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Mokoloko LL, Matsoso JB, Antonatos N, Mazánek V, Moreno BD, Forbes RP, Barrett DH, Sofer Z, Coville NJ. From 0D to 2D: N-doped carbon nanosheets for detection of alcohol-based chemical vapours. RSC Adv 2022; 12:21440-21451. [PMID: 35975088 PMCID: PMC9346501 DOI: 10.1039/d2ra03931a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 07/12/2022] [Indexed: 12/03/2022] Open
Abstract
The application of N-doped carbon nanosheets, with and without embedded carbon dots, as active materials for the room temperature chemoresistive detection of methanol and/or ethanol is presented. The new carbons were made by converting 0D N-doped carbon dots (NCDs) to 2D nitrogen-doped carbon nanosheets by heat treatment (200–700 °C). The nanosheets exhibited a lateral size of ∼3 μm and a thickness of ∼12 nm at the highest annealing temperature. Both Raman and TEM analyses showed morphological transitions of the dots to the sheets, whilst XPS analysis revealed transformation of the N-bonding states with increasing temperature. PDF analysis confirmed the presence of defective carbon sheets. Room temperature screening of the chemical vapours of two alcohols (methanol and ethanol), revealed that the structure and the type of N-configuration influenced the detection of the chemical vapours. For instance, the lateral size of the nanosheets and the high charge density N-configurations promoted detection of both methanol and ethanol vapours at good sensitivity (−16.8 × 10−5 ppm−1EtOH and 1.2 × 10−5 ppm−1MeOH) and low LoD (∼44 ppmEtOH and ∼30.3 ppmMeOH) values. The study showed that the composite nature as well as the large basal area of the carbon nanosheets enabled generation of adequate defective sites that facilitated easy adsorption of the VOC analyte molecules, thereby eliminating the need to use conducting polymers or the formation of porous molecular frameworks for the alcohol detection. 2D layered carbon nanostructures made by annealing 0D carbon dots, have been used as ethanol/methanol sensors.![]()
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Affiliation(s)
- Lerato L Mokoloko
- The Molecular Sciences Institute, School of Chemistry. University of the Witwatersrand Johannesburg 2050 South Africa .,DSI-NRF Centre of Excellence in Catalysis (cchange), University of the Witwatersrand Johannesburg 2050 South Africa
| | - Joyce B Matsoso
- Department of Inorganic Chemistry, University of Chemistry and Technology - Prague Technická 5, Dejvice 166 28 Praha 6 Czech Republic
| | - Nikolas Antonatos
- Department of Inorganic Chemistry, University of Chemistry and Technology - Prague Technická 5, Dejvice 166 28 Praha 6 Czech Republic
| | - Vlastimil Mazánek
- Department of Inorganic Chemistry, University of Chemistry and Technology - Prague Technická 5, Dejvice 166 28 Praha 6 Czech Republic
| | - Beatriz D Moreno
- Canadian Light Source Inc. 44 Innovation Boulevard Saskatoon SK S7N 2V3 Canada
| | - Roy P Forbes
- The Molecular Sciences Institute, School of Chemistry. University of the Witwatersrand Johannesburg 2050 South Africa .,DSI-NRF Centre of Excellence in Catalysis (cchange), University of the Witwatersrand Johannesburg 2050 South Africa
| | - Dean H Barrett
- The Molecular Sciences Institute, School of Chemistry. University of the Witwatersrand Johannesburg 2050 South Africa
| | - Zdeněk Sofer
- Department of Inorganic Chemistry, University of Chemistry and Technology - Prague Technická 5, Dejvice 166 28 Praha 6 Czech Republic
| | - Neil J Coville
- The Molecular Sciences Institute, School of Chemistry. University of the Witwatersrand Johannesburg 2050 South Africa .,DSI-NRF Centre of Excellence in Catalysis (cchange), University of the Witwatersrand Johannesburg 2050 South Africa
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Selepe CT, Gwebu SS, Matthews T, Mashola TA, Sikeyi LL, Zikhali M, Maxakato NW. Effect of Sn Doping on Pd Electro-Catalysts for Enhanced Electro-Catalytic Activity towards Methanol and Ethanol Electro-Oxidation in Direct Alcohol Fuel Cells. NANOMATERIALS 2021; 11:nano11102725. [PMID: 34685167 PMCID: PMC8537662 DOI: 10.3390/nano11102725] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 10/08/2021] [Accepted: 10/09/2021] [Indexed: 11/16/2022]
Abstract
Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which facilitates the dispersion of Pd and Sn nanoparticles. Raman spectrum displays two prominent peaks of carbonaceous materials which correspond to the D and G bands. The Pd-Sn/CNOs electro-catalyst demonstrates improved electro-oxidation of methanol and ethanol performance compared to Pd/CNOs and commercial Pd/C electro-catalysts under alkaline conditions.
