Exploring one-pot colloidal synthesis of klockmannite CuSe nanosheet electrode for symmetric solid-state supercapacitor device

In this study, we successfully synthesized klockmannite CuSe nanosheets, showing their promising potential for application in supercapacitors. Importantly, this marks the first-ever report of synthesizing klockmannite CuSe by using a one-pot colloidal method. The exceptional hexagonal nanostructure, distinguished by its single-crystalline composition and unique klockmannite phase, is appealing for supercapacitor applications. We carry out detailed characterization of the CuSe nanosheets. Using CuSe nanosheets as an electrode material, we achieve a significant specific capacitance of 718 F g⁻¹ (equivalent to 322 mF cm⁻²) at a scan rate of 2 mV s⁻¹. These CuSe electrodes also exhibit extraordinary cycling performance, retaining 96% of their initial capacitance after 3500 cycles. The observed specific capacitance for klockmannite CuSe nanosheet electrodes demonstrates superior performance compared to metal chalcogenide nanostructures previously reported in the scientific literature. Additionally, a CuSe nanosheet electrode and PVA-NaOH gel electrolyte are used to fabricate and analyze CuSe symmetric solid-state supercapacitor devices. These devices show an astounding 74% retention of cyclic stability after 10 000 cycles, along with an energy density of 14 W h kg⁻¹ at a power density of 1.1 kW kg⁻¹. These findings establish CuSe nanosheets as a highly stable and feasible candidate for use as an electrode material in supercapacitor devices.