2.3. Decoration of Nanotubes with Pt Nanoparticles. The
decoration of Pt nanoparticles on the TiO2 nanotubes was examined
according to a previous report.25 After calcinations at 450 °C for 3 h
under air (Fulltech, Model FT-101FM, Japan; heating rate = 2 °C
min−1
), the TiO2 nanotube arrays were transferred into a roundbottom
reaction flask filled with 100 mL of an aqueous solution containing 0.01 mM H2PtCl6 (Kojima Chemical, Japan) and 0.06 mM NaOH (Kanto, Japan). Subsequently, the flask was maintained at 100 °C in an oil bath for 48 h under air. To obtain metallic Pt nanoparticles on the surface of the TiO2 nanotubes, the Pt-iondecorated TiO2 nanotube arrays were put in a tube furnace (Asone, TMF-500N, Japan) under N2 and H2 (1.5 vol %) gas flow at 200 °C for 4 h.