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3 results on '"Surface oxygen functional group"'

1. Surface-Oxidised Carbon Nanofibre-Based Nanofluids: Structural, Morphological, Stability and Thermal Properties.

Author

Mohd Saidi, Norshafiqah, Abdullah, Norli, Norizan, Mohd Nurazzi, Janudin, Nurjahirah, Mohd Kasim, Noor Azilah, Osman, Mohd Junaedy, Mohamad, Imran Syakir, and Mohd Rosli, Mohd Afzanizam

Subjects
*NANOFLUIDS, *THERMAL properties, *THERMAL stability, *FIELD emission electron microscopy, *THERMAL conductivity, *SURFACE defects
Abstract

The reputation of nanofluids as a convenient heat transfer media has grown in recent years. The synthesis of nanofluids is often challenging, particularly carbon-based nanofluids, due to the rapid agglomeration of the nanoparticles and the instability of the nanofluids. In this regard, surface modification and surfactant addition are potential approaches to improve the physical and thermal properties of carbon-based nanofluids that have been studied and the structural, morphological, and thermal characteristics of surface-oxidised carbon nanofibre (CNF)-based nanofluids has been characterised. Commercial CNF was first subjected to three different acid treatments to introduce surface oxygen functional groups on the CNF surface. Following the physical and thermal characterisation of the three surface-oxidised CNFs (CNF-MA, CNF-MB, and CNF-MC), including Raman spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM), the CNF-MB was selected as the best method to synthesise the surface-oxidised CNF-based nanofluid. A total of 40 mL of ultrapure water was used as a pure base fluid and mixed with the surface-oxidised CNF at a concentration range of 0.1–1.0 wt.%, with a fixed of 10 wt.% amount of polyvinylpyrrolidone (PVP). The thermal conductivity of CNF-based nanofluid was then characterised at different temperatures (6, 25, and 40 °C). Based on the results, surface oxidation via Method B significantly affected the extent of surface defects and effectively enhanced the group functionality on the CNF surface. Aside from the partially defective and rough surface of CNF-MB surfaces from the FESEM analysis, the presence of surface oxygen functional groups on the CNF wall was confirmed via the Raman analysis, TGA curve, and FTIR analysis. The visual sedimentation observation also showed that the surface-oxidised CNF particles remained dispersed in the nanofluid due to the weakened van der Waals interaction. The dispersion of CNF particles was improved by the presence of PVP, which further stabilised the CNF-based nanofluids. Ultimately, the thermal conductivity of the surface-oxidised CNF-based nanofluid with PVP was significantly improved with the highest enhancement percentage of 18.50, 16.84, and 19.83% at 6, 25, and 40 °C, respectively, at an optimum CNF concentration of 0.7 wt.%. [ABSTRACT FROM AUTHOR]

Published
2022
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2. Understanding ageing mechanisms of porous carbons in non-aqueous electrolytes for supercapacitors applications

Author

Camelia Matei Ghimbeu, Yinghui Liu, Benoît Soucaze-Guillous, Bénédicte Réty, Patrice Simon, Pierre-Louis Taberna, Centre interuniversitaire de recherche et d'ingenierie des matériaux (CIRIMAT), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Réseau sur le stockage électrochimique de l'énergie (RS2E), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Aix Marseille Université (AMU)-Université de Pau et des Pays de l'Adour (UPPA)-Université de Nantes (UN)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Institut de Science des Matériaux de Mulhouse (IS2M), Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Technocentre Renault [Guyancourt], RENAULT, Aix-Marseille Université - AMU (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Collège de France (FRANCE), Ecole Nationale Supérieure de Chimie de Paris - ENSCP (FRANCE), Ecole Nationale Supérieure de Chimie de Montpellier - ENSCM (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Institut polytechnique de Grenoble (FRANCE), Institut universitaire de France - IUF (FRANCE), Sorbonne Université (FRANCE), Université de Strasbourg - UNISTRA (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université de Nantes (FRANCE), Université de Picardie Jules Verne (FRANCE), Renault SAS (FRANCE), Université de Pau et des Pays de l'Adour - UPPA (FRANCE), Université de Haute Alsace - UHA (FRANCE), Université de Montpellier (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Université de Nantes (UN)-Aix Marseille Université (AMU)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Université de Picardie Jules Verne (UPJV)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA), Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), univOAK, Archive ouverte, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )

