Bifunctional versus Defect‐Mediated Effects in Electrocatalytic Methanol Oxidation

Abstract

The most prominent and intensively studied anode catalyst material for direct methanol oxidation fuel cells consists of a combination of platinum (Pt) and ruthenium (Ru). Classically, their high performance is attributed to a bifunctional reaction mechanism where Ru sites provide oxygen species at lower overpotential than Pt. In turn, they oxidize the adsorbed carbonaceous reaction intermediates at lower overpotential; among these, the Pt site‐blocking carbon monoxide. We demonstrate that well‐defined Pt modified Ru(0001) single crystal electrodes, with varying Pt contents and different local PtRu configurations at the surface, are unexpectedly inactive for the methanol oxidation reaction. This observation stands in contradiction with theoretical predictions and the concept of bifunctional catalysis for this reaction. Instead, we suggest that pure Pt defect sites play a more critical role than bifunctional defect sites on the electrodes investigated in this work.

Hierarchical platinum–nickel@platinum–tin core@shell nanowires achieve efficient fuel cell catalysis

“…19 Thereinto, the additional introduction of oxyphilic metals has been verified as an available approach to prevent CO poisoning through the bifunctional mechanism and ligand effect. 20 Among various non-precious elements for alloying with Pt, tin (Sn) is nearly the best choice for inherently improving the MOR kinetics and anti-poisoning ability owing to its easy adsorption of hydroxyl group radicals, which is conducive to the oxidative removal of CO intermediates. 21 Accordingly, the PtSn alloy is a more active bimetallic electrocatalyst than other PtM-based alloys investigated by far for alcohol oxidation.…”

Facile synthesis of PEG-glycerol coated bimetallic FePt nanoparticle as highly efficient electrocatalyst for methanol oxidation

“…The bifunctional effect provided by this alloyed material help in easy adsorption of hydroxyl groups (OH − ) at more negative potential and catalysed the electrooxidation of adsorbed CO thereby reducing poisoning effect on catalyst. Also, the addition of second metal results in an electronic exchange interaction with Pt and make Pt surface to be less affected by intermediate species 14 , 15 .…”