Electronic Structures and Photocatalytic Properties of New Vanadates Semiconductor Photocatalysts

摘要

Semiconductor photocatalysts have attracted increasing interests because of their functions in generating "clean-energy" hydrogen from water and air/water purification. However, most of the photocatalysts developed up to now have wide band gaps that they only respond to the ultra violet (UV) light, which occupies only about 4% of the solar spectrum. Research and development of visible light driven photocatalysts is indispensable from the viewpoint of efficient utilization of solar energy. Recently, we have succeeded in developing the world-first visible light responding photocatalysts, (In_(1-x)Ni_x)TaO_4 (x = 0～0.2). The photocatalysts can split water into H_2 and O_2 in a 2:1 stoichiometric manner, under visible light irradiation (λ > 420nm). Moreover, with 5d metal Ta being substituted by 4d metal Mb or 3d metal V, a systematic variation on the photophysical and photocatalytic properties reflecting strong effects of electronic structures was observed. In this study, we focused our concerns on the transition metal V and further substituted In by the trivalent rare earth elements to investigate the effects of f electron on the electronic and photophysical properties of the catalysts. Understandings on the relations among the materials syntheses, crystal, electronic structures, and photocatalytie activities of these new photocatalysts, obtained from theoretical calculations based on the first-principle method and experiments included crystal structure analyses, UV-vis diffuse reflectance spectroscopy, photocatalytie activity measurement, etc., will be discussed.