Hierarchical Mesoporous Carbon Structure Enabling Outstanding Fuel Cell Cold‐Start and Normal‐Operation Performance

ABSTRACT The cold start of proton exchange membrane fuel cells (PEMFCs) at subzero temperatures is hindered by ice formation during the process. We developed a hierarchical mesoporous carbon structure, denoted as TMC‐GC, showing strong suppression of heterogeneous ice nucleation. The water/TMC‐GC mixture exhibited a phase transition temperature 4.2°C lower than that of the mixture containing commercial carbon black (XC72). Low‐field nuclear magnetic resonance reveals that TMC‐GC can sustain a larger fraction of unfrozen water with higher molecular mobility compared to XC72 at −30°C, thereby favoring more effective removal of supercooled water during cold start. Adopting TMC‐GC as the carbon support, the Pt/TMC‐GC catalyst achieved an isothermal operational time of 25.3 min at −10°C, 3.7 times that of commercial Pt/C (6.8 min), in single‐cell PEMFC tests, demonstrating the state‐of‐the‐art cold‐start performance. Stack‐level theoretical projections indicate that replacing Pt/C with Pt/TMC‐GC enhances PEMFC robustness, enables faster startup, and reduces preheating energy demand (by 28.9% at −20°C) during cold starts. Owing to the superior mass‐transport characteristics of the hierarchical mesoporous carbon structure, the Pt/TMC‐GC delivers key performance metrics that surpass the U.S. Department of Energy targets and are competitive with leading catalysts under normal‐operation conditions.