• • CO electrooxidation onset potential of ~0.13 V vs. RHE, determined by two independent methods (background-corrected current >0 mA cm-2 in COOR tests and forward scan current exceeding N2 background in CO-stripping), enabling low-potential CO removal that reduces anode overpotential and improves PEMFC efficiency under reformate operation.
• • Maximum power density under 100 ppm CO exceeds that of reported advanced catalysts (Table S5), demonstrating superior CO tolerance and potential for direct integration with reformate hydrogen without complex purification, lowering system cost and complexity.
• • Hydrophilic Cr single-atom sites weaken CO adsorption on Pt through electronic regulation while promoting water activation, addressing the fundamental bottleneck of Pt poisoning by trace CO that plagues conventional PEMFC anodes.
• • The dual-function mechanism—electronic modulation and water activation—provides a design principle for anti-poisoning catalysts, potentially extending to other noble-metal systems and reducing reliance on high Pt loadings, with industrial implications for automotive and stationary fuel cell applications.