Construction of strongly coupled 2D-2D SnS₂/CdS S-scheme heterostructures for photocatalytic hydrogen evolution

The fabrication of neoteric photocatalysts with high-efficiency charge separation for the solar-driven hydrogen evolution reaction (HER) remains a challenge. The construction of strongly coupled two-dimensional (2D)-2D heterostructures facilitates charge spatial migration due to the regulation of the interlayer forces and electronic structures. In this work, we demonstrate novel 2D-2D SnS₂/CdS heterostructures by loading SnS₂ nanosheets (SnS₂ NSs) onto CdS nanosheets (CdS NSs). The SnS₂/CdS heterostructures possess close face-to-face contact and strongly coupled interactions to improve the charge transfer kinetics, and the loading of SnS₂ can enhance light absorption and suppress the photocorrosion of CdS. The optimized S-scheme SnS₂/CdS heterostructures exhibit excellent photocatalytic hydrogen evolution activity in lactic acid sacrificial solution under visible light (λ ≥ 420 nm), affording the highest hydrogen evolution rate on SnS₂/CdS heterostructures with 35 wt% SnS₂ (5.18 mmol g⁻¹ h⁻¹), which is approximately 6-fold higher than that of pure CdS NSs (0.87 mmol g⁻¹ h⁻¹). In addition, a highest apparent quantum efficiency (AQE) of 59.3% was obtained at 420 nm. When methanol was used as the sacrificial agent, the hydrogen production rate reached 3.27 mmol g⁻¹ h⁻¹ and methanol was oxidatively reformed into methoxymethanol (CH₃OCH₂OH). This work provides a feasible method for designing strongly coupled 2D-2D heterostructure photocatalysts for energy storage and conversion applications.