Organic/inorganic composite membranes based on polybenzimidazole and nano-SiO2

Organic/inorganic composite membranes based on polybenzimidazole (PBI) and nano-SiO2 were prepared in this work. However, the preparation of PBI/SiO2 composite membrane is not easy since PBI is insoluble in water, while nano-SiO2 is hydrophilic due to the hydrophilicity of nano-SiO2 and water-insolubility of PBI. Thus, a solvent-exchange method was employed to prepare the composite membrane. The morphology of the composite membranes was studied by scanning electron microscopy (SEM). It was revealed that inorganic particles were dispersed homogenously in the PBI matrix. The thermal stability of the composite membrane is higher than that of pure PBI, both for doped and undoped membranes. PBI/SiO2 composite membranes with up to 15 wt% SiO2 exhibited improved mechanical properties compared with PBI membranes. The proton conductivity of the composite membranes containing phosphoric acid was studied. The nano-SiO2 in the composite membranes enhanced the ability to trap phosphoric acid, which improved the proton conductivity of the composite membranes. The membrane with 15 wt% of inorganic material is oxidatively stable and has a proton conductivity of 3.9 x 10(-3) S/cm at 180 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.