Chitosan/CaCO3solvent‐free nanofluid composite membranes for direct methanol fuel cells

Abstract

Natural polyelectrolyte chitosan (CS) has been considered to be a promising proton‐exchange membrane material for direct methanol fuel cells due to its low cost and excellent methanol barrier ability. To further improve the ionic conductivity and mechanical property of CS, calcium‐carbonate solvent‐free nanofluids (CaCO3‐SF) with unique flow behavior were prepared by an ion‐exchange method, and then used a novel nanofiller to modify CS to fabricate composite membranes. The surface‐grafted organic long chains on the surface of CaCO3nanoparticles could promote the homogeneous dispersion of CaCO3in the CS matrix, and thus improve the interfacial bonding and facilitate the load transfer from the matrix to stiff CaCO3. When the content of CaCO3‐SF was 6 wt%, the tensile strength and fracture elongation of the composite membrane were 28.25 MPa and 17.17%, respectively, which increased by 25% and 36% when compared with those of pure membrane. Moreover, the SO3H groups in the structure of organic long chains could form new proton transport sites, and thus enhance the proton conductivity of the membranes. Consequently, when compared with pure CS membrane (0.0131 S cm−1), incorporation of 6 wt% CaCO3‐SF (0.0250 S cm−1) exhibited about onefold increase of proton conductivity. POLYM. ENG. SCI., 59:2128–2135, 2019. © 2019 Society of Plastics Engineers