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Volume 8
Issue 2
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C, Volume 8, Issue 2 (June 2022) – 13 articles

Cover Story (view full-size image): A new purification procedure of carbon nanoforms is proposed. While synthesis leads to a distribution of unwished products, many purification strategies exist. A successful one is combustion. However, the temperature has to be carefully chosen to maximize the reaction selectivity. Moreover, it depends on many factors, such as the material but also the reactor and parameters of gas. Temperature optimization typically relies on fastidious multiple isotherms and analysis of the product or unprecise constant heating rate measurement. We demonstrate here that a thermogravimetric method, the constant decomposition rate thermal analysis, is particularly well adapted to answer this question. It successfully allowed purifying the challenging case of multiwall carbon nanotubes and should be valuable for other carbonaceous forms. View this paper
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14 pages, 4117 KiB  
Article
Development of Disposable and Flexible Supercapacitor Based on Carbonaceous and Ecofriendly Materials
by Giovanni G. Daniele, Daniel C. de Souza, Paulo Roberto de Oliveira, Luiz O. Orzari, Rodrigo V. Blasques, Rafael L. Germscheidt, Emilly C. da Silva, Leandro A. Pocrifka, Juliano A. Bonacin and Bruno C. Janegitz
C 2022, 8(2), 32; https://doi.org/10.3390/c8020032 - 7 Jun 2022
Cited by 3 | Viewed by 2838
Abstract
A novel flexible supercapacitor device was developed from a polyethylene terephthalate substrate, reused from beverage bottles, and a conductive ink based on carbon black (CB) and cellulose acetate (CA). The weight composition of the conductive ink was evaluated to determine the best mass [...] Read more.
A novel flexible supercapacitor device was developed from a polyethylene terephthalate substrate, reused from beverage bottles, and a conductive ink based on carbon black (CB) and cellulose acetate (CA). The weight composition of the conductive ink was evaluated to determine the best mass percentage ratio between CB and CA in terms of capacitive behavior. The evaluation was performed by using different electrochemical techniques: cyclic voltammetry, obtaining the highest capacitance value for the device with the 66.7/33.3 wt% CB/CA in a basic H2SO4 solution, reaching 135.64 F g−1. The device was applied in potentiostatic charge/discharge measurements, achieving values of 2.45 Wh kg−1 for specific energy and around 1000 W kg−1 for specific power. Therefore, corroborated with electrochemical impedance spectroscopy assays, the relatively low-price proposed device presented a suitable performance for application as supercapacitors, being manufactured from reused materials, contributing to the energy storage field enhancement. Full article
(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)
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<p>Experimental procedure representation: (1) elaboration of the CB and CA base dispersions; (2) ink preparation; (3) electrode assembly with screen printing technique over PET substrates; (4) finalized capacitor electrode ready for (5) electrochemical analyses.</p> Full article ">Figure 2
<p>Cyclic voltammograms of different CB/CA formulations: 33.3/66.7 (<b>black</b>), 50.0/50.0 (<b><span style="color:red">red</span></b>), 60.0/40.0 (<b><span style="color:blue">blue</span></b>), and 66.7/33.3% (<b><span style="color:fuchsia">pink</span></b>); in (<b>A</b>) 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub>, (<b>B</b>) 1.0 mol L<sup>−1</sup> KOH, and (<b>C</b>) 1.0 mol L<sup>−1</sup> Na<sub>2</sub>SO<sub>4</sub>; ν = 10 mV s<sup>−1</sup> (<b>D</b>) SC vs. scan rate plots for 66.7/33.3% CB/CA at equimolar 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub> (<span style="color:blue">▲</span>); Na<sub>2</sub>SO<sub>4</sub> (<span style="color:red">●</span>) and KOH (■) solutions.</p> Full article ">Figure 3
