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

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.