Photoelectrochemistry with the Rotating Optical Disk Ring Electrode: III . Thermal and Photoinduced Electron Transfer in Colloidal

Abstract

The rotating optical disk ring electrode (RODRE) has been successfully applied to study interfacial charge transfer phenomena in colloidal TiO2 particles. In this electrode, light enters the cell through a transparent quartz disk and photogenerated species are detected at a metal (Pt) ring surrounding the transparent disk. Measurement of dark currents as a function of rotation speed allows calculation of the heterogeneous electron transfer rate constant and the average number of conduction‐band electrons per particle. Illumination of the RODRE provides, from the dependence of the photocurrent on light intensity and rotation speed, an estimate of the stability of photogenerated conduction‐band electrons, the quantum yield of photoelectron generation, and the photoelectron lifetime. The results reported clearly illustrate that the RODRE is a useful and convenient technique for studying charge transfer phenomena in colloidal suspensions of semiconductor particles. The advantage of the disk ring technique (RODRE) over the alternative disk electrode technique (ORDE) is that, for the RODRE, there is no need to use any coating material to make the ring electrode conducting, while, for the ORDE, a semitransparent layer of normaln‐SnO2 is applied to make the transparent surface conducting. The nature of this coat imposes limitations in the kind of semiconductor materials that can be studied.