Utilization of Metal Sulfide Material of (CuGa)_1–<i>x</i>Zn_2<i>x</i>S₂ Solid Solution with Visible Light Response in Photocatalytic and Photoelectrochemical Solar Water Splitting Systems

Upon forming a solid solution between CuGaS₂ and ZnS, we have successfully developed a highly active (CuGa)_1–<i>x</i>Zn_2<i>x</i>S₂ photocatalyst for H₂ evolution in the presence of sacrificial reagents under visible light irradiation. The Ru-loaded (CuGa)_0.8Zn_0.4S₂ functioned as a H₂-evolving photocatalyst in a Z-scheme system with BiVO₄ of an O₂-evolving photocatalyst and Co complexes of an electron mediator. The Z-scheme system split water into H₂ and O₂ under visible light and simulated sunlight irradiation. The (CuGa)_1–<i>x</i>Zn_2<i>x</i>S₂ possessed a p-type semiconductor character. The photoelectrochemical cell with a Ru-loaded (CuGa)_0.5ZnS₂ photocathode and a CoO_<i>x</i>-modified BiVO₄ photoanode split water even without applying an external bias. Thus, we successfully demonstrated that the metal sulfide material group can be available for Z-scheme and electrochemical systems to achieve solar water splitting into H₂ and O₂