A series of highly active supported Pt catalysts, developed by sodium borohydride reduction under mild preparation conditions, were used to eliminate indoor formaldehyde (HCHO) at ambient temperature. The influences of oxidation state, support and size of Pt particles, and the operating parameters were investigated. The reduced Pt nanoparticles with different supports are highly active for catalytic oxidation of HCHO. For example, nearly 100% HCHO conversion was obtained on the reduced Pt/TiO(2) catalysts (denoted as Pt-TiO(2)) even with 0.1% Pt loading while it was less than 25% on the oxidized ones. Negatively charged metallic Pt nanoparticles, which probably facilitate the electron transfer and formation of active oxygen, provide the active sites for HCHO oxidation. The turnover frequencies (TOFs) of HCHO oxidation on Pt nanoparticles with different supports are not sensitive to the reducibility of support but somewhat affected by the Pt particle sizes. A maximum TOF of 2.87 s(-1) was obtained on the 1% Pt-MgO with Pt particle size of about 3 nm. The 0.1% Pt-TiO(2) catalyst remained highly active and stable in humid air with a wide gas hourly space velocity range between 40,000 and 240,000 h(-1) and initial HCHO concentration range between 5 and 30 ppm. (C) 2011 Elsevier Inc. All rights reserved.