共查询到20条相似文献,搜索用时 734 毫秒
1.
Yu‐Shiuan Wang Ting‐Ting_ Chen Yi‐Jen Huang Tzu‐Ping Huang Yin‐Yu Lee Hsin‐Tien Chiu Chi‐Young Lee 《中国化学会会志》2013,60(12):1437-1441
In dye‐sensitized solar cells (DSSCs), the charge recombination at the TiO2/dye/electrolyte interface greatly influences the photoelectron conversion efficiency. Hybrid semiconductor materials with matched band potentials are designed to reduce the charge recombination. In this study, SrTiO3/TiO2 hybridstructure was synthesized by using TiO2 nanoparticles as template in a hydrothermal, showing a negative shift in the flat band potential. The DSSC with the SrTiO3/TiO2 anode exhibits an increased photovoltage and a reduced photocurrent. The suppression of charge recombination at the TiO2/dye/electrolyte interface was observed in the electrochemical impedance spectroscopy, causing an improvement in the photovoltage. However, the SrTiO3/TiO2 system shows an obstructed electrons injection from the dye to SrTiO3/TiO2, limiting the photocurrent performance. The photoelectrochemical properties of the SrTiO3/TiO2 system are discussed in detail herein. 相似文献
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The mechanism by which the adsorbent guanidinium affects the open-circuit photovoltage of dye-sensitized TiO2 nanocrystalline solar cells was investigated. The influence of the guanidinium cation on the rate of recombination and band-edge movement was measured by transient photovoltage. When guanidinium is present in the electrolyte recombination becomes slower by a factor of about 20. At the same time, the adsorbent causes the band edges to move downward, toward positive electrochemical potentials, by 100 mV. The collective effect of both a downward shift of the band edges and slower recombination, owing to the presence of guanidinium, results in an overall improvement in the open-circuit photovoltage. 相似文献
4.
Mott-Schottky capacitance measurements are used to locate semiconductor band edges for a short-circuited p-type/n-type α-Fe2O3 assembly in aqueous solution. The thermodynamic feasibility of the catalytic photodiscussion of water without external bias is verified for this assembly from an energy level diagram obtained for the electrode/electrolyte interfaces. Photocurrent stability and Auger analysis of the electrode show no evidence of electrode dissolution. Oxygen evolution is monitored from an assembly using mass spectrometry and H218O enriched water. 相似文献
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Hematite has been considered as one of the most promising photoanode candidates for solar water‐splitting. However, its photoelectrochemical (PEC) efficiency is largely constrained by its sluggish oxygen evolution reaction. In this work, the photoelectrochemical performance of hematite was investigated in electrolytes containing different sacrificial agent. The photocurrent densities, onset potential, charge transfer resistance, Helmholtz capacitance at semiconductor liquid junctions (SCLJs), and their correlations were systematically studied. It was found that the onset potential is around the CH peak potential and is related to the photovoltage. The surface states pinning the Fermi levels of the hematite photoanode are related to the adsorbed water molecules regardless of the sacrificial agents in the electrolyte. 相似文献
6.
M. D. Krotova Yu. V. Pleskov A. A. Khomich V. G. Ralchenko D. N. Sovyk V. A. Kazakov 《Russian Journal of Electrochemistry》2014,50(2):101-107
The semiconductor properties of nitrogenated nanocrystalline diamond electrodes and their corrosion transformations caused by electrochemical experiment in indifferent electrolyte (1 M K2SO4) were studied by the electrochemical impedance spectroscopy method. It was shown that after electrochemical measurements a narrow diamond peak at 1335.7 cm?1 appears in the Raman spectrum; formerly the peak was hidden at a background of the intense signal inherent to graphite-like carbon. It was suggested that the corrosion damage caused by the exposure to electrochemical experiment resulted in a decrease of relative amount of nondiamond (graphite-like) carbon in the subsurface layer in the nanocrystalline diamond. By using Mott-Schottky plots, the nanocrystalline diamond was shown having n-type conductance. Within the bounds of the “effective medium” approach, the nanocrystalline diamond’s flat-band potential in aqueous solution and the noncompensated donor apparent concentration were estimated. 相似文献
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The semiconductor properties of the interface TiO2/electrolyte in high organized porous oxide structures were analyzed by means of impedance spectroscopy near the flat band
potential. The impedance and capacitance studies performed on the as-anodized and thermally treated samples (anatase) indicate
the presence of a duplex structure formed by (1) the oxide at the bottom of the pores and (2) the walls of pores with different
donor densities and surface state concentrations. 相似文献
9.
Alexander S. Bondarenko Genady A. Ragoisha 《Journal of Solid State Electrochemistry》2005,9(12):845-849
Potentiodynamic electrochemical impedance spectroscopy provides extraction of potential-dependent space charge layer capacitance
from potentiodynamic impedance spectra of non-stationary semiconductor–electrolyte interface. The new technique has been applied
for acquisition of Mott-Schottky plots of cathodically treated TiO2 anodic films. Cathodic treatment in 1 M H2SO4 increases donor density and flat band potential of TiO2. Freshly doped films show hysteresis in the space charge layer capacitance in cyclic potential scans. The subsequent cycling
eliminates the hysteresis but preserves the greater part of the doping effect.
Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16 March 2005 相似文献
10.
Camacho-Alanis F Castaneda H Zangari G Swami NS 《Langmuir : the ACS journal of surfaces and colloids》2011,27(18):11273-11277
Modifications to the space charge region of p+ and p-GaAs due to surface charge modulation by the pH-induced deprotonation of bound carboxylic acid terminal monolayers were studied by electrochemical impedance spectroscopy and correlated to flat-band potential measurements from Mott-Schottky plots. We infer that the negative surface dipole formed on GaAs due to monolayer deprotonation causes an enhancement of the downward interfacial band bending. The space charge layer modifications were correlated to intermolecular electrostatic interactions and semiconductor depletion characteristics. 相似文献
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共吸附剂修饰纳晶TiO2薄膜电极是目前染料敏化太阳电池研究的一个热点. 本文通过平带电势和电化学阻抗研究了二(3,3-二甲基丁基)次膦酸和鹅脱氧胆酸两种共吸附剂修饰对TiO2薄膜电极的平带电势和电极表面钝化能力的影响及其在染料敏化太阳电池中的应用. 结果表明, 二(3,3-二甲基丁基)次膦酸能更有效地钝化TiO2薄膜表面, 并使TiO2薄膜平带电势负移. 电化学阻抗谱测试结果表明, 在染料敏化太阳电池中, 相对于鹅脱氧胆酸, 二(3,3-二甲基丁基)次膦酸能更显著地提高器件的电子寿命和开路电压. 相似文献
12.
Louis Nadjo 《Journal of Electroanalytical Chemistry》1980,108(1):29-47
The electrochemical and photoelectrochemical behaviours of nCdTe and pCdTe singlecrystal semiconductors are investigated in acetonitrile solutions containing tetrabutylammonium tetrafluoroborate and various electroactive compounds, i.e. anthracene, phthalonitrile, nitromesitylene, 9-fluorenone, nitrobenzene, metatertiobutylnitrobenzene, benzoquinone and ferricenium tetrafluoroborate. The cyclic voltammograms at the semiconductor electrodes in the dark and illuminated with red light are compared to the Nernstian behaviour at a platinum disk electrode. The flat-band potential is estimated by using the photocurrent onset potential under continuous irradiation and Schottky-Mott plots. Consistent results have been obtained by these two methods. The usual band model is shown to predict roughly the observed behaviour of n- and pCdTe except for the cases where the presence of invisible films or surface states after polishing, and/or etching and/or the first reduction or oxidation voltammetric scan modifies the expected results. These surface modifications are capable of mediating electron transfer and explain the extension of photo effects far negative of the conduction band edge, using a 1.40-eV photon. 相似文献
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Bogdan Tzvetkov Martin Bojinov Assen Girginov 《Journal of Solid State Electrochemistry》2009,13(8):1215-1226
The influence of hydrofluoric acid (HF) concentration and applied potential on the processes of anodic oxidation of Nb in
sulphuric acid solution was studied by chronoamperometry, electrochemical impedance spectroscopy and scanning electron microscopy.
During the first stage of the process, a compact barrier film is formed. On top of this film, a porous overlayer starts to
form, then the nanopores grow into an ordered nanostructure. Subsequently, secondary 3D flower-shaped structures begin to
form. These structures gradually spread all over the surface as an irregular multilayer film. The rates of the process of
porous overlayer formation and subsequent growth of nanopore arrays increase with applied potential as well as with the HF
concentration. The films have been characterised ex situ by electrochemical impedance spectroscopy at open circuit potential
and capacitance vs. potential measurements to follow the different stages of nanoporous film formation with electrochemical
methods. The impedance spectra and capacitance vs. potential curves have been interpreted using previously proposed models
for the amorphous semiconductor/electrolyte interface. An attempt to rationalise the mechanism of nanoporous layer growth
is presented by using the conceptual views of the mixed-conduction model and recent ideas for porous film formation on valve
metals. 相似文献
14.
Harmonic Analysis of Pulsed Photovoltaic Response of Titanium Dioxide Films under Local Illumination
A change in the photoelectrochemical behavior of a semiconductor–electrolyte system after transition from overall to local illumination of the electrode surface is studied. The proposed model accounts for charge interactions between illuminated and dark electrode portions and describes the frequency spectrum of photopotential for an electrode locally illuminated by a periodic sequence of light pulses a few nanoseconds in length. As shown with polycrystalline thin-film TiO2electrodes, local values of concentrations of ionized donors and flat-band potentials of semiconductor electrodes may be determined with a harmonic analysis of frequency spectra of photovoltaic responses. The possibility of using the proposed approach in photoelectrochemical microscopy is discussed. 相似文献
15.
