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 RuCo2O4 with an effective surface area of 245 m(2) 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).