A series of Pt/TiO2 catalysts with various Pt particle sizes and chemical properties were facilely synthesized by NaBH4 reduction and heated at different temperatures. They were used to catalytically oxidize gaseous formaldehyde (HCHO) at ambient temperature. The influence of structural nature of Pt NPs on catalytic activity was investigated. The as-prepared Pt NPs are highly dispersed and very active for HCHO oxidation even at room temperature. The maximum Pt dispersion and HCHO removal efficiency reached 73.4% and 81.3%, respectively. The turnover frequencies (TOFs) of Pt NPs present size-dependent effect. The Pt NPs with average size of 10.1 nm had the highest TOF of 4.39 s(-1) for HCHO oxidation. (C) 2014 Elsevier B.V. All rights reserved.