Electrocatalytic reduction of oxygen by FePt alloy nanoparticles

FexP100-x nanoparticles of different compositions (x = 63, 58, 54, 42, 15, and 0) were prepared and loaded onto a glassy carbon (GC) electrode where their catalytic activities in the electroreduction of oxygen were examined and compared. Cyclic and rotating disk voltammetric studies of the resulting FexP100-x/GC electrodes showed that the catalytic activity for oxygen reduction exhibited a peak-shape dependence on the particle composition (x). Among the series of nanocatalysts under study, Fe42Pt58 particles showed the maximum activity for O-2 reduction in terms of the reduction overpotential and current density. This was accounted for by the effects of the Fe content on the electronic structures of the Pt active sites and the resulting Pt-O interactions. Kinetic analyses showed that direct four-electron reduction of adsorbed oxygen occurred on these catalyst surfaces. Additionally, the rate constant of O-2 reduction increased with increasing Pt content in the alloy particles; yet, at x <= 42, the rate constant exhibited only a very small increment. These studies suggest that the Fe42Pt58 particles might represent an optimal composition for oxygen reduction among the series of nanoparticle catalysts under the present study.