Photocatalytic decomposition of water–methanol solution over metal-doped layered perovskites under visible light irradiation

In search for efficient photocatalysts for water splitting under visible light, the effect of cation substitution on a layered perovskite, La2Ti2O7 has been studied. Among various types of dopants, only Cr and Fe showed intense absorption in the visible light region (λ>420 nm), over which H2 was produced photocatalytically from water–methanol solution. XPS measurements indicated that the oxidation state of doped Cr and Fe was +3. The band gap energies of Cr and Fe-doped La2Ti2O7 were 2.2 and 2.6 eV, respectively, and the H2 evolution rate was a little higher for the Cr-doped catalyst than that for the Fe-doped one. The theoretical calculation of electronic band structure revealed that the contribution of these dopants on the overall band structure of La2Ti2O7 was negligible, but that they formed a partially filled 3d band in the band gap of La2Ti2O7, from which photoelectrons are excited to the conduction band upon visible light absorption.