Pt electrocatalysts used in PEM fuel cells are easily poisoned by small amounts of carbon monoxide in hydrogen-rich fuel gas streams . It has been demonstrated that the CO-tolerance of Pt catalysts can be improved by the addition of a second metal due to either a bifunctional mechanism or an electronic effect . The single atom alloys (SAAs) consist of Pt atoms exclusively in dispersed, isolated sites  which only allow the weaker atop adsorption of CO that improves the CO tolerance of the Pt metal through a geometric effect.
Here we have investigated the CO tolerance performance of Pt/Cu SAAs. Nanoparticles of Pt/Cu SAAs were prepared by colloidal synthesis and subsequent galvanic replacement of Cu for trace amounts of Pt . The SAA geometry was found to enhance CO tolerance during H2 activation and hydrogenation of acetylene. The H2-D2 exchange reaction was used to probe the H2 activation activity of the Pt/Cu SAA and Pt monometallic catalyst. We show that the CO in the gas phase exerts a significantly smaller poisoning effect on the hydrogenation activity of Pt/Cu SAA compared to the Pt monometallic catalyst. The preparation, reactivity, and characterization of the SAA nanoparticles with IR, X-ray photoelectron spectroscopy, electron microscopy and X-ray absorption techniques will be presented. Using scanning tunneling microscopy (STM) and temperature programmed desorption/reaction (TPD/R), we show the atomic scale structure of these systems and demonstrate that Pt-Cu(111) SAAs bind CO much weaker than contiguous Pt.
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