A cellulose derivative, carboxymethyl cellulose (CMC), was synthesized by the reaction of cellulose from kenaf bast fiber with monochloroacetic acid. A series of biopolymer electrolytes comprised of the synthesized CMC and ammonium acetate (CH₃COONH₄) were prepared by the solution-casting technique. The biopolymer-based electrolyte films were characterized by Fourier Transform Infrared spectroscopy to investigate the formation of the CMC–CH₃COONH₄ complexes. Electrochemical impedance spectroscopy was conducted to obtain their ionic conductivities. The highest conductivity at ambient temperature of 5.77 × 10⁻⁴ S cm⁻¹ was obtained for the electrolyte film containing 20 wt% of CH₃COONH₄. The biopolymer electrolyte film also exhibited electrochemical stability up to 2.5 V. These results indicated that the biopolymer electrolyte has great potential for applications to electrochemical devices, such as proton batteries and solar cells.

This study was undertaken to investigate the solid biopolymer electrolytes based on a carboxymethyl κ-carrageenan/carboxymethyl cellulose blend complexed with lithium iodide of various weight ratios. The complexation of the doping salt with the polymer blend was confirmed by Fourier transform infrared spectroscopy. Ionic conductivity of the film was determined by impedance spectroscopy in the frequency range of 10 Hz to 4 MHz and in the temperature range of 303–338 K. The ionic conductivity increased with the increase in lithium iodide concentration as well as temperature. The membrane comprising 30 wt % of lithium iodide was found to give the highest conductivity of 3.89 × 10⁻³ S·cm⁻¹ at room temperature. The increase in conductivity was associated with the increase in the number as well as the mobility of the charge carries. The conductivity increase with temperature followed the Vogel–Tamman–Fulcher model. The fabricated dye-sensitive solar cell, FTO/TiO₂-dye/CMKC/CMCE-LiI (30 wt %) +I₂/Pt exhibited the highest conversion efficiency of 0.11% at a light intensity of 100 mW·cm⁻². This indicated that the biopolymer blend electrolyte system has potential for use in dye-sensitized solar cells.