Interrelation Between Ionic Conduction and Ions Fraction of Biopolymer Electrolytes Based on Alginate Doped With NH₄Cl

Abstract

In this report, the relationship between the ionic conduction properties of alginate (AL) based biopolymer electrolyte (BE), and the amount of NH₄Cl dopant and ethylene carbonate (EC) plasticizer is discussed. The BE was prepared via a solution casting method and characterized by using Fourier transform infrared (FTIR) and electrical impedance spectroscopy (EIS), respectively. The highest ionic conductivity attained for the AL-NH₄Cl BE was 3.18 × 10⁻⁸ S cm⁻¹ for 8 wt.% of NH₄Cl. Nonetheless, an increased optimum value of 1.46 × 10⁻⁶ S cm⁻¹ was obtained when plasticized with 4 wt.% of EC. It was observed that with the addition of the EC content between the range of 1 wt.% and 7 wt.% into the AL-NH₄Cl with 8 wt.% salt content increased the flexibility of the AL chains to facilitate free H⁺ ion transport. The weak bonding created through EC - NH₄⁺ allows higher dissociation of proton ions (H⁺), allowing more interaction to occur on the AL polymer backbone. These ions will hop from one complex site of AL to another, as revealed by FTIR analysis. Through the deconvolution analysis of the BE systems, it was demonstrated that the ionic conductivity for both systems was governed by the enhancement of the free ions fraction which, in turn, increased the number of mobile ions upon the addition of NH₄Cl.

Keywords:

• FTIR deconvolutions
• ionic conductivity
• polymer characterization
• polymer electrolytes

Additional information

Funding

The authors would like to thank the Ministry of Higher Education (MOHE) for Fundamental Research Grant Scheme (FRGS/1/2019/STG07/UMP/02/4) (grant no. RDU 1901114) and the University of Malaysia Pahang (UMP) for an internal grant (grant no. RDU 190389) for financial assistance, and the faculty of Industrial Sciences & Technology (FIST), University of Malaysia Pahang and the technical staff of the FIST laboratory for their research support.