Revealing the CO Tolerance Mechanism in Acidic Hydrogen Oxidation Reactions on Platinum‐Based Catalyst Surfaces

The presence of trace CO impurity gas in hydrogen fuel can rapidly deactivate platinum-based hydrogen oxidation reaction (HOR) catalysts due to poisoning effects, yet the precise CO tolerance mechanism remains debated. Our designed Au@PtX bifunctional core-shell nanocatalysts exhibit excellent performance of CO tolerance in acidic solution during HOR and possess exceptional Raman spectroscopy enhancement. Through capturing and analyzing in situ Raman spectroscopy evidences on *OH, metal-O species and *CO evolution under 0.3 V, we confirm that oxygen-containing species on PtRu and PtSn catalysts promote the oxidation and desorption of *CO. While Ru enhances *CO adsorption on Pt, the primary CO tolerance performance of PtRu arises from *CO oxidation via a bifunctional pathway. Additionally, electronic structure of Sn reduces *CO adsorption on Pt sites, complementing the bifunctional mechanism to further enhance the CO tolerance performance of PtSn. These discoveries significantly deepen our understanding of the anti-poisoning mechanism of Pt-based catalysts in the HOR process and offer valuable insights for rational catalyst design.