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

Abstract

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 °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 H₂–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.