Subjects
Energie électrique, Activated carbon oxidation, Temperature-programmed desorption coupled with mass spectrometry technique, Matériaux, Energy Engineering and Power Technology, chemistry.chemical_element, 02 engineering and technology, Electrolyte, [SPI.MAT] Engineering Sciences [physics]/Materials, 010402 general chemistry, 01 natural sciences, Oligomer, Catalysis, [SPI.MAT]Engineering Sciences [physics]/Materials, chemistry.chemical_compound, Adsorption, Desorption, Electrical and Electronic Engineering, Physical and Theoretical Chemistry, Acetonitrile, Supercapacitor ageing, Supercapacitor, Renewable Energy, Sustainability and the Environment, [SPI.NRJ]Engineering Sciences [physics]/Electric power, 021001 nanoscience & nanotechnology, Surface oxygen functional group, 0104 chemical sciences, chemistry, Chemical engineering, 0210 nano-technology, Carbon, [SPI.NRJ] Engineering Sciences [physics]/Electric power
Abstract

International audience; Two activated porous carbon powders with different surface functional groups content have been electrochemically polarized in tetraethylammonium tetrafluoborate (Et4NBF4) in acetonitrile electrolyte to study their ageing mechanism as supercapacitor electrodes. Temperature-programmed desorption coupled with mass spectrometry technique (TPD-MS) is used to track the change of carbon surface chemistry – surface functional groups and/or adsorption of degradation products occurring upon polarizations. A potentiostatic study of the carbons in a two-compartment cell unveil the catalytic role of water in the ageing mechanism. Combining these results with our previous work, we propose different scenarios to depict the ageing mechanisms of the two carbons. For carbon A, hydrolysis of BF4− at the positive electrode leads to carbon oxidation together with soluble poly-acetonitrile oligomer occurred from reaction between BF4• radicals and acetonitrile. Ageing mechanism is also assumed to set off with the hydrolysis of BF4− for carbon B; but, in here the formed oligomers react with acid functional groups present at the carbon surface to form a protective, passive-like layer at both positive and negative electrodes which hampers a further electrode ageing.

Published
2019
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3. Understanding ageing mechanisms of porous carbons in non-aqueous electrolytes for supercapacitors applications.

Author

Liu, Yinghui, Réty, Bénédicte, Matei Ghimbeu, Camélia, Soucaze-Guillous, Benoît, Taberna, Pierre-Louis, and Simon, Patrice

Subjects
*MASS spectrometry, *CARBON electrodes, *ELECTROLYTES, *SUPERCAPACITOR electrodes, *NEGATIVE electrode, *ACETONITRILE, *CARBON foams
Abstract

Two activated porous carbon powders with different surface functional groups content have been electrochemically polarized in tetraethylammonium tetrafluoborate (Et 4 NBF 4) in acetonitrile electrolyte to study their ageing mechanism as supercapacitor electrodes. Temperature-programmed desorption coupled with mass spectrometry technique (TPD-MS) is used to track the change of carbon surface chemistry – surface functional groups and/or adsorption of degradation products occurring upon polarizations. A potentiostatic study of the carbons in a two-compartment cell unveil the catalytic role of water in the ageing mechanism. Combining these results with our previous work, we propose different scenarios to depict the ageing mechanisms of the two carbons. For carbon A, hydrolysis of BF 4 − at the positive electrode leads to carbon oxidation together with soluble poly-acetonitrile oligomer occurred from reaction between BF 4 • radicals and acetonitrile. Ageing mechanism is also assumed to set off with the hydrolysis of BF 4 − for carbon B; but, in here the formed oligomers react with acid functional groups present at the carbon surface to form a protective, passive-like layer at both positive and negative electrodes which hampers a further electrode ageing. • Presence of water in the electrolyte catalyzes the ageing of supercapacitor. • Electrochemical ageing causes carbon oxidation and forms surface functional groups. • By-products of BF 4 − hydrolysis react with acetonitrile to form soluble oligomers. • Carbon surface functional groups plays an important role in the ageing mechanism. [ABSTRACT FROM AUTHOR]

Published
2019
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