<p>(<b>A</b>) Nyquist diagrams for H<sub>2</sub>SO<sub>4</sub> (■) and KOH (<span style="color:red">●</span>). (<b>B</b>) Cyclic voltammograms obtained in OCP by 66.7/33.3% CB/CA electrode, in equimolar 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub> (▬) and KOH (<span style="color:blue">▬</span>); ν = 10 mV s<sup>−1</sup>. Capacitance retention dispersion plots of 100 cycles in (<b>C</b>) 1.0 mol L<sup>−1</sup> KOH and (<b>D</b>) 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub>.</p> Full article ">Figure 4
<p>SEM images of the 66.67% CB/CA ink without CB (<b>A</b>–<b>C</b>), without CA (<b>D</b>–<b>F</b>) and the complete ink (<b>G</b>–<b>I</b>) at (<b>A</b>,<b>D</b>,<b>G</b>) 500×, (<b>B</b>,<b>E</b>,<b>H</b>) 1000×, and (<b>C</b>,<b>F</b>,<b>I</b>) 2000× magnification.</p> Full article ">Figure 5
<p>E vs. t plots of CB/CA PCD profiles in 1.0 mol L<sup>−1</sup> (<b>A</b>) H<sub>2</sub>SO<sub>4</sub>, (<b>B</b>) Na<sub>2</sub>SO<sub>4</sub>, (<b>C</b>) KOH, at different CD values: 0.5, 1.0, 2.0, 3.0, and 4.0 A g<sup>−1</sup>. (<b>D</b>) SP vs. SE (Ragone plots) for CB/CA in different and equimolar 1.0 mol L<sup>−1</sup> electrolytes: H<sub>2</sub>SO<sub>4</sub> (<span style="color:blue">▲</span>), Na<sub>2</sub>SO<sub>4</sub> (<span style="color:red">●</span>), and KOH (■). (<b>E</b>) Dispersion plot of PCDs SC vs. different current densities (0.5, 1.0, 2.0, 3.0, and 4.0 A g<sup>−1</sup>) for CB/CA in different and equimolar 1.0 mol L<sup>−1</sup> electrolytes: H<sub>2</sub>SO<sub>4</sub> (<span style="color:blue">▲</span>), Na<sub>2</sub>SO<sub>4</sub> (<span style="color:red">●</span>), and KOH (■). (<b>F</b>) Capacitor efficiency, in equimolar 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub> (<span style="color:blue">▲</span>), Na<sub>2</sub>SO<sub>4</sub> (<span style="color:red">●</span>), and KOH (■), for CB/CA devices.</p> Full article ">Figure 6
<p>Cyclic voltammograms of the flexibility study on the (<b>A</b>) curved device and (<b>B</b>) flat device, in 1.0 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub>; ν = 50 mV s<sup>−1</sup>. (<b>C</b>) I vs. the number of torsions dispersion plots for (▲) curved and (<span style="color:red">●</span>) flat electrodes. Data was collected at 0.0 V.</p> Full article ">
10 pages, 1964 KiB  
Communication
Burn Them Right! Determining the Optimal Temperature for the Purification of Carbon Materials by Combustion
by Emmanuel Picheau, Ferdinand Hof, Alain Derré, Sara Amar, Laure Noé, Marc Monthioux and Alain Pénicaud
C 2022, 8(2), 31; https://doi.org/10.3390/c8020031 - 24 May 2022
Cited by 4 | Viewed by 2221
Abstract
A new purification procedure for carbon nanoforms is proposed. It was tested on multiwall carbon nanotubes (MWCNTs) prepared by arc discharge, which is among the most challenging of cases due to the chemical and structural similarity between the MWCNTs and most of the [...] Read more.
A new purification procedure for carbon nanoforms is proposed. It was tested on multiwall carbon nanotubes (MWCNTs) prepared by arc discharge, which is among the most challenging of cases due to the chemical and structural similarity between the MWCNTs and most of the impurities to be removed. Indeed, the various methods for synthesizing carbon nanoforms lead to a distribution of carbonaceous products, such as carbon shells, carbon spheres, fullerenes, and a variety of other species. Thus, many strategies to purify the desired products have been developed. Among the most successful ones, thermal oxidation (combustion) seems particularly efficient. To be successful while preserving a reasonable amount of MWCNTs, the combustion temperature has to be carefully selected. Moreover, the ideal combustion temperature does not only depend on the material to be treated but also on the overall system used to perform the reaction, including the reactor type and the parameters of the gaseous reactant. Typically, the optimization of the purification relies on multiple experiments and analysis of the products. However, to the best of our knowledge, a strategy to determine a priori the most suitable temperature has not been reported yet. We demonstrate here that a thermogravimetric method, namely the constant decomposition rate thermal analysis (CRTA), is particularly well adapted to answer this question. An isothermal treatment based on the results obtained from a CRTA program allowed arc-MWCNTs to be successfully purified from graphenic shells while optimizing the yield of the MWCNTs. This strategy is believed to be valuable not only for purifying MWCNTs but also for the purification of other carbonaceous forms, including new carbon nanoforms. Full article
