Abstract
AbstractPt‐Sn bimetallic catalysts, especially Pt‐Sn alloys, are considered highly CO‐tolerant and are thus candidates for reformate derived hydrogen oxidation and for direct oxidation of fuel cell molecules. However, it remains unclear if this CO‐tolerance originates from Sn in the Pt‐Sn alloy or whether SnO2, present as a separate phase, also contributes. In this work, a carbon‐supported Pt‐SnO2 was carefully synthesized to avoid the formation of Pt‐Sn alloy phases. The resulting structure was analysed by scanning transmission electron microscopy (STEM) and detailed X‐ray absorption spectroscopy (XAS). CO oxidation voltammograms of the Pt‐SnO2/C and other SnO2‐modified Pt surfaces unambiguously suggest that a bifunctional mechanism is indeed operative at such Pt‐SnO2 catalysts for stable CO oxidation at low overpotentials. The results from these studies suggest that the bifunctional mechanism can be attributed to the co‐catalysis role of SnO2, in which the surface hydroxide of SnO2 (Sn‐OH) reacts with CO adsorbed on Pt surface (Pt‐COads) and regenerates via a SnII/SnIV reversible redox couple (−0.2–0.3 V vs. reversible hydrogen electrode).
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