One-Step Rapid Conversion of Electroactive CoMnO Nanostructures Using a Deep Eutectic Solvent as the Template, Solvent, and Source

Abstract

Here, a ternary deep eutectic solvent (DES) is employed as the reaction medium, reducing agent, template, and source for the preparation of cobalt manganese oxide (CoMnO) at room temperature. The hydrogen-bonding interaction between DES and manganese precursors resulted in a rapid conversion of CoMnO nanostructures, and the process was well controlled with the addition of water, which eventually reduced the bonding interaction between the formed nanostructures. The reaction between DES and potassium permanganate is carried out at different time intervals (1, 10, 30, 45, 60 min, 1.5, 2, 4, and 12 h) before the addition of water. With varying reaction times, the morphology, pore structure, surface area, and electrochemical properties of the synthesized CoMnO structures also vary. The highest specific capacitance of 242 F g–1 at 0.1 A g–1 is accomplished using CoMnO nanostructures, where KMnO4 and ternary DES reacted for 4 h. The CoMnO nanostructures prepared by the DES route also show excellent electrochemical stability with 97% initial capacitance retention at 10 A g–1 over 10 000 charge/discharge cycles. Further, the CoMnO-60 min sample shows outstanding electrochemical OER activity with 300 mV overpotential to obtain a current density of 10 mA cm–2 and a Tafel slope value of 73 mV dec–1.