Rational catalyst design for spatial separation of charge carriers in a multi-component photocatalyst for effective hydrogen evolution

Since direct solar energy conversion is considered to be crucial for the development of a sustainable society, photocatalytic hydrogen evolution has been extensively studied during the past few years. Despite the recent progress in solar-driven hydrogen evolution, photoactivity is still limited due to fast recombination of charge carriers and scaled production is hard to proceed with. The rational design of photocatalysts with spatially separated charge carriers has been shown to be one of the promising strategies for better photocatalyst charge separation efficiency. The spatial separation of photoinduced electrons and holes, as well as the rapid migration of electrons from the bulk to the reaction surface, results in suppressed charge recombination, prolongs the lifetime of photogenerated charges and blocks the backward reaction. In this review, the basic concepts of photocatalytic hydrogen production with heterojunction systems are introduced. Then, the rational designs of heterojunction photocatalyst systems to enable spatially separated reaction sites are summarized and categorized based on their dimensions and architectures. Finally, the outlook and research directions are discussed towards the set target of solar to hydrogen conversion efficiency and industrial production.