Selective Photocatalytic Oxidation of Aniline to Nitrosobenzene by Pt Nanoparticles Supported on TiO2 under Visible Light Irradiation

Visible light irradiation (λ > 450 nm) of Pt nanoparticles supported on Degussa P25 TiO2 (Pt/P25 catalyst) promotes efficient and selective aerobic oxidation of aniline to nitrosobenzene. This is facilicated via the interband excitation of Pt atoms by visible light followed by the transfer of activated electrons to the TiO2 conduction band. The positive charges formed on the Pt surface oxidize substrates, and the conduction band electrons reduce O2, promoting photocatalytic cycles. The high activity of Pt/P25 is due to the high electron density of Pt particles. They behave as Lewis base sites for reductive deprotonation of aniline, thus promoting efficient aniline oxidation. The Pt/P25 catalyst, when photoirradiated at a low temperature (∼283 K), suppresses subsequent condensation of aniline and the formed nitrosobenzene, successfully producing nitrosobenzene with a very high selectivity (90%).