(This article belongs to the Collection Young Carbon Scientists)
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<p>(<b>a</b>–<b>e</b>) TEM images of the raw material (before treatment) at different magnification scales. (<b>d</b>) Focus on a CNT end showing that CNTs are closed at their extremities. (<b>e</b>) Focus on a graphenic particle, typical of the kind of impurities present in the powder.</p> Full article ">Figure 2
<p>Thermogravimetric curve corresponding to the CRTA measurement of the raw material. The blue curve shows the % weight loss of the material versus time. The green curve represents the resulting temperature adopted by the apparatus (based on the weight-loss rate) versus time. The horizontal grey dotted line represents 590 °C.</p> Full article ">Figure 3
<p>Transmission electron microscopy images of the material after treatment). (<b>a</b>,<b>b</b>) Low magnification. (<b>c</b>,<b>d</b>) High resolution images. A significant amount of CNTs have been opened (see text).</p> Full article ">Figure 4
<p>Comparisons of Raman data for the raw (black dots) and treated (empty red squares) materials, built on 1024 individual spectra. (<b>a</b>) Distribution of the area ratio of the Raman D band over the Raman G band. This distribution is based on a histogram with bin size: 8.33 × 10<sup>−</sup><sup>3</sup> a.u.). The thin lines are Gaussian functions used for the fitting of the curves (thick lines). (<b>b</b>) Distribution of the full width at half maximum (FWHM) for the Raman G band and Gaussian fits. This distribution is based on a histogram with bin size: 0.58 cm<sup>−1</sup>.</p> Full article ">
9 pages, 1751 KiB  
Article
Plasma-Enhanced Carbon Nanotube Fiber Cathode for Li-S Batteries
by Yanbo Fang, Yu-Yun Hsieh, Mahnoosh Khosravifar, Paa Kwasi Adusei, Sathya Narayan Kanakaraj, Bely Stockman, Vamsi Krishna Reddy Kondapalli and Vesselin Shanov
C 2022, 8(2), 30; https://doi.org/10.3390/c8020030 - 22 May 2022
Viewed by 3043
Abstract
Fiber-shaped batteries have attracted much interest in the last few years. However, a major challenge for this type of battery is their relatively low energy density. Here, we present a freestanding, flexible CNT fiber with high electrical conductivity and applied oxygen plasma-functionalization, which [...] Read more.
Fiber-shaped batteries have attracted much interest in the last few years. However, a major challenge for this type of battery is their relatively low energy density. Here, we present a freestanding, flexible CNT fiber with high electrical conductivity and applied oxygen plasma-functionalization, which was successfully employed to serve as an effective cathode for Li-S batteries. The electrochemical results obtained from the conducted battery tests showed a decent rate capability and cyclic stability. The cathode delivered a capacity of 1019 mAh g−1 at 0.1 C. It accommodated a high sulfur loading of 73% and maintained 47% of the initial capacity after 300 cycles. The demonstrated performance of the fiber cathode provides new insights for the designing and fabrication of high energy density fiber-shaped batteries. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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<p>Low magnification SEM images of (<b>a</b>) OCNT-S, (<b>b</b>) CNT-S. High magnification SEM images of (<b>c</b>) OCNT-S, (<b>d</b>) CNT-S. The scale bars in the SEM images for (<b>a</b>,<b>b</b>) are 20 µm, and for (<b>c</b>,<b>d</b>) are 5 µm. (<b>e</b>) X-ray CT images of OCNT-S in XY slice. (<b>f</b>) X-ray CT images of OCNT-S in YZ slice. Scare bars for both (<b>e</b>,<b>f</b>) are 10 µm. (<b>g</b>) TGA curves for OCNT-S and CNT-S. (<b>h</b>) Raman spectra of CNT, OCNT, and OCNT-S, where characteristic peaks of sulfur were observed for CNT-S. The I<sub>D</sub>/I<sub>G</sub> ratios in all these samples are indicated. (<b>i</b>) Tensile stress vs. strain plot of pristine CNT and OCNT-S, respectively.</p> Full article ">Figure 1 Cont.
