Preparation and visible-light photocatalytic properties of BiNbO4 and BiTaO4 by a citrate method

Visible-light photcatalysts of BiNbO4 and BiTaO4 powders have been successfully synthesized by a citrate method. The formation of pure triclinic phase of BiNbO4 and BiTaO4 at low temperature of 700 °C can be attributed to the advantage of the citrate method. The photocatalytic activity and possible mechanism were investigated deeply. For BiNbO4 particles, the mechanism of methyl violet (MV) degradation under visible light irradiation involves photocatalytic and photosensitization pathways and the catalyst specific surface area has dominant influence. While for BiTaO4 particles, the dominant mechanism arises from photosensitization pathways and a trade off between high specific surface area and good crystallinity is achieved. BiNbO4 powder calcined at 700 °C shows the best photocatalytic efficiency among these catalysts, which is ascribed to its large surface area and more positive conduction band level. The optimal catalyst loading, additive H2O2 concentration and pH value is around 1 g/L, 2 mmol/L and 8 mmol/L, respectively. - Graphical abstract: Photodegradation performance and adsorption ability of BiNbO4 and BiTaO4 powders, respectively. BNO700 with the best photocatalytic efficiency is ascribed to its large surface area and more positive conduction band level. Highlights: ► Pure BiNbO4 and BiTaO4 powders were prepared by a citrate method. ► Excellent performance of visible-light degradation of MV was observed. ► Different MV degradation mechanism for BiNbO4 and BiTaO4 powders was proposed. ► BNO700 has large surface area and more positive conduction band level