Carbon nanofibers have emerged as a promising catalyst support material for proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) due to their unique structural and electrochemical properties. Their integration addresses several challenges associated with conventional supports like carbon black or graphene, particularly in terms of platinum (Pt) deposition, durability, and mass transport efficiency.

The deposition of Pt nanoparticles on carbon nanofibers is facilitated by their high surface area and well-defined graphitic structure. The graphitic edge planes of carbon nanofibers provide abundant nucleation sites for Pt, leading to a more uniform distribution of catalyst particles compared to amorphous carbon black. Studies indicate that Pt nanoparticles supported on carbon nanofibers exhibit smaller average diameters, typically in the range of 2–4 nm, with a narrow size distribution. This uniformity enhances the electrochemical active surface area (ECSA), a critical factor in improving the oxygen reduction reaction (ORR) kinetics in PEMFCs and methanol oxidation reaction (MOR) in DMFCs.

Durability is a major concern in fuel cell applications due to catalyst degradation mechanisms such as Pt dissolution, particle agglomeration, and carbon support corrosion. Carbon nanofibers demonstrate superior corrosion resistance compared to carbon black, primarily due to their higher degree of graphitization. The ordered graphitic structure reduces the oxidation rate of the support under harsh electrochemical conditions, such as high potentials encountered during startup-shutdown cycles. Accelerated stress tests reveal that Pt/carbon nanofiber electrodes retain over 70% of their initial ECSA after 30,000 potential cycles, whereas Pt/carbon black counterparts often degrade below 50% under identical conditions.

Mass transport advantages of carbon nanofibers stem from their fibrous morphology and open porous structure. Unlike carbon black, which forms dense agglomerates leading to tortuous diffusion pathways, carbon nanofibers create a more accessible network for reactant and product transport. This is particularly beneficial in DMFCs, where methanol and water diffusion must be optimized to prevent flooding or concentration polarization. The straight, interconnected pores in carbon nanofiber-based catalyst layers reduce mass transport resistance, contributing to higher power densities at high current densities.

Comparisons with graphene-based supports reveal trade-offs between activity and stability. Graphene offers an exceptionally high surface area and excellent electrical conductivity, often leading to higher initial ORR activity than carbon nanofibers. However, graphene’s tendency to restack and its susceptibility to oxidative degradation under long-term operation limit its durability. In contrast, carbon nanofibers provide a balanced combination of moderate surface area, structural robustness, and corrosion resistance, making them more suitable for practical fuel cell applications.

The mechanical properties of carbon nanofibers further enhance their suitability as catalyst supports. Their fibrous nature allows for the fabrication of freestanding electrodes without the need for polymeric binders, which can introduce additional contact resistance and degradation pathways. Binder-free electrodes based on carbon nanofibers exhibit improved mechanical integrity and reduced interfacial resistance, contributing to better long-term performance.

In terms of manufacturing scalability, carbon nanofibers can be produced via cost-effective methods such as electrospinning followed by thermal treatment. This contrasts with the more complex synthesis routes required for high-quality graphene supports. The ability to tailor carbon nanofiber diameter, porosity, and surface chemistry during synthesis provides additional flexibility in optimizing catalyst layer design for specific fuel cell operating conditions.

While carbon black remains widely used due to its low cost and established processing techniques, its limitations in durability and mass transport are increasingly apparent in advanced fuel cell systems. Carbon nanofibers present a viable alternative that addresses these shortcomings without the complexities associated with graphene-based materials. Future developments may focus on further enhancing the graphitic order of carbon nanofibers or incorporating heteroatom dopants to improve their interfacial interactions with Pt nanoparticles, thereby pushing the performance boundaries of PEMFCs and DMFCs.

The integration of carbon nanofibers in fuel cell electrodes represents a strategic advancement in catalyst support technology. By offering a unique combination of durability, mass transport efficiency, and ease of fabrication, they bridge the gap between conventional carbon materials and emerging nanostructured supports, paving the way for more reliable and high-performance fuel cell systems.