Time-Resolved Spectroscopy of ZnTe Photocathodes for Solar Fuel Production

Abstract

The negative conduction band potential and small bandgap of ZnTe make the material a promising photoelectrode for solar fuels production, photocatalyst, and solar cell component. However, the factors controlling the underlying efficiencies of the light-driven processes on ZnTe are not well understood. Here we report a combined spectroelectrochemical and transient absorption (TA) spectroscopic investigation of ZnTe photoelectrodes for CO2 reduction. In the visible region TA spectra are dominated by a broad positive photoinduced absorption at 540 nm following initial charge carrier relaxation (1150 nm. Shallow trapped electrons are generated and accumulate at potentials where photoelectrochemical H2 evolution and CO2 reduction occur, and we show these charges are able to undergo interfacial electron transfer to an acceptor molecule. The passivation of sites related to deep traps is proposed to be the key to optimize the photocatalytic and photoelectrochemical performance of ZnTe