A review of carbon material-based Z-scheme and S-scheme heterojunctions for photocatalytic clean energy generation

Carbon materials, including carbon nanotubes/nanofibers, graphene, graphene oxide, reduced graphene oxide, graphyne, graphdiyne, carbon quantum dots and fullerenes, have received considerable attention in recent years because of their unique properties such as high conductivity, excellent stability and biocompatibility. The integration of these materials into Z-scheme and S-scheme heterojunctions has emerged as a transformative strategy to increase their photocatalytic efficiency for energy conversion applications. We first consider the fundamental principles of clean energy generation such as photocatalytic H₂ generation and CO₂ reduction, elucidating their respective mechanisms and advantages. Various types of carbon materials, their synthesis and construction of Z-scheme and S-scheme heterojunctions are then discussed, emphasizing their role in promoting charge separation, reducing recombination losses and extending the spectral response range. With a focus on solar energy production, recent advances in carbon-based Z-scheme and S-scheme heterojunctions are discussed and summarized for photocatalytic H₂ generation and CO₂ reduction. Lastly, the current problems in the field of carbon-based photocatalysts are discussed with insights for the future development of this field.