Gel Electrolytes of Covalent Network Polybenzimidazole and Phosphoric Acid by Direct Casting. Issue 12 (13th November 2017) - Kirkebæk, Andreas
Abstract: Polybenzimidazole membranes imbibed with phosphoric acid can support high proton conductivity at 120–200 °C, and have therefore emerged as the state‐of‐the‐art electrolytes for fuel cells operating in this temperature range. This work presents a novel and operationally simple methodology for preparing mechanically robust covalent network polybenzimidazole membranes containing up to 95 wt% phosphoric acid. Diamino‐terminal pre‐polymers of different chain lengths are first prepared, followed by addition of a trifunctional carboxylic acid. The crude solutions are cast and subsequently heat treated at up to 230 °C, yielding free‐standing membranes of networked polybenzimidazole with high proton conductivity at up to 180 °C and encouraging fuel cell performance. Abstract : Covalent network polybenzimidazole membranes are obtained via a novel sequential direct casting procedure. Free‐standing and mechanically robust gel electrolytes are obtained with phosphoric acid contents of up to 95 wt%. It supports high proton conductivity at temperatures well above 100 °C as ultimately manifested by low internal resistance in fuel cells operating at 180 °C.