S-scheme regulated Ni2P-NiS/twinned Mn0.5Cd0.5S hetero-homojunctions for efficient photocatalytic H2 evolution

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 Mn0.5Cd0.5S (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 Mn0.5Cd0.5S (ZB-MCS) and wurtzite Mn0.5Cd0.5S (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.