Surface Coordination of Ruthenium Clusters on Platinum Nanoparticles for Methanol Oxidation Catalysts

Inorganic surface modification was used to prepare Pt/Ru/Vulcan catalysts by coordinating a triruthenium cluster [ Ru 3 (CO) 9 (MeCN) 3 ] on Pt nanoparticles. The method was used to provided a surface with catalytic activity for use in the direct methanol fuel cell. The cluster adsorptive process followed a Langmuir adsorption isotherm. The amount of Ru could be controlled by changing the experimental conditions of adsorption. The catalyst powder was characterized by energy-dispersive spectrocopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electrochemical studies. The proposed methodology provides a way to place Ru atoms on a Pt surface while avoiding metal segregation. The optimum results were obtained with a catalyst that presented a Ru/Pt ratio of 0.07, as given by XPS analysis. The peak current for methanol oxidation in cyclic voltammetry scans was similar to that of commercial true alloy catalysts. On the basis of these results, some considerations about how ruthenium segregation interferes with methanol oxidation are addressed.