MOF-Derived Porous 2D-ZnCo<sub>2</sub>O<sub>4</sub> Electrode: A Rational Design of Redox-Active Electrolytic Supercapacitor with Extraordinary Energy Density
Gowdhaman Arumugam, Balaji Chettiannan, Stanleydhinakar Mathan, Manickam Selvaraj, R. Ramesh
Abstract
In this work, we propose the preparation of 2D-ZnCo 2 O 4 sheets on nickel foam (NF) through simple calcination of in situ-grown ZnCo-MOF (metal–organic framework). The 2D-ZnCo 2 O 4 ultrathin sheets, possessing good surface properties, show a better electrochemical performance toward supercapacitor application. To further improve the performance of the 2D-ZnCo 2 O 4 sheets, the electrodes are examined in a different mole ratio of the redox additive-containing electrolyte. Here, we use K 4 [Fe(CN) 6 ] (potassium ferrocyanide) as a redox additive in 3 M KOH (potassium hydroxide) electrolyte at ratios of 0.025, 0.05, and 0.075 M. The ZnCo 2 O 4 @NF electrode exhibits a remarkable specific capacitance of 5.3 F cm –2 at 3.2 mA cm –2 (3639.5 C g –1 at 4 A g –1 ) in a 0.075 M K 4 [Fe(CN) 6 ] containing 3 M KOH electrolyte. We demonstrate a high-energy-density asymmetric supercapacitor (ASC) using ZnCo 2 O 4 @NF as a positive electrode and activated charcoal (AC) as a negative electrode with 0.075 M potassium ferrocyanide (K 4 [Fe(CN) 6 ]) containing 3 M KOH as an advanced electrolyte. The asymmetric supercapacitor exhibits an extraordinary energy density of 66.4 μW h cm –2 at a power density of 1125 μW cm –2 (132.9 W h kg –1 at 2.25 kW kg –1 ).