Photocatalytic hydrogen production from aqueous methanol solutions under visible light over Na(BixTa1−x)O3 solid-solution

A series of equivalent substitution solid-solution Na(BixTa1−x)O3 (x = 0–0.10) was prepared by a simple hydrothermal method using Ta2O5 and NaBiO3 as precursors. The Na(Bi0.08Ta0.92)O3 photocatalyst exhibited the highest performance of H2 evolution (59.48 μmol h−1 g−1) under visible-light irradiation (λ > 400 nm) without co-catalyst, whereas no H2 evolution is observed for NaTaO3 under the same conditions. The UV-Vis spectra indicate that the Na(Bi0.08Ta0.92)O3 powders can absorb not only ultraviolet light like pure NaTaO3 powder but also the visible-light spectrum. The absorption edge corresponds to a band gap of 2.88 eV. The results of density functional theory calculation illuminate that the visible-light absorption bands in the Na(BixTa1−x)O3 catalysts are attributed to the band transition from the O2p to the Bi2s + 2p + Ta5d hybrid orbital.