In Situ Construction of SnS₂@SnO₂ Heterostructure for Photo-Assisted Electrocatalysis of Oxygen Evolution Reaction

Photo-assisted electrocatalysis has arisen as a promising approach for hydrogen generation by incorporating photocatalysts into electrocatalysts. 2D SnS₂ is a photocatalyst that absorbs visible light. However, the rapid recombination of photo-generated electron-hole pairs significantly reduces the overall photocatalytic efficiency of SnS₂, limiting its practical application. Thus, this study prepares an in situ heterojunction SnS₂@SnO₂ using a one-step hydrothermal method. The degradation efficiency of methyl orange (MO) using SnS₂@SnO₂ is measured, achieving a degradation rate of 92.75% within 1 h, which is 1.9 times higher than that of pure SnS₂. Additionally, FeNiS/SnS₂@SnO₂ is synthesized and exhibited significant improvements in the photo-assisted oxygen evolution reaction (OER). It achieves an overpotential of 260 mV and a Tafel slope of 65.1 mV dec^-1 at 10 mA cm^-2, showing reductions of 11.8% and 31.8%, respectively, compared to FeNiS alone. These enhancements highlight the strong photo-response capability of SnS₂@SnO₂. Under the internal electric field of SnS₂@SnO₂, the photogenerated electrons in the conduction band of SnS₂ quickly move toward SnO₂, facilitating efficient photocatalytic reactions. FeNiS, with a lower Fermi energy level (E_F), facilitates electron transfer from SnS₂@SnO₂ and enhances OER performance by efficiently participating in the reaction. This study paves a new path for 2D photocatalyst materials.