Biosynthesis of zinc oxide-cobalt oxide nanocomposite as electrode material and its performance evaluation for the sustainable hybrid supercapacitor energy storage devices

Abstract

Novel energy storage techniques and systems have gained increasing importance in recent times to overcome the variability in the output of non-dispatchable renewable energy sources. Supercapacitors are energy storage systems that have attracted considerable attention from various stakeholders. However, the performance of an effective supercapacitor energy storage system depends mainly on the electrochemical behavior of the electrodes, and the methods used to fabricate the electrode materials. Sustainable methods for the fabrication of electrode materials such as green synthesis have recently attracted researchers. In this work, a method is proposed to synthesize zinc oxide and cobalt oxide nanocomposite using green synthesis to take advantage of their superior electrochemical properties and stability. Evaluation of the morphological and electrochemical performance of the fabricated nanocomposite showed good results. Further, the electrode material fabricated using the synthesized nanocomposite has shown energy density values in the range of 3.8 Wh/kg to 9.54 Wh/kg for the power density values of the range 3000 W/kg to 375.3 W/kg for the different chosen current densities. A retention capacity of approximately 85% was observed even after 5000 cycles which is one of the most important features of supercapacitors. Thus, green synthesis with its intrinsic advantages over chemical methods is expected to be a promising approach for the fabrication of electrode materials for supercapacitors in sustainable energy storage applications in the future.