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Affiliation(s)
- Cyril Tlou Selepe
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
| | - Sandile Surprise Gwebu
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
| | - Thabo Matthews
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
| | - Tebogo Abigail Mashola
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
| | - Ludwe Luther Sikeyi
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Braamfontein, Johannesburg 2050, South Africa;
| | - Memory Zikhali
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
| | - Nobanathi Wendy Maxakato
- Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa; (C.T.S.); (S.S.G.); (T.M.); (T.A.M.); (M.Z.)
- Correspondence: ; Tel.: +27-(0)-11-559-6151
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Zhang L, Jiang D, Shan X, Du X, Wei M, Zhang Y, Chen Z. Visible light-driven self-powered aptasensors for ultrasensitive Microcystin-LR detection based on the carrier density effect of N-doped graphene hydrogel/hematite Schottky junctions. Analyst 2021; 146:6220-6227. [PMID: 34523620 DOI: 10.1039/d1an01462e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In this work, a novel visible light-driven self-powered photoelectrochemical (PEC) platform was designed based on 3D N-doped graphene hydrogel/hematite nanocomposites (NGH/Fe2O3) via a facile one-pot hydrothermal route. The coupling NGH with Fe2O3 could generate a Schottky junction, which promoted the separation of charges. Moreover, Mott-Schottky measurements validated that the carrier concentration achieved by NGH/Fe2O3 was about 3.4 × 103 times in comparison to that of pure Fe2O3, which was beneficial for efficient charge transfer. Owing to the carrier density effect and Schottky junction, the photocurrent of the as-fabricated NGH/Fe2O3 nanocomposites was 6.9-fold higher than that of pure Fe2O3. On the basis of such excellent Schottky junctions, an ultrasensitive visible light-induced self-powered PEC aptasensor was developed using a Microcystin-LR (MC-LR) aptamer. The as-fabricated PEC aptasensor displayed good analytical performance toward MC-LR detection in terms of wide linear range (1 pM-5 nM), low detection limit (0.23 pM, S/N = 3), excellent selectivity and high stability. This new strategy can provide a way for regulating nanostructures for more sensitive PEC sensors by increasing the carrier density.
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Affiliation(s)
- Linhua Zhang
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China.
| | - Ding Jiang
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China. .,Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University, Changzhou 213164, China
| | - Xueling Shan
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China. .,Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University, Changzhou 213164, China
| | - Xiaojiao Du
- Oakland International Associated Laboratory, School of Photoelectric Engineering, Changzhou Institute of Technology, Changzhou, Jiangsu, 213032, P. R. China
| | - Meng Wei
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China.
| | - Yude Zhang
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China.
