Well-Alloyed PtFe∕C Nanocatalysts of Controlled Composition and Same Particle Size: Oxygen Reduction and Methanol Tolerance

Abstract

A study of the effect of iron concentration on the electrocatalysis of oxygen reduction reaction (ORR) on well-alloyed carbon-supported PtFe nanocatalysts with a controlled iron content and the same particle size is presented. To obtain the catalysts for this study, PtFe nanoparticles of different compositions were first obtained in a colloidal state in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)+n-butanol/n-heptane/water microemulsions and subsequently supported in high surface area carbon powder. Transmission electron microscopy evidenced that all PtFe/C nanocatalysts prepared are monodispersed and have nearly the same average particle size. X-ray diffraction studies showed that the lattice parameter of these PtFe/C catalysts varies linearly with iron content up to 50% (in atoms), while the compositions of the alloyed phases estimated by using Vegard's law are almost identical to the nominal values, indicating a high degree of alloying. The electrocatalytic activity for ORR of these catalysts was studied using the rotating disk electrode technique in O-2 saturated 0.5 mol L-1 H2SO4 solutions, while methanol tolerance was evaluated from curves taken in acid solutions containing 0.1 mol L-1 methanol. The results reported here reflect the dependence of the electrocatalytic activity for the ORR on iron concentration in the absence of particle size effects and metal segregation.