Joseph J. Steirer Jr. and Yushan Yan. Chemical and Environmental Engineering, University of California, Riverside, 900 University Avenue, Riverside, CA 92521
Layer double hydroxides are defined as a class of lamellar hydroxides with two or more kinds of metallic cations in the main layers and interlayers containing exchangeable hydrated anions. In an effort to improved hydroxide conductivity for anion exchange membranes used in fuel cells, this work focuses on the synthesis and characterization of layered double hydroxides. Layered double hydroxides synthesized and characterizaed in this work include LiAl2(OH)7·2H2O, Mg3Al(OH)8(NO3)·2H2O and Mg3Al(OH)9·2H2O. These materials are synthesized by coprecipitation, anion-exchange or rehydration methods. They were characterized by, scanning electron microscopy (SEM) with an energy-dispersive spectrometer (EDS), thermogravimetric analysis (TGA), infrared spectroscopy, Raman spectroscopy, powder x-ray diffraction (XRD), and anion conductivity measurements. Preliminary results show anion conductivity measurements for Mg3Al(OH)8(NO3)·2H2O and LiAl2(OH)7·2H2O are 5.2 x 10-3 S/cm and 3.0 x 10-2 S/cm, respectively. The conductivity for LiAl2(OH)7·2H2O is higher than the measured conductivity for commercial anion exchange membranes AHA and FAA (1-2 x 10-2 S/cm). This suggests significant promise for the use of layered double hydroxides in alkaline fuel cells. There is ongoing work on the synthesis and characterization inorganic membranes and inorganic-organic composite membranes.