Preparation and properties of alkyl benzene sulfonic acid coated boehmite/chitosan nanocomposite membranes with enhanced proton conductivity for proton exchange membrane fuel cells

In this study, alkyl benzene sulfonic acid coated boehmite nanofillers (OS2) were incorporated into chitosan (CS) to prepare novel CS/OS2 nanocomposite membranes for proton exchange membrane fuel cell applications, and then their microstructure and physicochemical properties were characterized. These nanocomposite membranes show high proton conductivity, good thermal stability, and improved mechanical characteristics. The electrostatic interactions between –SO3H groups of boehmite nanofillers and amine groups of CS can inhibit the mobility of CS chains, resulting in a decrease in the swelling area of the nanocomposite membrane in water and thus an increase in its dimensional stability. The development of acid–base pairs at the nanofiller interface facilitates the formation of consecutive transfer pathways to improve the proton conductivity of synthesized membranes. The maximum proton conductivity (0.033 S · cm–1) is obtained in the CS/OS2-5 nanocomposite membrane, which is equal to that of commercial Nafion 117. The eco-friendly and cost-effective nature of CS-based membrane makes it as a promising candidate for proton exchange membrane fuel cell applications.