Ultrafine ordered L12-Pt–Co–Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles (INPs) can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction (ORR) compared to the disordered atomic structures in ordinary solid-solution alloy NPs. Accordingly, through a facile and scalable synthetic method, a series of carbon-supported ultrafine Pt3CoxMn1–x ternary INPs are prepared in this work, which possess the “skin-like” ultrathin Pt shells, the ordered L12 atomic structure, and the high-even dispersion on supports (L12-Pt3CoxMn1–x/SPt INPs/C). Electrochemical results present that the composition-optimized L12-Pt3Co0.7Mn0.3/SPt INPs/C exhibits the highest electrocatalytic activity among the series, which are also much better than those of the pristine ultrafine Pt/C. Besides, it also has a greatly enhanced electrochemical stability. In addition, the effects of annealing temperature and time are further investigated. More importantly, such superior ORR electrocatalytic performance of L12-Pt3Co0.7Mn0.3/SPt INPs/C are also well demonstrated in practical fuel cells. Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocatalytic performance: the Pt–Co–Mn alloy-induced geometric and ligand effects as well as the extremely high L12 atomic-ordering degree. This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst, but also elucidates the corresponding “structure-function” relationship, which can be further applied in designing other intermetallic (electro)catalysts.