<p>Low magnification SEM images of (<b>a</b>) OCNT-S, (<b>b</b>) CNT-S. High magnification SEM images of (<b>c</b>) OCNT-S, (<b>d</b>) CNT-S. The scale bars in the SEM images for (<b>a</b>,<b>b</b>) are 20 µm, and for (<b>c</b>,<b>d</b>) are 5 µm. (<b>e</b>) X-ray CT images of OCNT-S in XY slice. (<b>f</b>) X-ray CT images of OCNT-S in YZ slice. Scare bars for both (<b>e</b>,<b>f</b>) are 10 µm. (<b>g</b>) TGA curves for OCNT-S and CNT-S. (<b>h</b>) Raman spectra of CNT, OCNT, and OCNT-S, where characteristic peaks of sulfur were observed for CNT-S. The I<sub>D</sub>/I<sub>G</sub> ratios in all these samples are indicated. (<b>i</b>) Tensile stress vs. strain plot of pristine CNT and OCNT-S, respectively.</p> Full article ">Figure 2
<p>(<b>a</b>) Rate capability of Li-S cells with CNT-S and OCNT-S cathodes up to 2 C. (<b>b</b>) Discharge/charge profiles in the second cycle of Li-S cells with CNT-S and OCNT-S cathodes at a current density of 0.2 C.</p> Full article ">Figure 3
<p>(<b>a</b>) Cycling performance of Li-S cells assembled with CNT-S and OCNT-S as cathodes at a current density of 0.1 C. (<b>b</b>) EIS spectra of the CNT-S and OCNT-S after 3 cycles and after 300 cycles.</p> Full article ">
21 pages, 2126 KiB  
Review
Recent Progress in Synthesis and Application of Activated Carbon for CO2 Capture
by Chong Yang Chuah and Afiq Mohd Laziz
C 2022, 8(2), 29; https://doi.org/10.3390/c8020029 - 14 May 2022
Cited by 7 | Viewed by 4606
Abstract
Greenhouse gas emissions to the atmosphere have been a long-standing issue that has existed since the Industrial Revolution. To date, carbon dioxide capture through the carbon capture, utilization, and storage approach has been one of the feasible options to combat the strong release [...] Read more.
Greenhouse gas emissions to the atmosphere have been a long-standing issue that has existed since the Industrial Revolution. To date, carbon dioxide capture through the carbon capture, utilization, and storage approach has been one of the feasible options to combat the strong release of carbon dioxide into the atmosphere. This review focuses in general on the utilization of activated carbon as a tool when performing the carbon-capture process. Activated carbon possesses a lower isosteric heat of adsorption and a stronger tolerance to humidity as compared to zeolites and metal–organic frameworks, despite the overall gas-separation performance of activated carbon being comparatively lower. In addition, investigations of the activation methods of activated carbon are summarized in this review, together with an illustration of CO2 adsorption performance, in the context of process simulations and pilot-plant studies. This is followed by providing future research directions in terms of the applicability of activated carbon in real CO2 adsorption processes. Full article
(This article belongs to the Collection Nanoporous Carbon Materials for Advanced Technological Applications)
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<p>Potential activation mechanism for the creation of activated carbon by intercalation of metals into the carbon lattice (C).</p> Full article ">Figure 2
<p>(<b>a</b>) Effect of the utilization of different sizes of the alkali metal ion on the average pore size of the developed activated carbon; (<b>b</b>) N<sub>2</sub> physisorption isotherm (77 K) and (<b>c</b>) CO<sub>2</sub> adsorption isotherm (273 K) of the activated carbon. Reprinted with permission from Ref. [<a href="#B49-carbon-08-00029" class="html-bibr">49</a>], Copyright 2016 Wiley-VCH Verlag GmbH &amp; Co., Germany; (<b>d</b>) Proposed reaction mechanism between Cs-activation and K-activation. Reprinted with permission from Ref. [<a href="#B50-carbon-08-00029" class="html-bibr">50</a>], Copyright 2020 Wiley-VCH Verlag GmbH &amp; Co., Germany.</p> Full article ">Figure 3
<p>Proposed activation mechanism for the proposed formation of activated carbon with the aid of ZnCl<sub>2</sub>. Reprinted with permission from Ref. [<a href="#B63-carbon-08-00029" class="html-bibr">63</a>] Creative Common License.</p> Full article ">Figure 4
<p>(<b>a</b>) Reaction scheme containing Ph, M formaldehyde; (<b>b</b>) N<sub>2</sub> physisorption isotherm of the developed activated carbon based on the reaction scheme in (<b>a</b>). Reprinted with permission from Ref. [<a href="#B36-carbon-08-00029" class="html-bibr">36</a>], Copyright 2019 Elsevier.</p> Full article ">Figure 5
<p>Measurement tools for effective investigation for CO<sub>2</sub>-based separation process: (<b>a</b>,<b>b</b>) equilibrium measurement via volumetric and gravimetric method; (<b>c</b>) dynamic breakthrough measurement. Reprinted with permission from Ref. [<a href="#B87-carbon-08-00029" class="html-bibr">87</a>], Copyright 2019 Elsevier, Amsterdam, The Netherlands.</p> Full article ">Figure 6
<p>Illustration for the calculation of working capacity (WC) for idealized (<b>a</b>) PSA and (<b>b</b>) TSA. Reprinted with permission from Ref. [<a href="#B17-carbon-08-00029" class="html-bibr">17</a>], Copyright 2018 Elsevier and Ref. [<a href="#B98-carbon-08-00029" class="html-bibr">98</a>], Copyright 2013 Royal Society of Chemistry, London, United Kingdom.</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic illustration of adsorption system for TSA operation; (<b>b</b>) regeneration heat and (<b>c</b>) power loss for effective CO<sub>2</sub> capture, with the use activated carbon (AC), monoethanolamine (MEA) and amine-appended adsorbent (PEI/silica) as the medium. Reprinted with permission from Ref. [<a href="#B99-carbon-08-00029" class="html-bibr">99</a>] Creative Common License.</p> Full article ">
13 pages, 1774 KiB  
Article
The Evaluation of Quality of the Co-Firing Process of Glycerine Fraction with Coal in the High Power Boiler
by Rafal Kozdrach and Andrzej Stepien
C 2022, 8(2), 28; https://doi.org/10.3390/c8020028 - 12 May 2022
Cited by 1 | Viewed by 2299
Abstract
The article presents the test results of the co-firing process of a glycerine fraction derived from the production of liquid biofuels (fatty acid methyl esters) with coal. The test was performed in industrial conditions using a steam boiler with a capacity of approx. [...] Read more.
