Improved Electrochemical Performance from Nano-Cobalt Oxide: Bifunctional Application in Energy Generation and Storage

Abstract

The bifunctional properties, supercapacitive and water splitting, of the electrodeposited nano-Co3O4 film grown on different substrates, namely, FTO, carbon paper, and carbon cloth, have been investigated. A comparative study shows that the underlying substrate, on which the nano-Co3O4 film is deposited, plays a role and affects the performance. A detailed electrochemical study carried out on the Co3O4@CC electrode reveals that the charge is stored at the electrode/electrolyte interface in the form of a redox state triggered by the faradaic reaction and thus provides a pseudocapacitive nature to the electrode by exhibiting a capacitance of 265 F/g at a current density of 2 A/g. Additionally, electrode’s stability, coulombic efficiency, and capacitance retention were found to be excellent. In addition to the energy storage, electrically assisted water-splitting property has also been observed at the electrode surface for which the nano-Co3O4 electrodes act as catalysts to exhibit the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at the electrode/electrolyte interface. The overpotential for HER and OER has been measured to be 580 and 620 mV with their respective Tafel slope of 171 and 270 mV dec–1. Overall, the Co3O4@CC electrode was found to be the best-performing electrode for bifunctional application in water splitting and supercapacitive energy storage.