Supercapacitor applications of natural gel electrolytes prepared by bone broth and egg white

Abstract

Bone broth (BB) and egg white (EW) gel electrolytes are prepared by containing NaCl and KCl salts. pH, conductivity and viscosity values are measured. Mass and energy changes with temperature are determined by thermogravimetric analysis and differential scanning calorimetry, respectively. Their molecular structures are investigated by Fourier transform infrared spectroscopy. Their suitability for supercapacitor devices is analyzed using pencil graphite (PGE)/polypyrrole (PPy) and PGE/PPy-Manganese oxide (MnOx) electrodes produced by electrodeposition. The interface between the electrode and the electrolyte is investigated by electrochemical impedance spectroscopy. The capacitive behavior of the electrodes is investigated by cyclic voltammetry and galvanostatic charge-discharge techniques. The highest specific capacitance value of the PGE/PPy-MnOx electrode is calculated as 450 F/g at a scan rate of 5 mV/s in a NaCl-BB gel electrolyte with a potential window between -0.1 and 1.0 V. The double layer and pseudo-capacitance contributions are calculated using Dunn's method. The pseudo-capacitance contribution is generally dominant. PGE/PPy-MnOx//NaCl-BB//PPy-MnOx/PGE and PGE/PPy-MnOx//KCl-EW//PPy-MnOx/PGE supercapacitor devices are fabricated and characterized. The calculated power densities are 320 and 600 W/kg and the cyclic stabilities are 52 % and 88 % after 200 cycles respectively. The values prove that these natural gels are quite suitable for energy storage applications.