Charge Transfer at Photoelectrochemical Solar Cells: Conclusions from the Open‐Circuit Impedance of p ‐ InP in  V 3 +  / 2 +

Abstract

Two resistance-capacitance (RC! time constants are detectable in the open-circuit impedance of illuminated (bare and Ag-treated) p-InP in contact with V 3/2+ + HC1 solution. The dependence of the time constants on illumination intensity and concentration of V 3+ and V 2 § is used to identify processes related to recombination and electrochemical charge transfer, respectively. Charge transfer (CT) rates at metal-treated electrodes [p-InP(Ag)] turn out to be somewhat smaller than at metallic Ag electrodes. For 0.3M V 3 §247 CT at p-InP(Ag) is sufficiently fast for solar cell operation under solar irradiation intensities (exchange current density io = 40 mA cm-e). CT at bare p-InP is much slower (io = 0.2 to 2 mAcm 2). Impedance data are fitted with two transformable equivalent circuits (differential models) which both yield similar values for recombination and CT elements. Thereby charging/discharging processes at the interface can be attributed either to a charging/ discharging of the differential Helmholtz capacity Cm~ or an interfacial defect capacity. Measured values for either element -~ -2 are equal or smaller than the CHH value of bulk metal electrodes [about 2 to 20 ~F cm " at pInP(Ag), < i ~F cm at bare p-InP].

Investigation of the Kinetics of a TiO2 Photoelectrocatalytic Reaction Involving Charge Transfer and Recombination through Surface States by Electrochemical Impedance Spectroscopy

“…As predicted by the theoretical analysis or model simulation results, the increased with increasing the applied potential bias as indicated in Figure while the arc diameter decreased, which is agreement with the previous reports. − …”

“…By contrast, electrochemical impedance spectroscopy (EIS) can also be used to obtain the electrode process occurring at illuminated SEI without such a limitation. In fact, by using EIS various equivalent circuit and mathematical models have been proposed to describe the PEC reactions at the illuminated SEI. − Surprisingly, little work has been reported on the investigation of the PEC degradation reaction of organic at the TiO 2 /electrolyte solution interfaces by EIS except for Liu's 25 and our reports . Recently, Liu et al have found only one arc on the EIS plane display that had a smaller size corresponding to a faster degradation of sulfosalicylic acid.…”

“…This treatment is not popular. In fact, many models for the lowly doped semiconductor electrodes supposed that the capacitance of the semiconductor side of the interface was much smaller than that of the Helmholtz layer and most applied potential dropped in the depletion layer. , Moreover, that time-dependent accumulation of surface charge at the surface may affect, in turn, the redistribution of potential over the depletion and Helmholtz layer and couple to the interfacial kinetics, while this effect is not taken into account for the most of PEC reactions at the semiconductor electrode including TiO 2 . In addition, during the early stages of the studies of semiconductor surface processes, the presence of surface states at the interface is commonly believed to be important in dictating the charge-transfer process. 12a,− For example, to account for a high current efficiency (almost 100%) for O 2 evolution during photoelectrolysis of water, a contribution of surface states in charge transfer has been proposed 12g.…”

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

“…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].…”

Investigating the Consistency of Models for Water Splitting Systems by Light and Voltage Modulated Techniques

“…The general EC corresponding to IS, IMPS, and IMVS can be obtained from the analytical models described above, and it is shown in Figure c. We remark that C μ cb has been replaced by a more general capacitance, the outer capacitance of the conduction band C out cb , which accounts for displacement currents such as charging of the Helmholtz layer, typically described as a capacitor C H . It can be noted that light modulation introduces a current source to the classical EC obtained with IS, which arises from the generation term in eq and .…”