Reinforced Hydroxylated Boron Nitride on Porous Sulfonated Poly(ether sulfone) with Excellent Electrolyte Properties for H2/O2 Fuel Cells

Designing a high-performing amorphous porous framework of the proton-conducting membrane with inherent SO3H moieties in the aromatic chain and impregnating the proton source is beneficial for developing an excellent electrolyte for the proton exchange membrane fuel cell. In this work, we synthesize the porous sulfonated poly(ether sulfone) (PSPES) nanocomposite membranes with excellent proton conductivity and stability via modified non-solvent-induced phase inversion. The hydroxylated boron nitride (HBN) was prepared from the bulk BN through simple liquid exfoliation and hydroxylation, which yielded the few-layered sheets. The direct inclusion of HBN into the PSPES will be anchoring or filling on the microporous channels of the membrane, yielding outstanding stability with HBN retention ability and high conductivity. Thereby, an excellent synergistic effect between the PSPES and HBN through the functional groups (SO3H–OH) is shown, producing the proton transport bridge and continuous proton transfer channels within the porous structure. Besides, the current and power density of the 3.5 wt % HBN reinforced PSPES (PSPES-HBN2) membranes were improved to 795 mA cm–2 and 220 mW cm–2. The interconnected microporous PSPES-HBN2 membrane shows an excellent proton conductivity of 77.4 ± 3.87 mS cm–1 at 80 °C with 100% humidity and notably reduced membrane degradation after a 120 h durability test.