Study On Organic-inorganic Methanol-rejective Proton Exchange Membrane For DMFC

Direct methanol fuel cell (DMFC) has attracted considerable attention as an alternative to the present power sources due to its high efficiency, high power density, low emissions and easy fuel storage and transportation et al. However, at present, two major technology problems in DMFC still restrict their performances and applications. One problem is the crossover of methanol through the electrolyte membrane. The other is slow methanol oxidation kinetics on the anode catalyst. In this study, development of methanol? rejective proton exchange membranes was attempted.Recognizing the coupling nature of proton, water and methanol transport, we analogized the desired proton exchange membrane (PEM) to a proton preferential proton-methanol separation membrane. Therefore, theories and experiences from the field of membrane separation, especially those from pervaporation were borrowed to this work. To investigate organic-inorganic hybrid PEM, which has the advantages of both the organic and inorganic membrane, is a new trend now. Accordingly, chitosan and NaY zeolite were chosen to synthesize CS-NaY hybrid membranes. In order to improve the interfacial morphology of hybrid membranes, APTES and MPTMS silane coupling agents were chosen to modify the NaY zeolite.IR, SEM, XRD and TG were used to characterize these membranes. The effect of zeolite modification, content of zeolite on the interfacial morphology, methanol permeability and proton conductivity was studied in detail. The methanol permeability of CS-NaY hybrid membrane decreases due to the incorporation of NaY zeolite and is much lower than that of Nafion117. Zeolite modification effectively improves the interfacial morphology and decreases methanol permeability. CS-SO3HY hybrid membranes show the best methanol barrier property because of the strong ion bonds between SO3HY and CS. When the methanol concentration is 12mol/L,the methanol permeability of CS-SO3HY40% membrane is lower than 1/10 of that of Nafion117.Because of the introduction of–SO3H, CS-SO3HY membranes show higher proton conductivity and overall membrane performance factor (β=σ/P) than that of other hybrid membranes. When the methanol concentration is 12mol/L,theβvalue of CS-SO3HY40% is three times higher of that of Nafion117.