The article presents the test results of the co-firing process of a glycerine fraction derived from the production of liquid biofuels (fatty acid methyl esters) with coal. The test was performed in industrial conditions using a steam boiler with a capacity of approx. 2 MW in one of the building materials manufacturing facilities. The process of co-firing a mixture of a 3% glycerine fraction and eco-pea coal was evaluated. The reference fuel was eco-pea coal. The combustion process, composition and temperature of exhaust gases were analyzed. Incorrect combustion of glycerine fraction may result in the emission of toxic, mutagenic, and carcinogenic substances, including polycyclic aromatic hydrocarbons. During the test of the combustion process of a mixture of glycerine fraction and eco-pea coal, a decrease in the content of O2, CO, and NOx was observed as well as an increase in the content of H2, CO2, and SO2 in the fumes and growth of temperature of exhaust gases in relation to the results of combustion to eco-pea coal. Reduced content of carbon monoxide in exhaust gases produced in the combustion could be caused by the high temperature of the grate or by an excessive amount of oxygen in the grate. The higher content of oxygen in glycerine changes the value of excess air coefficient and the combustion process is more effective. The bigger content of sulfur dioxide in burnt fuels containing the glycerine fraction could be caused by the presence of reactive ingredients contained in the glycerine fraction. The reduced content of nitrogen oxides in exhaust gases originating from the combustion of a fuel mixture containing a fraction of glycerine could be caused by lower content of nitrogen in the glycerine fraction submitted to co-firing with coal and also higher combustion temperature and amount of air in the combustion chamber. The increased content of carbon dioxide in exhaust gases originating from the combustion of fuel mixture containing glycerine fraction could be caused by the influence of glycerine on the combustion process. The increase of hydrogen in the glycerine fraction causes the flame temperature to grow and makes the combustion process more efficient. Full article
(This article belongs to the Section Combustion Emissions)
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<p>Steam boiler with a capacity of 2 MW in a silicate manufacturing plant in Żytkowice used for testing of the co-firing of coal with glycerine fraction; (<b>a</b>) view from the loading side, (<b>b</b>) view of the flue duct from the exhaust with a tube of gas analyzer.</p> Full article ">Figure 2
<p>The average temperature of exhaust gases during the test of combustion of coal and fuel composition consisting of coal and glycerine fraction.</p> Full article ">Figure 3
<p>Comparison of changes in the content of the carbon monoxide in exhaust gases produced during the test of the process of co-firing of coal and liquid waste (glycerine fraction) produced in biofuel production and combustion of eco-pea reference fuel.</p> Full article ">Figure 4
<p>Comparison of changes in the content of the sulfur dioxide in exhaust gases produced during the test of co-firing of coal and liquid waste (glycerine fraction) of biofuel production and the test of combustion of eco-pea reference fuel.</p> Full article ">Figure 5
<p>Comparison of changes in the content of nitrogen oxides in exhaust gases produced during the test of co-firing of coal and liquid waste (glycerine fraction) produced in biofuel production and of combustion of eco-coal reference fuel.</p> Full article ">Figure 6
<p>Comparison of changes in the content the oxygen in exhaust gases produced during the test of the process co-firing of eco-pea coal and liquid waste (glycerine fraction) produced in biofuel production and the process of combustion of eco-pea reference fuel.</p> Full article ">Figure 7
<p>Comparison of changes in the content of carbon dioxide in exhaust gases produced during the test ofthe process of co-firing of coal and liquid waste (glycerine fraction) produced in biofuel production and the test of combustion of eco-pea reference fuel.</p> Full article ">Figure 8
<p>Comparison of changes in the content of hydrogen in exhaust gases produced during the test of the process co-firing of coal and liquid waste (glycerine fraction) produced in biofuel production and the test of combustion of eco-pea reference fuel.</p> Full article ">
12 pages, 12257 KiB  
Article
Chemical Production of Graphene Oxide with High Surface Energy for Supercapacitor Applications
by Mehdi Karbak, Ouassim Boujibar, Sanaa Lahmar, Cecile Autret-Lambert, Tarik Chafik and Fouad Ghamouss
C 2022, 8(2), 27; https://doi.org/10.3390/c8020027 - 7 May 2022
Cited by 10 | Viewed by 3531
Abstract
The chemical exfoliation of graphite to produce graphene and its oxide is undoubtedly an economical method for scalable production. Carbon researchers have dedicated significant resources to developing new exfoliation methods leads to graphene oxides with high quality. However, only a few studies have [...] Read more.
