Photo-assisted electrocatalysis has arisen as a promising approach for hydrogen generation by incorporating photocatalysts into electrocatalysts. 2D SnS 2 is a photocatalyst that absorbs visible light. However, the rapid recombination of photo-generated electron-hole pairs significantly reduces the overall photocatalytic efficiency of SnS 2 , limiting its practical application. Thus, this study prepares an in situ heterojunction SnS 2 @SnO 2 using a one-step hydrothermal method. The degradation efficiency of methyl orange (MO) using SnS 2 @SnO 2 is measured, achieving a degradation rate of 92.75% within 1 h, which is 1.9 times higher than that of pure SnS 2 . Additionally, FeNiS/SnS 2 @SnO 2 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 SnS 2 @SnO 2 . Under the internal electric field of SnS 2 @SnO 2 , the photogenerated electrons in the conduction band of SnS 2 quickly move toward SnO 2 , facilitating efficient photocatalytic reactions. FeNiS, with a lower Fermi energy level (E F ), facilitates electron transfer from SnS 2 @SnO 2 and enhances OER performance by efficiently participating in the reaction. This study paves a new path for 2D photocatalyst materials.
To address the high cost and scarcity of traditional platinum (Pt) counter electrodes, this study designed a novel non-Pt counter electrode material: nitrogen-doped hollow mesoporous carbon sphere (NCS)-loaded SnS 2 @SnO 2 heterojunctions (SnS 2 @SnO 2 /NCSs). By optimizing the mass ratio of Sn/S precursors to NCSs, the morphology of the composite was tailored. Comprehensive characterization via XRD, XPS, SEM, TEM, and Raman spectroscopy revealed that SnS 2 @SnO 2 nanoparticles (10–20 nm) were uniformly distributed within the internal/external walls and cavities of the NCSs via mesoporous confinement, forming a 3D conductive network. Nitrogen doping (I D /I G = 1.12) endowed the carbon matrix with abundant active sites, while the band alignment of the SnS 2 @SnO 2 heterojunction significantly enhanced catalytic activity. Electrochemical tests demonstrated a charge transfer resistance (R ct = 22.25 Ω·cm 2 ) close to Pt (15.78 Ω·cm 2 ), with reduced low-frequency diffusion impedance. When integrated into dye-sensitized solar cells (DSSCs), the SnS 2 @SnO 2 /NCSs-based device achieved a power conversion efficiency (PCE) of 7.32% (J sc = 17.23 mA·cm⁻ 2 , V oc = 737.46 mV, FF = 0.57), representing a 36% improvement over the pure heterojunction (5.38%) and approaching Pt-based devices (8.39%). This work provides a cost-effective strategy for developing high-performance non-Pt counter electrodes.
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