Electrostatic interaction based hollow Pt and Ru assemblies toward methanol oxidation

Mastery over the structure and/or composition of metal nanoparticles is an effective way to improve their catalytic activity on a mass basis. Herein, we report a facile solution route for the assembly of hollow Pt nanospheres (hPt) and ultrafine Ru nanoparticles based on electrostatic interactions. In this approach, negatively charged hollow Pt nanospheres with an average size of 12 nm and positively charged ultrafine Ru nanoparticles with an average size of 0.9 nm are first prepared, followed by the successful fabrication of hPt-Ru assemblies upon mixing the particles with opposite charges. The hPt-Ru assemblies at a Pt/Ru molar ratio of 2 : 1 exhibit superior catalytic activity toward methanol oxidation in direct methanol fuel cells for the presence of a mixed-phase containing Pt and an effective oxophilic metal, and a smaller dilution effect on the Pt surface induced by Ru in the assemblies. This study offers a vivid example to demonstrate the integration of a second oxophilic metal into the active Pt catalyst capable of enhancing its catalytic properties by means of a physical construction.