Ultrathin Zinc cobalt oxide nanowalls for supercapacitive energy storage applications

• Ultrathin and flexible zinc-cobalt based nanowalls were synthesized and evaluated in this work. • The nano walls were supported on copper and were synthesized hydrothermally. • Charge transfer resistance of 13 ohms and a specific capacitance of 205 F/g were reported. The development of efficient energy storage devices with enhanced performance and stability is crucial to advance the next generation energy applications. Supercapacitors are of particular interest due to their fast charge-discharge cycles and durability that make them ideal for portable electronic devices and renewable energy systems. While functional, supercapacitors are often fabricated from high-cost materials. This work aims at synthesizing a lower cost, supercapacitor based on ultrathin zinc-cobalt (ZC) oxide nanowalls supported on a copper tape (Cu) via a hydrothermal method. The structural and electrochemical characteristics were evaluated for energy storage applications. The scanning electron microscope (SEM) and atomic force microscope (AFM) confirmed the formation of ultrathin ZC/Cu nanowalls with a surface roughness of 233 nm, while elemental analysis (XRF) revealed the presence of 32.3 % zinc and 67.7 % cobalt. The crystallinity degree of the prepared samples was examined via X-ray diffraction (XRD) and showed enhanced properties. The electrochemical analysis demonstrated an optimum specific capacitance of 205 F/g at a scanning rate of 10 mV/s within a potential window ranging from 0.0 (V) to 0.7 (V). The galvanostatic charge-discharge (GCD) curves exhibited an asymmetric triangular-like shape. The electrochemical impedance spectroscopy (EIS) data showed a low transfer resistance of 13Ω, demonstrating efficient transport of ions at the electrolyte/electrode interface. The results reported in this work suggest that the prepared ZC/Cu materials are promising for supercapacitive energy storage applications.