Preparation And Characterization Of Alkaline Anion Exchange Membrane For Fuel Cells Application

Anion exchange membrane fuel cells （AEMFCs） has attracted considerable attention as an alternative to the present power sources, since it has numerous benefits, including high efficiency, high power density, environmental friendliness, low cost and permeable to methanol, compared with proton exchange membrane fuel cells （PEMFCs）.As the core component of AEMFCs, anion exchange membranes （AEMs） have attracted much attentions. An excellent AEM for an AEMFCs must have good chemical and thermal stability, sufficient mechanical strength, and high ionic conductivity. In the past several years, the AEMs containing quaternary ammonium cationic groups have been extensively studied. However, it may suffer from poor mechanical properties, lower ionic conductivity and be not stable in long fuel cells operation, especially at elevated temperatures.In view of these considerations above, AEMs with favorable hydroxide conductivity and excellent alkaline, mechanical and thermal stabilities were developed in this study:（1） In this paper, an environment-friendly bio-material bacterial cellulose （BC） which has remarkable advantages such as good mechanic properties, good chemical stability, high purity, high specific surface area, great compatibility and environmentally friendly, is introduced to assist the preparation of TiO₂/BC nanofibers through electrostatic spinning technology. The membranes were characterized by XRD, SEM, XPS, and TG methods. The properties of the membranes, such as water uptake, swelling degree, thermalstability and mechanical properties were investigated. It was found that high quality cellulose nanofibers were obtained under the optimized electrospinging conditions as following:at room temperature the concentrations of cellulose:1.3-1.5wt%, the working distances 10-20cm, the positive voltages 16-17kv, the mass flow rates 0.02-0.04 ml/min. The BC/TiO₂ （0.03g TiO₂/20mlBC） membrane exhibited better comprehensive performance:favorable water uptake （101.9%）, excellent mechanical strength （stress:13.88 MPa, strain:25.47%）.（2） The BC/TiO₂/CHPTAC membranes for alkaline fuel cells were prepared via quaternization and alkalization successively. Meanwhile, in order to avoid the phenomena of leakage problems from fuels and improve the performance of fuel cells, the TiO₂/BC/CHPTAC-OH/PVA composite membrane was prepared by PVA casting. The properties of the composite membrane such as water uptake, swelling degree, mechanical properties, ion exchange capacity （IEC）, and ion conductivity were investigated. It was found the obtained AEMs exhibited high DS （1.16）, when the molar ratio of alkali and CHPTAC is 1.2 and the reaction time is 16h. The water uptake and IEC of BC/TiO₂/CHPTAC membrane were 140%, 1mmol/g, respectively. Meanwhile, the composite membranes have excellent dimensional stability. The mechanical properties of the composite films were increased by PVA addition and it exhibited better mechanical strength （stress:25.18MPa, strain:38.05%）. Meanwhile, the ionic conductivity of the composite film was 0.0093s/cm at 80℃. Compared with other membranes, the BC/TiO₂/CHPTAC-OH/PVA composite membrane exhibited comparable performances and were thus promising for application in fuel cells.