| | - Zhidong Chen
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China. .,Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University, Changzhou 213164, China
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Makhongoana A, Matsoso BJ, Mongwe TH, Coville NJ, Wamwangi D, Maubane-Nkadimeng MS. The role of oxygen in a carbon source (castor oil versus paraffin oil) in the synthesis of carbon nano-onions. NANOTECHNOLOGY 2021; 32:135603. [PMID: 33276354 DOI: 10.1088/1361-6528/abd0b1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The role of a carbon source containing oxygen groups on the physicochemical properties of carbon nano-onions (CNOs) was investigated. Two oils, castor oil (with O groups) and paraffin oil (without O groups) were converted to CNOs in gram-scale yields using an open flame pyrolysis procedure. The products were heated under argon at 900 °C for varying times (1 h, 2 h, 3 h), to investigate the temperature dependence on their structural properties. TGA studies indicated different decomposition behaviour for the different samples with the annealed paraffinic CNOs (CNOP) having a higher decomposition temperature (>600 °C) than the castor oil derived CNOs (CNOC) (<600 °C). TEM images revealed formation of typical chain-like quasi-spherical nanostructures with particles size distributions for the CNOP (22-32 ± 7.8 nm) and the CNOC (44-51 ± 9.9 nm) materials. A detailed Raman analysis of the CNOs revealed that the graphicity of the CNOs varied with both the carbon oil source and the annealing time. Deconvolution of the first order Raman spectra revealed changes in the parameters of the major Raman bands that were then correlated with defect density ratios. Finally, bandwidth analysis depicted the dependence of the graphicity of the CNOs with heat treatment. The data thus indicate that the presence of oxygen in the carbon source provides a method for producing different CNOs and that simple procedures can be used to produce these different CNOs.
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Affiliation(s)
- Annah Makhongoana
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa
| | - Boitumelo J Matsoso
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Laboratoires des Multimatériaux et Interfaces, UMR 5615 CNRS, Université Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex, France
| | - Thomas H Mongwe
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa
| | - Neil J Coville
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa
| | - Daniel Wamwangi
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Material Physics Research Institute (MPRI) and the School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Manoko S Maubane-Nkadimeng
- DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa
- Microscopy and Microanalysis Unit, University of the Witwatersrand, Johannesburg, South Africa
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Musyoka NM, Mutuma BK, Manyala N. Onion-derived activated carbons with enhanced surface area for improved hydrogen storage and electrochemical energy application. RSC Adv 2020; 10:26928-26936. [PMID: 35515807 PMCID: PMC9055538 DOI: 10.1039/d0ra04556j] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 07/14/2020] [Indexed: 11/21/2022] Open
Abstract
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. Graphene-like activated carbons (ACs), with excellent properties for enhanced hydrogen storage and supercapacitor applications, were prepared from waste onion peels.![]()
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Affiliation(s)
- Nicholas M. Musyoka
- Centre for Nanostructures and Advanced Materials (CeNAM)
- Chemicals Cluster
- Council for Scientific and Industrial Research (CSIR)
- Pretoria
- South Africa
| | - Bridget K. Mutuma
- Department of Physics
- Institute of Applied Materials
- SARCHI Chair in Carbon Technology and Materials
- University of Pretoria
- South Africa
| | - Ncholu Manyala
- Department of Physics
- Institute of Applied Materials
- SARCHI Chair in Carbon Technology and Materials
- University of Pretoria
- South Africa
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Nitridation Temperature Effect on Carbon Vanadium Oxynitrides for a Symmetric Supercapacitor. NANOMATERIALS 2019; 9:nano9121762. [PMID: 31835790 PMCID: PMC6956286 DOI: 10.3390/nano9121762] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 11/29/2019] [Accepted: 12/04/2019] [Indexed: 11/22/2022]
Abstract
In this work, porous carbon-vanadium oxynitride (C-V2NO) nanostructures were obtained at different nitridation temperature of 700, 800 and 900 °C using a thermal decomposition process. The X-ray diffraction (XRD) pattern of all the nanomaterials showed a C-V2NO single-phase cubic structure. The C-V2NO obtained at 700 °C had a low surface area (91.6 m2 g−1), a moderate degree of graphitization, and a broader pore size distribution. The C-V2NO obtained at 800 °C displayed an interconnected network with higher surface area (121.6 m2 g−1) and a narrower pore size distribution. In contrast, at 900 °C, the C-V2NO displayed a disintegrated network and a decrease in the surface area (113 m2 g−1). All the synthesized C-V2NO yielded mesoporous oxynitride nanostructures which were evaluated in three-electrode configuration using 6 M KOH aqueous electrolyte as a function of temperature. The C-V2NO@800 °C electrode gave the highest electrochemical performance as compared to its counterparts due to its superior properties. These results indicate that the nitridation temperature not only influences the morphology, structure and surface area of the C-V2NO but also their electrochemical performance. Additionally, a symmetric device fabricated from the C-V2NO@800 °C displayed specific energy and power of 38 W h kg−1 and 764 W kg−1, respectively, at 1 A g−1 in a wide operating voltage of 1.8 V. In terms of stability, it achieved 84.7% as capacity retention up to 10,000 cycles which was confirmed through the floating/aging measurement for up to 100 h at 10 A g−1. This symmetric capacitor is promising for practical applications due to the rapid and easy preparation of the carbon-vanadium oxynitride materials.
