Efficient H2 evolution over MoS2-NiS2/g-C3N4 S-scheme photocatalyst with NiS2 as electron mediator

Abstract

Low-cost transition metal sulfides are commonly utilized as photocatalysts for H₂ production owing to their exceptional conductivity and superior specific surface area. In this study, MoS₂-NiS₂ nanoflowers with multidimensional space structure was obtained through the sulphuration reaction between S²⁻ and NiMoO₄ under Kirkendall effect during hydrothermal reaction. Subsequently, MoS₂-NiS₂ was loaded on the surface of g-C₃N₄ nanosheets using a solvent self-assembly strategy to form 3D MoS₂-NiS₂/g-C₃N₄ heterojunctions. The experimental results demonstrate that the H₂ production rate of 20 wt% MoS₂-NiS₂/g-C₃N₄ reaches 22153 μmol g⁻¹ h⁻¹ under a 300 W Xe lamp irradiation, which is 59.5 and 201.4-folds than MoS₂-NiS₂ and g-C₃N₄, and surpasses 20 wt% MoS₂/g-C₃N₄ (211 μmolg⁻¹ h⁻¹) and 20 wt% NiS₂/g-C₃N₄ (6183 μmol g⁻¹ h⁻¹). The XPS and Superoxide radical capture experiments demonstrate that the charge transfer between MoS₂-NiS₂ and g-C₃N₄ follows the S-scheme route, and NiS₂ functions as an electron mediator, facilitating the transfer of electrons from MoS₂ to g-C₃N₄ to consume the holes, which enhances the efficiency of H₂ evolution reaction on g-C₃N₄. Furthermore, the S-scheme heterojunction of MoS₂-NiS₂/g-C₃N₄ with the multidimensional geometric structure can provide abundant active sites for catalytic reactions, this presents a promising approach for the development of cost-effective and high-performance g-C₃N₄-based heterojunctions. This work offers distinctive perspectives on the trajectory of renewable H₂ energy development.