Template Syntheses of Anatase Nanoparticles Using a Nanoporous Polyimide Membrane: Implications for Deposition of Platinum for Photocatalytic H₂ Evolution

A nanoporous polyimide membrane with a spherical pore having a diameter of ca. 50 nm was utilized as the template to obtain anatase nanoparticles with a size of ca. 16 nm by the infiltration of tetraisopropoxy titanium(IV) into the pore and the subsequent heat treatment at 500 °C. The anatase nanoparticles thus obtained were used as a photocatalyst for the H2 evolution from aqueous methanol by UV irradiation to show a higher catalytic activity than that of a commercially available anatase particle (Sigma-Aldrich) with a size of 100 nm. The difference in the activity was pronounced when weaker irradiation was employed, suggesting the positive effect of the smaller size of the present product. Pt was deposited on the anatase nanoparticles to improve the activity, and the Pt loading of 0.1 wt %, which is much smaller than the value (1 wt %) commonly employed for reported Pt-deposited anatase as a photocatalyst, gave the highest activity.