| Abstract
| - The potential- and coverage-dependent infrared absorption spectroscopy (IRAS) of linearly bound CO onsingle-phase polycrystalline arc-melted Pt, PtRu(1/1), PtRu(8/2), PtOs(8/2), PtRuOs(8/1/1), PtRuOs(65/25/10), and Ru electrodes in 0.5 M H2SO4 are correlated with the potential-dependent X-ray photoelectronspectroscopy (XPS) of the PtRu(1/1), PtOs(8/2), and PtRuOs(65/25/10) substrates. The CO stretchingfrequencies decrease as the mole fraction of Pt in the alloy is decreased. The CO oxidation onset on pure Ptat 100.0% CO coverage is 0.5 V vs a reversible hydrogen electrode and shifts negatively as the alloy molefraction of Pt is reduced. At CO dosing conditions that yield 100% coverage on pure Pt, the CO bandwidthsincrease with decreasing Pt mole fraction: on pure Pt the bandwidths increase as the CO coverage is reduced.The effects of CO coverage and bulk alloy composition on the Stark tuning rates (STRs) have beensystematically examined on Pt, and a series of binary and ternary alloy surfaces. The XPS data confirm apotential-dependent surface distribution of oxides and no significant surface segregation of the alloyingcomponents. The systematic displacement, to lower frequencies, of the linear STRs as the mole fraction ofPt is reduced suggests no significant island formation on the arc-melted alloy surfaces. The XPS data alsosuggest that the alloying metals, rather than Pt, are responsible for activation of the water required for methanoloxidation in the direct methanol fuel cell potential window.
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