title: Visible light sensitive photocatalyst, delafossite structured alpha-AgGaO(2).
abstract: Delafossite structured alpha-AgGaO(2) powder was successfully synthesized through a cation exchange reaction. alpha-AgGaO(2) has a band gap of 2.4 eV, absorbs visible light up to 520 nm, and effectively decomposes 2-propanol to CO2 via acetone by irradiating with either UV light (300-400 nm) or visible light (420-530 nm). The values of the quantum efficiency are similar (ca. 0.6%) under light irradiations with wavelengths of 365, 390, 430, 470, and 510 +/- 10 nm, but steeply decrease with wavelengths longer than 530 +/- 10 nm, which support a 2.4 eV band gap. In contrast, the other polymorph, alpha-AgGaO(2) powder, which has a band gap of 2.1 eV, shows a negligible activity when irradiating with either UV light or visible light. The higher oxidation activity of alpha-AgGaO(2) is probably due to its larger band gap, which is formed at the top of its valence band in a lower energy region as compared to alpha-AgGaO(2). Moreover, the first-principle calculations of alpha-AgGaO(2) and alpha-AgGaO(2) clearly indicate that alpha-AgGaO(2) has a remarkably larger dispersed valence band as compared to alpha-AgGaO(2), which is advantageous to the photocatalytic activity due to the efficient hole conduction.
authors.affiliation: Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Maruyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Irie
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Hashimoto