The chemical exfoliation of graphite to produce graphene and its oxide is undoubtedly an economical method for scalable production. Carbon researchers have dedicated significant resources to developing new exfoliation methods leads to graphene oxides with high quality. However, only a few studies have been dedicated to the effect of the starting graphite material on the resulting GO. Herein, we have prepared two different GOs through chemical exfoliation of graphite materials having different textural and structural characteristics. All samples have been subjected to structural investigations and comprehensive characterizations using Raman, X-ray diffraction, scanning electron microscopy, TGA, N2 physisorption, and FTIR spectroscopy. Our results provide direct evidence of how the crystallite size of the raw graphite affects the oxidation degree, surface functionality, and sheet size of the resulting GO. Building on these significant understandings, the optimized GO achieves a highly specific capacitance of 191 F·g−1 at the specific current of 0.25 A·g−1 in an aqueous electrolyte. This superior electrochemical performance was attributed to several factors, among which the specific surface area was accessible to the electrolyte ions and oxygenated functional groups on the surface, which can significantly modify the electronic structure of graphene and further enhance the surface energy. Full article
(This article belongs to the Collection Young Carbon Scientists)
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<p>(<b>a</b>) The Raman spectra, (<b>b</b>) the X-ray diffraction patterns, (<b>c</b>) the N<sub>2</sub> adsorption isotherms, and (<b>d</b>) the pore size distribution obtained from all GOs prepared and from both graphite precursors.</p> Full article ">Figure 2
<p>The SEM micrographs of the KS6 (<b>a</b>), SFG6 (<b>b</b>), GO-KS6 (<b>c</b>), and GO-SFG6 (<b>d</b>).</p> Full article ">Figure 3
<p>(<b>a</b>) The TGA profiles of all samples. (<b>b</b>) The FTIR specters of all samples. (<b>c</b>) The digital pictures of the GOs dispersions in various solvents. (<b>d</b>) The digital pictures of contact angle measurements of water in GO-KS6 and GO-SFG6 samples.</p> Full article ">Figure 4
<p>(<b>a</b>) The CV comparison between KS6 graphite and GO-KS6, (<b>b</b>) the CV comparison between SFG6 graphite and GO-SFG6, (<b>c</b>) the CV curves of GO-KS6 at different scan rates, (<b>d</b>) the CV curves of GO-SFG6 at different scan rates, (<b>e</b>) the capacitance retention at different scan rates, and (<b>f</b>) the specific capacitance at different specific currents in the galvanostatic charge–discharge.</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) The capacitive contribution of GOKS6 at different scan rates; (<b>c</b>,<b>d</b>) the capacitive contribution of GO-SFG6 at different scan rates.</p> Full article ">
19 pages, 3793 KiB  
Review
Recent Advances on Capacitive Proximity Sensors: From Design and Materials to Creative Applications
by Reza Moheimani, Paniz Hosseini, Saeed Mohammadi and Hamid Dalir
C 2022, 8(2), 26; https://doi.org/10.3390/c8020026 - 5 May 2022
Cited by 20 | Viewed by 10490
Abstract
Capacitive proximity sensors (CPSs) have recently been a focus of increased attention because of their widespread applications, simplicity of design, low cost, and low power consumption. This mini review article provides a comprehensive overview of various applications of CPSs, as well as current [...] Read more.
