Optimizing Mesoporous Structure of Nitrogen-Doped Carbon Supports to Enhance the Activity and Stability of PtCo Intermetallic Alloy toward Oxygen Reduction Reaction

Platinum is the most efficient electrocatalyst to accelerate the sluggish oxygen reduction reaction (ORR), a crucial process at the cathode of proton exchange membrane fuel cells (PEMFCs). Reducing platinum loading in PEMFCs is critical yet challenging due to its insufficient activity and stability. This study focuses on optimizing the mesoporous structure of nitrogen-doped carbon supports to enhance the activity and stability of the Pt-based catalysts. We synthesized nitrogen-doped mesoporous carbon (NMC) supports with different pore sizes via the hard templating method and then loaded a Pt₃Co intermetallic alloy inside the mesopores of NMCs. The resulting PtCo/NMC-4 (with an average mesopore size of ∼5 nm) catalyst exhibits superior ORR activity with a half-wave potential (E_1/2) of 0.939 V vs reversible hydrogen electrode and a mass activity of 2.36 A g_Pt^–1, which is about 1 order of magnitude higher than that of commercial Pt/C. Moreover, the physical confinement of mesopores and the strong metal–support interaction induced by nitrogen defects inhibit the aggregation of Pt₃Co alloy during cycling, leading to the remarkable durability of PtCo/NMC-4 with a loss in cell potential of 12.7 mV at 0.8 A cm^–2 after accelerated durability testing for 30,000 cycles. This study demonstrates the effectiveness of support optimization in enhancing the activity and stability of Pt-based ORR catalysts.