The role of the WOx ad-component to Pt and PtRu catalysts in the electrochemical CH3OH oxidation reaction

High surface area carbon-supported platinum-based catalysts, Pt/C, PtWOx/C, PtRu/C and PtRuWOx/C, were prepared via a chemical reduction route using single metal precursor salts. The catalyst particles were found to be in the nanoscale range, and the addition of Ru clearly decreased the particle size. The Ru was found to be partially incorporated into the face centered cubic lattice of Pt and to form a single Ru catalyst component. X-ray diffraction and X-ray photon spectroscopy did not provide evidence for electronic interactions between WOx and Pt as well as WOx and Ru. However, the addition of tungsten to the PtRuWOx/C catalyst resulted in a high degree of catalyst particle agglomeration. Both Ru containing catalysts showed significantly higher activities for the CH3OH oxidation reaction in terms of Pt+Ru mass as well as electroactive Pt+Ru surface area than the Pt/C and PtWOx/C catalysts. The addition of tungsten appeared to mainly result in some 'physical' modification of the catalytically active Pt and Ru surface components such as differences in electroactive surface area rather than promotion of the CH3OH oxidation reaction via a true catalytic mechanism.