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18 pages, 5262 KiB

Open AccessArticle

Modified NiFe₂O₄-Supported Graphene Oxide for Effective Urea Electrochemical Oxidation and Water Splitting Applications

by Fowzia S. Alamro, Shymaa S. Medany, Nada S. Al-Kadhi, Hoda A. Ahmed and Mahmoud A. Hefnawy

Molecules 2024, 29(6), 1215; https://doi.org/10.3390/molecules29061215 - 08 Mar 2024

Viewed by 537

The production of green hydrogen using water electrolysis is widely regarded as one of the most promising technologies. On the other hand, the oxygen evolution reaction (OER) is thermodynamically unfavorable and needs significant overpotential to proceed at a sufficient rate. Here, we outline [...] Read more.

The production of green hydrogen using water electrolysis is widely regarded as one of the most promising technologies. On the other hand, the oxygen evolution reaction (OER) is thermodynamically unfavorable and needs significant overpotential to proceed at a sufficient rate. Here, we outline important structural and chemical factors that affect how well a representative nickel ferrite-modified graphene oxide electrocatalyst performs in efficient water splitting applications. The activities of the modified pristine and graphene oxide-supported nickel ferrite were thoroughly characterized in terms of their structural, morphological, and electrochemical properties. This research shows that the NiFe₂O₄@GO electrode has an impact on both the urea oxidation reaction (UOR) and water splitting applications. NiFe₂O₄@GO was observed to have a current density of 26.6 mA cm⁻² in 1.0 M urea and 1.0 M KOH at a scan rate of 20 mV s⁻¹. The Tafel slope provided for UOR was 39 mV dec⁻¹, whereas the GC/NiFe₂O₄@GO electrode reached a current of 10 mA cm⁻² at potentials of +1.5 and −0.21 V (vs. RHE) for the OER and hydrogen evolution reaction (HER), respectively. Furthermore, charge transfer resistances were estimated for OER and HER as 133 and 347 Ω cm², respectively. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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14 pages, 946 KiB

Open AccessArticle

Stability of Graphene/Intercalated Oxygen/Ru(0001) as Studied by Thermal Desorption of CO and CO₂ Molecules

by Xiaofeng Yu and Steinar Raaen

Molecules 2023, 28(6), 2670; https://doi.org/10.3390/molecules28062670 - 15 Mar 2023

Cited by 1 | Viewed by 1192

Abstract

Formation of graphene on Ru(0001) by exposure to ethylene and subsequent annealing has been studied by low-energy electron diffraction, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. The stability of graphene/intercalated oxygen/Ru(0001) has been investigated by temperature programmed desorption spectroscopy. Desorption of CO and [...] Read more.

Formation of graphene on Ru(0001) by exposure to ethylene and subsequent annealing has been studied by low-energy electron diffraction, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. The stability of graphene/intercalated oxygen/Ru(0001) has been investigated by temperature programmed desorption spectroscopy. Desorption of CO and CO₂ was observed upon heating the samples to temperatures above 700 K. It was found that the graphene layer was partly intact after the desorption run and that the intercalated oxygen was removed. It was concluded that the oxygen-intercalated graphene layer was stable up to temperatures of about 700 K. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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17 pages, 3854 KiB

Open AccessArticle

The Study of Optimal Adsorption Conditions of Phosphate on Fe-Modified Biochar by Response Surface Methodology

by Jing Qian, Xiaoyu Zhou, Qingsong Cai, Jinjin Zhao and Xianhuai Huang

Molecules 2023, 28(5), 2323; https://doi.org/10.3390/molecules28052323 - 02 Mar 2023

Cited by 5 | Viewed by 1698

Abstract

A batch of Fe-modified biochars MS (for soybean straw), MR (for rape straw), and MP (for peanut shell) were prepared by impregnating biochars pyrolyzed from three different raw biomass materials, i.e., peanut shell, soybean straw, and rape straw, with FeCl₃ solution in [...] Read more.

