The role of number of overcoating and evolution of supercapacitor electrode performance in semi-hierarchical nickel-sulfide heterostructures: A research study on Hydrothermally grown Cobalt Oxide scaffolds

This work reports An investigation of the role of the number of overcoating in the evolution of the performance of supercapacitors based on hydrothermally grown cobalt oxide scaffolds. Nickel sulfides (NS) coated on cobalt oxide are synthesized by hydrothermally growing on Nickel foam and subsequently overcoating with NS via successive ionic layer adsorption and reaction (SILAR) reactions. The electrochemical performance of supercapacitors is systematically examined according to the number of SILAR-overcoating cycles that are applied. In the GCD cyclic stability study, h-NS20@CO outperforms pristine CO-based SSCs when viewed at 10,000 cycles. Synergetic effects caused by the heterostructure of NS20 on cobalt oxide scaffolds have contributed to the remarkable improvement in electrochemical performance, and experimental evidence that layer dependence exists is provided. It is also demonstrated successfully by designing a wirelessly controlled LED assembly using CO-based SSCs powered by NS20. By showing the LED operation, the portable energy storage device demonstrates potential functionality.


  • A new study shows that super-capacitors with nickel sulfides on cobalt oxide (h-NS@CO) retain 91.8% capacitance even after 10,000 cycles. More impressively, a wirelessly controllable LED assembly, powered by h-NS20@CO-based SSCs is successfully implemented.
  • A 3D architecture of h-NS@CO heterojunction assuming nano-wired array like morphology were integrated on a 3D porous NF scaffold. The overcoating improves the energy density of 66 and power density of 1750
  • A high theoretical specific surface area makes cobalt oxide a promising candidate. This material offers high capacitance (3500 Fg-1), excellent mechanical and thermal stability, natural abundance, and environmental-friendliness.
  • Electrochemical performance is influenced by the morphology of electrode materials, which modulates their active surface areas.
  • Researchers use sulfur treatment, doping with highly conductive materials, and growing core-shell structures in our devices.
  • Due to its low cost, pseudo-capacitive nature, and high electrical conductivity, nickel sulfide (Ni3S2) is a promising energy conversion and storage material.
  • Overcoating cobalt oxide layers with nickel sulfides has several advantages.
  • On the other hand, nickel sulfides is known to be non-toxic in comparison with CdS.
  • There is a high likelihood of nickel sulfides@cobalt oxide achieving an excellent Specific Capacitance and cyclic stability are superior to the new cobalt oxide-based electrodes.

Study design-

  • The hydrothermal method facilitates the direct growth of cobalt oxide on Nickel Foam.
  • In 60 mL of deionized (DI) water, four mmol of Co (NO3)2-6H2O was dissolved by vigorous stirring for 10 minutes.
  • 8mm of urea and 8mmol of NH3F were added to form a clear solution.
  • NF was cleaned and placed in the solution, after which the resulting nanoparticles of CO were grown in situ over the scaffold of Nickel Foam.

Image Source-

Key Findings-

  • The detailed preparation procedure for the synthesis of CO nanowire and heterostructure of h-NS-XX@CO is described schematically as illustrated CO Nanowires were directly grown on NF via a hydrothermal process followed by annealing in air at 400°C.
  • The SILAR process is a low-cost, facile, scalable, template free, room temperature synthesis technique.
  • The morphological evolution of the pristine CO samples, corresponding to the varying number of SILAR overcoating, was analyzed by scanning electron microscopy.
  • The pristine CO sample possesses nanowire like porous structure with uniform coverage on NF scaffolds, yielding enormous spatial voids for facilitating better electrolyte ions movement into the innermost region of the electrodes.
  • The crystallographic phase of CO and h-NS20@CO were characterized by XRD analysis.
  • The electronic state and chemical compositional were assessed by Xray photoelectron spectroscopy (XPS) analysis.
  • The XPS survey spectrum of CO and h-NS20@CO illustrating the XPS signal of the constituent element Co, O, Ni and S.
  • After overcoating, the deconvoluted XPS spectra for both Ni and Co confirmed the presence of multiple oxidation states.
  • The distinct nanowire configured nanostructure of CO can be clearly seen in TEM images at magnification of 200 nm.
  • As shown in the HRTEM images, the whole heterosheets of the CO and NS are covered with lattice lattice fringes with a spacing of 0.24 nm with a coherence in which is 0.3 1/2 plane of Co30, 1.1/2.

Generalized Results-

  • Three-electrode system is employed for evaluating the asprepared samples.
  • The same sample exhibited maximum sp. capacitance consistently at all the scan rates.
  • This remarkable improvement in the electrochemical performance is accredited to optimal number of nickel sulfide overcoating cycles.
  • The shape of the GCD profile for a particular sample illustrates the behavior of the supercapacitor.
  • The sample CO involves a shift from the triangular shape while overcoated samples shapeshift
  • Heterojunction of NS by SILAR overcoating on hydrothermally synthesized CO.
  • The effect of number of overcoating cycles on the equivalent circuit was analyzed by electrochemical impedance spectroscopy (EIS) test.
  • In an electrode/ electrolyte material system, Nyquist plot (or complex plane plot) primarily interprets the frequency response as a function of imaginary
  • The electrochemical performance and effectiveness of electrode material are evaluated by the cyclic performance.
  • The cycling stability of the as-prepared electrodes was tested by GCD method for 10,000 cycles at a higher current density.
  • A bluetooth controlled LED module was demonstrated, powered by the h-NS20@CO SSC device assembly.
  • The LED-lit/glow up system was programmed with the arduino and the after reaching the desirable charging voltage of SCs.

Future Work Perspectives-

  • Study results suggest that overcoating SILAR changes the nanostructure of CO, in turn promoting short diffusion paths and abundance of electroactive sites.
  • A portably accessible energy storage device can demonstrate its capabilities by the operation of its LED display.


A 3D architecture of h-NS@CO heterojunction assuming nano-wired array-like morphology where h-NS@CO heterojunctions with nanowire array-like structures have been constructed on porous NF scaffolds using a two-step approach.

The number of overcoating cycles for several samples is optimized based on their electrochemical performance.

The LED control via a mobile Bluetooth device using an h-NS20@CO-based SC was also demonstrated

Hierarchically-formed nickel sulfide heterostructure via SILAR on hydrothermally grown cobalt oxide scaffolds: Role of number of over-coating and evolution of electrochemical performance in supercapacitor electrodes

Research Paper Detail in PDF

About the author

About the Author

Dhananjay Mishra

  • Incheon National University, South Korea

Dhananjay Mishra is currently pursuing his Ph.D. in the Department of Electronics Engineering at Incheon National University, South Korea. He has worked as a junior research fellow in the Department of Mechanical Engineering, IIT Indore. His major interests include energy storage, supercapacitor, RRAM, and Neuromorphic applications.

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