Suppression of surface recombination on TiO2 anatase photocatalysts in aqueous solutions containing alcohol

Intensity-modulated photocurrent spectroscopy (IMPS) was applied to studyin g the mechanism of photoelectrochemical decomposition of a model organic co mpound, ethanol, on a TiO2 anatase photoelectrode in aqueous solution. The frequency spectra of the intensity-modulated photocurrents observed on the TiO2 photoelectrode at low band bending were drastically changed in the pre sence of alcohol. Without the alcohol, the frequency dependence of the modu lated photocurrents were similar to those reported previously for TiO2 elec trodes and were typical for the case of surface recombination occurring on surface states, while upon addition of alcohol the photocurrent frequency d ependence was no longer observed. This fact suggests that alcohol suppresse s the recombination processes at the surface of the TiO2 photoelectrode. Po ssible mechanisms for this phenomenon are discussed. The results demonstrat e that IMPS is a powerful tool for studying the mechanism of photocatalytic decomposition of organic pollutants on semiconductor electrodes.