Flower-like nanostructure MNb2O6 (M = Mn, Zn) with high surface area: Hydrothermal synthesis and enhanced photocatalytic performance

• MNb2O6 was prepared by a mild two-step hydrothermal method.
• Their flower-like nanostructure morphology was studied by SEM and TEM.
• High BET surface areas for MnNb2O6 (∼50 m2/g) and ZnNb2O6 (∼100 m2/g).
• Band gap energies were estimated by UV–vis diffuse reflectance spectra.
• Photocatalytic activities were evaluated under UV-light irradiation.

Nano-scaled MNb2O6 (M = Mn, Zn) was successfully synthesized via a two-step hydrothermal method. It is important to control the exact pH of the reaction solution in order to obtain pure products. The as-prepared samples both crystallize in the columbite structure. Interestingly, the products possess a flower-like morphology in a pseudo-six-fold symmetry, which is in fact arrayed by two-dimensional nanosheets. Their surface areas (51 m2/g for MnNb2O6 and 103 m2/g for ZnNb2O6) are about 25–50 times of those prepared by solid state reaction. UV–vis diffuse reflectance spectra show the nano-scaled sample has a stronger absorption and a narrower band gap than its bulk form. The estimated band gap energies are 2.70 eV (MnNb2O6) and 3.77 eV (ZnNb2O6), respectively. The nano-scaled ZnNb2O6 exhibits a double enhancement of photocatalytic activity in the decolorization of methylene blue than bulk ZnNb2O6.

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