Development of anhydrous proton exchange membrane fuel cell (PEMFC): an investigation of molecular design and synthesis of model compounds

Abstract

Benzimidazole-based model compounds are designed and synthesized in a systematic system, i.e., mono-, di- and tri-functional compounds. The characterizations indicate the formation of well-packing structure with hydrogen bond network exhibited in their crystal structures. The temperature dependency studies reveal that the stronger packing structure of the compounds is achieved when increasing the number of benzimidazole unit on molecule from mono- to di- and to tri-functional compound. Blending the compounds with sulfonated poly(ether ether ketone) (SPEEK) matrix is found to improve thermal stability and proton conductivity of SPEEK. Comparing between the benzimidazole model compounds, the tri-functional one is the most effective compounds giving the highest improvement in both thermal property and proton conductivity so SPEEK membrane. The increase in benzimidazole unit is found to strongly affect the structure of hydrogen bond network from the “isolated channel type” to the “layered interlinked channel type”. The presence of solvent molecules, although, leads to the obstruction of intermolecular hydrogen bond formation, it offers the “solvent assisted intramolecular hydrogen bond network” to the trifunctional benzimidazole compound.