Highly loaded fine PtCo intermetallic compounds on 3D N-doped porous graphene for enhanced and sustained efficiency in PEMFCs

Abstract

Currently, carbon supports are subject to corrosion during repetitive start-up/shut-down processes in proton exchange membrane fuel cells (PEMFCs), causing performance degradation. To address this issue, we developed highly graphitized, nitrogen-doped graphene (HGNG) through a plasma-enhanced chemical vapor deposition (PECVD) strategy, followed sequentially by high-temperature annealing and ammonia plasma activation. The HGNG features a three-dimensional hierarchical porous structure with a high specific surface area, a high degree of graphitization, and substantial nitrogen doping. This support enables the uniform distribution of a high Pt loading (45.9 wt%) of ordered face-centered tetragonal L1₀-PtCo nanoparticles (∼4.4 nm). As a result, the L1₀-PtCo/HGNG catalyst exhibits excellent oxygen reduction reaction (ORR) activity and durability in PEMFCs, exceeding the U.S. Department of Energy (DOE) 2025 targets for both catalyst and support stability. Impressively, after accelerated durability tests for the electrocatalyst and support, the L1₀-PtCo/HGNG-based membrane electrode assembly achieves a peak power density of 964 mW cm⁻² and exhibits voltage losses of only 19 mV and 17 mV at 0.8 A cm⁻² and 1.5 A cm⁻², respectively, less than the DOE target of 30 mV loss. This study demonstrates a synergistic design strategy for carbon supports, effectively reconciling the trade-off between graphitization, porosity, and surface functionality, thereby laying a foundation for designing efficient and durable catalysts for practical PEMFC applications.