Full Parametric Impedance Analysis of Photoelectrochemical Cells: Case of a TiO2 Photoanode

Abstract

Ferric oxide (α-Fe 2 O 3 , hematite) is an n-type semiconductor; due to its narrow band gap (E g = 2.1 eV), it is a highly attractive and desirable material for use in solar hydrogenation by water oxidation. However, the actual conversion efficiency achieved with Fe 2 O 3 is considerably lower than the theoretical values because the considerably short diffusion length (2-4 nm) of holes in Fe 2 O 3 induces excessive charge recombination and low absorption. This is a significant hurdle that must be overcome in order to obtain high solar-to-hydrogen conversion efficiency. In consideration of this, it is thought that elemental doping, which may make it possible to enhance the charge transfer at the interface, will have a marked effect in terms of improving the photoactivities of α-Fe 2 O 3 photoanodes. Herein, we report on the synthesis by pulsed electrodeposition of α-Fe 2 O 3 -based anodes; we also report on the resulting photoelectrochemical (PEC) properties. We attempted Ti-doping to enhance the PEC properties of α-Fe 2 O 3 anodes. It is revealed that the photocurrent density of a bare α-Fe 2 O 3 anode can be dramatically changed by controlling the condition of the electrodeposition and the concentration of TiCl 3 . Under optimum conditions, a modified α-Fe 2 O 3 anode exhibits a maximum photocurrent density of 0.4 mA/cm 2 at 1.23 V vs. reversible hydrogen electrode (RHE) under 1.5 G simulated sunlight illumination;this photocurrent density value is about 3 times greater than that of unmodified α-Fe 2 O 3 anodes.

Mechanistic Investigation with Kinetic Parameters on Water Oxidation Catalyzed by Manganese Oxide Nanoparticle Film

“…Additionally, β and γ are dispersion parameters with values between 0 and 1. The H–N function was originally devised to describe dielectric relaxation in organic materials. Subsequently, the H–N function was also applied to understand various dispersive phenomena in electrochemical processes in semiconductors, such as the Mott–Schottky response in TiO 2 photoanodes and current-constriction effects in the grain boundaries of polycrystalline Na 3 Sc 2 (PO 4 ) 2 . , The H–N function is also appropriate to demonstrate complicated electrochemical circumstances at the interface between the p-MnO NPs film and the electrolyte. At applying a potential, the interface was polarized by electrolyte ions and surface-charged intermediates.…”

In situ magnesiothermic reduction synthesis of a Ge@C composite for high-performance lithium-ion batterie anodes

“…Compared to the pure Ge electrode, the diameters of the semicircle are smaller in the Ge@C electrodes because of the higher electrical conductivity of the additional carbon matrix, indicating the decrease in charge transfer resistance of the composite electrodes. The EIS results were fitted using an equivalent circuit model, including an internal or electrolyte resistance ( R e ), a charge transfer resistance ( R ct ), and two constant phase elements (CPE) [ 65 ]. According to Table 2 , the charge transfer resistances of all Ge@C electrodes are much lower than the values of the pure Ge electrode, and Ge/C-iM750 exhibits the lowest value.…”

Mechanistic Understanding of Improved Performance of Graphene Cathode Inverted Organic Light-Emitting Diodes by Photoemission and Impedance Spectroscopy

“…On the other hand, the Havriliak–Negami model can represent the well-defined limiting capacitance of a physical significance, which is indeed experimentally observed, without the introduction of the resistance parameter. Recently, a parallel combination of the Havriliak–Negami capacitance functions has been shown to be a far superior description of the ac behavior of polycrystalline solid electrolytes with grain boundary blocking effects against the conventional R-CPE parallel circuit models. − …”