Room-Temperature Preparation of Platinized Nonstoichiometric Tungsten Oxide via Platinum Photodeposition Followed by Chemical Reduction: Kinetic Enhancement of Photocatalytic Oxidation and Disinfection under Low-Intensity Visible-Light Irradiation

Oxygen vacancy (OV) as the key site in promoting charge separation and visible-light harvesting in WO₃ has often been created through thermal annealing. However, this study proposes the sequential combination of Pt photodeposition followed by chemical reduction using NaBH₄ as a room-temperature approach to fabricate platinized oxygen vacant tungsten oxide (Pt/WO_3-x). OVs (or low-valence tungsten), detected using multispectroscopic techniques, occurred by catalytic hydrogenation featuring atomic hydrogen generated via H₂ (evolved from NaBH₄ hydrolysis) dissociation on surface-loaded Pt nanoparticles. The Pt phase necessity for H₂ splitting was supported based on the enhanced photocatalytic performance achieved when Pd photodeposition and hydrogen annealing were alternatively adopted as pre- and post-treatment steps, respectively. The superiority of Pt/WO_3-x over stoichiometric counterparts in terms of photocatalytic activity for aqueous-phase organic oxidation was demonstrated by a comparative assessment with varied Pt contents, light intensities, and target substrates. This aligned with the improved efficiency of Pt/WO_3-x for the photocatalytic decomposition of gaseous toluene and the inactivation of pathogenic microorganisms. Together with negligible performance loss and minor variation in tungsten/oxygen valences during repeated use, marked enhancement in the visible-light activity of Pt/WO_3-x via OV implantation at room temperature implied the potential of the proposed two-step method to produce oxygen-defective metal oxides.