Durable Electrocatalyst Support Materials Based on N-Doped Mesoporous Carbon Nanofibers with Titanium Nitride Overlay Coating for High-Performance Proton Exchange Membrane Fuel Cells

Sustainable endurance of the membrane electrode assembly (MEA) is a major obstacle that hinders the widespread commercialization of PEM fuel cell (PEMFC) technology. Herein, we have successfully demonstrated the construction of an efficient PEMFC using MEAs based on durable N-doped mesoporous carbon nanofibers (g-C3N4/m-PCNFs) functionalized with a thin overlay coating of titanium nitride (TiN) as catalyst support materials with well-distributed 2–3 nm Pt electrocatalysts (Pt/TiN/g-C3N4/m-PCNFs), which could significantly improve the carbon corrosion resistance and inhibit electrocatalyst degradation. Surface modification on the carbon support backbone using N-doping with g-C3N4 and Ti–N–C moieties provides strong metal support interactions to the catalyst layer on the MEA, facilitating ORR activity and stability. The surface-engineered Pt/TiN/g-C3N4/m-PCNFs exhibited outstanding electrocatalytic performance (electrochemical surface area (ECSA) = 95 m2/g) compared to commercial Pt/C (ECSA = 47 m2/g) and showed excellent durability with 93% retention in current density after 30,000 s and minor change in activity even after 10,000 potential sweeps. Compared to the commercial Pt/C electrocatalyst (151 mW/cm2), the Pt/TiN/g-C3N4/m-PCNF-based membrane electrode assembly exhibited 2 times higher power density (330 mW/cm2) and current density (919 mA/cm2) during single PEMFC testing owing to the favorable mass transport due to the accessible mesoporous structure and high specific surface area, N-doping, uniform distribution of Pt nanoparticles, and abundant active sites on the support material. TiN coating enhanced the oxidative/corrosion resistance of the Pt/TiN/g-C3N4/m-PCNFs, which is reflected in the short term durability assessment, where the corresponding MEA exhibited only 0.4% drop in the peak power density even after 8 h of durability testing under PEMFC conditions. Therefore, Pt/TiN/g-C3N4/m-PCNFs are believed to create a paradigm shift in developing robust electrocatalyst support materials toward durable PEMFCs.