Highly Stable and Active Pt−Cu Oxygen Reduction Electrocatalysts Based on Mesoporous Graphitic Carbon Supports

The activity of oxygen reduction catalysts for fuel cells often decreases markedly (30−70%) during potential cycling tests designed to accelerate catalyst degradation. Herein we achieved essentially no loss in electrochemical surface area and catalyst activity during potential cycling from 0.5 to 1.2 V for presynthesized Pt−Cu nanoparticles of controlled composition that were infused into highly graphitic disordered mesoporous carbons (DMC). The high stability is favored by the strong metal−support interactions and low tendency for carbon oxidation, which mitigates the mechanisms of degradation. Electrochemical dealloying transforms the composition from Pt 20 Cu 80 to Pt 85 Cu 15 with a strained Pt-rich shell, which exhibits an enhanced ORR activity of 0.46 A/mg Pt, >4 fold that of pure Pt catalysts. The high uniformity in particle size and composition both before and after dealloying, as a consequence of the presynthesis/infusion technique, is beneficial for elucidating the mechanism of catalyst activity and, ultimately, for designing more active catalysts.