Photocatalytic Activity of (Ga1-xZnx)(N1-xOx) for Visible-Light-Driven H2 and O2 Evolution in the Presence of Sacrificial Reagents

Abstract

The photocatalytic activity of (Ga1-xZnx)(N1-xOx), a solid solution of GaN and ZnO, for H2 and O2 evolution in the presence of methanol and silver nitrate as sacrificial reagents under visible light (λ > 420 nm) is investigated in detail. (Ga1-xZnx)(N1-xOx) evolves H2 from an aqueous methanol solution when loaded with nanoparticulate Rh2-yCryO3 as a cocatalyst, and evolves O2 from an aqueous silver nitrate solution without a cocatalyst. Structural analyses indicate that the H2 evolution activity is strongly dependent on the crystallinity and composition of the catalyst, while the rate of O2 evolution is proportionally related to the specific surface area. The activity for H2 evolution from methanol solution is of the same order as for overall water splitting, but is an order of magnitude lower than that for O2 evolution from silver nitrate solution. The results of photocatalytic reactions and photoelectrochemical measurements suggest that the rate-determining step for overall water splitting using (Ga1-xZnx)(N1-xOx) is the H2 evolution process.