In this work, thermal treatment of 0.2 wt.% Pt4+ deposited on SiO2 through vacuum calcination and H2 reduction is used to synthesize Pt particles less than 1 nm in diameter that are uniformly dispersed on the SiO2. Traditional treatments involving air calcination/H-2 reduction on the same 0.2 wt.% Pt4+/SiO2 result in the formation of inhomogeneous Pt particles with an average size of similar to 8.4 nm. The tiny Pt particles have an improved reaction rate at ambient temperature and better catalytic stability for formaldehyde (HCHO) oxidation. The formation mechanism of tiny Pt particles and the reaction mechanism of HCHO oxidation were investigated. The CO decomposition product from HCHO could be the essential intermediate in the course of HCHO oxidation, and the oxidative reaction pathway should be HCHO -> CO -> CO2. Adsorbed HCHO may bond to the Pt surface in the eta(2) configuration and form CO through a decomposition process. (C) 2017 Elsevier Inc. All rights reserved.