Synthesis and characterization of cobalt hydroxide carbonate nanostructures

Battery-type electrodes of three-dimensional (3D) hierarchical cobalt hydroxide carbonate arrays on Ni foam were fabricated using a hydrothermal method for use in supercapacitors. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize their structures and morphologies. The cobalt hydroxide carbonate synthesized with 10 h reaction time showed the highest specific capacitance (1381 F g−1 at a current density of 2 A g−1) and excellent cycling stability (92% capacitance retention after 5000 cycles). Moreover, its capacitance increased by 33% at 2 A g−1 and by 10% at 20 A g−1 after 5000 charge–discharge cycles. This cobalt hydroxide carbonate composite is a promising candidate for electrochemical energy-related applications

Hydrothermal synthesis of manganese phosphate/graphene foam composite for electrochemical supercapacitor applications

Please read abstract in the article.The South African Research Chairs Initiative (SARChI) of the Department of Science and Technology and the National Research Foundation (NRF) of South Africa (Grant No. 61056).https://www.elsevier.com/locate/jcis2018-05-31hb2017Physic

Electrochemical properties of asymmetric supercapacitor based on optimized carbon-based nickel-cobalt-manganese ternary hydroxide and sulphur-doped carbonized iron-polyaniline electrodes

Please read abstract in the article.The South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Grant No. 61056).http://www.elsevier.com/locate/electacta2021-02-20hj2020Physic

High-performance asymmetric supercapacitor based on vanadium dioxide and carbonized iron-polyaniline electrodes

Vanadium dioxide (VO2) monoclinic nanosheets were synthesized by a solvothermal method and carbonized iron-polyaniline (C-FP) nanograins were prepared by pyrolysis of iron-polyaniline (PANI) mixture under nitrogen ambient. An asymmetric device (VO2//C-FP) was evaluated with VO2 and C-FP as positive and negative material electrodes in aqueous 6 M KOH electrolyte respectively. The asymmetric supercapacitor (VO2//C-FP) exhibited a 47 mA h g-1 specific capacity and a specific energy of 30Wh kg−1 with an associated specific power of 713 W kg−1 at a gravimetric current of 1 A g−1 in a potential window of 1.6 V. It also displayed an 89% energy efficiency after 10000 galvanostatic charge-discharge cycles with a large improvement after ageing test at a gravimetric current of 10 A g-1.http://scitation.aip.orgcontent/aip/journal/advaam2019Physic

High electrochemical performance of hybrid cobalt oxyhydroxide/nickel foam graphene

In this study, we report the in-situ hydrothermal synthesis of mesoporous nanosheets of cobalt oxyhydroxide (CoOOH) on nickel foam graphene (Ni-FG) substrate, obtained via atmospheric pressure chemical vapour deposition (AP-CVD). The produced composite were closely interlinked with Ni-FG, which enhances the synergistic effect between graphene and the metal hydroxide, CoOOH. It is motivating that the synthesized CoOOH on the Ni-FG substrate showed a homogenous coating of well-ordered intersected nanosheets with porous structure. The electrochemical properties of the material as electrode showed a maximum specific capacity of 199 mA h g 1 with a capacity retention of 98% after 1000 cycling in a three electrode measurements.This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Grant No. 97994). T.M. Masikhwa and M.J. Madito acknowledge financial support from the University of Pretoria and the NRF for their PhD bursaries. A. Bello acknowledges the University of Pretoria’s financial support for his Postdoctoral fellowship.http//: www.elsevier.com/locate/jcis2017-12-31hb2017Physic

Simonkolleite-graphene foam composites and their superior electrochemical performance

