Novel cross-linked membranes based on polybenzimidazole and polymeric ionic liquid with improved proton conductivity for HT-PEMFC applications

Abstract

Abstract A series of cross-linked composite membranes based on polybenzimidazole (PBI) and polymeric ionic liquids (PILs) containing imidazole rings have been successfully prepared. The obtained PIL consisted of polymeric cation PBI-BuI and anion BF4−. Here, a concept of dual proton transfer channels was proposed, in which the anions of PIL served as proton receptor through electrostatic interaction and the imidazole rings accepted protons by acid-base effect simultaneously. In order to obtain proton exchange membranes based on PBI/PIL with excellent comprehensive properties, the cross-linkerγ-(2, 3-epoxypropoxy) propyltrimethoxysilane (KH560) is introduced into the matrix to strengthen the mechanical properties by hydrolyzing into Si–O–Si network structure. The composite membranes display excellent mechanical properties, oxidative and thermal stability. In particular, the cPBI-BF4-40 membranes with the highest content of PIL shows a proton conductivity of 0.117 S cm−1 at 170 °C and it is good enough both in mechanical and PA uptake, which will make an outstanding candidate over other PBI-based membranes for high temperature proton exchange membrane fuel cell (HT-PEMFC) applications.