Sputter Grown Hexagonal WSe2@Graphite Nanoflakes for Electrochemical Energy Storage

Abstract

In the pursuit of sustainable and efficient energy storage solutions, researchers have continuously explored novel materials and technologies to enhance the performance of energy storage devices. Recently, transition metal dichalcogenide (TMDCs) such as molybdenum disulfide (MoS2), molybdenum diselenides (MoSe2), and tungsten disulfide (WS2) with a honeycomb-like structure has sparked considerable interest in utilization as electrode material for supercapacitor (SCs) applications due to their unique layered structures. Generally, the small surface area of TMDCs in their bulk form restricts their practical usage in the SCs applications. Whereas TMDC in thin 2D form exhibits high surface area and flexibility to the electrode material which allows more charge storage and results in high capacitance and energy density. In the present work, high-quality tungsten diselenide (WSe2) thin film electrodes were deposited over graphite sheets (WSe2@Graphite) using DC magnetron sputtering technique at an elevated temperature of around 200 0C under the controlled argon atmosphere. The electrochemical properties of these WSe2@Graphite electrode were investigated in three electrodes configuration using 1M Na2SO4 aqueous electrolyte by recording CV, GCD, and EIS spectra. The hexagonal WSe2@graphite nanoflakes were found to exhibit an exceptionally high areal capacitance of 88.05 mF/cm2 and energy density of 7.83 µWh/cm2 at a scan rate of 5 mV/s. Further, GCD was performed, and the WSe2@graphite electrode exhibits a high areal capacitance of 37.5 mF/cm2 at the current density of 0.5 mA/cm2. The WSe2 thin film electrode shows a high energy density of 3.3 µWh/cm2 at a power density of 199.98 µW/cm2. Additionally, the WSe2@graphite thin film electrode demonstrates high cyclic stability with retaining ~ 90.33% capacitance even after 2000 consecutive GCD cycles. The obtained hexagonal nanoflakes-like morphology provides a high surface area and porous structure that helps to improve the electrochemical performance of the WSe2 thin film. The obtained results demonstrate that the WSe2@graphite thin film exhibit excellent electrochemical performance and can be utilized as a potential material for supercapacitor electrodes. Keywords- Transition metal dichalcogenide (TMDCs), tungsten diselenide (WSe2), DC magnetron sputtering, supercapacitor, and nanoflakes Figure 1