Recent advances in inorganic oxide semiconductor-based S-scheme heterojunctions for photocatalytic hydrogen evolution

Abstract

In recent years, inorganic oxide semiconductors have received vast attention as photocatalysts for hydrogen (H₂) evolution. However, poor H₂ evolution activity and rapid recombination of the photoexcited charge carriers confine their practical applications. To address these constraints of pure inorganic oxide semiconductor photocatalysts, the creation of S-scheme heterojunctions has emerged as a promising alternative, which efficiently enhances optical absorption, promotes efficient charge separation, and retains relatively strong redox potential compared to traditional heterojunctions. Herein, we overview the fundamentals of some representative inorganic oxide semiconductor (tungsten oxide, titanium oxide, zinc oxide, and copper oxide)-based step (S)-scheme heterostructures, including their preparation strategies, photocatalytic H₂ performance, and charge transfer mechanisms. This review covers recent developments in the formation of these heterostructures via different synthesis strategies that modulate electronic band alignments to enhance H₂ evolution. This review also comprehensively highlights the essential role of S-scheme charge transport mechanism in promoting the migration and separation of photoinduced electron–hole (e⁻/h⁺) pairs, which in turn improves the H₂ evolution activity. Additionally, the future prospects are discussed, which provide guidance for designing efficient inorganic oxide semiconductor-based photocatalysts and the development of sustainable H₂ generation technologies.