Enhancing Fuel\nCell Performance: The Role of a Copper\nMetal–Organic Framework in Phosphoric Acid-Doped Polybenzimidazole\nProton Exchange Membranes

Fuel\ncells using proton exchange membrane (PEM) technology,\nwhich\nexhibit superior performance across a wide temperature range, have\nattracted significant interest in fuel cell vehicle development. Poly(2,2′-<i>m</i>-phenylene-5,5′-benzimidazole) (m-PBI) serves as\na pivotal component in the construction of membranes for polymer electrolyte\nmembrane fuel cells (PEMFCs). m-PBI was synthesized via the melt polycondensation\nmethod from its monomers. The structure and molecular weight of m-PBI\nwere examined by proton Nuclear magnetic resonance (NMR) spectroscopy\nand gel permeation chromatography (GPC) techniques, respectively.\nHerein, we prepared a copper metal–organic framework (MOF)\nfrom its precursor and loaded it into the m-PBI membranes. Phosphoric\nacid (PA) doping strategically enhances the inherent properties of\nm-PBI, significantly improving the ionic conductivity within the PEM.\nThe MOF loading improved PEM’s PA uptake with extended, uninterrupted\nproton transport channels. The membranes’ physicochemical attributes\nshowed a direct correlation with MOF concentration, surpassing that\nof pristine m-PBI membranes. Due to their strong PA and water uptake\nabilities, the MOF-loaded m-PBI membranes exhibited enhanced conductivity\nover a wide range of temperatures (up to 80 °C) compared to the\nbare m-PBI membrane. At 80 °C, the PA-doped 3 wt % MOF-loaded\nm-PBI showed a peak power density of 371 mW/cm<sup>2</sup>, while\nthe PA-doped m-PBI had a power density of 255 mW/cm<sup>2</sup>. This\ninnovative PEM outperforms conventional materials due to its superior\ndesign when compared with current m-PBI-based PEMFC systems.