Spray-deposited cobalt-doped RuO2 electrodes for high-performance supercapacitors

RuO2 is widely used as the material in supercapacitors; however, there is little information on the doping RuO2 with cobalt using an aqueous/organic solvent mixture in the spray pyrolysis technique. The phase purity and rutile crystal structure of cobalt-doped RuO2 were validated using X-ray diffraction. Optical studies indicated that the bandgap can be decreased from 1.80 eV to 1.70 eV by doping the RuO2 with cobalt. In this study, the performance of electrochemical supercapacitors and their morphology are both significantly altered by cobalt doping. 1.00 mol% cobalt-doped RuO2 displays a high specific capacitance (1072 F g-1 at a 5 mV s-1 scan rate) compared with that of undoped RuO2 (893 F g-1 at a 5 mV s-1 scan rate). 1.00 mol% cobalt-doped RuO2 had the highest specific energy (96.02 W h kg-1) at a specific power value of 1.702 kW kg-1. The specific capacitance was improved (1158 F g-1 at 0.5 A g-1) in a 0.5 M H2SO4 electrolyte. After 1000 charge-discharge cycles, 94% of the capacity of a 1.00 mol% cobalt-doped RuO2 electrode was preserved, indicating outstanding long-term cyclic stability. This study endorses the view that 1.00 mol% cobalt-doped RuO2 is a promising material for supercapacitor applications.