Phosphoric acid-doped poly(ether sulfone benzotriazole) for high-temperature proton exchange membrane fuel cell applications

Abstract A novel proton exchange membrane poly(ether sulfone benzotriazole) (PESB) was synthesized by polycondensation of 4,4-difluorodiphenylsulfone and 4-Hydroxy-1H-benzotriazole. The polymer structure was characterized by FT‐IR, NMR and elemental analysis. The results were well consistent with the proposed structure. We introduced large amounts of benzotriazole into the polymer main chains by facile nucleophilic reaction, and proton transfer could be achieved through acid-base interactions of benzotriazole with phosphoric acid (PA). Compared with PA-doped m-PBI, the PA-doped PESB membrane showed higher proton conductivity due to the strong acid-base interactions between the benzotriazole and PA. The PA uptake of 221% PESB membrane displayed the proton conductivity of 0.073 S cm −1 at 160 °C, which was higher than that of m-PBI. The fuel cell performance of the PA-doped PESB was evaluated and was obtained a maximum peak power density of 427 mW cm −2 with an open cell voltage of 0.91 V at 160 °C.