Non-Precious Zn as a Key “Step” Promotes Spatial Separation of Photoexcited Excitons in Polymeric Carbon Nitride for Photocatalytic Overall Water Splitting

Abstract

The current photocatalytic water splitting generally refers to half-water splitting using sacrificial reagents. However, the scarcity of efficient co-catalysts for overall water splitting hampers the advancement of photocatalysis. This study demonstrates a highly efficient co-catalyst strategy on polymeric carbon nitride (CN), namely by inserting Zn between Pt and CN. This coordinative insertion of Zn achieves the spatial separation of photoexcited excitons, which not only effectively separates the oxidation and reduction sites of CN, but also inhibits the recombination of photoexcited electron-hole pairs. As a result, the evolved H2 and O2 satisfy the stoichiometric ratio of 2:1 and the H2 evolution rate is 9 times higher than that of single-loaded Pt as the co-catalyst. Our work provides a feasible routine to prepare a co-catalyst/photocatalyst structure, which significantly facilitates the transition from half-water splitting to overall water splitting.

Keywords: Overall water splitting, polymeric carbon nitride, photocatalysis, spatial separation, co-catalyst