Thermal Behaviours and Single Cell Performance of PBI‐OO/PFSA Blend Membranes Composited with Lewis Acid Nanoparticles for Intermediate Temperature DMFC Application

Abstract

AbstractBuilding on the improved proton conductivity at intermediate temperatures under anhydrous conditions using a ‘proton donor–proton acceptor' concept demonstrated for the first time in the composite membrane made of inorganic lewis acid (boron‐based electron‐deficient nanoparticles) and a poly‐[(1‐(4,4′‐diphenylether)‐5‐oxybenzimidazole)‐benzimidazole] (PBI‐OO)/perfluorosulfonic acid (PFSA) blend, we report here the thermal behaviours and direct methanol fuel cell (DMFC) single cell performance of these membranes at intermediate temperatures (90–120 °C). It is found that the PFSA/PBI‐OO blends and PFSA/PBI‐OO/nano‐BN composites show decreased thermal stability compared to pristine PFSA. We attribute this to a proton transfer reaction between the sulfonic acid and imidazole moieties of the constituent polymers inducing a decreased stability of the resulting sulfonate group. When operated with dry oxygen and methanol/water vapour, the single cell performance of PFSA/PBI‐OO blends is slightly improved compared to that of pristine PFSA. The PFSA/PBI‐OO/nano‐BN composite membranes exhibit much better single cell performance at intermediate temperatures, which could be mainly attributed to its higher anhydrous proton conductivity.