Capacitive proximity sensors (CPSs) have recently been a focus of increased attention because of their widespread applications, simplicity of design, low cost, and low power consumption. This mini review article provides a comprehensive overview of various applications of CPSs, as well as current advancements in CPS construction approaches. We begin by outlining the major technologies utilized in proximity sensing, highlighting their characteristics and applications, and discussing their advantages and disadvantages, with a heavy emphasis on capacitive sensors. Evaluating various nanocomposites for proximity sensing and corresponding detecting approaches ranging from physical to chemical detection are emphasized. The matrix and active ingredients used in such sensors, as well as the measured ranges, will also be discussed. A good understanding of CPSs is not only essential for resolving issues, but is also one of the primary forces propelling CPS technology ahead. We aim to examine the impediments and possible solutions to the development of CPSs. Furthermore, we illustrate how nanocomposite fusion may be used to improve the detection range and accuracy of a CPS while also broadening the application scenarios. Finally, the impact of conductance on sensor performance and other variables that impact the sensitivity distribution of CPSs are presented. Full article
(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)
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<p>Number of published proximity-sensor-related papers during recent years.</p> Full article ">Figure 2
<p>Schematic of a capacitive proximity sensor.</p> Full article ">Figure 3
<p>Schematic of two basic CPT sensors [<a href="#B31-carbon-08-00026" class="html-bibr">31</a>]: (<b>a</b>) mutual capacitance sensor, and (<b>b</b>) self-capacitance sensor.</p> Full article ">Figure 4
<p>Application of proximity sensors proposed by Refs. [<a href="#B12-carbon-08-00026" class="html-bibr">12</a>,<a href="#B15-carbon-08-00026" class="html-bibr">15</a>,<a href="#B19-carbon-08-00026" class="html-bibr">19</a>,<a href="#B24-carbon-08-00026" class="html-bibr">24</a>,<a href="#B47-carbon-08-00026" class="html-bibr">47</a>]: (<b>a</b>) solid-shell curvy model, (<b>b</b>) 3D-printed thermoplastic polyurethane (TPU)/PVA model, (<b>c</b>) 3D printing a shell model before wiring, (<b>d</b>) signal of relative capacitance as measured by a choker sensor while the phrase “melody” is repeated four times, (<b>e</b>) recording pulse signal when a fiber-sensor is attached to the wrist, (<b>f</b>) optical images demonstrating the resulting flexible conductive films, (<b>g</b>) PAM (white) and PAM-FGO (black) fragments in optical photos of the healed specimens, (<b>h</b>) the PAM-FGO film-based proximity sensors allow for remote monitoring of human movements, (<b>i</b>) image of a graphene electrode-based wearable capacitive touch sensor, (<b>j</b>) optoelectronic characteristics of capacitive sensor, and (<b>k</b>) bendability and wearability of the proposed sensor.</p> Full article ">Figure 5
<p>Measurement setup proposed by Ref. [<a href="#B78-carbon-08-00026" class="html-bibr">78</a>] for CPSs.</p> Full article ">Figure 6
<p>Measured capacitance versus the vertical gap of the proposed CPS in Ref. [<a href="#B83-carbon-08-00026" class="html-bibr">83</a>].</p> Full article ">Figure 7
<p>3D representation of capacitance changes for three shapes: cone, ring, and sphere [<a href="#B24-carbon-08-00026" class="html-bibr">24</a>].</p> Full article ">Figure 8
<p>Construction process of IDC CPS sensor proposed by Ref. [<a href="#B85-carbon-08-00026" class="html-bibr">85</a>].</p> Full article ">Figure 9
<p>Measurement setup and the results proposed by Refs. [<a href="#B15-carbon-08-00026" class="html-bibr">15</a>,<a href="#B79-carbon-08-00026" class="html-bibr">79</a>,<a href="#B81-carbon-08-00026" class="html-bibr">81</a>,<a href="#B88-carbon-08-00026" class="html-bibr">88</a>]: (<b>a</b>) touchless piano being played optically with a human finger hovering 40 mm above the keyboard, (<b>b</b>) schematic representation of sensor sensing, (<b>c</b>) increase in relative capacitance with response to an approaching object, (<b>d</b>) performance comparison of the proposed setup with previous works, (<b>e</b>) printed proximity sensors on fabric with filled design, (<b>f</b>) printed proximity sensors on fabric with spiral design, (<b>g</b>) printed proximity sensors on fabric with loop design, (<b>h</b>) maximum detection distance as a function of the proximity sensor width, (<b>i</b>) capacitance change simulation via COMSOL, (<b>j</b>) sandwich structure of CPS with the AgNWs stripes serving as the row and column electrodes, placed orthogonally on the top and bottom PET substrates, (<b>k</b>) capacitance variation as a function of vertical distance from the intersection, (<b>l</b>) contour graphics depicting the estimated capacitance change profile of a center pixel and its four closest neighbors with varying degrees of sensitivity, (<b>m</b>) proximity sensing depiction of two metal bars, the intersections of which are denoted by dashed black boxes, (<b>n</b>) relative capacitance change vs. response time during four cycles, (<b>o</b>) a schematic representation of a TPU/carbon nanotube proximity sensor configuration, (<b>p</b>) noise minimization using semi-planner 45° probes, and (<b>q</b>) mutual capacitance becomes apparent when an item is moved near to the sensor. Shunting the initial electric lines results in a highly strong and distributed fring field between the object, film, and probes, resulting in a dramatic decrease in capacitance. (<b>r</b>) Comparing the maximum sensitivity of various weight percentages of carbon nanotubes (CNTs).</p> Full article ">
23 pages, 2606 KiB  
Article
Pore Structure and Gas Diffusion Features of Ionic Liquid-Derived Carbon Membranes
by Ourania Tzialla, Anastasios Labropoulos, Georgios Pilatos, Georgios Romanos and Konstantinos G. Beltsios
C 2022, 8(2), 25; https://doi.org/10.3390/c8020025 - 29 Apr 2022
Cited by 1 | Viewed by 2024
Abstract
In the present study, the concept of Ionic Liquid (IL)-mediated formation of carbon was applied to derive composite membranes bearing a nanoporous carbon phase within their separation layer. Thermolytic carbonization of the supported ionic liquid membranes, prepared by infiltration of the IL 1-methyl-3-butylimidazolium [...] Read more.
