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 H₂ evolution, i.e. 102.5 μmol h⁻¹ under visible light irradiation (λ ≥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.