Investigation of different electrolytes on the electrochemical behaviour of Transition metal dichalcogenides (TMDCs)

Abstract

The accelerating global demand for sustainable and high-efficiency energy storage systems has catalysed intensive research into next-generation technologies that address the limitations of conventional batteries and capacitors. Among these, supercapacitors have emerged as pivotal components in bridging the gap between high energy density and high power density requirements. Their unique capability for rapid charge-discharge cycles, long operational lifespans, and environmental adaptability renders them highly promising for diverse applications, including electric mobility, renewable energy integration, aerospace systems, and smart electronics. However, challenges such as relatively low energy density and material instability under prolonged cycling persist, necessitating the development of novel electrode materials and electrolyte systems with superior electrochemical and mechanical performance. Transition metal dichalcogenides (TMDCs), particularly in their two-dimensional (2D) forms, have garnered considerable interest as potential electrode materials for electrochemical energy storage. These materials, represented by the general formula MX2 (where M is a transition metal and X is a chalcogen), exhibit a unique lamellar structure that allows for facile ion intercalation, high surface-to-volume ratio, and tunable electronic properties. Notably, their polymorphic versatility, with phases ranging from semiconducting 2H to metallic 1T and distorted 1T ', enables the tailoring of their electrical conductivity and redox activity. This thesis investigates the electrochemical potential of tungsten diselenide (WSe2) and modified molybdenum diselenide (Mo15Se19) as next-generation electrode materials for supercapacitors, with a special emphasis on the role of electrolytes and synthesis methodologies in modulating their charge storage performance. The present research is structured around four primary objectives: (i) Fabrication of tungsten diselenide based thin film electrodes using a single step additive or binder free DC sputtering technique and analysis of electrochemical compatibility, (ii) Electrochemical study of tungsten diselenide based supercapacitors in different aqueous electrolytes containing alkali metal cations, (iii) Impact of pH on the Electrochemical Properties of WSe2 Nano-cauliflowers: A Comparative Study of Acidic, Neutral, and Basic Electrolytes, (iv) Modification of bulk MoSe2 to defect rich Molybdenum rich Mo15Se19 based thin films for enhanced electrochemical performance. These objectives are addressed through an integrative experimental strategy encompassing advanced synthesis, detailed structural characterization, and rigorous electrochemical testing.