THERMAL AND ELECTROCHEMICAL PROPERTIES OF SOLID BIOPOLYMER ELECTROLYTES FROM STARCH OF DIFFERENT BOTANICAL ORIGIN

Background: Solid biopolymer electrolytes are a type of material with high technological potential used in the development of solar cells, batteries, fuel cells, among others, due to their biodegradable nature and low environmental impact. Aim: This study aimed to evaluate the effect of the botanical origin of the starch used to prepare solid biopolymeric electrolyte films on its electrochemical and thermal properties and to establish the variations in thermal decomposition temperatures and redox potentials depending on the botanical origin of the starch used. Methods: Films of solid biopolymer electrolyte were made by thermochemical synthesis processes using corn starch, cassava starch, potato starch, glycerol, polyethylene glycol, and glutaraldehyde as plasticizers and lithium perchlorate salt. The synthesis solutions were taken to an oven at 70 °C for 48 hours. The films were characterized electrochemically by cyclic voltammetry using a dry electrochemical cell and thermally by differential scanning calorimetry and thermogravimetric analysis. Results and Discussion: The results showed that the electrochemical behavior of the films was similar in terms of registered redox processes. However, the potential values of the oxidation and reduction were different, as are the stability and intensity of the processes. On the other hand, the thermal analysis allowed establishing two decomposition processes in each of the films studied; the first process was due to dehydration and depolymerization phenomena in the films. The temperatures recorded were 59.0 °C, 58.9 °C, and 89.9 °C for potato starch, cassava starch, and corn starch films. The second process evidenced the thermal decomposition at different temperatures, 267.7 °C in potato starch films, 280.6 °C in corn starch films, and 287.1 °C in cassava starch films. Conclusions: It could be concluded that the botanical origin of the starch used in the synthesis of solid biopolymer electrolyte films affects its behavior and electrochemical and thermal stability.

The Effect of Ammonium Bromide on Methylcellulose Biopolymer Electrolytes for Electrical Studies

The development of biopolymer electrolytes based on methylcellulose (MC) has been accomplished by incorporating ammonium bromide (NB) to the polymer-salt system. The biopolymer electrolytes were prepared via solution-casting method. The conductivity and permittivity characteristics of the material were studied. The biopolymer-salt complex formation have been analysed through Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The conductivity of the sample was measured by EIS HIOKI. Upon addition of 20 wt.% of NB, highest conductivity of 3.25×10-4 μScm-1 was achieved at ambient temperature. The temperature dependence of the biopolymer electrolytes exhibit Arrhenius behaviour. This result had been further proven in FTIR study.