Study On The Interfacial Morphology And Methanol Permeation Resistance Of Organic-inorganic Hybrid DMFC Membrane

Based on the systematic analysis of organic-inorganic interfacial morphology, a novel idea was proposed to suppress the non-ideal defect of organic-inorganic interface and consequently improve the methanol resistance property of DMFC membrane through decreasing the stress with polymer chains. Chitosan/mordenite hybrid membranes, CS/M(X)-I and CS/M(X)-II, together with sorbitol plasticized chitosan/mordenite hybrid membranes, CS/M(X)/S(30), were prepared. IR, SEM, XRD, DS, PALS and TG were used to characterize these membranes, and their interfacial morphology and methanol permeability were investigated detailedly.The effects of membrane preparation processes and sorbitol on interfacial morphology and methanol permeability of hybrid membrane were studied. CS and mordenite interact with each other through hydrogen bonding, and stress produced in polymer during membrane formation led to CS rigidification and voids at the interface. At lower mordenite content, smaller particle size and intensive dispersion process with ultrasonic and stirring resulted in improved interfacial morphology. However, as mordenite content increased, the improvement became less pronounced. Addition of sorbitol and solvent evaporation under 60℃significantly reduced Tg of CS, resulting in the increase of flexibility and decrease of stress of polymer chains, and consequently the remarkable decrease of CS rigidification and interfacial voids.Organic-inorganic interfacial morphology is the determinant of methanol crossover through hybrid membranes. The improvement of interfacial morphology, ascribed to sorbitol, resulted in enhanced methanol barrier property. At 25℃, the methanol permeabilityies of CS/M(15)/S(30), CS/M(15)-II and CS membranes were 1.4×10^-6cm²/s, 1.8×10^-6cm²/s and 2.9×10^-6cm²/s respectively in 2mol/L methanol/water solution, and 4.9×10^-7cm²/s, 5.3×10^-7cm²/s and 8.7×10^-7cm²/s in 12mol/L methanol/water solution. In addition, CS-based membranes showed a decreased methanol permeability as the methanol concentration of feed increased, which enabled CS/M(X)/S(30) membrane with promising application potential for DMFC membrane.