Synergistic enhancement of PEM fuel cell performance for heavy-duty applications: PtCo/N-doped carbon catalyst and short-side-chain ionomer integration

This study systematically investigates a synergistic catalyst–ionomer design strategy integrating catalyst architecture, support chemistry, and ionomer structure to enable proton exchange membrane fuel cell (PEMFC) performance relevant to heavy-duty applications. A non-commercial PtCo alloy catalyst supported on nitrogen doped mesoporous carbon (PtCo/MFCS) enhances intrinsic oxygen reduction reaction activity via alloying while promoting ionomer dispersion, proton accessibility, and favorable interfacial interactions through surface nitrogen functionalities. In parallel, a short-side-chain (SSC) PFSA ionomer (Aquivion® D79) is introduced to improve proton conductivity and water retention under low-humidity conditions. In a systematic MEA campaign, PtCo/MFCS delivers over 16× higher mass activity at 0.9 V (537 vs 32 mA mgPt⁻¹) than a commercial Pt/Vulcan catalyst, despite 43% lower Pt loading, supported by higher electrochemically active surface area and improved dispersion. Beyond kinetic gains, the mesoporous nitrogen-doped support enhances mid-to-high current density performance by facilitating oxygen transport and water management. Replacing Nafion® with Aquivion® D79 further sustains performance under partial humidification down to 33% RH, demonstrating that SSC ionomer benefits emerge only when coupled with appropriate support porosity and chemistry. Overall, the results reveal strong catalyst–support–ionomer synergy, enabling robust, balance-of plant-friendly PEMFC operation and offering a credible pathway toward DOE heavy-duty fuel cell targets.