Kennith McLoud

He/him

Education: Bachelor of Science in mechanical engineering and physics (May 2019)

McNair Project: Transition Metal Dichalcogenide (TMD) and Their Uses as Supercapacitors/Batteries (2018)

Mentors: Gurpreet Singh, Ph.D., and Santanu Mukherjee, Ph.D.

With the ever-growing use of portable electronic devices, the demand for energy storage is even greater now than before. Conventional electrodes have their own issues: insufficient charge storage, poor conductivity, complicated fabrication techniques and inability to last for sufficient cycles of operation. As such, the desire to develop more efficient, effective, and economically practical electrodes are of paramount importance. Fabrication of novel electrodes of high surface area provide a path forward for this ever-demanding industry.

Transition metal dichalcogenides (TMDs) are a group of inorganic compounds that exhibit remarkable properties e.g. MoS₂, WSe₂ etc. These materials in their bulk form can be exfoliated rather easily to provide 2D layered structures. These layered structures have several advantageous properties from their precursor bulk material in particular: high surface area, greater number of electrochemically active sites, enhanced mechanical strength and a diverse range of electronic properties from semiconducting to semi-metal like. Also, another important advantageous property is their ease of fabrication and scalability; most of these TMDs needed for electrochemical energy storage applications are obtained by a simple liquid-based exfoliation of their bulk precursors. Consequently, TMDs are being looked at as for potential applications in supercapacitor and battery electrodes.

This research focused on the studying of TMDs (MoS₂, WS₂, MoSe₂, MoTe₂) materials for supercapacitor applications and the role of varying the transition metal as well as the chalcogen atom. Electrodes have been prepared using a thin film-based coating technique, whereby the slurries (containing carbon black, Polyvinylidene fluoride and N-Methyl-2-pyrrolidone) of each electrode material is smeared/pasted on a stainless-steel mesh. A consistent mass loading was achieved, and a 3-electrode setup was used for electrochemical testing purposes; the TMD being the active electrode, Ag/AgCl reference electrode and Pt counter electrode with 1M Na₂SO₄ electrolyte. Cyclic voltammetry at various scan rates, and a potential of 0 – 1.2 volts.

Results have indicated that WS₂ electrode performs the best at all scan rates and MoS₂ and MoTe₂ perform almost identically when just tested by CV. However, with GCD, MoS₂ provides a better aerial capacitance than WS₂. It is also observed that the sulfide electrodes consistently outperform the selenide and the telluride electrodes. The superior electrochemical performance of the sulfides may be attributed to uniformity of the electrodes during fabrication, better conductivity and lower diffusion coefficient.