The Effect of Methanol on the Photodeposition of Pt Nanoparticles on Tungsten Oxide

Abstract Formation of platinum nanoparticles on tungsten oxide by photodeposition from acidic [PtCl₆]²⁻ solutions in the absence or presence of methanol is studied in detail. Without methanol, [PtCl₆]²⁻‐ions adsorbed on the WO₃ surface are converted to highly dispersed PtO/Pt(OH)₂ particles upon illumination, the maximum achievable amount being limited to 10–30% of [PtCl₆]²⁻ present in solution. Inclusion of methanol not only promotes adsorption of [PtCl₆]²⁻ ions, but upon illumination results in a deposited Pt quantity close to 100% of [PtCl₆]²⁻. The obtained Pt particles are in the metallic state, large, and often clustered. The limited loading and presence of PtO/Pt(OH)₂ in the absence of methanol is explained by reduction of WO₃‐surface sites, accompanied by water oxidation catalyzed by PtO/Pt(OH)₂ deposits. The extensive reduction of Pt in methanol solutions is likely induced by methoxy‐radicals, oxidatively formed by reaction of methanol with photogenerated holes. This study provides guidelines for optimization of synthesis procedures of Pt/WO₃ (photo)catalysts.