Recent advances in g-CN composites within four types of heterojunctions for photocatalytic CO reduction.

Studies of photocatalytic conversion of CO into hydrocarbon fuels, as a promising solution to alleviate global warming and energy issues, are booming in recent years. Researchers have focused their interest in developing g-CN composite photocatalysts with intriguing features of robust light harvesting ability, excellent catalysis, and stable performance. Four types of heterojunctions (type-II, Z-scheme, S-scheme and Schottky) of the g-CN composites are widely adopted. This review aims at presenting and comparing the photocatalytic mechanisms, characteristics, and performances of g-CN composites concerning these four types of heterojunctions. Besides, perspectives and undergoing efforts for further development of g-CN composite photocatalysts are discussed. This review would be helpful for researchers to gain a comprehensive understanding of the progress and future development trends of g-CN composite heterojunctions for photocatalytic CO reduction.