Titanium nitride doped flexible carbon nanofiber membranes as self-supporting microporous layers for proton exchange membrane fuel cells

The gas diffusion layer (GDL) plays a pivotal role in optimizing proton exchange membrane fuel cell (PEMFC) performance. This study presents a novel flexible titanium nitride doped carbon nanofiber membrane (TiN-CNFM) as a self-supporting microporous layer (MPL) that significantly simplifies GDL assembly processes and improves commercial viability. TiN-CNFM is prepared through a systematic fabrication process involving electrospinning of a polyacrylonitrile/tetrabutyl titanate precursor solution, followed by sequential pre-oxidation and carbonization treatments. TiN-CNFM exhibits excellent flexibility, hydrophobicity, conductivity, and optimal pore structure, which allow direct lamination with carbon paper layer by layer to assemble membrane electrode assembly (MEA). The thickness of TiN-CNFM can be precisely regulated by controlling the spinning time. When the thickness of TiN-CNFM is 15 μm, the corresponding MEA achieves the highest peak power density of 1525.1 mW cm -2 at 60% RH, significantly surpassing than that of the conventional carbon black MPL (1144.4 mW cm -2 ). In addition, the hydrophobicity and mechanical strength of TiN-CNFM are enhanced by a simple polytetrafluoroethylene (PTFE) impregnation, which further enhances the output performance of MEA. Furthermore, the feasibility of using TiN-CNFM with a thickness of 150 μm as an integrated GDL directly is explored.