Effect of Functionalized Chitosan Nanoparticles on the Properties of Sulfonated Polybutylene Fumarate Membranes for Direct Methanol Fuel Cells

ABSTRACT A nanocomposite proton exchange membrane based on newly developed sulfonated poly(butylenefumarate) (SPBF) and surface‐modified chitosan (CS) nanoparticles have been successfully prepared, and employed as a highly efficient for proton exchange membrane applications. CS, owing to its surface richness in amino groups, can be surface‐modified through electrostatic interactions with Phosphotungstic acid (PWA). The successful surface functionalization of CS was substantiated by FTIR and ICP‐OES analyses. SPBF/CSPWA membranes show better proton conductivity than pure SPBF membrane due to the strong electrostatic interaction between the SO3H groups of SPBF and the NH2 groups of CS, which can restrict the mobility of SPBF chain. Moreover, this interaction facilitates the formation of acid–base pairs, leading to an enhancement in proton conductivity from 3.36 mS.cm −1 (SPBF) to 3.67 mS.cm −1 (SPBF/CSPWA). Additionally, the methanol diffusion coefficient of the composite membrane was found to be lower than that of the pure SPBF. This reduction is attributed to the introduction of tortuous diffusion pathways within the composite structure, which effectively decrease methanol crossover. Furthermore, the ion exchange capacity (IEC), water uptake behavior and crystalline structure of the membranes were evaluated. From these results, it is evident that SPBF/CSPWA nanocomposite PEMs have great potential for applications in DMFCs.