Synthesis and characterization of pectin-based biopolymer electrolyte for electrochemical applications

An attempt has been made to synthesize a polymer electrolyte based on biopolymer pectin with ammonium thiocyanate (NH ₄ SCN) salt by solution casting technique. Amorphous/crystalline nature of the polymer electrolyte has been studied by X-ray diffraction technique. The complexation between polymer and salt has been confirmed by Fourier transform infrared spectroscopy. A shift in glass transition temperature of the pectin: NH ₄ SCN electrolytes have been observed from the differential scanning calorimetry thermograms. Ionic conductivity of the electrolytes was measured through impedance spectroscopic technique. The frequency and temperature dependence of ionic conductivity has been studied. The highest conductivity of 1.5 × 10 ⁻³  S cm ⁻¹ was observed for 40 mol% pectin: 60 mol% NH ₄ SCN sample. Transference number measurement was carried out to confirm the nature of the charge transport species in the polymer electrolyte. Electrochemical stability of the highest conducting sample was studied by linear sweep voltammetry (LSV). The value is found to be 3.69 V. Using highest proton-conducting membrane, a proton battery has been constructed.