Electrodeposited three-dimensional hierarchical architecture of MgO anchored with Ag nanoparticles for high-performance symmetric supercapacitors

Abstract

A blossom-like, three-dimensional (3D) hierarchical architecture of MgO anchored with silver nanoparticles (Ag NPs) is developed using a simple galvanostatic electrodeposition method. This study shows how electrochemical performance is improved by the incorporation of Ag NPs within a 3D framework. The 3D blossom-like scaffold comprises thin 2D petals, whose porous lace-like patterns provide a large surface area and many channels for the rapid diffusion of electrolyte ions. The anchored Ag NPs increase the electrical conductivity of the MgO structure and enhance redox reactions. An optimum Ag loading of 10 vol% on MgO (MgO@Ag-10) affords a 100-fold enhancement in specific capacitance over that of MgO. This hybrid MgO@Ag-10 electrode on a stainless-steel substrate yields a specific capacitance of 388.6 F.g−1 (134.85 mF.cm−2) at a current density (CD) of 1 mA.cm−2, whereas pure MgO delivers only 3.72 F.g−1 (3.1 mF.cm−2) at the same CD in a three-electrode system. The MgO@Ag-10 electrode also exhibits 88.6 % capacitance retention over 5000 charge–discharge cycles. A symmetric supercapacitor device comprising two MgO@Ag-10 electrodes exhibits a specific capacitance of 42 F.g−1, an energy density of 23.33 Wh.kg−1, and a power density of 8000 W.kg−1 at 4 mA.cm−2 in aqueous KOH.