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

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 RuCo₂O₄with an effective surface area of 245 m²g⁻¹. By virtue of nanofibrous networks, amorphous behavior and high surface area, RuCo₂O₄exhibits a superior specific capacity of 372 mA h g⁻¹at 3.3 A g⁻¹with 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 RuCo₂O₄and 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