A model for the current-voltage curve of photoexcited semiconductor electrodes

Abstract

A model to describe the behavior of photoexcited electrodes in an electrochemical cell is developed. In addition to the bulk semiconductor properties, the important parameters are a surface recombination parameter Sr and a surface electron transfer parameter St. It is the electron transfer process across the interface that leads to current in the external circuit. Using experimental curves for oxygen evolution at an n-type TiO2 electrode and Hall-Shockley-Read recombination to determine Sr, it is shown that the I-V curve in anodic bias is controlled by the competition between Sr and St. The physical basis for St is discussed and experimental approaches to investigate surface reactions are suggested.