The effect of the electrolyte redox potential on photoelectrochemical properties of bismuth oxoiodide

Abstract

Photoelectrochemical behavior of semiconductor bismuth oxoiodide BiOI in solutions containing [Fe(CN)₆]^3-/[Fe(CN)₆]^4-or I₃^-/I^- redox system has been studied. The effect of photocurrent sign inversion with the electrode potential change has been observed. It has been shown that this effect is governed by both thermodynamic conditions (shifting of the conduction band position and equilibrium potential E_Ox/Red) and by kinetic factor (the capture rate of photogenerated charged particles by oxidizing or reducing agents). Photoelectrochemical reactions are diffusion-controlled, and photocurrent is a function of the surface concentrations of oxidized and reduced forms of the redox system. Specific structure of BiOI coating consisting of thin plate-like crystallites (40-60 nm thick) provides good contact of its surface with the reaction medium and high efficiency of photoinduced processes.