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)-butanol/-heptane/water microemulsions and subsequently supported in high surface area carbon powder. Transmission electron microscopy evidenced that all nanocatalysts prepared are monodispersed and have nearly the same average particle size. X-ray diffraction studies showed that the lattice parameter of these 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 saturated solutions, while methanol tolerance was evaluated from curves taken in acid solutions containing 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.