S-scheme bimetallic sulfide ZnCo2S4/g-C3N4 heterojunction for photocatalytic H2 evolution

Abstract Transition bimetallic sulfides have attracted widespread attention because of their superior electrochemical characteristics compared to their parent materials. Herein, ternary ZnCo2S4 was deposited on g-C3N4 (CN) to enhance the photocatalytic water splitting reactivity of CN. The hydrogen (H2) evolution rate of 25 wt%-ZnCo2S4/CN reached 6619 μmol h−1 g−1, which was 55.2 times higher than that of CN alone. Under the same conditions, ZnS/CN and Co3S4/CN were also synthesized, and their H2 evolution rates were both inferior to that of ZnCo2S4/CN. Investigations showed that the presence of both zinc and cobalt ions in ZnCo2S4 lowered the H2 evolution overpotential and charge recombination rate, leading to excellent H2 release activity. In addition, the composite maintained its activity even after reacting for 20 h, and the charge transfer mechanism between ZnCo2S4 and CN was subject to the S-scheme charge transfer route according to trapping experiments for active species. This work revealed a promising and efficient bimetallic sulfide heterojunction to enhance H2 evolution during water splitting and thus achieved improved conversion efficiency for solar energy applications.