Preparation and Characterization of <scp>MOF</scp> ‐Doped Sulfonated Polybenzimidazole Proton Exchange Membranes

ABSTRACT High concentrations of phosphoric acid (PA) doping will severely compromise the mechanical properties of polybenzimidazole proton exchange membranes (PEMs). Meanwhile, it also leads to PA leaching from membranes. Therefore, it is necessary to balance the advantages of high proton transport performance resulting from high PA doping with the associated reduction in mechanical properties. In this study, sulfonated polybenzimidazole (SPBI) was synthesized, and SPBI@UN PEMs with varying doping levels were prepared by incorporating amino‐functionalized metal–organic framework material UiO‐66‐NH 2 (UN) into SPBI. It was observed that when the UN doping ratio did not exceed 15 wt%, the proton conductivity as well as the tensile strength of the SPBI@UN PEMs increased with rising UN doping ratios after PA treatment, while there was a concomitant decrease in PA uptake and swelling ratio. A high proton conductivity of 0.090 S cm −1 was recorded at 160°C and 30% relative humidity for the SPBI@UN15% membrane under a lower PA uptake of 138.6%, significantly surpassing that of the SPBI membrane under a high PA uptake of 174.7% (0.044 S cm −1 ). Additionally, the tensile strength subsequent to the doping with PA improved from 11.48 MPa for the SPBI membrane to 16.79 MPa for the SPBI@UN15% membrane. In single cell tests, the SPBI@UN15% membrane exhibited remarkable performance. At 140°C, it reached a peak power density of 658 mW cm −2 .