Photoinduced Deposition of Platinum from (Bu₄N)₂[Pt(NO₃)₆] for a Low Pt-Loading Pt/TiO₂ Hydrogen Photogeneration Catalyst

Abstract

An efficient method for the deposition of ionic platinum species PtO_<i>x</i> onto a TiO₂ surface was developed on the basis of light-induced activation of the [Pt(NO₃)₆]^2- anion. The deposited PtO_<i>x</i> species with an effective Pt oxidation state between +4 and +2 have an oxygen-made environment and include single ion centers {PtO_<i>n</i>} and polyatomic ensembles {Pt_<i>n</i>O_<i>m</i>} connected to a TiO₂ surface with Pt-O-Ti bonds. The resulting PtO_<i>x</i>/TiO₂ materials were tested as photocatalysts for the hydrogen evolution reaction (HER) from a water ethanol mixture and have shown uniquely high activity with the rate of H₂ evolution achieving 11 mol h^-1 per gram of Pt, which is the highest result for such materials reported to date. A combination of spectral methods shows that, under HER conditions, reduction of the supported PtO_<i>x</i> species leads to the formation of well-dispersed nanoparticles of metallic platinum attached on the surface of TiO₂ by Ti-O-Pt bonds. The high activity of the PtO_<i>x</i>/TiO₂ materials is believed to result from a combination of uniform distribution of small platinum nanoparticles over the titania surface and their close interaction with TiO₂.