Semiconductor based photoelectrochemical cells for solar energy conversion—An overview

Phys. Chem. Chem. Phys.

Formal

et al. 2014

174

134

The electrochemical behavior of α-Fe2O3 photoelectrodes prepared by spray pyrolysis with different thicknesses was examined under dark and illumination conditions. The main charge transport phenomena occurring in the PEC cell photoelectrodes were characterized by electrochemical impedance spectroscopy (EIS) operating under dark conditions. The impedance spectra were fitted to an equivalent electrical circuit model for obtaining relevant information concerning reaction kinetics and charge transfer phenomena occurring at the semiconductor/electrolyte interface. A three-electrode configuration was used to carry out the electrochemical measurements allowing a detailed study concerning the double charged layer at the semiconductor/electrolyte interface that arises under dark conditions. The model parameters determined by EIS were then related with film thickness to assess the role of electronic conduction on the performance of the cell. Moreover, correlating the samples thickness differences with their electrochemical impedance spectroscopy response, it was possible to discriminate the two main phenomena occurring on semiconductor/electrolyte interfaces of photoelectrochemical systems under dark conditions: the space charge layer and the electrical double layer.

Section: 25mentioning

confidence: 99%

Hematite photoelectrodes for water splitting: evaluation of the role of film thickness by impedance spectroscopy

Phys. Chem. Chem. Phys.

Formal

et al. 2014

174

134

“…This effect is enhanced by the decrease of the bandgap at higher temperatures -Equation (1). Mass transport is also favored by an increased temperature as stated by the Einstein relation: [36] kT D μ q  B ii (3) where q is the elementary charge and µi is the mobility of species i.…”

Section: Theorymentioning

confidence: 99%

“…[1][2][3] An attractive strategy to turn over the actual energy problem is the use of solar radiation, the most abundant and sustainable renewable energy source. The variability of sunlight conditions arising from the night hours or the atmospheric and seasonal changes is one of the main challenges for the extensive use of energy from the Sun.…”

Section: Introductionmentioning

confidence: 99%

Temperature effect on water splitting using a Si-doped hematite photoanode

Dias

Journal of Power Sources

et al. 2014

The influence of temperature on the performance of a photoelectrochemical (PEC) cell prepared with Si-doped hematite photoanode was studied for water splitting. The cell performance was characterized by photocurrent-voltage (J-V) characteristic curves and electrochemical impedance spectroscopy at different cell operating temperatures, from 25 ºC to 65 ºC. A standard three-electrode configuration comprehending the photoelectrode of hematite, the counterelectrode of pure platinum wire (99.9 %) and the reference electrode of Ag/AgCl/Sat.KCl was used. The identification of possible degradation pathways was addressed. It was observed that the generated photocurrent-density 2 increased with temperature. However, the photoelectrode became unstable above 50 ºC. The experiments performed concerning the study of the temperature effect and the aging showed that the optimal operation temperature of the PEC cell is ca. 45 ºC; this temperature ensures simultaneously the highest photocurrent-density and stability. This study is important for understanding the behavior of hematite photoelectrodes operating under real outdoor conditions.

“…This layer is also denoted as depletion layer since the region is depleted of majority charge carriers. Additionally, a charged layer appears on the electrolyte interface side, consisting of charged ions adsorbed on the solid electrode surface e Helmholtz layer [28,29]. Under illumination, photons with energy higher than the semiconductor band gap are absorbed, originating electron-hole pairs or excitons.…”

Section: Electrochemical Impedance Measurementsmentioning

confidence: 99%

“…However, part of these photons may be absorbed in the depletion layer, where the separation of the electron-hole pairs occurs by means of the influence of electric fields. As a consequence, the semiconductor Fermilevel shifts toward its flat-band potential and the Fermi level returns toward its original position before the semiconductoreelectrolyte junction was established [29].…”

Section: Electrochemical Impedance Measurementsmentioning

confidence: 99%

Characterization of photoelectrochemical cells for water splitting by electrochemical impedance spectroscopy

International Journal of Hydrogen Energy

Ribeiro

et al. 2010

258

164

a b s t r a c tThe photocurrent-voltage characteristic of a photoelectrochemical cell for solar hydrogen production via water splitting, using undoped-hematite as photoanode, was obtained.Photoelectrochemical characteristics of the cell were also investigated by electrochemical impedance spectroscopy. Both techniques were carried out in the dark and under illumination. The analysis of the frequency spectra for the real and imaginary parts of the complex impedance allowed obtaining equivalent electrical analogs for the PEC cell operating in the dark and under 1 sun simulated illumination. Additionally, different electrode configurations were used (two and three-electrode arrangements). The twoelectrode configuration allowed the study of the overall charge transfer phenomena occurring at the semiconductor, within the electrolyte and at the counter-electrode side of the cell, whereas the three-electrode configuration gave more detailed information concerning the double charged layer at the semiconductor/electrolyte interface.