Green synthesis of novel CuCo₂O₄ nanocomposite for stable hybrid supercapacitors by deep eutectic solvents

Currently, many transition metal oxides (TMOs) have been demonstrated as attractive nanomaterials for application in supercapacitors for energy storage/conversion systems. Among TMOs, CuCo₂O₄ has presented excellent electrochemical properties, including higher electrical behavior. Also, they are readily accessible in earth, ecofriendly and cost effective compared to other nanocompunds. In this research, we have for the first time synthesized CuCo₂O₄ (CCO) nanomaterials using a deep eutectic solvents (DES) method for supercapacitor (SC) applications. We systematically studied the effect of annealing temperature of CCO on its structural, morphological, and electrical properties. The CCO was annealed at different temperature of 150, 200, 250, and 300 °C for 3 h. CCO annealed at 250 °C exhibited the superior performance compared to other as-synthesized and annealed samples. The optimized CCO electrode shows outstanding supercapacitive properties with specific capacity 421 mAh g⁻¹ at 10 mV s⁻¹, excellent GCD capability, and super cycling stability. This indicates that the DES-prepared CCO shows better electrochemical performance due to highly porous nanostructure providing more active sites for easy transformation of the ions.