Deep eutectic solvent-assisted synthesis of RuCoO: 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 RuCo 2 O 4 with an effective surface area of 245 m 2 g −1 . By virtue of nanofibrous networks, amorphous behavior and high surface area, RuCo 2 O 4 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 RuCo 2 O 4 and reduced graphene oxide as a positive and negative electrode, respectively. The proposed RuCo 2 O 4 //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 . Preparation of deep eutectic solvents for the synthesis of RuCo 2 O 4 to fabricate hybrid supercapacitors with high specific energy.