Structural and Electrochemical Characterization of Binary, Ternary, and Quaternary Platinum Alloy Catalysts for Methanol Electro-oxidation

• DOI: 10.1021/jp982887f
• Publication Date: 2002-07-26T05:28:13Z
• Authors: Bogdan Gurau; Rameshkrishnan Vi...; Renxuan Liu; Todd J. Lafrenz; Kevin L. Ley; E. S. Smotkin; Erik Reddington; Anthony Sapienza; Benny C. Chan; Thomas E. Mallouk; S. Sarangapani
• Keywords: Nanocrystalline material; Lattice constant

The bifunctional model for methanol electro-oxidation suggests that competent catalysts should contain at least two types of surface elements: those bind and activate its C−H bonds adsorb water. Our previous work considered phase equilibria relative Pt−C M−O (M = Ru, Os) bond strengths in predicting improved activity among single-phase Pt−Ru−Os ternary alloys. By addition a correlation with M−C Pt, Ir), it is possible to rationalize the recent combinatorial discovery further Pt−Ru−Os−Ir quaternaries. X-ray diffraction experiments show these quaternary are composed primarily nanocrystalline face-centered cubic (fcc) phase, combination an amorphous minor component. For relatively high Ru content, lattice parameter deviates positively from corresponding arc-melted fcc alloy, suggesting Pt-rich. Anode catalyst polarization curves direct fuel cells (DMFC's) 60 °C best compositions markedly superior Pt−Ru, despite higher specific area latter. A remarkable difference between revealed by concentration dependence current density. Although rate oxidation zero order [CH3OH] potentials relevant DMFC operation (250−325 mV vs RHE) approximately first electrodes. This finding implies will be far Pt−Ru DMFC's constructed electrolyte membranes resist crossover, which concentrations can used.