An effective method for fabricating crosslinked multilayer biomembranes with excellent stability and methanol resistance

To develop the proton exchange membranes with excellent comprehensive performance, especially high methanol resistance, the multilayer biomembranes were first prepared by alternately depositing chitosan and selfmade functionalized organosilane on the surface of crosslinked chitosan via layer-by-layer self-assembly and were further treated via immersing in sulfuric acid and then heating at high temperature. SEM and FTIR spectra confirmed the presence of thin self-assemble layers with good adhesion on the substrate due to the interactions and the condensation reaction. The introduction of self-assemble layers and crosslinked structure significantly improved the stability and methanol resistance of biomembrane. The methanol diffusion coefficient of 15 bilayers modified biomembrane was only 2.6 x 10-8 cm2 S-1 in 12 M methanol, which was very favorable for its application in direct methanol fuel cell with high methanol concentration. Furthermore, the crosslinked multilayer biomembranes exhibited enhanced stability and the functionalized organosilane with high conductive groups ensured the biomembranes with better proton conductivity. The biomembrane with 15 bilayers showed extremely high selectivity value (1.05 x 106 Sscm- 3), indicating its attractive potential as proton exchange membrane in direct methanol fuel cell.