Materials

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15 pages, 4581 KiB

Open AccessArticle

Enhanced Thermal Stability, Mechanical Properties and Structural Integrity of MWCNT Filled Bamboo/Kenaf Hybrid Polymer Nanocomposites

by J. M. Prabhudass, K. Palanikumar, Elango Natarajan and Kalaimani Markandan

Materials 2022, 15(2), 506; https://doi.org/10.3390/ma15020506 - 10 Jan 2022

Cited by 29 | Viewed by 1743

Abstract

Recently, there has been an inclination towards natural fibre reinforced polymer composites owing to their merits such as environmental friendliness, light weight and excellent strength. In the present study, six laminates were fabricated consisting of natural fibres such as Kenaf fibre (Hibiscus [...] Read more.

Recently, there has been an inclination towards natural fibre reinforced polymer composites owing to their merits such as environmental friendliness, light weight and excellent strength. In the present study, six laminates were fabricated consisting of natural fibres such as Kenaf fibre (Hibiscus cannabinus L.) and Bamboo fibre, together with multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers in the epoxy matrix. Mechanical testing revealed that hybridization of natural fibres was capable of yielding composites with enhanced tensile properties. Additionally, impact testing showed a maximum improvement of ≈80.6% with the inclusion of MWCNTs as nanofiller in the composites with very high energy absorption characteristics, which were attributed to the high specific energy absorption of carbon nanotubes. The viscoelastic behaviour of hybridised composites reinforced with MWCNTs also showed promising results with a significant improvement in the glass transition temperature (Tg) and 41% improvement in storage modulus. It is worth noting that treatment of the fibres in NaOH solution prior to composite fabrication was effective in improving the interfacial bonding with the epoxy matrix, which, in turn, resulted in improved mechanical properties. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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11 pages, 2235 KiB

Open AccessArticle

Pencil Graphite Electrodes Decorated with Platinum Nanoparticles as Efficient Electrocatalysts for Hydrogen Evolution Reaction

by Lorena-Cristina Balint, Iosif Hulka and Andrea Kellenberger

Materials 2022, 15(1), 73; https://doi.org/10.3390/ma15010073 - 23 Dec 2021

Cited by 5 | Viewed by 2913

Abstract

Platinum-based materials are widely known as the most utilized and advanced catalysts for hydrogen evolution reaction. For this reason, several studies have reported alternative methods of incorporating this metal into more economical electrodes with a carbon-based support material. Herein, we report on the [...] Read more.

Platinum-based materials are widely known as the most utilized and advanced catalysts for hydrogen evolution reaction. For this reason, several studies have reported alternative methods of incorporating this metal into more economical electrodes with a carbon-based support material. Herein, we report on the performance of pencil graphite electrodes decorated with electrochemically deposited platinum nanoparticles as efficient electrocatalysts for hydrogen evolution reaction. The electrodeposition of platinum was performed via pulsed current electrodeposition and the effect of current density on the electrocatalytic activity was investigated. The obtained electrodes were characterized using cyclic voltammetry, while the electrocatalytic activity was assessed through linear sweep voltammetry. Field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy were utilised to gain an insight into surface morphology and chemical analysis of platinum nanoparticles. The best performing electrocatalyst, at both low and high current densities, was characterized by the highest exchange current density of 1.98 mA cm⁻² and an ultralow overpotential of 43 mV at a current density of 10 mA cm⁻². The results show that, at low current densities, performances closest to that of platinum can be achieved even with an ultralow loading of 50 µg cm⁻² Pt. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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13 pages, 6802 KiB

Open AccessArticle

Growing Tungsten Nanophases on Carbon Spheres Doped with Nitrogen. Behaviour as Electro-Catalysts for Oxygen Reduction Reaction

by Teresa Briz-Amate, Jesica Castelo-Quibén, Esther Bailón-García, Abdalla Abdelwahab, Francisco Carrasco-Marín and Agustín F. Pérez-Cadenas

Materials 2021, 14(24), 7716; https://doi.org/10.3390/ma14247716 - 14 Dec 2021

Cited by 2 | Viewed by 2143

Abstract

This work shows the preparation of carbon nanospheres with a high superficial nitrogen content (7 wt.%), obtained by a simple hydrothermal method, from pyrocatechol and formaldehyde, around which tungsten nanophases have been formed. One of these nanophases is tungsten carbide, whose electro-catalytic behavior [...] Read more.

