Controllable fabrication of platinum nanospheres with a polyoxometalate-assisted process

Pt nanospheres with an average diameter of 60 +/- 10 nm have been successfully synthesized at room temperature through a facile polyoxometalate(POM)-assisted process. Characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) clearly showed that these Pt nanospheres consisted of 2-7 nm Pt nanodots. During the formation of such unique nanostructures, POMs were found to serve as both catalyst and stabilizer. The size of the as-synthesized Pt nanospheres could be controlled solely by adjusting the molar ratio of POMs to H2PtCl6. A possible formation mechanism based on POMs-mediated electron transfer from ascorbic acid (AA) to PtCl62- and AA-assisted aggregation was tentatively proposed to rationalize the formation of such nanostructures. Importantly, these specific Pt nanospheres exhibited good electrocatalytic activity towards the oxidation of methanol, making them promising for applications in direct methanol fuel cells. (C) 2010 Elsevier Inc. All rights reserved.