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.