Development of Visible Light Responsive Photocatalysts for Solar Hydrogen Production

Abstract

Photocatalytic water splitting using semiconductor materials has attracted considerable interest due to its potential for clean production of H₂ from water by utilizing abundant solar light. We have developed a new type of photocatalysis system that can split water into H₂ and O₂ under visible light irradiation, which was inspired by the two-step photoexcitation (Z-scheme) mechanism of natural photosynthesis in green plants. The introduction of a Z-scheme mechanism with appropriate redox couples reduces the energy required to drive each photocatalysis process, extending the usable wavelengths significantly from that in conventional water splitting systems. The key in constructing such Z-scheme systems is to clarify and utilize the reactivities of redox couples based on their adsorption onto the photocatalyst surfaces, on which photogenerated carriers (electrons and holes) react with the redox couples.