S-scheme heterojunction photocatalysts: Mechanism, challenges and opportunities

S-scheme heterojunction photocatalysts hold great promise in sustainable energy production for attractive solar to chemical conversion efficiencies based on designable semiconductor heterostructures . In the past decades, S-scheme heterojunctions were widely investigated in the development of various solar fuels. Conventionally, the concern was mainly focused on the effects of band structure alignment in dealing with the formation mechanisms of S-scheme heterojunction photocatalysts. In this review, more attentions are paid to the effects of light absorption ability, interfacial recombination centers, selective interface contact, and ferroelectric polarization on the formation of S-scheme heterojunctions. And the different S-scheme charge transfer pathways are surveyed in the framework of the band structure theory. Based on the outlined mechanisms, specific design strategies of S-scheme heterojunction photocatalysts are proposed, and the challenges and opportunities in developing S-scheme heterojunctions for chemical energy production are addressed as well.