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

Abstract

In recent years, inorganic oxide semiconductors received vast attention as photocatalysts for hydrogen (H2) evolution. However, poor H2 evolution activity and the rapid recombination of photoexcited charge carriers confine their practical applications. To address these constraints of pure inorganic oxide semiconductor photocatalysts, the creation of S-scheme heterojunctions emerged as a promising alternative, which efficiently enhances optical absorption, promotes efficient charge separation, and retain relatively strong redox potentials compared to traditional heterojunctions. Herein, we overview the fundamentals of some representative inorganic oxide semiconductors (tungsten oxides, titanium oxides, zinc oxides, and copper oxides)-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. The 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 H2 production activity. Additionally, the future prospects are discussed, which provides guidance for designing efficient inorganic oxide semiconductor-based photocatalysts and the development of sustainable H2 generation technologies.