Single site Co-S anchored on carbon nitride as a highly active cocatalyst for photocatalytic hydrogen evolution

The low utilization rate of photo-generated carriers in graphite-phase carbon nitride (g-C 3 N 4 ) is the main factor limiting its photocatalytic performance. In this work, to begin with single-atom Co was inserted into the structure of g-C 3 N 4 , then it was vulcanized to prepare composite Co-S single-site in g-C 3 N 4 . The results show that the Co-S single-site cocatalyst was successfully synthesized and was stably anchored in the structure of g-C 3 N 4 . As an active site, it can not only enhance the reaction activity, but also capture electrons to provide transfer channels for the photo-generated carrier, thereby enhancing the photocatalytic hydrogen evolution performance of g-C 3 N 4 . The hydrogen production of Co-S single-site modified g-C 3 N 4 reaches 72.85 μmol (per 0.02 g photocatalyst) under visible light, which is 9 times higher than that of pure g-C 3 N 4 . This work provides a reasonable method for the preparation of composite single-site cocatalyst. • Single-atom Co was firstly anchored on a CN substrate, on the basis of which the composite single-site Co-S modified CN photocatalyst was obtained by sulphuration, providing a feasible strategy for the preparation of composite single-site co-catalysts. • The electronic structure of the single atom Co was altered through the sulphidation process, as a result, the Co site is easier to attract electrons for HER. • The modified g-C3N4 exhibits excellent photocatalytic performance with a hydrogen production of 72.85 μmol (per 0.02 g photocatalyst) in 4 h.