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Effect of porosity enhancing agents on the electrochemical performance of high-energy ultracapacitor electrodes derived from peanut shell waste. Sci Rep 2019; 9:13673. [PMID: 31541191 PMCID: PMC6754434 DOI: 10.1038/s41598-019-50189-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 09/06/2019] [Indexed: 11/09/2022] Open
Abstract
In this study, the synthesis of porous activated carbon nanostructures from peanut (Arachis hypogea) shell waste (PSW) was described using different porosity enhancing agents (PEA) at various mass concentrations via a two-step process. The textural properties obtained were depicted with relatively high specific surface area values of 1457 m2 g−1, 1625 m2 g−1 and 2547 m2 g−1 for KHCO3, K2CO3 and KOH respectively at a mass concentration of 1 to 4 which were complemented by the presence of a blend of micropores, mesopores and macropores. The structural analyses confirmed the successful transformation of the carbon-containing waste into an amorphous and disordered carbonaceous material. The electrochemical performance of the material electrodes was tested in a 2.5 M KNO3 aqueous electrolyte depicted its ability to operate reversibly in both negative and positive potential ranges of 0.90 V. The activated carbon obtained from the carbonized CPSW:PEA with a mass ratio of 1:4 yielded the best electrode performance for all featured PEAs. The porous carbons obtained using KOH activation displayed a higher specific capacitance and the lower equivalent series resistance as compared to others. The remarkable performance further corroborated the findings linked to the textural and structural properties of the material. The assembled device operated in a neutral electrolyte (2.5 M KNO3) at a cell potential of 1.80 V, yielded a ca. 224.3 F g−1 specific capacitance at a specific current of 1 A g−1 with a corresponding specific energy of 25.2 Wh kg−1 and 0.9 kW kg−1 of specific power. This device energy was retained at 17.7 Wh kg−1 when the specific current was quadrupled signifying an excellent supercapacitive retention with a corresponding specific power of 3.6 kW kg−1. These results suggested that peanut shell waste derived activated carbons are promising candidates for high-performance supercapacitors.
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Wolf M, Fischer N, Claeys M. Preparation of isolated Co 3O 4 and fcc-Co crystallites in the nanometre range employing exfoliated graphite as novel support material. NANOSCALE ADVANCES 2019; 1:2910-2923. [PMID: 36133606 PMCID: PMC9417318 DOI: 10.1039/c9na00291j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 06/07/2019] [Indexed: 06/16/2023]
Abstract
The inert nature of graphitic samples allows for characterisation of rather isolated supported nanoparticles in model catalysts, as long as sufficiently large inter-particle distances are obtained. However, the low surface area of graphite and the little interaction with nanoparticles result in a challenging application of conventional preparation routes in practice. In the present study, a set of graphitic carbon materials was characterised in order to identify potential support materials for the preparation of model catalyst systems. Various sizes of well-defined Co3O4 nanoparticles were synthesised separately and supported onto exfoliated graphite powder, that is graphite after solvent-assisted exfoliation via ultrasonication resulting in thinner flakes with increased specific surface area. The stability of the supported nanoparticles during reduction to metallic cobalt in H2 was monitored in situ by means of X-ray diffraction and smaller crystallite sizes were found to be harder to reduce than their larger counterparts. A low cobalt loading of 1 wt% was required to avoid aggregates in the parent catalyst, and this allowed for the preparation of supported cobalt nanoparticles which were resistant to sintering at reduction temperatures below 370 °C. The developed model catalysts are ideally suited for sintering studies of isolated nano-sized cobalt particles as the graphitic support material does not provide distinct metal-support interaction. Furthermore, the differently sized cobaltous particles in the various model systems render possible studies on structural dependencies of activity, selectivity, and deactivation in cobalt oxide or cobalt catalysed reactions.
