Structural, photophysical and photocatalytic properties of Bi2MTaO7 (M = La and Y)

Bi2MTaO7 (M = Y and La) were synthesized by solid-state reaction method and their structural and photocatalytic properties were investigated. The results indicated that these compounds crystallize in the pyrochlore-type structure, cubic system with space group Fd-3 m. In addition, the band gaps of Bi2LaTaO7 and Bi2YTaO7 were estimated to be about 2.17(3) and 2.22(7) eV, respectively. For the photocatalytic water splitting reaction, H2 or O2 evolution was observed from pure water respectively with Bi2MTaO7 (M = Y and La) as the photocatalysts under ultraviolet light irradiation. Photocatalytic degradation of aqueous methylene blue (MB) dye over these compounds was further investigated under visible light irradiation. Bi2MTaO7 (M = Y and La) showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation under visible light irradiation. Complete removal of aqueous MB was observed after visible light irradiation for 190 min with Bi2LaTaO7 as the photocatalyst and for 200 min with Bi2YTaO7 as the photocatalyst. The decrease of the total organic carbon (TOC) and the formation of inorganic products, SO 4 2− and NO 3 − , demonstrated the continuous mineralization of aqueous MB during the photocatalytic process.