Proton conductivity and dimensional stability of proton exchange membrane: A dilemma solved by chitosan aerogel framework

Abstract

Increasing proton conductivity of polymer electrolyte membrane (PEM) by introducing more number of proton transfer species, especially sulfonated groups always lead to a decrease in mechanical/dimensional stability. The present work proposes the solution to overcome this dilemma by applying chitosan (CS) interconnected with sulfonated poly(ether ether ketone) (SPEEK) to provide not only the 3D framework for dimensional stability but also the sulfonated groups and amino groups play the role in proton transfer. By simply crosslinking CS with succinic acid (SA) followed by lyophilizing, the stable 3D-framework (CS-x)-SA can be obtained. This (CS-x)-SA framework allows the incorporation of SPEEK during membrane formation results in semi-interpenetrating (CS-x)-SA-SPEEK. The (CS-0.25)-SA-SPEEK membrane obtained performs mechanical stability in terms of tensile strength for 12%, with a proton conductivity increment for 34% as compared to SPEEK. The present work demonstrates an approach to achieve the 3D interconnected composite PEM to achieve the improvement in proton transfer efficiency and mechanical strength as well as dimensional stability.