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Affiliation(s)
- Moritz Wolf
- Catalysis Institute, DST-NRF Centre of Excellence in Catalysis cchange, Department of Chemical Engineering, University of Cape Town Rondebosch 7701 South Africa
| | - Nico Fischer
- Catalysis Institute, DST-NRF Centre of Excellence in Catalysis cchange, Department of Chemical Engineering, University of Cape Town Rondebosch 7701 South Africa
| | - Michael Claeys
- Catalysis Institute, DST-NRF Centre of Excellence in Catalysis cchange, Department of Chemical Engineering, University of Cape Town Rondebosch 7701 South Africa
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Deciphering the Structural, Textural, and Electrochemical Properties of Activated BN-Doped Spherical Carbons. NANOMATERIALS 2019; 9:nano9030446. [PMID: 30884783 PMCID: PMC6474088 DOI: 10.3390/nano9030446] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 02/25/2019] [Accepted: 03/11/2019] [Indexed: 12/01/2022]
Abstract
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.
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Mutuma BK, Garcia-Martinez CI, Dias RC, Matsoso BJ, Coville NJ, Hümmelgen IA. Nitrogen-doped hollow carbon spheres as chemical vapour sensors. NEW J CHEM 2019. [DOI: 10.1039/c9nj00628a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The sensitivities of N-HCSs and annealed HCSs towards various analytes revealing a decrease in water sensitivity of the N-HCSs.
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Affiliation(s)
- Bridget K. Mutuma
- DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute
- School of Chemistry
- University of the Witwatersrand
- Johannesburg
- South Africa
| | | | - Rodrigo C. Dias
- Departamento de Física
- Universidade Federal do Parana
- 8153-980 Curitiba
- Brazil
| | - Boitumelo J. Matsoso
- DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute
- School of Chemistry
- University of the Witwatersrand
- Johannesburg
- South Africa
| | - Neil J. Coville
- DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute
- School of Chemistry
- University of the Witwatersrand
- Johannesburg
- South Africa
| | - Ivo A. Hümmelgen
- Departamento de Física
- Universidade Federal do Parana
- 8153-980 Curitiba
- Brazil
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11
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Wolf M, Mutuma BK, Coville NJ, Fischer N, Claeys M. Role of CO in the Water-Induced Formation of Cobalt Oxide in a High Conversion Fischer–Tropsch Environment. ACS Catal 2018. [DOI: 10.1021/acscatal.7b04177] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Moritz Wolf
- Catalysis Institute, Department of Chemical Engineering, University of Cape Town, Rondebosch 7701, South Africa
- DST-NRF Centre of Excellence in Catalysis c*change, Rondebosch 7701, South Africa
| | - Bridget K. Mutuma
- DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Wits 2050, South Africa
| | - Neil J. Coville
- DST-NRF Centre of Excellence in Catalysis c*change, Rondebosch 7701, South Africa
- DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Wits 2050, South Africa
| | - Nico Fischer
- Catalysis Institute, Department of Chemical Engineering, University of Cape Town, Rondebosch 7701, South Africa
- DST-NRF Centre of Excellence in Catalysis c*change, Rondebosch 7701, South Africa
| | - Michael Claeys
- Catalysis Institute, Department of Chemical Engineering, University of Cape Town, Rondebosch 7701, South Africa
- DST-NRF Centre of Excellence in Catalysis c*change, Rondebosch 7701, South Africa
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