Enhancing CO Tolerance in PEMFC Anodes via Thermal Oxidation Induced RuO₂ Blocking Shell on a PtRu/C Catalyst

CO poisoning in Pt-based anode catalysts significantly hampers the proton exchange membrane fuel cell (PEMFC) performance. Despite great advances in CO-tolerant catalysts, their effectiveness is often limited to fundamental three-electrode systems, which is inadequate for practical PEMFC applications. Herein, we present a straightforward thermal oxidation strategy for constructing a Ru oxide blocking layer on commercial PtRu/C through a one-step Ru-segregation-and-oxidation process. The resulting 0.7 nm thick Ru oxide layer effectively inhibits CO adsorption while maintaining hydrogen oxidation activity. PtRu@RuO₂/C demonstrates exceptional CO tolerance, enduring 1% CO in rotating disk electrode tests, an ∼10-fold improvement compared to that of PtRu/C. Crucially, it retains high HOR activity and CO tolerance in PEMFC, with negligible polarization curve loss in the presence of 100 ppm CO. Notably, 85% HOR activity is retained after a 4 h stability test. This enhancement contributes to the Ru oxide layer decelerating CO adsorption kinetics, rather than promoting CO oxidation via the classic bifunctional mechanism.