Effective proton transport and anti-free radical oxidation: construction of interpenetrating network via co-crosslinking polybenzimidazole with proton conductors

Abstract

High temperature proton exchange membranes with good chemical stability and proton conductivity are desired for practical application. A crosslinkable allyl-cyanuric trisulfonic (ACSA) proton conductor and allyl-mPBI (APBI) are designed and synthesized to approach this aim. More stable basic sites (N) are endowed on ACSA and APBI through the reaction of oxidizable –NH groups to fundamentally achieve anti-free radical oxidation of membranes. The co-crosslinking of ACSA and APBI forms a monolithic crosslinked interpenetrating network in APBI-ACSA membranes, while the abundant basic sites construct dense hydrogen-ionic bond networks with –SO3H. The synergy of both networks locks ACSA in networks, avoids leaching and achieves uniform dispersion and high addition level of ACSA, thus providing good membrane stability of mechanical and dimensional. Molecular dynamics simulation shows that the microphase separation structure promotes the formation of continuous proton transport microchannels (including hydrogen-ionic bond network and hydration channel) over wide relative humidity (RH) ranges. Under 100%, 50% and 0% RH, the proton conductivity of APBI-ACSA(40) membrane is 0.158, 0.082 and 0.035 S/cm at 180 °C, respectively. There is almost no decay in conductivity after the durability tests. Meanwhile, APBI-ACSA membranes exhibited good fuel crossover resistance over Nafion membranes for both gas and liquid phase fuels.