (SEM), atomic force microscope (AFM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). XPS results show that the conducting polymer dye, bearing a carboxylic acid group, is more strongly bound to the TiO2 layer in comparison with other groups. Various experimental parameters affecting the cell efficiency are optimized, including the scan rate, number of potential cycles, and terthiophene monomer concentration. Of these polymers, the best cell efficiency is attained for poly-TTCA containing a carboxylic acid group. The optimized cell with the poly-TTCA dye shows a short-circuit current of 6.78 mA cm−2, an open-circuit voltage of 0.54 V, and a fill factor of 63.6. An energy conversion efficiency of 2.32% is obtained with a cell area of 0.24 cm2 under an air mass 1.5 solar simulated light irradiation of 100 mW cm−2. 相似文献
16.
Perovskite structure Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) powders have been successfully synthesized by glycine–nitrate combustion process. A porous and crack-free BSCF cathode is obtained by spraying the slurry of BSCF powders and terpineol onto LSGM pellet. The oxygen reduction reaction mechanism has been investigated by AC impedance spectroscopy and cyclic voltammetry method. AC impedance spectroscopy analysis shows that there are two different processes in the cathode reaction which are related to oxygen dissociation/adsorption and bulk oxygen diffusion. And the molecular oxygen is involved in the rate-determining step. The polarization resistance decreases with an increase of temperature and the oxygen partial pressure. With an increase of the applied DC bias, the logarithm of the polarization resistance decreases linearly due to additional oxygen vacancies and the lowered chemical potential of oxygen at the BSCF/LSGM interface by the applied voltage. The exchange current density reaches to 182 mA cm−2 at 700 °C, suggesting that the ORR kinetics at the BSCF/LSGM interface is high due to the excellent mixed ionic and electronic conductivity of BSCF. 相似文献
17.
Xiao-Jian Guo Yi-Xiao LiMin Zheng Jian-Ming ZhengJie Li Zheng-Liang GongYong Yang 《Journal of power sources》2008
A series of cathode materials with molecular notation of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li1/3Mn2/3]O2·0.4Li[Ni1/3Mn1/3Co1/3]O2 (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g−1 between 2.0 and 4.8 V at 18 mA g−1. 相似文献
18.
《International Journal of Hydrogen Energy》2022,47(90):38219-38228
Generating oxygen vacancies is an effective way to improve photoelectrochemical (PEC) water splitting performance of semiconductor materials owing to the formation of shallow donor level and the supply of additional electron donor. Herein, oxygen vacancies were introduced into In2O3 nanorods by a hydrothermal reduction method using NaBH4 solution as the reductant, and the effects of hydrothermal reduction time on the oxygen vacancy concentration, optoelectronic property and PEC water splitting activity over In2O3 nanorods were systematically investigated. The results of LSV, EIS and MS showed that the reduced samples displayed superior PEC performance and In2O3-x-1 exhibited a highest photocurrent density of 0.97 mA cm?2 at 1.23 V vs. RHE under the irradiation of visible light, which was roughly 4 times of bare In2O3. The remarkable performance of In2O3-x-1 is mainly ascribed to the introduction of oxygen vacancies, which leads to better light absorption capacity, higher carrier concentration, and increased electron transport efficiency at the electrode/electrolyte interface. 相似文献
19.
《International Journal of Hydrogen Energy》2019,44(42):23775-23783
Spinel-type nickel cobaltite with numerous oxygen vacancies is successfully synthesized by hydrothermal and thermal reduction using hydrogen. The effects of oxygen vacancies on the electrochemical activity and stability for the oxygen reduction reaction are investigated. The prepared catalyst displays significantly enhanced oxygen reduction reaction (ORR) catalytic performance under alkaline conditions, which is comparable to that of commercial Pt/C. The oxygen-deficient NiCo2O4 exhibits a very high limiting current density of −5.44 mA cm−2 with onset and half-wave potentials of 0.93 and 0.78 V versus the reversible hydrogen electrode (RHE), respectively. Additionally, it shows excellent durability and resistance to methanol. The enhanced ORR activity and stability of the catalyst can be ascribed to the synergistic effects of the relatively large electrochemical surface area, more exposed active sites, and good electrical conductivity derived from abundant oxygen vacancies. 相似文献
20.
The amorphous citrate precursor method was employed to prepare perovskite of La0.6Ca0.4Co0.8Ir0.2O3 as a bi-functional electrocatalyst for oxygen reduction and evolution in an alkaline electrolyte. The X-ray diffraction pattern of the as-synthesized powders exhibited a majority phase identical to that of La0.6Ca0.4CoO3, indicating successful incorporation of Ir4+ at the Co cation sites. Scanning Electron Microscope images demonstrated a foam-like microstructure with a surface area of 13.31 m2 g−1. For electrochemical characterization, the La0.6Ca0.4Co0.8Ir0.2O3 particles were supported on carbon nanocapsules (CNCs) and deposited on commercially available gas diffusion electrodes with a loading of 2.4 mg cm−2. In current–potential polarizations, La0.6Ca0.4Co0.8Ir0.2O3/CNCs revealed more enhanced bi-functional catalytic abilities than La0.6Ca0.4CoO3/CNCs. Similar behaviors were observed in galvanostatic profiles for oxygen reduction and evolution at current densities of 50 and 100 mA cm−2 for 10 min. Moreover, notable changes from zeta potential measurements were recorded for La0.6Ca0.4Co0.8Ir0.2O3 relative to La0.6Ca0.4CoO3. In lifetime determinations, where a repeated 3 h sequence of oxygen reduction/resting/oxygen evolution/resting was imposed, La0.6Ca0.4Co0.8Ir0.2O3/CNCs delivered a stable and sustainable behavior with moderate degradation. 相似文献