This work shows the preparation of carbon nanospheres with a high superficial nitrogen content (7 wt.%), obtained by a simple hydrothermal method, from pyrocatechol and formaldehyde, around which tungsten nanophases have been formed. One of these nanophases is tungsten carbide, whose electro-catalytic behavior in the ORR has been evaluated together with the presence of nitrogen surface groups. Both current and potential kinetic density values improve considerably with the presence of tungsten, despite the significant nitrogen loss detected during the carbonization treatment. However, the synergetic effect that the WC has with other electro-catalytic metals in this reaction cannot be easily evaluated with the nitrogen in these materials, since both contents vary in opposite ways. Nevertheless, all the prepared materials carried out oxygen electro-reduction by a mixed pathway of two and four electrons, showing remarkable electro-catalytic behavior. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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17 pages, 6685 KiB

Open AccessArticle

Highly Porous Expanded Graphite: Thermal Shock vs. Programmable Heating

by Alexander G. Bannov, Arina V. Ukhina, Evgenii A. Maksimovskii, Igor Yu. Prosanov, Artyom A. Shestakov, Nikita I. Lapekin, Nikita S. Lazarenko, Pavel B. Kurmashov and Maksim V. Popov

Materials 2021, 14(24), 7687; https://doi.org/10.3390/ma14247687 - 13 Dec 2021

Cited by 7 | Viewed by 2515

Abstract

Highly porous expanded graphite was synthesized by the programmable heating technique using heating with a constant rate (20 °C/min) from room temperature to 400–700 °C. The samples obtained were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, Raman [...] Read more.

Highly porous expanded graphite was synthesized by the programmable heating technique using heating with a constant rate (20 °C/min) from room temperature to 400–700 °C. The samples obtained were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetry, and differential scanning calorimetry. A comparison between programmable heating and thermal shock as methods of producing expanded graphite showed efficiency of the first one at a temperature 400 °C, and the surface area reached 699 and 184 m²/g, respectively. The proposed technique made it possible to obtain a relatively higher yield of expanded graphite (78–90%) from intercalated graphite. The experiments showed the advantages of programmable heating in terms of its flexibility and the possibility to manage the textural properties, yield, disorder degree, and bulk density of expanded graphite. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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15 pages, 4948 KiB

Open AccessArticle

Modified Mesoporous Carbon Material (Pb-N-CMK-3) Obtained by a Hard-Templating Route, Dicyandiamide Impregnation and Electrochemical Lead Particles Deposition as an Electrode Material for the U(VI) Ultratrace Determination

by Katarzyna Tyszczuk-Rotko, Rafał Olchowski, Jędrzej Kozak, Olga Sekerzh-Zenkovich and Ryszard Dobrowolski

Materials 2021, 14(21), 6490; https://doi.org/10.3390/ma14216490 - 29 Oct 2021

Cited by 2 | Viewed by 1574

Abstract

In this paper, a dicyandiamide-impregnated mesoporous carbon (N-CMK-3), electrochemically modified in situ with lead film (Pb-N-CMK-3), was tested as an electrode material for U(VI) ultratrace determination. The prepared carbon material was characterized by XRD, SEM-EDX, Raman, FT-IR, XPS analysis and nitrogen sorption measurements. [...] Read more.

In this paper, a dicyandiamide-impregnated mesoporous carbon (N-CMK-3), electrochemically modified in situ with lead film (Pb-N-CMK-3), was tested as an electrode material for U(VI) ultratrace determination. The prepared carbon material was characterized by XRD, SEM-EDX, Raman, FT-IR, XPS analysis and nitrogen sorption measurements. The changes of electrochemical properties of glassy carbon electrodes (GCE) after the N-CMK-3 and Pb-N-CMK-3 modification were studied using CV and EIS methods. The modification of the GCE surface by the N-CMK-3 material and Pb film increases the electroactive area of the electrode and decreases the charge transfer residence and is likely responsible for the electrochemical improvement of the U(VI) analytical signal. Using square-wave adsorptive stripping voltammetry (SWAdSV), two linear calibration ranges extending from 0.05 to 1.0 nM and from 1.0 to 10.0 nM were observed, coupled with the detection and quantification limits of 0.014 and 0.047 nM, respectively. The Pb-N-CMK-3/GCE was successfully applied for U(VI) determination in reference materials (estuarine water SLEW-3 and trace elements in natural water SRM 1640a). Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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16 pages, 3100 KiB

Open AccessArticle

Synthesis of Magnetic Adsorbents Based Carbon Highly Efficient and Stable for Use in the Removal of Pb(II) and Cd(II) in Aqueous Solution

by Safa Benjedim, Luis A. Romero-Cano, Hesham Hamad, Esther Bailón-García, Václav Slovák, Francisco Carrasco-Marín and Agustín F. Pérez-Cadenas

Materials 2021, 14(20), 6134; https://doi.org/10.3390/ma14206134 - 15 Oct 2021

Cited by 3 | Viewed by 1827

Abstract

In this study, two alternative synthesis routes for magnetic adsorbents were evaluated to remove Pb(II) and Cd(II) in an aqueous solution. First, activated carbon was prepared from argan shells (C). One portion was doped with magnetite (Fe₃O₄ [...] Read more.

