RuO2/Co3O4 thin films prepared by spray pyrolysis technique for supercapacitors

Abstract

RuO2/Co3O4 thin films with different RuO2 content were successfully prepared on fluorine-doped tin oxide coated glass plate substrates by spray pyrolysis method, and their capacitive behavior was investigated. Electrochemical property was performed by cyclic voltammetry, constant current charge/discharge, and electrochemical impedance spectra. The capacitive performance of RuO2/Co3O4 thin films with different RuO2 content corresponded to a contribution from a main pseudocapacitance and an additional electric double-layer capacitance. The specific capacitance of pure Co3O4, 15.5%, 35.6%, and 62.3% RuO2 composites at the current density of 0.2 A g−1 were 394 ± 8, 453 ± 9, 520 ± 10, and 690 ± 14 F g−1, respectively; 62.3% RuO2 composite presented the highest specific capacitance value at various current densities, whereas 35.6% RuO2 composite exhibited not only the largest specific capacitance contribution from RuO2 (CspRuO2) at the current density of 0.5, 1.0, 1.5, and 2.0 A g−1 but also the highest specific capacitance retention ratio (46.3 ± 2.8%) at the current density ranging from 0.2 to 2.0 A g−1. Electrochemical impedance spectra showed that the contact resistance dropped gradually with the decrease of RuO2 content, and the charge-transfer resistance (Rct) increased gradually with the decrease of RuO2 content.