Nitrogen doping to accelerate the phase transition to ordered intermetallic Pt3Co catalyst for the oxygen reduction reaction in fuel cells

Ordered intermetallic Pt-M alloys are foreseen to be promising as next-generation low-Pt catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) due to their high catalytic activity and stability. Nevertheless, the disorder-to-order intermetallic phase transition often needs to proceed at elevated annealing temperature for a long time, which leads to severe particle agglomeration. Herein, an efficient nitrogen (N)-doping strategy is developed to speed up such phase transition in an intermetallic Pt3Co alloy catalyst, which shortens the annealing duration by 3-5 fold at a temperature of 600-800 degrees C. Such a strategy can not only minimize the particle agglomeration but also effectively optimize the electronic structure of surface Pt atoms with the incorporated N. The prepared N-doped ordered intermetallic Pt3Co catalyst exhibits high ORR activity among the best of the state-of-the-art, with mass activities of 1.21 and 1.20 A mg(Pt)(-1) at 0.90 V in rotating disk electrode (RDE) and proton exchange membrane fuel cell (PEMFC) tests, respectively. Moreover, with the total Pt loading of 0.15 mg(Pt) cm(-2), the H-2-air PEMFC delivers a power density of 1.27 W cm(-2) at 150 kPa(abs) and 0.6 V, corresponding to a high Pt utilization of 0.118 g(Pt) kW(-1) that has surpassed the DOE 2025 target (0.125 g(Pt) kW(-1)). This study paves a new way to develop high-performance low-Pt ORR catalysts for PEMFCs.