In this study, two alternative synthesis routes for magnetic adsorbents were evaluated to remove Pb(II) and Cd(II) in an aqueous solution. First, activated carbon was prepared from argan shells (C). One portion was doped with magnetite (Fe₃O₄+C) and the other with cobalt ferrite (CoFe₂O₄+C). Characterization studies showed that C has a high surface area (1635 m² g⁻¹) due to the development of microporosity. For Fe₃O₄+C the magnetic particles were nano-sized and penetrated the material’s texture, saturating the micropores. In contrast, CoFe₂O₄+C conserves the mesoporosity developed because most of the cobalt ferrite particles adhered to the exposed surface of the material. The adsorption capacity for Pb(II) was 389 mg g⁻¹ (1.88 mmol g⁻¹) and 249 mg g⁻¹ (1.20 mmol g⁻¹); while for Cd(II) was 269 mg g⁻¹ (2.39 mmol g⁻¹) and 264 mg g⁻¹ (2.35 mmol g⁻¹) for the Fe₃O₄+C and CoFe₂O₄+C, respectively. The predominant adsorption mechanism is the interaction between -FeOH groups with the cations in the solution, which are the main reason these adsorption capacities remain high in repeated adsorption cycles after regeneration with HNO₃. The results obtained are superior to studies previously reported in the literature, making these new materials a promising alternative for large-scale wastewater treatment processes using batch-type reactors. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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19 pages, 7526 KiB

Open AccessArticle

Design of Self-Supported Flexible Nanostars MFe-LDH@ Carbon Xerogel-Modified Electrode for Methanol Oxidation

by Ghada M. Abdelrazek, Mohamed M. EL-Deeb, Ahmed A. Farghali, Agustín F. Pérez-Cadenas and Abdalla Abdelwahab

Materials 2021, 14(18), 5271; https://doi.org/10.3390/ma14185271 - 13 Sep 2021

Cited by 8 | Viewed by 2296

Abstract

Layered double hydroxides (LDHs) have emerged as promising electrodes materials for the methanol oxidation reaction. Here, we report on the preparation of different LDHs with the hydrothermal process. The effect of the divalent cation (i.e., Ni, Co, and Zn) on the electrochemical performance [...] Read more.

Layered double hydroxides (LDHs) have emerged as promising electrodes materials for the methanol oxidation reaction. Here, we report on the preparation of different LDHs with the hydrothermal process. The effect of the divalent cation (i.e., Ni, Co, and Zn) on the electrochemical performance of methanol oxidation was investigated. Moreover, nanocomposites of LDHs and carbon xerogels (CX) supported on nickel foam (NF) substrate were prepared to investigate the role of carbon xerogel. The results show that NiFe-LDH/CX/NF is an efficient electrocatalyst for methanol oxidation with a current density that reaches 400 mA·m⁻² compared to 250 and 90 mA·cm⁻² for NiFe-LDH/NF and NF, respectively. In addition, all LDH/CX/NF nanocomposites show excellent stability for methanol oxidation. A clear relationship is observed between the electrodes crystallite size and their activity to methanol oxidation. The smaller the crystallite size, the higher the current density delivered. Additionally, the presence of carbon xerogel in the nanocomposites offer 3D interconnected micro/mesopores, which facilitate both mass and electron transport. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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12 pages, 1532 KiB

Open AccessArticle

Study of the Interaction of an Iron Phthalocyanine Complex over Surface Modified Carbon Nanotubes

by María Pérez-Cadenas, Esther Asedegbega-Nieto, Jonathan Carter, James A. Anderson, Inmaculada Rodríguez-Ramos and Antonio Guerrero-Ruiz

Materials 2021, 14(15), 4067; https://doi.org/10.3390/ma14154067 - 21 Jul 2021

Cited by 4 | Viewed by 2439

Abstract

Carbon nanotubes (CNT) were prepared by a modified chemical vapor deposition (CVD) method. The synthesized carbon materials were treated with acidic and basic solutions in order to introduce certain surface functional groups, mainly containing oxygen (OCNT) or amine (ACNT) species. These modified CNTs [...] Read more.

Carbon nanotubes (CNT) were prepared by a modified chemical vapor deposition (CVD) method. The synthesized carbon materials were treated with acidic and basic solutions in order to introduce certain surface functional groups, mainly containing oxygen (OCNT) or amine (ACNT) species. These modified CNTs (OCNT and ACNT) as well as the originally prepared CNT were reacted with a non-ionic Fe complex, Iron (II) Phthalocyanine, and three composites were obtained. The amount of metal complex introduced in each case and the interaction between the complex and the CNT materials were studied with the aid of various characterization techniques such as TGA, XRD, and XPS. The results obtained in these experiments all indicated that the interaction between the complex and the CNT was greatly affected by the functionalization of the latter. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Carbon Materials)

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