A batch of Fe-modified biochars MS (for soybean straw), MR (for rape straw), and MP (for peanut shell) were prepared by impregnating biochars pyrolyzed from three different raw biomass materials, i.e., peanut shell, soybean straw, and rape straw, with FeCl₃ solution in different Fe/C impregnation ratios (0, 0.112, 0.224, 0.448, 0.560, 0.672, and 0.896) in this research. Their characteristics (pH, porosities, surface morphologies, crystal structures, and interfacial chemical behaviors) and phosphate adsorption capacities and mechanisms were evaluated. The optimization of their phosphate removal efficiency (Y%) was analyzed using the response surface method. Our results indicated that MR, MP, and MS showed their best phosphate adsorption capacity at Fe/C ratios of 0.672, 0.672, and 0.560, respectively. Rapid phosphate removal was observed within the first few minutes and the equilibrium was attained by 12 h in all treatment. The optimal conditions for phosphorus removal were pH = 7.0, initial phosphate concentration = 132.64 mg L⁻¹, and ambient temperature = 25 °C, where the Y% values were 97.76, 90.23, and 86.23% of MS, MP, and MR, respectively. Among the three biochars, the maximum phosphate removal efficiency determined was 97.80%. The phosphate adsorption process of three modified biochars followed a pseudo-second-order adsorption kinetic model, indicating monolayer adsorption based on electrostatic adsorption or ion exchange. Thus, this study clarified the mechanism of phosphate adsorption by three Fe-modified biochar composites, which present as low-cost soil conditioners for rapid and sustainable phosphate removal. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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10 pages, 3885 KiB

Open AccessArticle

Effect of Fiber–Matrix Interface Friction on Compressive Strength of High-Modulus Carbon Composites

by Sarvenaz Ghaffari, Guillaume Seon and Andrew Makeev

Molecules 2023, 28(5), 2049; https://doi.org/10.3390/molecules28052049 - 22 Feb 2023

Cited by 3 | Viewed by 1700

Abstract

Carbon-fiber-reinforced polymers (CFRPs) enable lightweight, strong, and durable structures for many engineering applications including aerospace, automotive, biomedical, and others. High-modulus (HM) CFRPs enable the most significant improvement in mechanical stiffness at a lower weight, allowing for extremely lightweight aircraft structures. However, low fiber-direction [...] Read more.

Carbon-fiber-reinforced polymers (CFRPs) enable lightweight, strong, and durable structures for many engineering applications including aerospace, automotive, biomedical, and others. High-modulus (HM) CFRPs enable the most significant improvement in mechanical stiffness at a lower weight, allowing for extremely lightweight aircraft structures. However, low fiber-direction compressive strength has been a major weakness of HM CFRPs, prohibiting their implementation in the primary structures. Microstructural tailoring may provide an innovative means for breaking through the fiber-direction compressive strength barrier. This has been implemented by hybridizing intermediate-modulus (IM) and HM carbon fibers in HM CFRP toughened with nanosilica particles. The new material solution almost doubles the compressive strength of the HM CFRPs, achieving that of the advanced IM CFRPs currently used in airframes and rotor components, but with a much higher axial modulus. The major focus of this work has been understanding the fiber–matrix interface properties governing the fiber-direction compressive strength improvement of the hybrid HM CFRPs. In particular, differences in the surface topology may cause much higher interface friction for IM carbon fibers compared to the HM fibers, which is responsible for the interface strength improvement. In situ Scanning Electron Microscopy (SEM)-based experiments were developed to measure interface friction. Such experiments reveal an approximately 48% higher maximum shear traction due to interface friction for IM carbon fibers compared to the HM fibers. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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15 pages, 7882 KiB

Open AccessArticle

Decoration of Polyfluorene-Wrapped Carbon Nanotubes with Photocleavable Side-Chains

by Dialia Ritaine and Alex Adronov

Molecules 2023, 28(3), 1471; https://doi.org/10.3390/molecules28031471 - 03 Feb 2023

Cited by 2 | Viewed by 1860

Abstract

Functionalizing polyfluorene-wrapped carbon nanotubes without damaging their properties is effective via Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC). However, the length and nature of polymer side-chains can impact the conductivity of polyfluorene-SWNT films by preventing close contact between the nanotubes. Here, we investigate the functionalization of [...] Read more.

