Tailoring the Surface Morphology of a Nanostructured CuCo₂S₄ Electrode by Surfactant-Assisted Electrodeposition for Asymmetric Supercapacitors with High Energy and Power Density

Abstract

Direct electrodeposition of ternary transition metal sulfides is extremely imperative, yet challenging. Here, we report a one-step potentiostatic electrodeposition procedure of CuCo 2 S 4 -nanostructured electrode materials as high-performance faradaic supercapacitor cathodes. The morphological evolution was carried out systematically as an effect of the surfactant additive in the electrodeposition process, resulting in exclusive control of the morphology as nanoplates (without surfactant) and nanotubes (with surfactant). To circumvent the difficulties of the hard template synthetic route, here we adopted electrodeposition to design CuCo 2 S 4 nanotubes, where surfactants act as soft templates. Besides, the hydrogen gas bubbles generated during the electrodeposition process adjusted the surface electronic structure by creating a significant porous nature, which acts as a reservoir for ion/electron transportation and storage during redox processes. The surface and structural factors of as-fabricated CuCo 2 S 4 metal nanoplates (CCS-1) and nanotubes (CCS-2) were analyzed thoroughly, ensuring their high crystalline nature, attractive morphological phenomena, and increased surface area. The preliminary electrochemical tests of CCS-2 and CCS-1 electrodes in an aqueous medium (3 M KOH) as a faradaic electrode material provided specific capacities of 1199 and 639 C g –1 at 10 A g –1 current density, respectively. Despite the high applied current density value of 30 A g –1, CCS-2 and CCS-1 showed retention values of 83.17 and 72.31% for 5000 cycles, respectively. The superior-functioning CCS-2 electrode was used as a cathode in constructed asymmetric supercapacitor (ASC) device assembly, which delivered 360.27 C g –1 at 10 A g –1 and a reserved capacity value with 95.23% retention while cycling at 30 A g –1 current density over 5000 charge/discharge cycles. The very minimal interfacial resistance (Rs = 0.334 and Rct = 5.461) and relaxation time (0.409 s) values were observed for fabricated ASCs with a CCS-2 cathodic material, expressed at an increased energy density and power density value of 164.52 Wh kg –1 (at 10 A g –1 ) and 46.37 kW kg –1 (at 30 A g –1 ), respectively.

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