Low-temperature synthesis of oval-shaped CoWO4 nanomaterials for enhanced asymmetric supercapacitor performance

Abstract

The electrochemical supercapacitor has been shown to be a reliable and innovative type of energy storage technology over the years. Recent research has shown that CoWO₄ is a potential material for supercapacitor applications because of its unique characteristics, which make it suitable for energy storage. CoWO₄ nanostructures are synthesized using a low-temperature hydrothermal method followed by calcination at 300 °C for 2 h. The powder was characterized through XRD with Rietveld refinement, FE-SEM, TEM, Raman spectroscopy, FTIR, XPS, BET and electrochemical techniques. XRD analysis revealed a monoclinic crystal framework of CoWO₄ with a space group of P2/c. FE-SEM and TEM results are in good agreement with each other and reveal elongated oval-shaped nanostructures of CoWO₄. BET analysis indicates the mesoporosity in the nanostructures, which helps in the increased active sites for an efficient supercapacitor application. XPS results confirm the presence of a Co²⁺ oxidation state in the CoWO₄ nanostructure. The electrochemical characterizations were carried out using a three-electrode system. The CoWO₄ electrode indicates a high specific capacitance of 235 F g⁻¹ at 10 mV s⁻¹ in 6 M KOH electrolyte between −0.15 V to 0.45 V potential window and retains 93.25% capacitance even after 10 000 cycles. Additionally, an asymmetric supercapacitor is assembled using the CoWO₄ and activated carbon as the positive and negative electrodes, respectively, achieving a maximum energy density of 51.8 W h kg⁻¹ and an excellent capacity retention of 96.43% after 10 000 cycles at 3 A g⁻¹. This work will be helpful in the development of high-capacitive, durable, and safe supercapacitor devices for future energy needs.