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

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

Enhanced electrochemical performance of supercapattery derived from sulphur-reduced graphene oxide/cobalt oxide composite and activated carbon from peanut shells

Please read abstract in the article.The South African Research Chairs Initiative of the Department of Science and Technology (DST) and National Research Foundation (NRF) of South Africa.http://www.elsevier.com/locate/he2021-10-06hj2021Physic

Effect of porosity enhancing agents on the electrochemical performance of high-energy ultracapacitor electrodes derived from peanut shell waste

Please read abstract in the article.The South African Research Chairs Initiative (SARChI) of the Department of Science and Technology, the National Research Foundation (NRF) of South Africa and the NSF through the University of Pennsylvania Materials Research Science and Engineering Center (MRSEC).http://www.nature.com/sreppm2020Physic

Onion-derived activated carbons with enhanced surface area for improved hydrogen storage and electrochemical energy application

High surface area activated carbons (ACs) were prepared from a hydrochar derived from waste onion peels. The resulting ACs had a unique graphene-like nanosheet morphology. The presence of N (0.7%) and O content (8.1%) in the OPAC-800 C was indicative of in situ incorporation of nitrogen groups from the onion peels. The specific surface area and pore volume of the best OPAC sample was found to be 3150 m2 g 1 and 1.64 cm3 g 1, respectively. The hydrogen uptake of all the OPAC samples was established to be above 3 wt% (at 77 K and 1 bar) with the highest being 3.67 wt% (800 C). Additionally, the OPAC- 800 C achieved a specific capacitance of 169 F g 1 at a specific current of 0.5 A g 1 and retained a capacitance of 149 F g 1 at 5 A g 1 in a three electrode system using 3 M KNO3. A symmetric supercapacitor based on the OPAC-800 C//OPAC-800 C electrode provided a capacitance of 158 F g 1 at 0.5 A g 1. The maximum specific energy and power was found to be 14 W h kg 1 and 400 W kg 1, respectively. Moreover, the device exhibited a high coulombic efficiency of 99.85% at 5 A g 1 after 10 000 cycles. The results suggested that the high surface area graphene-like carbon nanostructures are excellent materials for enhanced hydrogen storage and supercapacitor applications.The South Africa's National Research Foundation (NRF) and the South African Research Chairs Initiative (SARChI) of the Department of Science and Innovation.http://pubs.rsc.org/en/journals/journalissues/raam2021Physic

Generation of radical species in CVD grown pristine and N-doped solid carbon spheres using H2 and Ar as carrier gases

Solid carbon spheres (CSs, d ≈ 200 nm) were synthesized (yield, <40%) in a vertically oriented chemical vapor deposition (CVD) reactor using acetylene as a carbon source and Ar or H2 as the carrier gas. The CSs synthesized in the presence of H2 exhibited a broader thermal gravimetric derivative curve and a narrower paramagnetic signal than the CSs synthesized in Ar. Post synthesis doping of both types of CSs with nitrogen was achieved by passing acetonitrile at 800 °C for 1 h over the CSs in a CVD reactor. The N-doped CSs (NCSs) synthesized under both H2 and Ar displayed an increase in ID/IG ratios as obtained from Raman spectroscopy and showed an increase in the paramagnetic signal due to the presence of nitrogen induced defects compared to the undoped CSs. The NCSs synthesized in H2 had less graphitic-N (22%) than those produced in Ar (50%). The presence of a higher percentage of pyridinic-N and pyrrolic-N for the NCSs prepared with H2 as carrier gas suggested H2 etching effects on the CSs. Further, the N-doped carbon spheres obtained in the presence of H2 gave a higher N/C ratio (5.0) than in the presence of Ar (3.7). The introduction of edge defects and paramagnetic centers in CSs in the presence of H2 gas without the aid of a metal catalyst opens up a platform for regulating surface and catalytic reactions of CSsEM201

Pullulan-ionic liquid-based supercapacitor: A novel, smart combination of components for an easy-to-dispose device

Strategies that simultaneously target energy/power performance, sustainable manufacturing processes, valorization of green raw materials, and easy recycling of supercapacitors are urgently needed. Today, efforts have to be devoted not only to improve system performance but also to address the sustainability of materials and devices manufacturing and recyclability. Specifically, pullulan is herein proposed as a novel bio-degradable binder and separator for green supercapacitors. It is processed by electrospinning from aqueous solutions, therefore overcoming issues related to conventional membrane processing by organic solvents. Furthermore, combining the water-soluble, biodegradable pullulan with a hydrophobic ionic liquid electrolyte brings about a novel approach for end-of-life management of devices. The use of pullulan is demonstrated in a supercapacitor with carbon electrodes obtained from pepper-seeds waste and 1-Ethyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide as the electrolyte. The supercapacitor delivers up to 5 kW kg 121 specific power and 27.8 Wh kg 121 specific energy at 3.2 V, that well compare with conventional electrical double-layer capacitor performance with the added value of being eco-friendly and cheap

Nitrogen-doped hollow carbon spheres as chemical vapour sensors

Please read abstract in the article.The NRF, the University of the Witwatersrand and the DST-NRF Centre of Excellence in Strong Materials.http://rsc.li/njc2020-04-12hj2019Physic

Ex-situ nitrogen-doped porous carbons as electrode materials for high performance supercapacitor

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://www.elsevier.com/locate/jcis2021-06-01hj2020Physic

Nitridation temperature effect on carbon vanadium oxynitrides for a symmetric supercapacitor

Please read abstract in article.(SARChI) of the Department of Science and Technology and National Research Foundation (NRF) of South Africa.http://www.mdpi.com/journal/nanomaterialspm2020Physic