Core@Shell Pt<sub>3</sub>Co@Pt/C Nanoparticles as\nan Electrocatalyst for the Oxygen Reduction Reaction

Introducing\ntransition metals to form platinum-based alloys is\nan effective strategy for optimizing oxygen reduction reaction (ORR)\nperformance, while the disordered nanostructure of the alloy catalyst\nhas limited improvement in the ORR durability. Especially, there are\npractical challenges in controlling and maintaining the ordered nanostructure\nof platinum-based alloys during the ORR. In this study, a highly ordered\ncore–shell structural Pt<sub>3</sub>Co@Pt/C catalyst was synthesized\nvia a facile impregnation-annealing and acid-washing procedure with\nfinely controlling the Pt/Co atom ratio, annealing temperature, and\ntime. The obtained Pt<sub>3</sub>Co@Pt/C catalyst exhibited a core–shell\nnanostructure as well as enhanced ORR activity when compared to commercial\nPt/C, with a mass activity (MA) of A mg<sub>Pt</sub><sup>–1</sup> and a specific activity (SA) of 0.72 mA cm<sup>–2</sup>,\nmarking improvements by factors of 2.05 and 2.67, respectively. The\nsuperior catalytic performance is attributed to the optimized electronic\nstructure of Pt induced by Co doping, which was revealed by further\nphysicochemical characterization analysis. Following 30,000 cycles\nof accelerated degradation testing (ADT), Pt<sub>3</sub>Co@Pt/C retained\n73.58% of its initial electrochemical surface area (ECSA), 40% of\nMA, and 55.56% of SA, with both MA and SA remaining 2 to 4 times higher\nthan commercial Pt/C. Notably, the catalyst displayed minimal performance\ndeterioration between 10,000 and 30,000 ADT cycles and nearly negligible\ncatalyst nanoparticle aggregation, attributable to the efficacious\nshielding provided by the acid-washed core–shell nanostructure.\nThis work developed highly durable core–shell Pt<sub>3</sub>Co@Pt/C nanoparticles for the ORR, as well as provided a universal\nreference strategy for controlling the ordered structure of platinum-based\nalloys doped with other transition metals.