Engineering 2D transition metal dichalcogenide electrodes with tunable band structures for enhanced capacitive performance

Increasing energy demands from consumer electronics and electric vehicles can be met through improvements to devices called supercapacitors. These devices offer fast charge and discharge rates and long lifetimes. A promising class of crystalline materials that can be used in supercapacitors are two-dimensional transition metal dichalcogenides (2D-TMDs). These materials support fast charging and discharging, long lifespans, and the potential to meet growing demands for efficient, scalable energy storage. However, large discrepancies in their performance have been observed depending on synthesis and measurement techniques. This work will focus on adjusting key parameters in the electrochemical performance of 2D TMDs - thickness of the material and the amount of defects in the material’s crystal structure. Results from this project will deepen the scientific understanding of how 2D materials store charge and could lead to more effective, cost-efficient supercapacitor electrodes. The project will train graduate and undergraduate students in advanced research techniques, incorporate research outcomes into new coursework, and provide local high school students with hands-on exposure to materials science and nanotechnology. This research will employ a modified Hall method to probe the role of defects and layered structure of 2D-TMDs on quantum capacitance and double-layer capacitance in a range of electrolyte solutions. Using chemical vapor deposition, the team will synthesize MoS₂ and WS₂ with controlled layer numbers, engineered defects, and heterostructuring. Devices will be fabricated in a Hall bar geometry to enable direct extraction of charge carrier density under electrolyte gating, allowing precise measurements of total and quantum capacitance using a modified Hall effect method. Three main research thrusts will be pursued: (1) determining how layer-dependent density of states impacts capacitance in 2D-TMDs; (2) quantifying how specific defects influence quantum and total capacitances; and (3) evaluating the effect of heterostructure formation and stacking order on electrochemical behavior. A range of materials characterization techniques will be employed to understand the structure-property relationships governing performance, including Raman spectroscopy, photoluminescence, XPS, SEM/EDS, and electrical transport methods. The work will also assess the influence of different electrolytes and provide benchmarking via traditional electrochemical impedance spectroscopy. This project will clarify key structure–property relationships in TMDs and develop methodologies for scalable electrode design in high-performance electrochemical capacitors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.