Green synthesis of cobalt oxide thin films as an electrode material for electrochemical capacitor application

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In this study, we report on the fabrication and characterization of cobalt oxide (Co 3 O 4 ) thin film that is potentially important for electrochemical capacitor applications. For that purpose, the precursor powder of Co 3 O 4 was prepared using the cost-effective sol-gel synthesis route and heat treatment at a relatively low temperature. A thin film of Co 3 O 4 was prepared on a fluorine-doped tin oxide (FTO) substrate using a simple doctor-blade method. X-ray diffraction and Raman spectroscopy confirmed the formation of pure Co 3 O 4 thin film on FTO, and scanning and transmission electron microscopy confirmed the nanoscale nature of the particles in the film. The electrochemical studies revealed a specific capacitance of 237 ​F ​g -1 for the Co 3 O 4 electrode, with a remarkable cycling stability in 1 ​M NaOH electrolyte, and 77% capacity retention after 2000 cycles at 5 ​mA ​cm -2 current density (833 ​mA ​g -1 ); this demonstrates that Co 3 O 4 is a promising material for electrochemical devices. Further, the electrochemical impedance measurements revealed an internal (solution) of 10 ​Ω, whereas the charge transfer resistance between the electrode and the electrolyte was roughly 40 ​Ω. In this study, we report on the fabrication and characterization of cobalt oxide (Co 3 O 4 ) thin film that is potentially important for electrochemical capacitor applications. The electrochemical studies revealed a specific capacitance of 237 ​F ​g -1 for the Co 3 O 4 electrode, with a remarkable cycling stability in 1 ​M NaOH electrolyte, and 77% capacity retention after 2000 cycles at 5 ​mA ​cm -2 current density; this demonstrates that Co 3 O 4 is a promising material for electrochemical devices. Further, the electrochemical impedance measurements revealed an internal resistance of 10 ​Ω for the Co 3 O 4 electrode, whereas the charge transfer resistance between the electrode and the electrolyte was roughly 40 ​Ω. ∙ Cobalt oxide synthesized by simple and cost-effective Sol-gel method. ∙Films of cobalt oxide were prepared on fluorine doped tin oxide (FTO) substrate by unsophisticated doctor blade method. ∙Cobalt oxide electrode exhibited specific capacitance value of 237 ​F ​g -1 @ 1 ​mA ​cm -2 in NaOH electrolyte. ∙Cobalt oxide electrode showed high cyclic stability (77% retention of initial specific capacitance) Up to 2000 cycles @ 5 ​mA ​cm -2 current density.