Photocatalytic CO2 Reduction Enabled by Interfacial S-Scheme Heterojunction between Ultrasmall Copper Phosphosulfide and g-C3N4

Abstract

Transition metal phosphosulfides (TMPSs) have gained much interest due to their highly enhanced photocatalytic activities compared to their corresponding phosphides and sulfides. However, the application of TMPSs on photocatalytic CO₂ reduction remains a challenge due to their inappropriate band positions and rapid recombination of photogenerated electron–hole pairs. Herein, we report ultrasmall copper phosphosulfide (us-Cu₃P|S) nanocrystals anchored on 2D g-C₃N₄ nanosheets. Systematic studies on the interaction between us-Cu₃P|S and g-C₃N₄ indicate the formation of an S-scheme heterojunction via interfacial P–N chemical bonds, which acts as an electron transfer channel and facilitates the separation and migration of photogenerated charge carriers. Upon the composite formation, the band structures of us-Cu₃P|S and g-C₃N₄ are altered to enable the enhanced photocatalytic CO generation rate of 137 μmol g^–1 h^–1, which is eight times higher than that of pristine g-C₃N₄. The unique phosphosulfide structure is also beneficial for the enhanced electron transfer rate and provides abundant active sites. This first application of Cu₃P|S to photocatalytic CO₂ reduction marks an important step toward the development of TMPSs for photocatalytic applications.