Functionalizing polyfluorene-wrapped carbon nanotubes without damaging their properties is effective via Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC). However, the length and nature of polymer side-chains can impact the conductivity of polyfluorene-SWNT films by preventing close contact between the nanotubes. Here, we investigate the functionalization of a polyfluorene-SWNT complex using photocleavable side-chains that can be removed post-processing. The cleavage of the side-chains containing an ortho-nitrobenzyl ether derivative is efficient when exposed to a UV lamp at 365 nm. The photoisomerization of the o-nitrobenzyl ether linker into the corresponding o-nitrosobenzaldehyde was first monitored via UV-Vis absorption spectroscopy and ¹H-NMR spectroscopy on the polymer, which showed efficient cleavage after 2 h. We next investigated the cleavage on the polyfluorene-SWNT complex via UV-Vis-NIR absorption spectroscopy. The precipitation of the nanotube dispersion and the broad absorption peaks after overnight irradiation also indicated effective cleavage. In addition, Raman spectroscopy post-irradiation showed that the nanotubes were not damaged upon irradiation. This paper reports a proof of concept that may find applications for SWNT-based materials in which side-chain removal could lead to higher device performance. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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19 pages, 3669 KiB

Open AccessArticle

Biochars and Activated Biocarbons Prepared via Conventional Pyrolysis and Chemical or Physical Activation of Mugwort Herb as Potential Adsorbents and Renewable Fuels

by Małgorzata Wiśniewska, Kacper Rejer, Robert Pietrzak and Piotr Nowicki

Molecules 2022, 27(23), 8597; https://doi.org/10.3390/molecules27238597 - 06 Dec 2022

Cited by 6 | Viewed by 1622

Abstract

The main objective of this study was to prepare a series of biochars and activated biocarbons via conventional pyrolysis as well as chemical or physical activation of solid residue after solvent extraction of wild growing plant (popular weed)–mugwort. The influence of the variant [...] Read more.

The main objective of this study was to prepare a series of biochars and activated biocarbons via conventional pyrolysis as well as chemical or physical activation of solid residue after solvent extraction of wild growing plant (popular weed)–mugwort. The influence of the variant of the thermochemical treatment of the precursor on such parameters as elemental composition, textural parameters, acidic-basic character of the surface as well as adsorption abilities of the prepared carbonaceous materials was checked. Moreover, the suitability of the biochars prepared as renewable fuels was also investigated. It has been shown that the products obtained from the mugwort stems differ in many respects from the analogous materials obtained from mugwort leaves. The products were micro/mesoporous materials with surface area reaching 974.4 m²/g and total pore volume–1.190 cm³/g. Surface characterization showed that chemical activation with H₃PO₄ results in the acidic character of the adsorbents surface, whereas products of pyrolysis and especially physical activation show strongly alkaline surface properties. All the adsorbents were used for methylene blue and iodine adsorption from the aquatic environment. To understand the nature of the sorption process, the Langmuir, Freundlich and Temkin isotherm models were employed. The Langmuir model best described the experimental results, and the maximum sorption capacity calculated for this model reached 164.14 mg of methylene blue per gram of adsorbent. In case of iodine removal, the maximum capacity reached 948.00 mg/g. The research carried out for the biochars prepared via conventional pyrolysis showed that the value of their heat of combustion varies in the range from 21.74 to 30.27 MJ/kg, so they can be applied as the renewable fuels. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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14 pages, 2022 KiB

