Preparation of new sulfur-doped and sulfur/nitrogen co-doped CsTaWO6 photocatalysts for hydrogen production from water under visible light

Abstract

Wide band gap semiconductor photocatalyst CsTaWO6 (3.8 eV) was anion-doped via simple gas–solid reactions to extend its absorption into the visible light range. Sulfur doping and sulfur/nitrogen co-doping were performed, using sulfur powder and ammonia as precursors, resulting in decreased band gaps of doped CsTaWO6 down to 2.06 eV. The resulting materials CsTaWO6−xSx and CsTaWO6−x−ySxNy were investigated concerning their chemical and electronic structures via experimental characterizations and first principle calculations. Sulfur and sulfur/nitrogen doped CsTaWO6 crystals showed a clear red shift in absorption, and the anionic dopants were detected using X-ray photoelectron spectroscopy. Photocatalytic performance tests for the doped materials evaluated the capability of generating ˙OH radicals for photocatalytic reactions. Water splitting tests of the photocatalysts using a new type of setup including quadrupole mass spectrometry revealed that the doped materials were more efficient in H2 production under simulated solar irradiation, in contrast to the undoped CsTaWO6 or P25. Co-doped CsTaWO6−x−ySxNy turned out to be the best material for H2 production, due to its capability in efficiently utilizing the visible light in the solar spectrum.