Composite proton exchange membrane for fuel cells based on chitosan modified by acid-base amphoteric nanoparticles

Currently, achieving a simultaneous improvement in proton conductivity and mechanical properties is a key challenge in using chitosan (CS) as a proton exchange membrane (PEM) substrate in direct methanol fuel cells (DMFCs). Herein, a novel nanofiller-zwitterionic molecule, (3-(3-aminopropyl) dimethylammonio) propane-1-sulfonate, ADPS)-modified polydopamine (PDA) (PDA-ADPS) was synthesized by the Michael addition reaction and was incorporated into a CS matrix to prepare CS/PDA-ADPS composite membranes. PDA-ADPS, which contains an acid-based ion pair can create new proton conduction channels in the composite membrane, improving proton conductivity. The proton conductivity of the CS/PDA-ADPS composite membrane was as high as 38.4 mS cm^-1 at 80 °C. Moreover, due to the excellent compatibility and dispersibility of PDA-ADPS in the CS matrix, the obtained CS/PDA-ADPS composite membranes exhibited favorable mechanical properties. Such outstanding proton conductivity and mechanical properties guarantee good performance of the composite membranes in fuel cells. The peak power density of the CS/PDA-ADPS composite membranes was 30.2 mW cm^-2 at 70 °C. This work provides a new strategy for fabricating high-performance CS based PEMs for DMFCs.