Open AccessArticle

Removal of Non-Steroidal Anti-Inflammatory Drugs from Drinking Water Sources by GO-SWCNT Buckypapers

by Mariafrancesca Baratta, Antonio Tursi, Manuela Curcio, Giuseppe Cirillo, Aleksey Vladimirovich Nezhdanov, Alexandr Ivanovic Mashin, Fiore Pasquale Nicoletta and Giovanni De Filpo

Molecules 2022, 27(22), 7674; https://doi.org/10.3390/molecules27227674 - 08 Nov 2022

Cited by 4 | Viewed by 1303

Abstract

Pharmaceutical products such as antibiotics, analgesics, steroids, and non-steroidal anti-inflammatory drugs (NSAIDs) are new emerging pollutants, often present in wastewater, potentially able to contaminate drinking water resources. Adsorption is considered the cheapest and most effective technique for the removal of pollutants from water, [...] Read more.

Pharmaceutical products such as antibiotics, analgesics, steroids, and non-steroidal anti-inflammatory drugs (NSAIDs) are new emerging pollutants, often present in wastewater, potentially able to contaminate drinking water resources. Adsorption is considered the cheapest and most effective technique for the removal of pollutants from water, and, recently, membranes obtained by wet filtration method of SWCNT aqueous solutions (SWCNT buckypapers, SWCNT BPs) have been proposed as self-standing porous adsorbents. In this paper, the ability of graphene oxide/single-walled carbon nanotube composite membranes (GO-SWCNT BPs) to remove some important NSAIDs, namely Diclofenac, Ketoprofen, and Naproxen, was investigated at different pH conditions (pH 4, 6, and 8), graphene oxide amount (0, 20, 40, 60, and 75 wt.%), and initial NSAIDs concentration (1, 10, and 50 ppm). For the same experimental conditions, the adsorption capacities were found to strongly depend on the graphene oxide content. The best results were obtained for 75 wt.% graphene oxide with an adsorption capacity of 118 ± 2 mg g⁻¹ for Diclofenac, 116 ± 2 mg g⁻¹ for Ketoprofen, and 126 ± 3 mg g⁻¹ for Naproxen at pH 4. Overall, the reported data suggest that GO-SWCNT BPs can represent a promising tool for a cheap and fast removal of NSAIDs from drinking water resources, with easy recovery and reusability features. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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16 pages, 6894 KiB

Open AccessFeature PaperArticle

Microstructure, Mechanical and Electrical Properties of Hybrid Copper Matrix Composites with Fe Microspheres and rGO Nanosheets

by Xinjiang Zhang, Meng He, Yongzhong Zhan, Wenchao Yang and Kaifeng Wu

Molecules 2022, 27(19), 6518; https://doi.org/10.3390/molecules27196518 - 02 Oct 2022

Cited by 1 | Viewed by 1135

Abstract

Copper matrix composites have a wide application as magnetic conductive materials, electromagnetic materials, electrical discharge machining materials, etc. Such materials are expected to have a good combination of excellent electrical conductivity and good mechanical strength. In this work, micro/nano hybrid reinforcements with Fe [...] Read more.

Copper matrix composites have a wide application as magnetic conductive materials, electromagnetic materials, electrical discharge machining materials, etc. Such materials are expected to have a good combination of excellent electrical conductivity and good mechanical strength. In this work, micro/nano hybrid reinforcements with Fe microspheres and reduced graphene oxide (rGO) nanosheets were developed for copper matrix composites. The rGO/Fe/Cu powders were firstly wet-mixed and then densified by the vacuum hot-pressing sintering to obtain the bulk compacts. Microstructure, electrical conductivity and mechanical properties of such compacts were investigated. Microstructural result of as-sintered compacts shows that the Fe microspheres could distribute in the matrix uniformly, and rGO nanosheets exhibit both agglomerated and dispersed states. The grain size of Cu matrix decreased with the increase of the rGO content. Hardness, compression and tensile 0.2% yield strength of the as-sintered compacts were improved evidently by the addition of the hybrid Fe/rGO, comparing with pure Cu and single Fe-added composites. However, a lower electrical conductivity appeared in the more rGO-added composites, but still reached more than 33.0% international annealing copper standard (IACS). These performance change could be sought in the spatially geometrical distribution and characteristics of such micro/nano Fe/rGO hybrid addition, and the relevant mechanisms were discussed. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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Review

