Novel core–shell CuO nanostructures grown on Cu powder particles by hot water treatment for binder-free supercapacitor electrodes

Abstract

This research has successfully prepared three-dimensional leaf-like copper oxide (CuO) nanostructures on micro-sized Cu powder particles via hot water treatment (HWT). This innovative approach has led to the development of a new core–shell, binder-free, and high-surface-area supercapacitor electrode. The synthesis process involved a simple immersion of Cu powder into hot water stabilized at 75 °C for 24 h. The CuO/Cu powder obtained was combined with DI water and then deposited onto a Cu plate and subjected to annealing at 200 °C in a vacuum furnace to produce a binder-less electrode for electrochemical evaluations. Utilizing SEM and EDS, we thoroughly analyzed the morphology and composition of the CuO nanostructures. X-ray diffraction (XRD) analysis was utilized to unveil the crystal structure of the CuO nanostructures, confirming the presence of leaf-like morphology of CuO. Thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) were employed to measure the mass of the active material and its specific surface area, respectively. The electrochemical properties of CuO nanostructures were examined by cyclic voltammetry (CV) over various scan rates. The electrochemical resistance of the electrode material was observed using electrochemical impedance spectroscopy (EIS). The results from the electrochemical tests indicated that a peak-specific capacitance of around 220 F/g was achieved when the scan rate was set at 5 mV/s using Na₂SO₄ electrolyte. Furthermore, the capacitance retention rate was about 38% after 1500 consecutive cycles. Our findings indicate that the HWT-grown CuO/Cu nanostructured powder shows promise for pseudo-supercapacitor applications, which could potentially bring about a revolution in the field of energy storage.

Graphical Abstract