Vinylic-addition Polynorbornene-based Anion-Exchange Membranes with Semi-Interpenetrating Polymer Networks for Water Electrolysis

Anion-exchange membranes (AEMs) with high conductivity and stability are essential components of hydrogen related water electrolysis and fuel cell applications. During the past decades, polynorbornene (PNB)-based AEMs have shown excellent performance due to their saturated all-carbon-based backbones and diverse strategies to prepare cross-linked membranes. However, nearly all previously reported PNB-based AEMs rely on the alkyl-substituted norbornene monomers, whose low-yielding synthesis leads to high-cost of the AEMs. In addition, the cross-linked PNB-based AEMs usually suffered from mechanical brittleness. Herein, we propose a novel semi-interpenetrating polymer network (s-IPN) strategy to simultaneously enhance mechanical modulus and ionic conductivity, while using commercial 5-vinyl-2-norbornene (VNB) as the single norbornene derivatives to prepare high-performance AEMs. A diallylphenol quaternary ammonium salt was used for photo-induced cross-linking with poly-VNB and various dithiols to produce AEMs with s-IPN structures. The resultant membranes have excellent hydroxide conductivities and alkaline stability in 1 mol/L KOH at 80 °C, and are successfully applied in alkaline anion-exchange membrane water electrolyzers to stably operate for over 150 h.