Effect of cathodic deposition potential on the performance of nanostructured cobalt-based film for asymmetric supercapacitor fabrication

The energy density of a rechargeable device may be determined by the specific capacity of electrodes and the potential difference between the anode and cathode. Therefore, high specific capacitances are required for energy storage devices with high energy densities. Electrodes with high surface areas generally provide good contact between the electrode and electrolyte, hence, the electrode material is important for supercapacitor applications. The structure and surface area of the electrodes may be affected by fabrication parameters and processes used. As the structure of the electrode is related to the performance of energy storage devices, electrodeposition parameters of electrodes were studied. In this research, the effect of electrodeposition potential on cobalt structure and capacitive performance of resulting electrodes were reported. Co-based film was cathodically electrodeposited by applying different potentials (−1.3 V to −1.7 V) on the graphite electrode. Morphological and structural characteristics of coatings were examined by SEM and FTIR. The electrodes were then immersed in an alkaline (KOH) bath for capacitance measurements. The rate limiting reactions of the electrodes in KOH depending on deposition potential was studied. The galvanostatic charge-discharge curves for the negative graphite electrode and positive cobalt-based electrode were obtained. Electrochemical performances of the nano-composite electrodes varied with the applied voltages. The electrode showed a maximum specific capacity of 1692 F g−1 at 5 mV s−1. Capacitance retention of Co-based films after 1000 cycles in KOH varied from 26% to 108% depending on the deposition potentials. [Display omitted] •Co-based film which can be used in supercapacitor applications was prepared.•Different voltages were applied for electrodeposition of the Co-based film.•Plating process affected morphology and capacitance behaviour of the films.•Maximum specific capacity of the cobalt-based film was 1692 F g−1.