On the influence of the metal loading on the structure of carbon-supported PtRu catalysts and their electrocatalytic activities in CO and methanol electrooxidation

摘要

PtRu(1:1)catalysts supported on low surface area carbon of the Sibunit family(S_(BET)= 72 m~2 g~(-1))with a metal percentage ranging from 5 to 60% are prepared and tested in a CO monolayer and for methanol oxidation in H2SO4 electrolyte.At low metal percentage small(<2 nm)alloy nanoparticles,uniformly distributed on the carbon surface,are formed.As the amount of metal per unit surface area of carbon increases,particles start coalescing and form first quasi two-dimensional,and then three-dimensional metal nanostructures.This results in a strong enhancement of specific catalytic activity in methanol oxidation and a decrease of the overpotential for CO monolayer oxidation.It is suggested that intergrain boundaries connecting crystalline domains in nanostructured PtRu catalysts produced at high metal-on-carbon loadings provide active sites for electrocatalytic processes.