Fabrication of Nanoscale Indium Sulfide and Their Effects on Ternary Electrode-Based Supercapacitors

Liew, Jian Hong (2026) Fabrication of Nanoscale Indium Sulfide and Their Effects on Ternary Electrode-Based Supercapacitors. Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

This thesis focused on developing a modified one-pot synthesis of active electrode materials and studying their effect in a symmetrical supercapacitor architecture after the completion of structural and electrochemical characterization. The active electrodes materials synthesised were indium sulfide (In2.77S4), binary composite of indium sulfide with exfoliated graphite (denoted B-10InS) and its ternary composite with exfoliated graphite and multiwalled-carbon-nanotubes (denoted T-10InS). All materials were synthesized via a microwave heating of a uniform mixture of precursors in a green solvent benzyl alcohol at 200 ℃ for 5 minutes. This was made possible by integrating the rapid microwave-assisted thermolysis of indium chloride-thiourea complex at 200 ℃, as well as the effective exfoliation of EG and stable dispersion formation of MWCNTs in polar benzyl alcohol. The polar nature and high boiling point (205 ℃ at 1 atm) of benzyl alcohol were crucial in enhancing the crystallinity of the nanoscale indium sulfide produced. Synthesized In2.77S4, B-10InS and T-10InS were structurally characterized through a combination of analysis including PXRD, FESEM, EDS, HRTEM and BET surface area analysis. Indium sulfide alone was found to adopt a pristine 3D-nanoflower structure while smaller nanoflower-like nanocrystals were found to deposit predominantly the exfoliated graphite moiety in both the binary and ternary system. The electrochemical performance of all electrode materials (In2.77S4, B-10InS and T-10InS) were methodically elucidated via cyclic voltammetry and galvanostatic charge-discharge method to assess their specific capacitance as well as electrochemical stability. Furthermore, their performance in a symmetrical supercapacitor configuration was evaluated via electrochemical impedance spectroscopy to analyse internal resistance and ion transport characteristics. The incorporation of carbon-based materials shows significant enhancement in electrochemical performance, as the T-10InS electrodes experienced a 113% increase in specific capacitance compared to the In2.77S4 electrodes in a symmetrical supercapacitor. T-10InS electrodes also exhibit an excellent cyclic stability of 93% capacitance retention after 4,000 cycles of charge-discharge process at 1 A/g current density, when paired with a mild aqueous sodium sulfite (Na₂SO₃) electrolyte in a symmetrical supercapacitor set-up.