Diffusion-dominated redox performance of hydrated copper molybdate for high-performance energy storage

Development of cost-effective metal molybdates with enhanced energy storage capabilities have garnered significant attention as promising redox-active electrodes for asymmetric supercapacitors (ASCs). In this work, we synthesized binder-free copper molybdate (CMO) nanostructures on nickel foam using a simple hydrothermal process and thoroughly investigated their structural and electrochemical properties. The resulting CMO nanostructures exhibited a hybrid nanosheet-nanoplate morphology with a layered structure, providing an increased electroactive surface area. The structural integrity and elemental composition were confirmed using X-ray diffraction, X-ray photoelectron and X-ray (EDX) spectroscopy, showing a homogeneous distribution of copper, molybdenum, and oxygen elements. Electrochemical analysis showed that the hydrated CMO (CMOBH) electrode provides higher specific capacitance and redox behavior than the thermally treated CMO (CMOAH) electrode. The higher performance is attributed to the CMOBH superior conductivity and the presence of hydroxyl groups, which enhance redox-type charge storage. Moreover, the ASC device fabricated using the hydrated CMOBH and activated carbon electrodes achieved a high operating voltage of 1.6 V with a maximum specific capacitance of 142.1 F/g at 1 A/g, an energy density of 48.6 Wh/kg and power density of 12.5 kW/kg, respectively. Additionally, the device demonstrated excellent cycling stability, retaining 89.1% of its capacitance after 10,000 cycles. The ASCs also successfully powered light-emitting diodes, emphasizing their potential for practical energy storage applications.