NiSe₂/Twinned-MnCdS Dual-Junction for Enhanced Photocatalytic Hydrogen Performance

Efficient charge separation and migration are crucial for advancing semiconductor photocatalysis. Herein, a twinned MnCdS homojunction (T-MCS) composed of wurtzite MnCdS (WZ-MCS) and zinc-blende MnCdS (ZB-MCS) was synthesized via a hydrothermal method and then coupled with NiSe₂ through an oil-bath method to construct a homo-heterojunction system. The internal twin boundaries in T-MCS facilitate electron redistribution and enhance carrier transfer, while the interface coupling with NiSe₂ further promotes spatial charge separation through the heterojunction. Notably, the optimized 5 wt% NiSe₂/T-MCS achieves a remarkable hydrogen production rate of 5.17 mmol g^-1 h^-1, which is 3.9 and 10.5 times higher than those of pristine T-MCS (1.33 mmol g^-1 h^-1) and pure WZ-MCS (0.49 mmol g^-1 h^-1), respectively. Density functional theory (DFT) calculations, combined with experimental analysis, demonstrate that the synergistic interaction between twin homojunction and NiSe₂-based heterojunction constructs multiple internal electric fields, thereby facilitating directional charge migration and suppressing recombination, resulting in a superior photocatalytic performance of NiSe₂/T-MCS. This research offers a prospective strategy for designing efficient photocatalysts by integrating twinned structure engineering with a dual-junction approach.