47 research outputs found
Asymmetric supercapacitor based on activated expanded graphite and pinecone tree activated carbon with excellent stability
This work presents results obtained from the production of low-cost carbons from expanded graphite (EG) and pinecone (PC) biomass, activated in potassium hydroxide (KOH) and finally carbonized in argon and hydrogen atmosphere. A specific surface area of 808 m2 g−1 and 457 m2 g−1 were measured for activated pinecone carbon (APC) and activated expanded graphite (AEG), respectively. The electrochemical characterization of the novel materials in a 2-electrode configuration as supercapacitor electrode shows a specific capacitance of 69 F g−1 at 0.5 A g−1, high energy density of 24.6 W h kg−1 at a power density of 400 W kg−1. This asymmetric supercapacitor also exhibits outstanding stability after voltage holding at the maximum voltage for 110 h, suggesting that the asymmetric device based on different carbon materials has a huge capacity for a high-performance electrode in electrochemical applications.The National Research Foundation of South Africa (Grant Number: 61056).http://www.elsevier.com/locate/apenergy2018-12-01hj2018Electrical, Electronic and Computer Engineerin
P3HT:PCBM/nickel-aluminum layered double hydroxide-graphene foam composites for supercapacitor electrodes
In this paper, a simple dip-coating technique is used to deposit a P3HT:PCBM/Nickel
Aluminum layered double hydroxide-graphene foam (NiAl-LDH-GF) composite onto a nickel
foam (NF) serving as a current collector. A self-organization of the polymer chains is
assumed on the Ni-foam grid network during the slow “dark” drying process in normal air.
Electrochemical cyclic voltammetry (CV) and constant charge-discharge (CD) measurements
show an improvement in the supercapacitive behavior of the pristine P3HT:PCBM by an
order of magnitude from 0.29 F cm-2 (P3HT:PCBM nanostructures) to 1.22 F cm-2
(P3HT:PCBM/NiAl-LDH-GF composite structure) resulting from the addition of NiAl-LDH-GF
material at a current density of 2 mA cm-2. This capacitance retention after cycling at 10 mA
cm-2 also demonstrates the electrode material’s potential for supercapacitor applications.South African Research Chairs Initiative (SARChI) of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://link.springer.com/journal/100082015-08-30hb201
Functionalized graphene foam as electrode for improved electrochemical storage
We report on a non-covalent functionalization of
graphene foam (GF) synthesized via chemical vapour deposition
(CVD). The GF was treated with pyrene carboxylic acid
(PCA) which acted as a source of oxygen and/or hydroxyl
groups attached to the surface of the graphene foam for its
electrochemical performance improvement. The modified
graphene surface enabled a high pseudocapacitive effect on
the GF. A specific capacitance of 133.3 F g−1, power density ∼
145.3 kW kg−1 and energy density ∼ 4.7 W h kg−1 were
achieved based on the functionalized foam in 6 M KOH
aqueous electrolyte. The results suggest that non-covalent
functionalization might be an effective approach to overcome
the restacking problem associated with graphene electrodes
and also signify the importance of surface functionalities in
graphene-based electrode materials.South African Research Chairs Initiative of the Department of Science and Technology (SARCHi-DST), the National Research Foundation (NRF) and University of Pretoria.http://link.springer.com/journal/100082015-09-30hb201
Renewable pine cone biomass derived carbon materials for supercapacitor application
The environmental degradation and hazard to human life caused by the depletion of fossils fuels and the
urgent need for sustainable energy sources to meet the rising demand in energy has led to the
exploration of novel materials that are environmentally friendly, low cost and less hazardous to human
life for energy storage application using the green chemistry approach. Herein, we report on the
transformation of the readily abundant pine cone biomass into porous carbon via KOH activation and
carbonization at 800 C as electrode materials for supercapacitors. The porous carbon material
