Study: Ni-Co double hydroxide coated on microsphere nanocomposite of graphene oxide and single-walled carbon nano-nanocords as a supercharger electrode material. Image credit: Peter Sobolev/Shutterstock.com The new supercapacitor electrode material Ni-Co LDH and GO/SWCNHs based on the composite is a potential choice for pseudocapacitor applications due to its superior electrochemical properties and ease of fabrication, which is ideal for various commercial and industrial applications.
Why are supercapacitors so important?
Clean and renewable energy technologies are currently being explored to address global energy consumption and sustainability challenges. As a result, competition for more efficient energy storage systems such as supercapacitors and regenerative batteries has increased dramatically. Supercapacitors have attracted great interest in scientific communities due to their high energy density, fast charge/discharge rate, and extended cycle stability. Supercapacitors are classified as electric double layer capacitors (EDLCs) or pseudocapacitors, depending on their energy storage mechanism. Energy storage in an EDLC is related to a non-Faradic mechanism involving physical absorption and dissociation of electroactive species at the surfaces of the supercapacitor electrode material and electrolytes. On the other hand, energy storage in pseudocapacitors mainly depends on reversible Faradaic interactions between the interfacial functional groups of the supercapacitor electrode material.
Supercapacitor electrode material: Overview and challenges
Graphene oxide (GO) has attractive properties for supercapacitor electrode material applications, such as numerous reactive groups and multimodal ion transport pathways. However, graphene oxide-based supercapacitor electrode material also has significant drawbacks, such as the discharge of graphene layers during the reduction reaction, insulating properties, and poor bulk density. SWCNHs have also been explored as a supercapacitor electrode material due to their large specific surface area (SSA), tunable porous structure, and excellent electrical conductivity. SWCNHs with conical tubular structures form strong spherical aggregates and have closed graphitic single-walled structures comparable to single-walled carbon nanotubes (SWCNTs). However, unlike SWCNTs with excellent crystallinity, SWCNHs contain various structural defects such as pentagons and heptagons, allowing the development of nanoscale holes at the interface of SWCNHs in oxidizing environments, limiting their utility as suitable supercapacitor electrodes.
Ni-Co layered double hydroxide as supercapacitor electrode material
Electrode materials such as metal oxides, metal hydroxides, and conducting polymers are considered highly ideal candidates for pseudocapacitive energy storage technologies due to bidirectional Faradaic processes at electrode-electrolyte contacts. Layered nickel-cobalt (Ni-Co) double hydroxide with tunable topologies is an attractive supercapacitor electrode material due to its cheap cost, non-toxicity, abundance in nature, and excellent electrochemical stability. Hydrothermal and electrolytic deposition techniques generally create Ni-Co nanostructures. The structural morphologies significantly affect the electrolytic capacities of double hydroxide electrodes with Ni-Co layers. Therefore, Ni-Co nanostructured composites and porous carbon substances such as graphene oxide (GO) and SWCNHs should be explored to increase the performance of Ni-Co LDH-based supercapacitor electrode material.
Highlights of current research
In this study, the researchers developed a two-step technique to produce composites composed of Ni-Co LDH, graphene oxide (GO), and oxidized single-walled carbon nanohorns (SWCNHs). The initial step was spray-drying a combination of GO and SWCNH to create spherical hybrid particles ideal for mass production due to the simple and economical process. In the second step, ultrathin nickel-cobalt (Ni-Co) LDH nanosheets were hydrothermally coated on graphene oxide microspheres and single-walled carbon nanohorns to fabricate the new supercapacitor electrode material. The pseudocapacitive activity of the hybrid supercapacitor electrode material was evaluated in terms of specific capacitance and cycle efficiency. During the study, the effects of activated carbon substrate composition on the morphology and electrolytic efficiency of Ni-Co LDH were also investigated.
Important findings of the study
The graphene oxide and SWCNHs-based composite had comparatively high SSA and electrical conductivity, resulting in a significant effective area for interactions between the supercapacitor electrode material and electrolyte ions during the electrolysis reaction. The new Ni-Co LDH and GO/SWCNHs supercapacitor electrode material based on the composite exhibited significantly high specific gravimetric capacity and excellent specific capacitance stability in an aqueous electrolyte environment. These remarkable findings can be attributed to the high electrical conductivity and pseudo-capacitance of GO/SWCHN nanohybrids and coated Ni-Co LDHs. Based on these results, it is reasonable to state that the new supercapacitor electrode material developed in this work has significant potential for future energy storage applications.
Report
Kim, JH et al. (2022). Ni-Co layered double hydroxide coated on a nanocomposite of graphene oxide microspheres and single-walled carbon nanohorns as supercapacitor electrode material. International Journal of Energy Research. Available at: https://onlinelibrary.wiley.com/doi/10.1002/er.8657 Disclaimer: The views expressed here are those of the author expressed in his capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork, owner and operator of this website. This disclaimer forms part of the Terms and Conditions of use of this website.
