Conductivity study of Zeolitic Imidazolate Frameworks, Tetrabutylammonium hydroxide doped with Zeolitic Imidazolate Frameworks, and mixed matrix membranes of Polyetherimide/Tetrabutylammonium hydroxide doped with Zeolitic Imidazolate Frameworks for proton conducting applications

• Published in: Electrochimica acta 2017-12, Vol.258, p.153-166
• Main Authors: Vega, J., Andrio, A., Lemus, A.A., del Castillo, L.F., Compañ, V.
• Format: Article
• Language: English
• Subjects: Bimetals; Carrier density; Charge density; Conductivity; Current carriers; Diffusion coefficient; Fillers; Matrix; Membranes; Metal-organic frameworks; Mixed Matrix Membranes; PEI/ZIFsT membranes; Polyetherimides; Protons; Temperature; Temperature dependence; Transport; Zeolites; Zeolitic Imidazolate Frameworks
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2017.10.095

ZIF-8 (Z8), ZIF-67 (Z67), and ZMix, a Zn/Co bimetallic zeolitic imidazolate framework (ZIF), were synthesized and doped with tetrabutylammonium hydroxide (ZIFsT). The obtained powders were used as fillers for polyetherimide (PEI) at a concentration of 20wt %. The presence of the three ZIFsT in the polymeric matrix enhanced proton transport relative to that observed for PEI or ZIFs alone. The real and imaginary parts of the complex conductivity were obtained for each of the six materials, and the temperature and frequency dependence of the real part was analyzed. The results at different temperatures show that the dc-conductivity are about three orders of magnitude higher for the doped ZIFsT materials than for the PEI/ZIFsT membranes. In addition, the conductivity of the PEI/ZIFsT membranes increases five or six times when the temperature is changed from 25°C to 55°C. For these materials, the conductivity measurements have a linear dependency with frequency, which allowed for the creation of a master curve. It was also found that the PEI/ZMixT membrane activation energy is four times smaller than that of PEI/Z8T membranes and five times smaller than that of PEI/Z67T. Similarly, the real and imaginary parts of the complex dielectric constant were obtained, and the tan δ was evaluated. Using this value, the diffusion coefficient and the charge carrier density were obtained. A discussion of the proton transport mechanism through the membrane is given, and a comparison of this work with those on similar electrolyte membranes is included. [Display omitted] •The ionic pair of tetrabutylammonium hydroxide was introduced within the Z8, Z67 and ZMix.•Mixed matrix membrane of PEI/ZIFsT prepared using the modified ZIFs as fillers have been characterized.•The relative amount of host molecules in Z8, Z67 and ZMix was determined.•The local electric anisotropy characteristic of ZMix favors the amount of doping the TBAH salt.•Activation energies for ZMixTW fillers and PZMixTW membranes were 0.13 and 0.14eV, respectively.