exhibited a mesoporous framework with a specific surface area of 1515 m2 g 1, a high voltage window of
2.0 V, a gravimetric capacitance of 137 F g 1, energy density of 19 W h kg 1 and excellent cyclability in
neutral 1 M Na2SO4 electrolyte for a symmetric carbon/carbon electrode cell. The result shows that the
material is robust and shows great promise with neutral electrolytes in high-performance energystorage
devices.South African Research Chairs Initiative of the Department of Science
and Technology and National Research Foundation of South
Africa (Grant No. 97994).http://www.rsc.orgadvances2017-07-31hb2016Institute of Applied MaterialsPhysic
Symmetric supercapacitors based on porous 3D interconnected carbon framework
The construction and design of novel porous carbons for electric double-layer capacitors (EDLCs) application to meet the increasing demand and supply of energy is eminent. This is important because the pore volume (PV)/micropore volume (MV) in the porous network architecture of the carbon is mostly responsible for the ion traps in energy storage. Three dimensional carbon materials based on graphene materials with relatively high specific surface area (SSA) represents a promising material candidate for EDLCs applications. In this work, we synthesized highly porous carbon from graphene foam (GF) and polyvinyl alcohol PVA as a sacrificial template, and investigate their performance as electrodes for EDLCs applications. The as-produced carbons present a fairly large surface area (502 m2 g−1), and a highly porous interconnected framework with mesopore walls and micropore texture which are suitable as electrode for energy storage. As electrode material in a symmetric configuration the activated graphene foam (AGF) showed a specific capacitance of 65 F g−1, energy density of 12 Wh kg−1, power density of 0.4 kW kg−1, good rate performance and excellent long term stability in 1 M Na2SO4 aqueous with no capacitance loss after 3000 cycles.A. Bello acknowledges University of Pretoria and NRF financial support for his Postdoc fellowship, while D. Y. Momodu and F. Barzegar acknowledge financial support from University of Pretoria and the NRF for PhD bursaries.http://www.elsevier.com/locate/electactahj201
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
Pulsed laser deposited Cr2O3 nanostructured thin film on graphene as anode material for lithium-ion batteries
Pulsed laser deposition technique was used to deposit Cr2O3 nanostructured thin film on a
chemical vapour deposited few-layer graphene (FLG) on nickel (Ni) substrate for application
as anode material for lithium-ion batteries. The experimental results show that graphene can
effectively enhance the electrochemical property of Cr2O3. For Cr2O3 thin film deposited on
Ni (Cr2O3/Ni), a discharge capacity of 747.8 mA h g-1 can be delivered during the first
lithiation process. After growing Cr2O3 thin film on FLG/Ni, the initial discharge capacity of
Cr2O3/FLG/Ni was improved to 1234.5 mA h g-1. The reversible lithium storage capacity of
the as-grown material is 692.2 mA h g-1 after 100 cycles, which is much higher than that of
Cr2O3/Ni (111.3 mA h g-1). This study reveals the differences between the two material
systems and emphasizes the role of the graphene layers in improving the electrochemical
stability of the Cr2O3 nanostructured thin film.This work was sponsored within the framework of the UNESCO UNISA Africa Chair in
Nanosciences & Nanotechnology and the Nanosciences African Network (NANOAFNET)
by the National Research Foundation of South Africa, the African Laser Centre (ALC), the
University of South Arica (UNISA) in collaboration with the Vice-Chancellor of the
University of Pretoria, the National Research Foundation (NRF) of South Africa, iThemba
LABS and the Abdus Salam ICTP-Trieste, Italy.http://www.elsevier.com/locate/jalcom2016-07-31hb2016Physic
Preparation and characterization of porous carbon from expanded graphite for high energy density supercapacitor in aqueous electrolyte
In this work, we present the synthesis of low cost carbon nanosheets derived from expanded
graphite dispersed in Polyvinylpyrrolidone, subsequently activated in KOH and finally
