Calcium germanate nanowires by vanadium doping with improved photocatalytic activity

Vanadium-doped calcium germanate nanowires were prepared by a simple hydrothermal method. The samples were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and solid UV–Vis diffuse reflectance spectrum. The photocatalytic activity of the vanadium-doped calcium germanate nanowires was investigated by the degradation of methylene blue (MB) under solar light irradiation. The results show that the vanadium-doped calcium germanate nanowires are composed of rhombohedral Ca3GeO5 and orthorhombic CaV3O7 phases. The nanowires have the diameter and length of 50–200 nm and several dozens of micrometres, respectively. The band gap of the vanadium-doped calcium germanate nanowires strongly depends on the vanadium doping mass percentage. The absorption spectrum can be broadened to visible light region. The photocatalytic activity of the vanadium-doped calcium germanate nanowires is remarkably improved. Vanadium-doped calcium germanate nanowires with the vanadium doping mass percentage of 10% have the highest photocatalytic activity for MB degradation under solar light irradiation.