Improvement of the Pseudocapacitive Performance of Cobalt Oxide-Based Electrodes for Electrochemical Capacitors

Abstract

Cobalt oxide nanopowders are synthesized by the pyrolysis of aerosol particles of water solution of cobalt acetate. Cobalt nanopowder is obtained by subsequent reduction of obtained cobalt oxide by annealing under a hydrogen atmosphere. The average crystallite size of the synthesized porous particles ranged from 7 to 30 nm, depending on the synthesis temperature. The electrochemical characteristics of electrodes based on synthesized cobalt oxide and reduced cobalt oxide are investigated in an electrochemical cell using a 3.5 M KOH solution as the electrolyte. The results of electrochemical measurements show that the electrode based on reduced cobalt oxide (Re-Co3O4) exhibits significantly higher capacity, and lower Faradaic charge–transfer and ion diffusion resistances when compared to the electrodes based on the initial cobalt oxide Co3O4. This observed effect is mainly due to a wide range of reversible redox transitions such as Co(II) ↔ Co(III) and Co(III) ↔ Co(IV) associated with different cobalt oxide/hydroxide species formed on the surface of metal particles during the cell operation; the small thickness of the oxide/hydroxide layer providing a high reaction rate, and also the presence of a metal skeleton leading to a low series resistance of the electrode.

Specific capacitance behavior of Co‐Co 3 O 4 nanocomposite thin films synthesized via different electrodeposition modes

“…4 The first redox peak (A1 (0.38 V), C1 (0.24 V)) and the third redox peaks (A3 (0.52 V), C3 (0.51 V)) can be correlated to the redox reaction of Co 2+ /Co 3+ as depicted in Equation (1). 30 The second pair of redox peaks (A2 (0.45 V), C2 (0.33 V) is correlated to the redox reaction of Co 3+ /Co 4+ shown in Equation (2). 30,31 Co…”

“…30 The second pair of redox peaks (A2 (0.45 V), C2 (0.33 V) is correlated to the redox reaction of Co 3+ /Co 4+ shown in Equation (2). 30,31 Co…”

“…This phenomenon where low specific capacitance values are attributed to the poor electrochemical reactivity between the electrolytes and the electrode materials has been commonly observed by other authors. 2,15,29,30 The high capacitance of the type 4 (CV PRP) thin film electrode could be attributed to the interconnected nanoflake-like morphology decorated with cloudy structures providing maximum surface area at electrode/ electrolyte interface. Additionally, the higher O/Co atomic ratio obtained from the EDX compositional analysis may also contribute to the high charge storage capacity.…”

Pseudocapacitive Effect of Carbons Doped with Different Functional Groups as Electrode Materials for Electrochemical Capacitors

“…The latter, given by Equation (2), can be improved either by introducing new electrode materials with higher charge storage capability through pseudocapacitive charge storage or by controlling and improving the porosity parameters (i.e., S and D) of the electroactive material [10]. Transition metal oxide-based active materials store energy pseudocapacitively and exhibit a higher specific capacitance and consequently a higher energy density when compared with traditional carbon-based electrode materials that store energy in the form of electric double-layer capacitance (EDLC) [10][11][12][13]. However, transition metal oxides suffer from higher equivalent series resistance (ESR) which results in their lower power density [6,14].…”

Enabling methanol oxidation by an interacting hybrid nanosystem of spinel Co3O4 nanoparticle decorated MXenes

“…Co 3 O 4 with the mixed-valence state exhibits a spinel structure, where the tetrahedral and octahedral positions are occupied by Co(II) and Co(III) ions, respectively. 16 Recently, spinel Co 3 O 4 has emerged as a versatile material in various applications such as energy storage and conversion due to its enriched redox chemistry, less toxicity, good reversibility, high thermal and mechanical stability, and high electrocatalytic ability. [17][18][19] To compensate for the low conductivity and surface area of Co 3 O 4 , it is hybridized with various carbon-based supports like carbon nanofibers, graphene, porous carbon, carbon nanotubes, and reduced graphene oxide.…”