Deep eutectic solvent-assisted synthesis of RuCo2O4: an efficient positive electrode for hybrid supercapacitors

Abstract

Bimetallic oxides attract significant interest for application in supercapacitors because of their multivalent active sites, which render them highly efficient materials. Herein, we develop a new approach for the synthesis of a bimetallic oxide using a choline chloride and urea (1 : 2)-based deep eutectic solvent. We synthesize a unique amorphous nanofibrous network of RuCo₂O₄ with an effective surface area of 245 m² g⁻¹. By virtue of nanofibrous networks, amorphous behavior and high surface area, RuCo₂O₄ exhibits a superior specific capacity of 372 mA h g⁻¹ at 3.3 A g⁻¹ with an excellent rate capability (55% after 41 A g⁻¹) and cycling stability (94% after 10 000 cycles). Additionally, an aqueous hybrid supercapacitor cell is fabricated using RuCo₂O₄ and reduced graphene oxide as a positive and negative electrode, respectively. The proposed RuCo₂O₄//rGO hybrid supercapacitor cell demonstrates an extended potential window of 1.4 V with an excellent energy density of 59.7 W h kg⁻¹.