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Arutyunyan, V. M.; Arakelyan, V. M.; Shakhnazaryan, G. E.; Stepanyan, G. M.; Turner, John A.; Khaselev, O.

doi:10.1023/a:1015383703991

Cited by 10 publications

(12 citation statements)

References 3 publications

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“…Moreover, a second region at lower frequencies is present. The assignment of this region to a transport process related with diffusion of the products and/or the charge carriers in the semiconductor − was discarded because diffusion processes emerge in EIS as straight lines with a slope of 45° (usually they are represented as Warburg elements in equivalent circuits). In this case, the angle is comprised between 40 and 60°, and it changes with the applied potential.…”

Section: Resultsmentioning

confidence: 99%

Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Díez‐García

Gómez

2016

ACS Appl. Mater. Interfaces

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Artificial photosynthesis constitutes one of the most promising alternatives for harvesting solar energy in the form of fuels, such as hydrogen. Among the different devices that could be developed to achieve efficient water photosplitting, tandem photoelectrochemical cells show more flexibility and offer high theoretical conversion efficiency. The development of these cells depends on finding efficient and stable photoanodes and, particularly, photocathodes, which requires having reliable information on the mechanism of charge transfer at the semiconductor/solution interface. In this context, this work deals with the preparation of thin film calcium ferrite electrodes and their photoelectrochemical characterization for hydrogen generation by means of electrochemical impedance spectroscopy (EIS). A fully theoretical model that includes elementary steps for electron transfer to the electrolyte and surface recombination with photogenerated holes is presented. The model also takes into account the complexity of the semiconductor/solution interface by including the capacitances of the space charge region, the surface states and the Helmholtz layer (as a constant phase element). After illustrating the predicted Nyquist plots in a general manner, the experimental results for calcium ferrite electrodes at different applied potentials and under different illumination intensities are fitted to the model. The excellent agreement between the model and the experimental results is illustrated by the simultaneous fit of both Nyquist and Bode plots. The concordance between both theory and experiments allows us to conclude that a direct transfer of electrons from the conduction band to water prevails for hydrogen photogeneration on calcium ferrite electrodes and that most of the carrier recombination occurs in the material bulk. In more general vein, this study illustrates how the use of EIS may provide important clues about the behavior of photoelectrodes and the main strategies for their improvement.

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Section: Resultsmentioning

confidence: 99%

Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Díez‐García

Gómez

2016

ACS Appl. Mater. Interfaces

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“…In the first case, for example, difficulties in finding an adequate theoretical explanation for the frequency dependences were observed. In the second case, the difficulties lie in finding an equivalent circuit whose impedance is the closest to the one measured experimentally [9][10][11][12][13].…”

Section: Resultsmentioning

confidence: 99%

Investigations of the structure of the iron oxide semiconductor–electrolyte interface

Aroutiounian

Arakelyan

Shahnazaryan

et al. 2005

Comptes Rendus. Chimie

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“…A number of studies have been carried out on the photoanodic properties of α-Fe 2 O 3 in wet-type solar cells since α-Fe 2 O 3 has a relatively small band gap of 2.2 eV and photoelectrochemical stability in aqueous solutions. − α-Fe 2 O 3 has, however, small optical absorption coefficient and carrier mobility, both of which are disadvantages for photoanodic properties. , Improvements of absorption coefficient and carrier mobility would lead to an increase in quantum efficiency and energy conversion efficiency. Increasing the carrier mobility, however, would be difficult because the minority carrier diffusion length is small at 2−4 nm in α-Fe 2 O 3 3 due to the hopping mechanism .…”

Section: Introductionmentioning

confidence: 99%

“…Increasing the carrier mobility, however, would be difficult because the minority carrier diffusion length is small at 2−4 nm in α-Fe 2 O 3 3 due to the hopping mechanism . An increase in carrier concentration has been attempted by doping α-Fe 2 O 3 with various metal cations, − which often introduce energy traps, however, leading to reduced carrier mobility.…”

Section: Introductionmentioning

confidence: 99%

Photoanodic Properties of Sol−Gel-Derived Fe₂O₃ Thin Films Containing Dispersed Gold and Silver Particles

2003

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α-Fe2O3 films containing dispersed Au and Ag particles 5−20 nm in size were prepared on nesa silica glass substrates by the sol−gel method, using solutions of a mole ratio Fe(NO3)3·9H2O: (HAuCl4·4H2O or AgNO3):CH3COCH2COCH3:CH3OCH2CH2OH = 1:0.06:2:20 as the coating solution. The anodic photocurrent−potential characteristics and the action spectra were investigated in a three-electrode cell employing the film electrode as the working electrode. When the film electrode was illuminated with intense white light, the embedded metal particles did not affect the photoanodic properties of the electrode significantly. When the film electrode was illuminated with weak white light or weak monochromatic light, the metal particles, especially Au particles, enhanced the anodic photocurrent; the Au particles embedded in the electrode enhanced the quantum efficiency, IPCE, by about 8 times at a wavelength of 400 nm. Deposition of Au particles just on the surface of the Fe2O3 film also increased the photoanodic current, suggesting that the enhanced photocurrent is provided by the Au particles on the electrode surface, which are supposed to catalytically promote the transfer of the hole in the conduction band of Fe2O3 to the electrolyte.

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Untitled

Cited by 10 publications

References 3 publications

Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Investigations of the structure of the iron oxide semiconductor–electrolyte interface

Photoanodic Properties of Sol−Gel-Derived Fe₂O₃ Thin Films Containing Dispersed Gold and Silver Particles

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Untitled

Cited by 10 publications

References 3 publications

Investigating Water Splitting with CaFe2O4 Photocathodes by Electrochemical Impedance Spectroscopy

Investigating Water Splitting with CaFe2O4 Photocathodes by Electrochemical Impedance Spectroscopy

Investigations of the structure of the iron oxide semiconductor–electrolyte interface

Photoanodic Properties of Sol−Gel-Derived Fe2O3 Thin Films Containing Dispersed Gold and Silver Particles

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Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Investigating Water Splitting with CaFe₂O₄ Photocathodes by Electrochemical Impedance Spectroscopy

Photoanodic Properties of Sol−Gel-Derived Fe₂O₃ Thin Films Containing Dispersed Gold and Silver Particles