Synthesis and characterization of carbon-based nanostructured material electrodes for designing novel hybrid supercapacitors

Recent research efforts are focused on alternative energy production instead of fossil fuels. Meanwhile, the developments of more efficient energy storage devices are driven by many factors. One is related to our environment. There is a need to significantly control emission of greenhouse gases, and reduce the amount of global warming majorly caused by fossil fuels. The products of combustion processes from fossil fuel usually lead to environmental pollution and poisonous atmospheric smog in our environment. In spite of growing developments in addressing various issues inherent to energy storage devices, supercapacitors continue to exhibit low energy density when compared with lithium ion batteries. The study in this thesis has utilized low-cost and environmentally-friendly carbon-based nanostructured hybrid materials as electrodes for designing a novel hybrid supercapacitor, which allows for a bolstering alliance of characteristics of dissimilar components in synergistic combinations, therefore providing enhanced energy and power densities by combining battery and supercapacitor materials storage mechanisms. Morphologies, compositions, structures and surface area/pore size distribution of the as-prepared materials nanocomposites were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and X-ray fluorescence (XRF), while the performance characteristics were electrochemically evaluated through cyclic voltammetry and charge/discharge cycling in both three- and two-electrode configurations. Electrodes fabricated from both graphene oxide (GO) nanogel gel and carbon nanorods materials gave a maximum specific capacitance of 436.5 F g-1 and 719.5 F g-1 corresponding to specific capacities of 48.5 mAh g-1 and 80.8 mAh g-1 at a specific current of 0.5 A g-1 respectively. The assembled hybrid asymmetric supercapacitor with carbonized iron cations (C-FP) selected as the negative electrode, NiCo-MnO2//C-FP proved a specific capacitance of 130.67 F g-1, high energy and power densities of 48.83 Wh kg-1 and 896.88 W kg-1 at 1 A g-1 respectively, with an excellent cycling stability for up to 10,000 cycles. Also, an assembled Ti3C2-Mn3O4//C-FP delivered a specific capacity of 78.9 mAh g-1, high energy and power densities of 28.3 Wh kg-1 and 463.4 W kg-1 at 1 A g-1 respectively. The device showed good cycling stability with an energy efficiency of 90.2% and capacitance retention of 92.6% for up to 10,000 cycles at a specific current of 3 A g-1 over a voltage window of 1.5 V. It is can be observed that electrolyte selection is critically important to achieving better performance for carbon-based material electrodes for enhanced supercapacitors electrochemical performance. Thus, this work is subjected to further studies by exploiting organic and ionic liquid electrolytes that may greatly enhanced the energy density and stability of the device.PhysicsPhDUnrestricte

High specific energy asymmetric supercapacitor based on alpha-manganese dioxide/activated expanded graphite composite and activated carbon-polyvinyl alcohol

Please read abstract in the article.South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa.https://www.elsevier.com/locate/est2021-12-01hj2020Physic

Sulphur-reduced graphene oxide composite with improved electrochemical performance for supercapacitor applications

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.http://www.elsevier.com/locate/hehj2021Physic

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 analysis of Co3(PO4)2·4H2O/graphene foam composite for enhanced capacity and long cycle life hybrid asymmetric capacitors

In this paper, we explore the successful hydrothermal approach to make Co3(PO4)2·4H2O/GF micro-flakes composite material. The unique sheet-like structure of the graphene foam (GF) significantly improved the conductivity of the pristine Co-based material, which is a key limitation in supercapacitors application. The composite electrode material exhibited superior capacitive conduct in 6 M KOH aqueous electrolyte in a 3-electrode set-up as compared to the pristine cobalt phosphate material. The material was subsequently adopted as a cathode in an asymmetric cell configuration with carbonization of Fe cations adsorbed onto polyaniline (PANI) (C-Fe/PANI), as the anode. The Co3(PO4)2·4H2O/GF//C-FP hybrid device showed outstanding long life cycling stability of approximately 99% without degradation up to 10000 cycles. A specific energy density as high as 24 W h kg−1, with a corresponding power density of 468 W kg−1 was achieved for the device. The results demonstrated the efficient utilization of the faradic-type Co3(PO4)2·4H2O/GF composite along with a functionalized carbonaceous electric double layer (EDL)-type material to produce a hybrid device with promising features suitable for energy storage applications.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). Abdulmajid A. Mirghni acknowledges the financial support from University of Pretoria, the NRF through the SARChI in Carbon Technology and Materials, and also Al Fashir University, Sudan.http://www.elsevier.com/locate/electacta2019-09-01hj2018Physic

Deciphering the structural, textural, and electrochemical properties of activated BN-doped spherical carbons

In this study, the effect of K2CO3 activation on the structural, textural, and electrochemical properties of carbon spheres (CSs) and boron and nitrogen co-doped carbon spheres (BN-CSs) was evaluated. Activation of the CSs and BN-CSs by K2CO3 resulted in increased specific surface areas and ID/IG ratios. From the X-ray photoelectron spectroscopy (XPS) results, the BN-CSs comprised of 64% pyridinic-N, 24% pyrrolic-N and 7% graphitic-N whereas the activated BN-CSs had 19% pyridinic-N, 40% pyrrolic-N and 22% graphitic-N displaying the effect of activation on the type of N configurations in BN-CSs. A possible BN-co-doping and activation mechanism for the BN-CSs is proposed. Electrochemical analysis of the electrode materials revealed that BN doping, carbon morphology, structure, and porosity played a crucial role in enhancing the capacitive behavior of the CSs. As a proof of concept, a symmetric device comprising the activated BN-CSs displayed a specific power of 800 W kg 1 at a specific current of 1 A g 1 within an operating cell potential of 1.6 V in a 3 M KNO3 electrolyte. The study illustrated for the first time the role of K2CO3 activation in influencing the physical and surface properties of template-free activated BN-CSs as potential electrode materials for energy storage systems.The South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa (Grant No. 61056). B.K.M. and B.J.M. would like to thank the University of the Witwatersrand and the DST-NRF Centre of Excellence in Strong Materials (CoESM) for financial support. B.K.M. would also like to acknowledge financial support from the NRF and the University of Pretoria for her postdoctoral fellowship grant.http://www.mdpi.com/journal/nanomaterialsam2019Physic

Recycling of biomass wastes from amarula husk by a modified facile economical water salt method for high energy density ultracapacitor application

Please read abstract in the article.South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa.https://www.elsevier.com/locate/esthj2023Physic

A study of Co-Mn phosphate supported with graphene foam as promising electrode materials for future electrochemical capacitors

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.http://wileyonlinelibrary.com/journal/erhj2023Physic

Waste chicken bone-derived porous carbon materials as high performance electrode for supercapacitor applications

Please read abstract in the article.South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa.https://www.elsevier.com/locate/esthj2023Physic