Evaluating the effect of annealing temperatures on sol-gel synthesized Ni3V2O8 nanostructure for effective water splitting and supercapacitor applications

The simple and economical sol-gel method was utilized to prepare nickel vanadate nanostructure (NVO-NS), which provides an economical pathway to high-performance energy devices. In this work, the effect of different annealing temperatures on NVO-NS and their role is studied in the field of electrocatalytic and electrochemical activities. However, the functional NVO-NS were analyzed using various physio-chemical methods to confirm the structure and surface morphology. As a result, at a calcination temperature of 650oC, the NVO-NS gives better results as an electrocatalyst with a low overpotential of 186 and 65 mV at 10 mA/cm2, a moderate value for Tafel slope of 62 and 33 mV/dec for oxygen evolution (OER) and hydrogen evolution reaction (HER) over other electrodes respectively. In particular, the NVO-NS-based electrolysis cell needs an output voltage of 1.51 V in the alkaline medium for the water-splitting phenomenon to deliver a current density of 10 mA/cm2. Additionally, the prepared electrodes were functionalized for the energy storage system, which shows better electrochemical performance in an aqueous KOH electrolyte. From the result, the irregularly shaped NVO-NS exhibit a specific capacitance of 1027 F/g at 5 mA/cm2, implying better charge storage capacity and rate performance. Furthermore, the NVO-NS and activated carbon-based asymmetric device delivers a maximum energy density (Ed) of 24 Wh/kg at a power density (Pd) of 1166 W/kg with superior cycling stability of 86 % after 5000 cycles.