Fabrication of Transparent Pt-TiO Sol and Its Photocatalytic Activity for Hydrogen Evolution.

Titanium dioxide doped with Pt(IV) ions was synthesized via a sol-gel method, incorporating a sol purification process through dialysis. The doped Pt(IV) ions were reduced by UV light irradiation to obtain a transparent Pt-TiO sol, with Pt(0) acting as a cocatalyst for hydrogen evolution. The hydrogen evolution activity of Pt-TiO sol was evaluated under UV light irradiation using methanol as a sacrificial reagent. 0.05 atom % Pt-TiO sol remained in the sol state without precipitation after 10 h of UV light irradiation. The amount of hydrogen produced after 10 h of light irradiation was 1195 μmol, with a turnover number (TON) of 664.1, a turnover frequency (TOF) of 66.4 h, and an apparent quantum yield (AQY) of 0.86%. The sol-gel synthesis from the molecular level is thought to result in Pt ions being doped inside the TiO particles, maintaining high dispersibility by suppressing particle growth due to the aggregation of Pt(0) during the UV reduction of Pt(IV) ions. These results show that the Pt-TiO photocatalyst has a high renewable energy factor because it can be synthesized at room temperature, and the aggregation of Pt-TiO particles is suppressed by making full use of a sol-gel method.