Z-Schematic Solar Water Splitting Using Fine Particles of H2-Evolving (CuGa)0.5ZnS2 Photocatalyst Prepared by a Flux Method with Chloride Salts

We successfully improved a (CuGa)(0.5)ZnS2 metal sulfide photocatalyst by preparation in a molten LiCl-CsCl flux for sacrificial H-2 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)(0.5)ZnS2 as the H-2-evolving photocatalyst drastically affected the Z-schematic water splitting activity driven by interparticle electron transfer with RGO-(CoOx/BiVO4) as an O-2-evolving photocatalyst. When the (CuGa)(0.5)ZnS2 photocatalyst with a small particle size was used, the Zschematic water splitting was enhanced by an increase in the collision frequency between Pt/(CuGa)(0.5)ZnS2 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 H-2 and O-2.