Ion beam modification of Pt electrocatalyst nanoparticles for polymer electrolyte membrane fuel cells

Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Koshikawa, Hiroshi

This study concerns our attempt to improve catalytic properties of nanoparticles of Pt and Pt-group metals by modification with ion beams. We expected that a completely high electronic excitation induced by high-energy ion beams could achieve new atomic arrangement and electronic states at the nanoparticle surface. Pt nanoparticles were prepared on a glassy carbon plate by a sputtering method and then irradiated with proton beams at energies of 0.38 and 10 MeV at room temperature. Cyclic voltammetry in a 0.5 M sulfonic acid aqueous solution suggested that the lower-energy beam irradiation enhanced the active surface area of the Pt nanoparticles, calculated from the coulombic charge for hydrogen adsorption. Thus, the nanoparticles will be modified by the proton-beam excitation so that they have higher surface reactivity. The mechanism determining this irradiation effect is still unclear at present, but we may discuss it in relation to a change in the interfacial crystal structure induced by the irradiation.