Electrochemical characteristics for the nanoporous carbon|Et4NBF4+acetonitrile interface have been studied by cyclic voltammetry and impedance spectroscopy methods. The influence of the electrolyte concentration and thickness of the nanoporous electrode material on the shape of the cyclic voltammetry and impedance curves has been established and the reasons for these phenomena are discussed. A value of zero charge potential, depending slightly on the structure and concentration of the electrolyte, the region of ideal polarizability and other characteristics have been established. The nanoporous nature of the carbon electrodes introduces a distribution of resistive and capacitive elements, giving rise to complicated electrochemical behaviour. Analysis of the complex plane plots shows that the nanoporous carbon|Et4NBF4+acetonitrile electrolyte interface can be simulated by an equivalent circuit, in which two parallel conduction paths in the solid and liquid phases are interconnected by the double-layer capacitance in parallel with the complex admittance of the hindered reaction of the charge transfer or of the partial charge transfer (i.e. adsorption stage limited) process. The values of the characteristic frequency depend on the electrolyte concentration and electrode potential, i.e. on the nature of the ions adsorbed at the surface of the nanoporous carbon electrode. The value of the solid state phase resistance established is independent of the thickness of the electrode material. 相似文献
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Transient photovoltage and photocurrent measurements have been employed to determine the recombination and transport kinetics in operating dye-sensitized photovoltaic cells as a function of potential and temperature. Photocurrent transients have been taken at the open circuit potential, as opposed to the standard measurement at short circuit. Kinetic results have been used to calculate the activation energy as function of the Fermi level position in the TiO(2). In the calculation of activation energies, we have explicitly taken into account the temperature dependence of the offset between the electrolyte redox potential and the conduction band edge. This new method gives activation energies that decrease linearly as the Fermi level position moves toward the conduction band edge, as expected, but not found in previous studies. The results are consistent with the presence of a distribution of traps below the TiO(2) conduction band, the detrapping from which limits both the transport and the recombination of electrons. 相似文献
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The position of electronic energy levels in a phase depends on the surface potentials at its boundaries. Bringing two phases in contact at an interface will alter the surface potentials shifting the energy levels relative to each other. Calculating such shifts for electrochemical interfaces requires a combination of methods from computational surface science and physical chemistry. The problem is closely related to the computation of potentials of electrochemically inactive electrodes. These so-called ideally polarizable interfaces are impossible to cross for electrons. In this perspective we review two density functional theory based methods that have been developed for this purpose, the workfunction method and the hydrogen insertion method. The key expressions of the two methods are derived from the formal theory of absolute electrode potentials. As an illustration of the workfunction method we review the computation of the potential of zero charge of the Pt(111)-water interface as recently published by a number of groups. The example of the hydrogen insertion method is from our own work on the rutile TiO(2)(110)-water interface at the point of zero proton charge. The calculations are summarized in level diagrams aligning the electronic energy levels of the solid electrode (Fermi level of the metal, valence band maximum and conduction band minimum of the semiconductor) to the band edges of liquid water and the standard potential for the reduction of the hydroxyl radical. All potentials are calculated at the same level of density functional theory using the standard hydrogen electrode as common energy reference. Comparison to experiment identifies the treatment of the valence band of water as a potentially dangerous source of error for application to electrocatalysis and photocatalysis. 相似文献
19.
A. G. Krivenko N. S. Komarova L. N. Sviridova E. V. Stenina 《Russian Journal of Electrochemistry》2009,45(9):1064-1071
The effect of camphor adsorption on the differential capacitance of electrodes of nanostructured carbon of different morphology
(single-walled carbon nanotubes, filiform carbon, and columnar structures) in aqueous electrolyte solutions and also on the
electrochemical reactions in these systems is studied. It is shown that irrespective of the ac frequency, the differential
capacitance of the nanopaper and columnar electrodes increases 3–5-fold throughout the studied potential range. This experimental
fact is explained by the substantial increase in the electrode surface accessible for electrolyte, which is a manifestation
of the Rehbinder effect in electrochemistry. The revealed different kinds of effects of camphor adsorption layers formed at
the nanostructured carbon/electrolyte interface on the electron transfer processes are as follows: partial inhibition of both
the electron injection and the K3[Fe(CN)6] reduction; complete suppression of the reduction of sodium nitrate and nitrite; the absence of effects on the OH radical
reduction and solvated electron oxidation. 相似文献
20.
Souteyrand E Chen C Cloarec JP Nesme X Simonet P Navarro I Martin JR 《Applied biochemistry and biotechnology》2000,89(2-3):195-207
The principles of the electrochemical and optoelectrochemical impedance measurements on bare electrolyte/dielectric/semiconductor structures are described. The analysis of the experimental curves allows access to several indications concerning the electrical behavior of such structures. The application of these techniques to follow the electrical behavior of structures modified with two biological systems was investigated. The antibody/antigen recognition did not change the surface charge and, therefore, did not affect the impedance curves with respect to the applied potential. By contrast, the hybridization of two complementary DNA strands on the surface of the structure induced a variation of flat band potential of the semiconductor leading to a shift of impedance curves along the potential axis. This means that it is possible to detect directly the DNA hybridization without the use of labeled probes. The use of light allows the surface to be probed locally. In the future, the application of this technique for direct detection of hybridization on DNA chips should be possible. 相似文献