Constructing proton transport channels in low phosphoric-acid doped polybenzimidazole membrane by introducing metal–organic frameworks containing phosphoric-acid groups

Proton-exchange membranes (PEMs) are considered as core components of high-temperature fuel cells. Phosphoric acid (PA) plays a pivotal role in the performance of PEMs and is especially vital for conductivity. This work reports the firstly successful preparation of metal–organic frameworks grafted with phosphate functionalized ligand, which introduce efficient, high-performance proton transport channels. At a ligand replacement ratio of 1:2, the conductivity of 40% hydroxyphosphono-acetic acid-type [email protected] membrane is 0.097 S cm−1 at 160 °C (0% RH), and the power density of the fuel cell achieves 640 mW cm−2. When the UIO-66 ligand is replaced with glyphosine containing two phosphate groups at the same ratio (1:2, 40% composition), the highest conductivity of the composite membrane is 0.124 S cm−1, and the power density of the fuel cell reaches 725 mW cm−2 at 160 °C (0% RH). The composite membrane fuel-cell stably withstand a constant current discharge of 200 mA cm−2 for 200 h (160 °C, 0% RH) with a voltage attenuation rate of only 0.042 mV h−1 from 60 to 200 h, lower than that of the 1:2H–[email protected] membrane (0.066 mV h−1) under the same conditions.