Heterojunction semiconductor SnO2/SrNb2O6 with an enhanced photocatalytic activity: The significance of chemically bonded interface

Heterojunction photocatalysts SnO₂/SrNb₂O₆ were synthesized by a milling–annealing technique. The powders were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and UV–vis diffuse reflection spectroscopy (DRS). Their UV-induced photocatalytic activities were evaluated by the degradation of methyl orange and methylene blue. The results generally show that the binary semiconductors SnO₂/SrNb₂O₆, with matching band potentials, exhibit better photocatalytic properties than the single phase SrNb₂O₆ or SnO₂. The effective electron–hole separation both at the chemically bonded interface and in the two semiconductors is believed to be mainly responsible for the increased photocatalytic performance of composites. The formation of chemically bonded interfaces between SnO₂ and SrNb₂O₆ particles makes the interparticle charge transfer more spatially available and smoother, which is significant to enhance the photocatalytic activity.