Cation-Doped SrTaO2N Prepared through a Flux Method for Visible-Light-Driven Water Splitting

Abstract

Semiconductor photocatalysts for water splitting is considered one of the most promising technologies for solar energy conversion. SrTaO2N has a band gap of 2.1 eV and is a candidate for achieving visible-light-driven water splitting. However, its poor charge separation efficiency limits its water splitting efficiency, which can be attributed to the charge recombination induced by reduced Ta4+ sites, which act as recombination centers. This study focuses on the improvement of photocatalytic activity of SrTaO2N by introducing foreign metal cations with a low oxidation state to suppress the formation of reduced Ta4+ sites. Among the investigated samples, 1.0 mol % Ga3+-doped SrTaO2N was found to improve the photocatalytic activity significantly. X-ray photoelectron spectroscopy (XPS) data show that the formation of Ta4+ species is suppressed after Ga doping, which might be responsible for the photocatalytic activity improvement of SrTaO2N.