PtRu Alloy Colloids as Precursors for Fuel Cell Catalysts: A Combined XPS, AFM, HRTEM, and RDE Study

The electrocatalytic activity of bimetallic colloids supported on Vulcan XC72 toward the oxidation of CO and mixtures was investigated by using a newly developed method to characterize supported catalysts in a rotating disk electrode configuration. Prior to the electrochemical measurements, the surfactant was removed by reactive annealing. Parallel atomic force microscopy (AFM) measurements on a planar model system [ on highly oriented pyrolitic graphite] indicate minor sintering in good agreement with high‐resolution transmission electron microscopy (HRTEM) measurements on the Vulcan‐supported catalyst which yield a dispersion of ∼43%. At 60 °C, the electrochemical activity of the PtRu colloid catalyst toward the oxidation of 2% CO in is equal to or slightly higher than that of a commercial PtRu catalyst (E‐TEK). Comparison of the CO tolerance of the PtRu‐colloid/Vulcan with that of proton exchange membrane (PEM) fuel cells was facilitated on the basis of mass‐specific current densities, providing a scale‐up method for predicting the performance of catalysts in a PEM fuel cell.