Facile fabrication of Bi2O3/Bi-NaTaO3 photocatalysts for hydrogen generation under visible light irradiation

Abstract

A new series of Bi2O3/Bi-NaTaO3 photocatalysts were fabricated by a modified solid state reaction method. After an optimal amount of bismuth doping into NaTaO3, the incorporated bismuth forms a separate oxide phase instead of remaining in the originally doped form. The band gaps of the Bi2O3/Bi-NaTaO3 samples were tuned to effectively absorb visible light and induced visible light photocatalytic activity, with varying bismuth concentration. Photoluminescence studies confirmed that the optimum amount of bismuth, found to be 0.3 Bi2O3/Bi-NaTaO3, effectively suppresses the recombination rate of photogenerated charge carriers. A further increase in bismuth concentration (>0.3 molar ratio) leads to impurity formation and creates defect states which inhibit the photocatalytic activity of the Bi2O3/Bi-NaTaO3. The energy band positions of Bi2O3 and Bi-NaTaO3 were calculated by PEC measurement. The 0.3 Bi2O3/Bi-NaTaO3 photocatalyst exhibited the highest performance in terms of H-2 evolution, i.e. 102.5 mu mol h(-1) under visible light irradiation (lambda >= 400 nm) in aqueous methanol solution as the sacrificial reagent. The photocatalytic activities of Bi2O3/Bi-NaTaO3 composites were explained on the basis of the photosensitizing effect of Bi2O3, electron-hole separation and PL intensity.