Facile Synthesis of Co ₃ V ₂ O ₈ Interconnected Flakes at <i>n</i> -Butanol/Water Interface for Supercapacitor Electrodes

Achieving high-performance supercapacitors (SC) necessitates the development of electrodes that exhibit both high conductivity and a large specific surface area. In this study, we synthesized cobalt vanadium oxide (CVO) interconnected nanoflakes as a potential electrode material for SC using a liquid/liquid interface-assisted strategy with n-butanol and water as solvents. The formation of cobalt vanadium oxide was confirmed through X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. Morphological analysis using FE-SEM revealed a progressive transformation of the product morphology from individual flakes to interconnected structures, and subsequently to an aggregated structure, as the concentration of the urea precursor increased. Brunauer–Emmett–Teller (BET) analysis of the compounds’ surface area revealed a high value for the sample with an interconnected flake structure and a urea concentration of 12 mM (CVO-12U). The progressive development of the product morphology and the enhancement of their crystallinity over time were confirmed through high-resolution transmission electron microscopy (HR-TEM) and the corresponding selected area electron diffraction (SAED) patterns. The supercapacitance characteristics of the products were evaluated, with CVO-12U demonstrating a superior specific capacitance value of 330 F g–1 at a current density of 1 A g–1. To elucidate the underlying mechanism of pseudocapacitive behavior of the material at the atomic scale, density functional theory (DFT) calculations were carried out. The results identify vanadium as the most energetically favorable site for OH adsorption from the electrolyte. Moreover, Bader charge analysis reveals a notable electron transfer from vanadium to the oxygen atom in the OH group, underscoring strong electronic interactions that contribute to the pseudocapacitive charge storage mechanism. The optimized sample was subsequently utilized to construct an asymmetric supercapacitor, in conjunction with activated carbon serving as the negative electrode, yielding promising results.