Preparation and Properties of Poly(2,5-benzimidazole)/Sulfonated Sepiolite Composite Proton Exchange Membrane

Abstract

Phosphoric acid doped polybenzimidazole membranes with good electrochemical properties at high temperature have been under increasing study in recent years for application in high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The disadvantages associated with these types of membranes include reduced proton conductivity due to acid leaching under continuous usage. The aforementioned drawbacks can be partly overcome by the addition of modified inorganic particles. This work reports the synthesis of poly (2,5-benzimidazole)/sulfonated sepiolite composite membrane (ABPBI/S-Sep) via in-situ method following by phosphoric acid doping procedure. The sulfonation modification of Sep was successfully characterized by XRD and contact angle test. SEM shows that S-Sep particles are well dispersed in the ABPBI matrix. The introduction of S-Sep into ABPBI helps to improve the water uptake, phosphoric acid doping level and proton conductivity of the composite membrane compared to the virgin ABPBI. With the similar phosphoric acid doping level, the proton conductivity of the composite membrane exhibits the highest value of 2.31mS/cm at 90oC which is four times of phosphoric acid doped pristine ABPBI membranes, indicating that the sulfonated sepiolite modified ABPBI composite membrane could be a prospective candidate applying in PEMFC to extend its operating temperature ranges.