NiSe 2 /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 NiSe 2 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 NiSe 2 further promotes spatial charge separation through the heterojunction. Notably, the optimized 5 wt% NiSe 2 /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 NiSe 2 ‐based heterojunction constructs multiple internal electric fields, thereby facilitating directional charge migration and suppressing recombination, resulting in a superior photocatalytic performance of NiSe 2 /T‐MCS. This research offers a prospective strategy for designing efficient photocatalysts by integrating twinned structure engineering with a dual‐junction approach.