Polybenzimidazole‐Reinforced Terphenylene Anion Exchange Water Electrolysis Membranes

Anion exchange membrane water electrolysis (AEMWE) for hydrogen production combines the advantages of proton exchange membrane water electrolysis and alkaline water electrolysis. Several strategies have been adopted to improve the performance of AEMWE and to obtain membranes with high hydroxide ion conductivity, low gas permeation, and high durability. In this work AEMs reinforced with poly[2,2’‐(p‐oxydiphenylene)‐5,5’‐benzimidazole] (PBIO) polymer fibres have been developed. A fibre web of PBIO prepared by electrospinning was impregnated into the poly(terphenylene) mTPN ionomer. The membranes are strengthened by the formation of a strong surface interaction between the reinforcement and the ionomer and by the expansion of the reinforcement over the membrane thickness. The hydroxide ion conductivity, thermal stability, dimensional swelling, mechanical properties, and hydrogen crossover of the reinforced membranes were compared with the characteristics of the non‐reinforced counterpart. The incorporation of PBIO nanofibre reinforcement into the membrane reduced hydrogen crossover and improved tensile properties, without affecting hydroxide conductivity. PBIO‐reinforced mTPN membrane was assessed in a PGM‐free 5 cm2 AEMWE single cell using NiFe oxide anode and NiMo cathode catalysts, at a cell temperature of 50 °C and with 1 M KOH fed to the anode. The performance of the cell increased continuously over the 260 hours test period, reaching 2.06 V at 1.0 A cm−2. Anion exchange membranes based on poly(terphenylene) were reinforced with poly[2,2’‐(p‐oxydiphenylene)‐5,5’‐benzimidazole] fibres. The formation of a strong surface interaction between the ionomer and the reinforcement and the expansion of the reinforcement over the membrane thickness was the key to reduce hydrogen crossover and improve tensile properties, without affecting hydroxide conductivity, leading to high membrane stability and water electrolysis performance.