Synthesis and characterization of bio-polymer electrolyte based on iota-carrageenan with ammonium thiocyanate and its applications

Abstract

Solid polymer electrolyte based on iota-carrageenan (i-carrageeenan) with ammonium thiocyanate (NH4SCN) has been prepared by solution casting technique using distilled water as solvent. Increase of amorphous nature of the polymer/salt complex has been confirmed by XRD analysis. The complex formation between the polymer and salt has been confirmed by FTIR analysis. A shift in glass transition temperature (Tg) of the i-carrageeenan/ NH4SCN electrolytes has been observed from the DSC thermograms. From AC impedance spectroscopy, the maximum conductivity value has been found to be 3.56 × 10−3 S/cm for i-carrageeenan (1 g): NH4SCN (0.3 wt%) at room temperature. Also it has been observed that the activation energy evaluated from the Arrhenius plots has been found to be low (0.21 eV) for i-carrageeenan (1 g): NH4SCN (0.3 wt%) polymer electrolyte. The ionic transference number has been measured using DC Wagner’s polarization method for highest conducting polymer membrane and the result indicates that the conductivity of the electrolyte is predominantly due to ions. The electrochemical stability of the electrolyte i-carrageeenan (1 g): NH4SCN (0.3 wt%) has been studied by linear sweep voltammetry. Using this maximum ionic conductivity polymer electrolyte, the proton battery and fuel cell have been constructed and the cell parameters have been reported.