Carbon-supported metal nanoclusters were prepared by chemical method of Pt precursor reduction onto chemically treated carbon blacks (CBs). The size and the loading level of Pt metal clusters were dependent on surface characteristics of CBs. Base-treated CBs-supported Pt showed the smallest particle size of 2.65 nm and the highest loading level of 97% among the chemical-treated CBs-supported Pt catalysts. The electroactivity of the catalysts had been enhanced when the CBs supports were treated by basic or neutral agents, while the electroactivity had been decayed for the acid-treated CBs-supported Pt. (c) 2006 Elsevier B.V. All rights reserved.