Regulating coordination environment of atomic dimer catalysts for high performance oxygen reduction reaction in fuel cells

To successfully implement proton exchange membrane fuel cells (PEMFCs), it is critical to develop electrocatalysts for the oxygen reduction reaction (ORR) with excellent activity and durability. Herein, an innovative strategy is proposed to achieve the Pt-Fe bimetallic dimer coordinated with pyrrolic nitrogen sites for the ultrahigh active and stable catalyst in PEMFCs. Thanks to the strong metal-support interaction and synergy between Pt and Fe atoms, the bimetallic Pt1Fe1-NC/AC dimer catalyst shows 24 times enhanced mass activity of 3.94 A mgPt-1 (at 0.9 V vs. RHE) and excellent stability with 20,000 potential cycles in the acidic electrolyte. More importantly, the Pt1Fe1-NC/AC dimer catalyst achieves ultra-low Pt loading of 0.02 mgPt cm-2 in the cathode application of PEMFCs, which shows the peak power density (73.3 W mgPt-1) 16 times higher than that of the benchmarking Pt/C catalyst. The reaction mechanism indicated that the coordination of Pt1Fe1 dimers with pyrrolic N synergistically boosts ORR activity by optimizing the electronic structure of active sites and reducing the energy barrier in the rate-determine step.