Construction of core-shell structured WO₃@SnS₂ hetero-junction as a direct Z-scheme photo-catalyst

An ideal photocatalyst not only offers high photo-generated electron-hole pairs separation ability, but also has suitable redox potential. Here, a direct Z-scheme core-shell structured WO₃@SnS₂ hetero-junction photo-catalyst was prepared via two-step hydrothermal method, in which the core-shell structure, rod morphology and micro-composition of hetero-junction were confirmed through X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectra, field emission scanning electron microscope (FE-SEM), transmission electron microscope (FEI-TEM) and X-ray photoelectron spectra (XPS). Their enhanced photo-catalytic abilities were evaluated by photo-degradation of Rhodamine (RhB), photo-reduction of dichromate (Cr⁶⁺) solution and photo-catalytic H₂ production through comparing with pure WO₃, SnS₂ or the mixture of WO₃ and SnS₂ (WO₃/SnS₂). The absorption spectra and electrochemical properties were used to estimate the band gap of samples, the expanded spectral absorption capacity and improved electron-hole separation ability, which are important factors for enhanced photocatalytic performance. Furthermore, the direct Z-scheme charge transfer mechanism of WO₃@SnS₂ hetero-junction was determined through the combination of theoretical calculation and experimental characterizations, which played a decisive role for retaining excellent redox potential and increasing photo-catalytic ability of WO₃ and SnS₂.