(544cl) High-Performance Pt-Based Cathode Catalysts: Novel Carbon Supports and in-Situ Generation of Alloy Structure

Polymer electrolyte membrane fuel cells (PEMFCs) have been widely considered as one of environmentally friendly and highly efficient electric power sources for a wide variety of power applications. Pt supported on carbon black remains the most effective cathode catalyst to catalyze the kinetically sluggish oxygen reduction reaction (ORR). However, owing to the agglomeration of Pt nanoparticles and Ostwald ripening, the performance degradation is often observed for traditional Pt/C catalysts which can be attributed to the loss of electrochemical active surface area and carbon support oxidation. In this research, platinum nanoparticles deposited on nitrogen/metal co-doped graphene tubes (NGTs) via polyol reduction method followed by post-treatment, serving as cathode catalysts, with high activity and stability under potential cycling conditions in acidic media, was studied. The mass activity of Pt supported on graphene tubes is much higher than that of traditional commercial Pt/C catalysts. More importantly, after 30,000 cycles (1.0-1.5V vs RHE) at room temperature, the carbon tube structure was well maintained and no ECSA loss of this Pt-based catalyst was observed, which means the graphene tubes are corrosion-resistant. Even at elevated 60 °C, this excellent Pt cathode catalyst shows no degradation during accelerated stress tests. The improved activity and stability are attributed to the formation of Pt-M alloy phase, intrinsically active and highly graphitized NGTs, and possible synergistic effects between the carbon support and the Pt nanoparticles.