Abstract: Effective bulk phase and surface charge separation is critical for charge utilization during the photocatalytic energy conversion process. In this work, the ternary Ni₂P-NiS/twinned Mn_0.5Cd_0.5S (T-MCS) nanohybrids were successfully constructed via combining Ni₂P-NiS with T-MCS solid solution for visible light photocatalytic H₂ evolution. T-MCS is composed of zinc blende Mn_0.5Cd_0.5S (ZB-MCS) and wurtzite Mn_0.5Cd_0.5S (WZ-MCS) and those two alternatively arranged crystal phases endow T-MCS with excellent bulk phase charge separation performance for the slight energy level difference between ZB-MCS and WZ-MCS. S-scheme carriers transfer route between NiS and T-MCS can accelerate the interfacial charge separation and retain the active electrons and holes, meanwhile, co-catalyst Ni₂P as electron receiver and proton reduction center can further optimize the H₂ evolution reaction kinetics based on the surface Schottky barrier effect. The above-formed homo-heterojunctions can establish multiple charge transfer channels in the bulk phase of T-MCS and interface of T-MCS and Ni₂P-NiS. Under the synergistic effect of twinned homojunction, S-scheme heterojunction, and Schottky barrier, the ternary Ni₂P-NiS/T-MCS composite manifested an H₂ production rate of 122.5 mmol h^-1 g^-1, which was 1.33, 1.24, and 2.58 times higher than those of the NiS/T-MCS (92.4 mmol h^-1 g^-1), Ni₂P/T-MCS (98.4 mmol h^-1 g^-1), and T-MCS (47.5 mmol h^-1 g^-1), respectively. This work demonstrates a promising strategy to develop efficient sulfides photocatalyst toward targeted solar-driven H₂ evolution through homo-heterojunction engineering.

Key words: Photocatalytic H₂ evolution, Twinned Mn_0.5Cd_0.5S, Homojunction, S-scheme heterojunction, Schottky barrier