Water Splitting and CO₂ Reduction under Visible Light Irradiation Using Z-Scheme Systems Consisting of Metal Sulfides, CoOx-Loaded BiVO₄, and a Reduced Graphene Oxide Electron Mediator

Metal sulfides are highly active photocatalysts for water reduction to form H₂ under visible light irradiation, whereas they are unfavorable for water oxidation to form O₂ because of severe self-photooxidation (i.e., photocorrosion). Construction of a Z-scheme system is a useful strategy to split water into H₂ and O₂ using such photocorrosive metal sulfides because the photogenerated holes in metal sulfides are efficiently transported away. Here, we demonstrate powdered Z-schematic water splitting under visible light and simulated sunlight irradiation by combining metal sulfides as an H₂-evolving photocatalyst, reduced graphene oxide (RGO) as an electron mediator, and a visible-light-driven BiVO₄ as an O₂-evolving photocatalyst. This Z-schematic photocatalyst composite is also active in CO₂ reduction using water as the sole electron donor under visible light.