Unveiling the role of Corallocarpus epigeous leaf extract on electrochemical properties of CoWO4 for supercapacitor applications

The pursuit of sustainable, high-performance materials for energy storage has prompted investigations into green synthesis strategies. This study synthesised cobalt tungstate nanoparticles (CoWO₄ NPs) using two methods: a green approach utilising Corallocarpus epigeous leaf extract (CoWO₄-G) and a conventional hydrothermal chemical method (CoWO₄-H) to compare their electrochemical performance. X-ray diffraction (XRD) analysis confirmed the formation of monoclinic CoWO₄, with crystallite sizes measured at 24.18 nm for the green method and 27.45 nm for the chemical method. FTIR analysis confirmed the phase formation and FESEM images demonstrated agglomerated spherical morphologies in both samples. The use of HRTEM and particle size histograms validated nanoscale dimensions and corroborated the crystallite size results obtained from Debye-Scherrer and Williamson–Hall analyses. BET surface area analysis indicated a significantly greater surface area in the CoWO₄-G sample (77.3 m²/g) relative to the CoWO-H sample (49.6 m²/g), thereby enhancing charge storage capabilities. Elemental mapping verified the consistent distribution of Co and W. Electrochemical measurements conducted in 3 M KOH, encompassing cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and Tafel polarization, revealed that the CoWO₄-G displays enhanced specific capacitance, reduced charge transfer resistance, and improved cycling stability up to 10,000 cycles. The enhancements result from the influence of phytochemicals in the leaf extract on the surface properties and electronic behaviour of the material. This research emphasizes the viability of Corallocarpus epigeous assisted synthesis as a sustainable approach for developing high-performance electrode materials intended for supercapacitor applications.