Semiconductor-cocatalyst interfacial electron transfer in actual photocatalytic reaction

Abstract

ABSTRACT

Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction. However, the formed potential barriers severely slow this interfacial electronic process by thermionic emission. Although trap-assisted charge recombination can transfer electrons from semiconductor to cocatalyst and can even be evident under weak illumination, the parallel connection with thermionic emission makes the photocatalytic photon utilization encounter a minimum along the variation of light intensity. By this cognition, the light-intensity-dependent photocatalytic behaviors can be predicted by simulating the photoinduced semiconductor-cocatalyst interfacial electron transfer that mainly determines the reaction rate. We then propose a (photo)electrochemical method to evaluate the time constants for occurring this interfacial electronic process in actual photocatalytic reaction without relying on extremely high photon flux that is required to generate discernible optical signal in common instrumental methods based on ultrafast pulse laser. The evaluated decisecond-second timescale can accurately guide us to develop certain strategies to facilitate this rate-determining step to improve photon utilization.