SnS2/SnS heterojunction: An all-weather-active photocatalyst for Cr(VI) removal

Photoreduction is a sustainable method for the removal of the harmful heavy metal ions. However, the low photocatalytic activity due to limited solar energy utilization and sluggish separation of photogenerated electrons/hole pairs is a major challenge. Here, we report the design and preparation of SnS2/SnS heterojunction nanosheets with full-band response for efficient photoreduction of Cr(VI). The SnS2/SnS heterojunction has a three-dimensional lamellar structure with tight interfacial links that facilitate inter-electron hole transport. Among the samples, SnS2/SnS-2 (Sn4+: Sn2+ = 1: 0.218) shows optimal photoreduction of Cr(VI) under simulated solar light. Remarkably, SnS2/SnS-2 exhibited a high removal rate of Cr(VI) under all-weather conditions, with 50% removal achieved in 2 h under sunlight and 10% removal in 2 h under cloudy condition in neutral lake water, indicating practical catalytic performance and energy-saving potential. The presence of SnS not only improves the optical absorption capacity in the near-infrared region and enhances the photo-thermal conversion efficiency, but also accelerates the separation ability of photogenerated carriers, leading to high photocatalytic efficiency. Our work provides a promising concept for continuous Cr(VI) removal under all-weather conditions, including weak light irradiation.