Z-Schematic Solar Water Splitting Using Fine Particles of H<sub>2</sub>-Evolving (CuGa)<sub>0.5</sub>ZnS<sub>2</sub> Photocatalyst Prepared by a Flux Method with Chloride Salts
Shunya Yoshino, Akihide Iwase, Yun Hau Ng, Rose Amal, Akihiko Kudo
Abstract
We successfully improved a (CuGa)0.5ZnS2 metal sulfide photocatalyst by preparation in a molten LiCl–CsCl flux for sacrificial H2 evolution compared to the counterpart prepared by a solid-state reaction. The particle size of the metal sulfide was controlled by changing the synthetic temperature of the flux method. The particle size of (CuGa)0.5ZnS2 as the H2-evolving photocatalyst drastically affected the Z-schematic water splitting activity driven by interparticle electron transfer with RGO-(CoOx/BiVO4) as an O2-evolving photocatalyst. When the (CuGa)0.5ZnS2 photocatalyst with a small particle size was used, the Z-schematic water splitting was enhanced by an increase in the collision frequency between Pt/(CuGa)0.5ZnS2 and RGO-(CoOx/BiVO4) particles for accelerating the interparticle electron transfer. This Z-scheme photocatalyst system gave an apparent quantum yield (AQY) of 0.80% at 440 nm and a solar-to-hydrogen conversion efficiency (STH) of 0.024% for water splitting into H2 and O2.