Defect-decorated Cu2MoS4 as a new efficient hydrogen evolution cocatalyst: Rich active sites, rapid charge transfer and optimized hydrogen adsorption

Herein, a new defect-decorated Cu2MoS4 cocatalyst was successfully synthesized using a sacrificial-template method. Detailed characterizations confirmed the presence of multivalent metal ions (Cu2+/Cu+, Mo6+/Mo4+) and abundant sulfur vacancies. To assess its cocatalytic performance, Cu2MoS4/Cd0.5Zn0.5S Schottky heterojunction was constructed and achieved a hydrogen production rate of 11.83 mmol∙g−1∙h−1, which is 6.33 and 2.03 times higher than pristine Cd0.5Zn0.5S and MoS2/Cd0.5Zn0.5S, respectively. The superior photocatalytic activity is attributed to multiple factors. Sulfur vacancies regulate the charge density of neighboring atoms and induce production of more coordination-unsaturated atoms as active sites to accelerate hydrogen generation. Meanwhile, the high conductivity of Cu2MoS4, Schottky heterojunction, and redox couples could synergistically boost charge transfer and separation efficiency. Theoretical calculations further illustrated the key role of sulfur vacancies in optimizing H2-evolution kinetics, which reduced the hydrogen adsorption free energy of in-plane S atoms. This work demonstrates that Cu2MoS4 has significant potential as an efficient cocatalyst material, enhancing the photocatalytic performance of metal sulfides.