Construction of Ni-doped SnO₂-SnS₂ heterojunctions with synergistic effect for enhanced photodegradation activity

Construction of heterostructures with proper band alignment and effective transport and separation of photogenerated charges is highly expected for photocatalysis. In this work, Ni-doped SnO₂-SnS₂ heterostructures (NiSnSO) are simply prepared by thermal oxidation of Ni-doped hierarchical SnS₂ microspheres in the air. When applied for the photodegradation of organic contaminants, these NiSnSO exhibit excellent catalytic performance and stability due to the following advantages: (1) Ni doping leads to the enhancement of light harvesting of SnS₂ in the visible light regions; (2) the formed heterojunctions promote the transport and separation of photogenerated electrons from SnS₂ to SnO₂; (3) Ni-SnO₂ quantum dots facilitate the enrichment of reactants, provide more reactive centers and accelerate product diffusion in the reactive centers; (4) the SnS₂ hierarchical microspheres constituted by nanoplates provide abundant active sites, high structural void porosity and accessible inner surface to faciliate the catalytic reactions. As a result, the optimized NiSnSO can photodegrade 92.7% methyl orange within 80 min under the irradiation of simulated sunlight, greatly higher than those of pure SnS₂ (29.8%) and Ni-doped SnS₂ (52.1%). These results reveal that the combination of heteroatom doping and heterostructure fabrication is a very promising strategy to deliver nanomaterials for effectively photocatalytic applications.