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23 pages, 3697 KiB

Open AccessReview

Carbon-Based Nanomaterials for Catalytic Wastewater Treatment: A Review

by Lagnamayee Mohapatra, Dabin Cheon and Seung Hwa Yoo

Molecules 2023, 28(4), 1805; https://doi.org/10.3390/molecules28041805 - 14 Feb 2023

Cited by 14 | Viewed by 2954

Abstract

Carbon-based nanomaterials (CBM) have shown great potential for various environmental applications because of their physical and chemical properties. The unique hybridization properties of CBMs allow for the tailored manipulation of their structures and morphologies. However, owing to poor solar light absorption, and the [...] Read more.

Carbon-based nanomaterials (CBM) have shown great potential for various environmental applications because of their physical and chemical properties. The unique hybridization properties of CBMs allow for the tailored manipulation of their structures and morphologies. However, owing to poor solar light absorption, and the rapid recombination of photogenerated electron-hole pairs, pristine carbon materials typically have unsatisfactory photocatalytic performances and practical applications. The main challenge in this field is the design of economical, environmentally friendly, and effective photocatalysts. Combining carbonaceous materials with carbonaceous semiconductors of different structures results in unique properties in carbon-based catalysts, which offers a promising approach to achieving efficient application. Here, we review the contribution of CBMs with different dimensions, to the catalytic removal of organic pollutants from wastewater by catalyzing the Fenton reaction and photocatalytic processes. This review, therefore, aims to provide an appropriate direction for empowering improvements in ongoing research work, which will boost future applications and contribute to overcoming the existing limitations in this field. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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27 pages, 17526 KiB

Open AccessReview

Thermoelectric Materials for Textile Applications

by Kony Chatterjee and Tushar K. Ghosh

Molecules 2021, 26(11), 3154; https://doi.org/10.3390/molecules26113154 - 25 May 2021

Cited by 22 | Viewed by 4386

Abstract

Since prehistoric times, textiles have served an important role–providing necessary protection and comfort. Recently, the rise of electronic textiles (e-textiles) as part of the larger efforts to develop smart textiles, has paved the way for enhancing textile functionalities including sensing, energy harvesting, and [...] Read more.

Since prehistoric times, textiles have served an important role–providing necessary protection and comfort. Recently, the rise of electronic textiles (e-textiles) as part of the larger efforts to develop smart textiles, has paved the way for enhancing textile functionalities including sensing, energy harvesting, and active heating and cooling. Recent attention has focused on the integration of thermoelectric (TE) functionalities into textiles—making fabrics capable of either converting body heating into electricity (Seebeck effect) or conversely using electricity to provide next-to-skin heating/cooling (Peltier effect). Various TE materials have been explored, classified broadly into (i) inorganic, (ii) organic, and (iii) hybrid organic-inorganic. TE figure-of-merit (ZT) is commonly used to correlate Seebeck coefficient, electrical and thermal conductivity. For textiles, it is important to think of appropriate materials not just in terms of ZT, but also whether they are flexible, conformable, and easily processable. Commercial TEs usually compromise rigid, sometimes toxic, inorganic materials such as bismuth and lead. For textiles, organic and hybrid TE materials are more appropriate. Carbon-based TE materials have been especially attractive since graphene and carbon nanotubes have excellent transport properties with easy modifications to create TE materials with high ZT and textile compatibility. This review focuses on flexible TE materials and their integration into textiles. Full article

(This article belongs to the Special Issue Carbon Materials in Materials Chemistry)

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