LAUSR

It remains a big challenge to remarkably improve both oxygen reduction reaction (ORR) activity and long-term durability of Pt-M bimetal electrocatalysts simultaneously in the harsh cathode environment toward widespread commercialization of polymer electrolyte fuel cells (PEFC). In this account we found double-promotional effects of carbon micro coil (CMC) support on ORR performance and durability of octahedral Pt3 Ni nanoparticles (Oh Pt3 Ni/CMC). The Oh Pt3 Ni/CMC displayed remarkable improvements of mass activity (MA; 13.6 and 34.1 times) and surface specific activity (SA; 31.3 and 37.0 times) compared to those of benchmark Pt/C (TEC10E20E) and Pt/C (TEC10E50E-HT), respectively. Notably, the Oh Pt3 Ni/CMC revealed a negligible MA loss after 50,000 triangular-wave 1.0-1.5 VRHE (startup/shutdown) load cycles, contrasted to MA losses of 40 % (TEC10E20E) and 21.5 % (TEC10E50E-HT) by only 10,000 load cycles. It was also found that the SA increased exponentially with the decrease in the CO stripping peak potential in a series of Pt-M/carbon (M: Ni and Co), which predicts a maximum SA at the curve asymptote. Key factors for simultaneous improvements of performance and durability of core-shell Pt3 Ni/carbon electrocatalysts toward superior PEFC is also discussed.