The mechanism of current-doubling reactions at ZnO photoanodes

Abstract

The mechanism of photocurrent-doubling reactions at ZnO single-crystal electrodes in aqueous formate, tartrate and methanol solutions has been reinvestigated. On the basis of steady-state photocurrent measurements in a wide range of light intensity it is concluded that, in the case of formate and tartrate, the electron-injecting species arises from a reaction between the current-doubling agent and oxygen, formed in the photoanodic decomposition of ZnO. This is not the case for methanol. These conclusions are supported by the results of electrical impedance and intensity-modulated photocurrent spectroscopy measurements.