Rapid template-free synthesis and photocatalytic performance of visible light-activated SnNb2O6 nanosheets

Visible light-activated SnNb2O6 nanosheets (NSs) with high surface area and small crystallites have been prepared by a microwave-assisted template-free hydrothermal method without exfoliation for the first time. This approach could be used to prepare the functional materials efficiently and extended to synthesizing two-dimensional nanosheet materials directly as well. The crystalline phases, photoabsorption performances, and surface areas and porosity of the samples are characterized by XRD, UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and N-2-adsorption. Results show that a hypsochromic shift of the photoabsorption edge is observed, which reflects an obvious quantum size effect. TEM images reveal SnNb2O6 nanosheets with a thickness of 1-4 nm versus several hundred nanometres in lateral size. Based on the experimental results, the formation mechanism of SnNb2O6 nanosheets is also studied and proposed, which reasonably follows a synergy interaction of reaction-crystallization and dissolution-recrystallization processes. Due to the unique morphology, larger surface area, smaller crystallites and stronger redox ability of the photogenerated hole-electron pair, these photocatalysts show much higher photocatalytic activities for the degradation of rhodamine B (RhB) compared with their counterparts prepared by the traditional solid-state reaction. The reaction rate is enhanced by over 4 times and the RhB molecule can be mineralized into CO2 and H2O over SnNb2O6 NSs. The decomposition mechanism of RhB over SnNb2O6 under visible light irradiation and the active species in the photocatalytic process have also been discussed.