Hierarchical Carbon Nanotube Hybrid Films Modified Gas Diffusion Layer for High-Performance Proton-Exchange Membrane Fuel Cells

The functional gas diffusion layer (GDL), serving as a water-gas transfer control medium, significantly influences the performance of proton-exchange membrane fuel cells (PEMFCs). To improve simultaneously the water retention and gas transport rates, we present a straightforward and effective strategy to prepare carbon nanotube (CNT) hybrid films as functional interlayers in GDLs. With single-walled CNTs and multiwalled CNTs in the weight ratio of 1:1, the as-prepared GDL exhibits optimized electrochemical performance under all of the experimental cases. Especially, the current density is increased to 3.36 A cm^-2 at 0.6 V under 26% relative humidity (RH) and 4.87 A cm^-2 at 0.2 V under 100% RH. It is because the CNT hybrid films with hierarchical pore structures in GDLs are valid for enhancing both self-humidification and mass-transfer performance. The micropores with reasonable wettability serve as capillary vessels for absorbing water to promote the retention of moisture in the proton-exchange membrane, while the mesopores provide preferential transport pathways for reaction gas. Our results demonstrate that the CNT-based GDL may illuminate the potential application of PEMFCs.