carbonized in Ar atmosphere. Interconnected sheet-like structure with low concentration of
oxygen (9.0 at.%) and a specific surface area of 457 m2 g-1 was obtained. The electrochemical
characterization of the carbon material as supercapacitor electrode in a 2-electrode
configuration shows high specific capacitance of 337 F g-1 at a current density of 0.5 A g-1 as well
as high energy density of 37.9 Wh kg-1 at a power density of 450 W kg-1.This electrical double
layer capacitor electrode also exhibits excellent stability after floating test for 120 h in 6 M KOH
aqueous electrolyte. These results suggest that this activated expanded graphite (AEG) material
has great potential for high performance electrode in energy storage applications.South African Research Chairs Initiative (SARChi) in Carbon Technology and Materials of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://www.elsevier.com/locate/cose2017-03-31hb2016Institute of Applied MaterialsInsurance and Actuarial ScienceInvestment and Trade Policy Centre (ITPC)JournalismJurisprudenceLaboratory for Microscopy and MicroanalysisLaw ClinicLaw Student AffairsLife Cycle EngineeringMammal Research InstituteMapungubwe museumMarketing and Communication ManagementMarketing ManagementMaterials Science and Metallurgical EngineeringMathematics and Applied MathematicsMaxillo-Facial and Oral SurgeryMechanical and Aeronautical EngineeringMedical MicrobiologyMedical OncologyMedical VirologyMercantile LawMicrobiology and Plant PathologyMining EngineeringModern European LanguagesMusicNeurologyNeuroscience ResearchNew Testament StudiesNuclear MedicineNursing ScienceObstetrics and GynaecologyOccupational TherapyOdontologyOld Testament StudiesOral Pathology and Oral BiologyOrthodonticsOrthopaedic SurgeryOtorhinolaryngologyPaediatrics and Child HealthParaclinical SciencesPeriodontics and Oral MedicinePharmacologyPhilosophyPhilosophy and Ethics of Mental HealthPhysic
Coniferous pine biomass : a novel insight into sustainable carbon materials for supercapacitors electrode
Low-cost biomass-derived activated porous carbon from natural pine cones is synthesized using hydrothermal
approach followed by KOH activation and carbonization. The produced carbon materials have
a high surface area of 1515 m2 g1 with a well-developed meso/micropores structure which is advantageous
and favorable for mass transfer and ion accommodation for fast rate performance by providing
pathways for electrolyte permeation and contact probability. Symmetric device fabricated using the
obtained carbon material as electrode, exhibited good electrochemical performance with no degradation
of capacitance after voltage holding at 1 V for about 60 h demonstrating good rate capability of the
fabricated device. The results demonstrate the exciting potential of the pine cone derived carbons as a
promising candidate for high-performance electrode materials for supercapacitors if fully explored.The South African Research Chairs Initiative of the Department of Science and
Technology and National Research Foundation of South Africa (Grant No. 97994).http://www.elsevier.com/locate/matchemphys2017-10-31hb2016Physic
Asymmetric supercapacitor based on nanostructured graphene foam/polyvinyl alcohol/formaldehyde and activated carbon electrodes
We present the electrochemical results of highly porous and interconnected carbon material by activation
of graphene foam/polyvinyl alcohol-formaldehyde composite material designated as GF/PVA-F.
Asymmetric supercapacitor devices were fabricated using the activated material (GF/PVA-F) and activated
carbon (AC) as the positive and negative electrodes respectively. The device exhibited a maximum
energy density of 42 mWh cm 2, a power density of 0.5 W cm 2 and 98% retention of its initial
capacitance after 2000 cycles in an extended cell potential window of 1.8 V in 1 M Na2SO4 aqueous
electrolyte. This work shows the great potential of this material for high performance energy storage
application.A. Bello, acknowledges University of Pretoria
financial support for his PostDoc fellowship, while D. Y. Momodu
and F. Barzegar acknowledge financial support from University of
Pretoria and NRF for their PhD bursaries.http://www.elsevier.com/locate/jpowsourhj201