| Abstract
| - Macroporous films of oxophilic metals (Ru, Re, Os, RuRe, and RuOs) patterned on a Pt substrate were used as model catalysts for methanol electrooxidation. The films contained distinct and quantifiable interfaces between Pt and the oxophilic metal, thereby enabling a direct comparison of the activities of different pair sites.
- Macroporous Ru, Os, Re, RuOs, and RuRe films were deposited on the Pt substrate by a hard templatemethod in which electrodeposition of the oxophilic metal was confined to the interstices formed by annealedclosely packed uniform polystyrene spheres self-assembled on the Pt substrate. X-ray diffractometryindicated that co-deposited RuOs and RuRe adopted the ruthenium's hcp (hexagonal close-packed) structurewith some negative shifts in the Bragg angles. X-ray photoelectron spectroscopy detected the followingmajor oxidation states on the metal surface: Pt0 on Pt; Ru0 on Ru, RuOs, and RuRe; Os0 on Os andRuOs; and ReVII on Re and RuRe. Both CO stripping voltammetry and chronoamperometric measurementsshowed that the Pt−RuOs pair sites were most active for sustained CO oxidation, followed by the Pt−RuRe, Pt−Ru, and Pt−Os pair sites, in that order. The trend is explained in terms of the strength of OHadsorption on the oxophilic metals and the contributions of OHad to the overall methanol oxidation reaction.The use of regular structured porous films on the Pt substrate with distinct Pt−oxophilic metal(s) interfacesremoves many of the ambiguities in assigning the observed activity difference to the effects of differentPt−oxophilic metal pair sites.
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