Harnessing the interfacial sulfur-edge and metal-edge sites in ZnIn2S4/MnS heterojunctions boosts charge transfer for photocatalytic hydrogen production

Abstract

Rapid carrier recombination and slow charge transfer dynamics have significantly reduced the performance of photocatalytic hydrogen production. Construction of heterojunctions via utilizing the sulfur-edge and metal-edge sites of metal sulfide semiconductor for improving photocatalytic activity remains a significant challenge. Herein, a novel ZnIn₂S₄/MnS S-scheme heterojunction was prepared by hydrothermal synthesis to accelerate charge carrier transfer for efficient photocatalysis. Notably, ZnIn₂S₄/MnS exhibited excellent photocatalytic hydrogen evolution activity (7.95 mmol g⁻¹ h⁻¹) under visible light irradiation (≥420 nm), up to 4.7 times higher than that of pure ZnIn₂S₄. Additionally, cycling experiments showed that ZM-2 remained high stability after four cycles. Density-functional theory (DFT) calculations and in situ XPS results confirm the formation of S-scheme heterojunction, indicating that the tight interfacial contact between ZnIn₂S₄ and MnS with the presence of Mn-S bonds (the unsaturated Mn edges of MnS and the uncoordinated S atoms in the edge of ZnIn₂S₄) promoted faster charge transfer. Besides, the unsaturated S atom on the surface of MnS is an active site with strong H⁺ binding ability, which can effectively reduce the overpotential or activation barrier for hydrogen evolution. This study illustrates the critical influence of the interfacial Mn-S bond on the ZnIn₂S₄/MnS S-scheme heterojunction to achieve efficient photocatalytic hydrogen production and provides relevant guidance for carrying out rational structural/interfacial modulation.