Simonkolleite-graphene foam (SimonK/GF) composite has been synthesized by a facile solvothermal and environmentally friendly technique with excellent electrochemical properties. The obtained product was initially analyzed by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Fourier transform infrared resonance (FTIR) spectroscopy and cyclic voltammetry (CV) techniques. The microscopy results reveal hexagonal sheets interlaced with each other and adjacent graphene sheets. The existence of graphene foam in the simonK/GF composite is further confirmed from the structural and the optical characteristics obtained from XRD and FTIR respectively. The BET results obtained indicate an improvement in the surface area due to the addition of graphene foam to a value of 39.58 m2 g 1. The N2 adsorption/desorption also shows the presence of active mesopores required for charge transport. As a promising electrode material for supercapacitors, the composite shows a high specific capacitance value of 1094 F/g at 1 A/g with a coulombic efficiency of 100% after 1000 cycles. These results show a potential for adoption of this composite in energy storage applications.South African Research Chairs Initiative (SARChi) of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://www.elsevier.com/locate/electactahb201

Asymmetric supercapacitor based on VS2 nanosheets and activated carbon materials

VS2 nanosheets as the positive electrode and the activated carbon (AC) as the negative electrode with a 6 M KOH solution as electrolyte were fabricated as an asymmetric supercapacitor. These materials were combined to maximize the specific capacitance and to enlarge the potential window, therefore improving the energy density of the device. A specific capacitance of 155 F g-1 at 1 A g-1 with a maximum energy density as high as 42 Wh kg-1 and a power density of 700 W kg-1 was obtained for the asymmetric supercapacitor within the voltage range of 0 – 1.4 V. The supercapacitor also exhibited a good stability with ∼ 99% capacitance retention and no capacitance loss after 5000 cycles at a current density of 2 Ag-1.The South African Research Chairs Initiative of the Department of Science and Technology (SARChI-DST) and the National Research Foundation (NRF).http://www.rsc.org/journals-books-databases/about-journals/rsc-advances2017-04-30hb2016Physic

Electrochemical performance of two-dimensional Ti3C2-Mn3O4 nanocomposites and carbonized iron cations for hybrid supercapacitor electrodes

Please read abstract in the article.The South African Research Chairs Initiative of the Department of Science and Technology, South Africa and National Research Foundation of South Africa (Grant No. 61056). K. O. appreciates the financial assistance from the University of Pretoria, South Africa and National Research Foundation (NRF) of South Africa for studentship grants.http://www.elsevier.com/locate/electacta2020-04-01hj2019Physic

Raman analysis of bilayer graphene film prepared on commercial Cu(0.5 at% Ni) foil

This study reports the Raman analysis of bilayer graphene films prepared on commercial dilute Cu(0.5 at% Ni) foils using atmospheric pressure chemical vapor deposition. A bilayer graphene film obtained on Cu foil is known to have small areas of bilayer (islands) with a significant fraction of non-Bernal stacking, while that obtained on Cu/Ni is known to grow over a large area with Bernal stacking. In the Raman optical microscope images, a wafer-scale monolayer and large-area bilayer graphene films were distinguished and confirmed with Raman spectra intensities ratios of 2D to G peaks. The large-area part of bilayer graphene film obtained was assisted by Ni surface segregation because Ni has higher methane decomposition rate and carbon solubility compared with Cu. The Raman data suggest a Bernal stacking order in the prepared bilayer graphene film. A four-point probe sheet resistance of graphene films confirmed a bilayer graphene film sheet resistance distinguished from that of monolayer graphene. A relatively higher Ni surface concentration in Cu(0.5 at% Ni) foil was confirmed with time-of-flight secondary ion mass spectrometry. The inhomogeneous distribution of Ni in a foil and the diverse crystallographic surface of a foil (confirmed with proton-induced X-ray emission and electron backscatter diffraction, respectively) could be a reason for incomplete wafer-scale bilayer graphene film. The Ni surface segregation in dilute Cu(0.5 at% Ni) foil has a potential to impact on atmospheric pressure chemical vapor deposition growth of large-area bilayer graphene film.The South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation (NRF) of South Africa (grant no. 97994). M.J. Madito acknowledges the financial support from University of Pretoria and NRF for his PhD studies.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-45552017-05-31Physic

Synthesis of ternary NiCo-MnO2 nanocomposite and its application as a novel high energy supercapattery device

Please read abstract in the article.The South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Grant No. 61056). K. O. Oyedotun acknowledges financial support from the University of Pretoria and National Research Foundation (NRF) for his PhD studies.http://http://www.elsevier.com/locate/cej2019-03-01hj2017Physic