Composite membranes based on polybenzimidazole and ionic liquid functional Si–O–Si network for HT-PEMFC applications

Polybenzimidazole (PBI)/ionic liquid (IL) functional Si–O–Si network composite membranes are prepared from PBI with 1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride. The IL can be hydrolyzed to form Si–O–Si network structure under acidic conditions. And such IL functional Si–O–Si network (NP) in the composite membranes could improve phosphoric acid doping levels and proton conductivities simultaneously. The ability of retaining more PA is also reflected in the high proton conductivity value of PBI/NP-15% membrane which shows almost three-fold increment compared to the pristine PBI. All the PBI/NP-X composite membranes display excellent chemical stability and improved mechanical strength . This is attributed to Si–O–Si network structure. Moreover, PBI/NP composite membranes have demonstrated high thermal stability up to 250 °C, which is attractive for high-temperature (>200 °C) proton exchange membrane fuel cells.