Interfacial charge transfer via Mo–S bonds in MoSe2/Mn0.5Cd0.5S S-scheme heterojunction for efficient photocatalytic H2 evolution

Photocatalytic hydrogen production (PHE) technology has emerged as a sustainable approach to convert solar energy into hydrogen energy, exhibiting significant potential for clean energy applications. In this study, an ultrasonic-assisted method was adopted to fabricate S-scheme MoSe₂/Mn_0.5Cd_0.5S (MoSe₂/MCS) composites, where intimate heterostructures are formed through interfacial Mo–S bonds between MCS and MoSe₂. The atomic-level Mo–S bonds establish charge transport pathways and enable directional control of charge transfer. The as-constructed S-scheme MoSe₂/MCS photocatalysts exhibit two critical advantages: enhanced charge carrier separation rate and improved overall redox capacity. Under visible-light irradiation, the MoSe₂/MCS composites significantly outperform pure MCS in PHE performance. The optimal 5-MoSe₂/MCS composite demonstrates the superior PHE activity, achieving an apparent quantum yield value of 71.16 % at 400 nm and remarkable photocatalytic stability. Key characterization techniques, including (solution-based) time-resolved photoluminescence technique, theoretical calculation, photoelectrochemical measurements, were employed to elucidate the positive correlation between ion-carrier interaction and charge separation efficiency, thereby enhancing the PHE performance. Based on experimental analysis and theoretical calculation, a plausible PHE mechanism for the S-scheme MCS composites is revealed and discussed in detail. These findings provide valuable insights for designing high-efficiency S-scheme heterostructured composites with interfacial chemical bonds.