Enhancing CO\nTolerance in PEMFC Anodes via Thermal\nOxidation Induced RuO<sub>2</sub> Blocking Shell on a PtRu/C Catalyst

CO poisoning in Pt-based anode catalysts significantly\nhampers\nthe proton exchange membrane fuel cell (PEMFC) performance. Despite\ngreat advances in CO-tolerant catalysts, their effectiveness is often\nlimited to fundamental three-electrode systems, which is inadequate\nfor practical PEMFC applications. Herein, we present a straightforward\nthermal oxidation strategy for constructing a Ru oxide blocking layer\non commercial PtRu/C through a one-step Ru-segregation-and-oxidation\nprocess. The resulting 0.7 nm thick Ru oxide layer effectively inhibits\nCO adsorption while maintaining hydrogen oxidation activity. PtRu@RuO<sub>2</sub>/C demonstrates exceptional CO tolerance, enduring 1% CO in\nrotating disk electrode tests, an ∼10-fold improvement compared\nto that of PtRu/C. Crucially, it retains high HOR activity and CO\ntolerance in PEMFC, with negligible polarization curve loss in the\npresence of 100 ppm CO. Notably, 85% HOR activity is retained after\na 4 h stability test. This enhancement contributes to the Ru oxide\nlayer decelerating CO adsorption kinetics, rather than promoting CO\noxidation via the classic bifunctional mechanism.