A comprehensive review of S-scheme heterojunction photocatalysts for CO2 reduction: Design principles, mechanisms, and material classification

CO 2 , a major greenhouse gas emitted by industries, contributes to the greenhouse effect and global warming. The photocatalytic reduction of CO 2 into hydrocarbon fuels, such as methane or methanol, using sunlight has emerged as an effective strategy for mitigating environmental pollution and energy crisis. S-scheme heterojunction photocatalysts are particularly preferred for photocatalytic CO 2 reduction owing to their ability to enhance carrier separation and optimize redox potential. This paper provides a comprehensive review of the research progress on S-scheme heterojunction in photocatalytic CO 2 reduction, including their design principles, characterization methods, mechanisms, and influencing factors of this reaction. Common photocatalytic materials used to construct S-scheme heterojunctions for CO 2 reduction are summarized, including g-C 3 N 4 , TiO 2 , ZnO, CdS, Znln 2 S 4 , and BiVO 4 , metal-organic frameworks, and covalent organic frameworks. The impact of S-scheme charge-transfer pathways in these heterojunctions and the unique properties of the photocatalysts on the CO 2 reduction process are thoroughly elucidated. • Update the development, design, and characterization of S-scheme heterojunctions. • Focus on the principles and factors of photocatalytic CO 2 reduction reaction (PCO 2 RR). • Overview of recent advances in various types of S-scheme heterojunctions for PCO 2 RR. • New insights on challenges and trends of S-scheme heterojunctions for PCO 2 RR.