Conduction mechanism of enhanced CMC-NH4Br biopolymer electrolytes

This study deals with the ionic conduction mechanism of carboxymethyl cellulose (CMC) – NH4Br biopolymer electrolytes (BPEs) plasticized with ethylene carbonate (EC) prepared via solution-casting technique. The ionic conductivity of BPEs system was characterized by using impedance spectroscopy and shows the highest conductivity at ambient temperature for CMC–NH4Br BPEs is 1.12 x 10-4 S/cm and enhanced to 3.31 x 10-3 S/cm with the addition of 8 wt. % EC. The conductivity–temperature plot of the BPEs system obeys Arrhenius law where R2~1. The dielectric values were found to increase with increasing temperature thus divulged that the BPEs system to be non-Debye type. The temperature dependence of the power law exponent shows the CMC–NH4Br–EC BPEs system follows the quantum mechanical tunneling (QMT) model of conduction mechanism, where the enhanced protonation of NH4Br with addition of EC makes the charge transfer (polarons) able to tunnel through the potential barrier that exists between the lone pair electrons in carboxyl group of CMC and NH4Br.