In the present study, the concept of Ionic Liquid (IL)-mediated formation of carbon was applied to derive composite membranes bearing a nanoporous carbon phase within their separation layer. Thermolytic carbonization of the supported ionic liquid membranes, prepared by infiltration of the IL 1-methyl-3-butylimidazolium tricyanomethanide into the porous network of Vycor® porous glass tubes, was applied to derive the precursor Carbon/Vycor® composites. All precursors underwent a second cycle of IL infiltration/pyrolysis with the target to finetune the pore structural characteristics of the carbonaceous matter nesting inside the separation layer. The pore structural assets and evolution of the gas permeation properties and separation efficiency of the as-derived composite membranes were investigated with reference to the duration of the second infiltration step. The transport mechanisms of the permeating gases were elucidated and correlated to the structural characteristics of the supported carbon phase and the analysis of LN2 adsorption isotherms. Regarding the gas separation efficiency of the fabricated Carbon/Vycor® composite membranes, He/CO2 ideal selectivity values as high as 4.31 at 1 bar and 25 °C and 4.64 at 0.3 bar and 90 °C were achieved. In addition, the CO2/N2 ideal selectivity becomes slightly improved for longer second-impregnation times. Full article
(This article belongs to the Collection Nanoporous Carbon Materials for Advanced Technological Applications)
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<p>Apparatus for conduction of thermolytic processes on supported ionic liquid membranes: (1) gas cylinder (Ar); (2) mass flow controller; (3) pressure gauge; (4) refractory tube; (5) PID temperature controller; (6) tubular furnace; (7) heating zone; (8) ceramic capsule; (9) vent.</p> Full article ">Figure 2
<p>Permeance of He, N<sub>2</sub>, CO, CO<sub>2</sub>, C<sub>3</sub>H<sub>6</sub>, and C<sub>4</sub>H<sub>8</sub> gases through the CΜ_1 membrane at 25 °C, with respect to the pressure.</p> Full article ">Figure 3
<p>Permeance of He, H<sub>2</sub>, N<sub>2</sub>, and CO<sub>2</sub> gases through the CΜ_2 membrane at 90 °C, with respect to the pressure.</p> Full article ">Figure 4
<p>Permeance of (<b>a</b>) He, N<sub>2</sub>, CO<sub>2</sub>, and SF<sub>6</sub> gases at 25 °C and (<b>b</b>) CO<sub>2</sub> gas at 25, 50, and 90 °C, through the CΜ_3 membrane, with respect to the pressure.</p> Full article ">Figure 5
<p>Permeance of (<b>a</b>) H<sub>2</sub> and Ν<sub>2</sub> gases at 25 and 90 °C and (<b>b</b>) H<sub>2</sub>, He, Ν<sub>2</sub>, and CO<sub>2</sub> gases at 90 °C, through the CΜ_3 membrane, as a function of the pressure.</p> Full article ">Figure 6
<p>Permeance of H<sub>2</sub>, He, Ν<sub>2</sub>, and CO<sub>2</sub> gases through the CΜ_3 membrane at 90 °C, with respect to their kinetic diameter.</p> Full article ">Figure 7
<p>Permeance of (<b>a</b>) He, N<sub>2</sub>, CO<sub>2</sub>, H<sub>2</sub>, C<sub>3</sub>H<sub>6</sub>, C<sub>4</sub>H<sub>8</sub>, and SF<sub>6</sub> gases at 25 °C and (<b>b</b>) He, Ν<sub>2</sub>, CO<sub>2</sub>, and SF<sub>6</sub> gases at 25, 70, and 100 °C, through the CM4 membrane, as a function of the pressure.</p> Full article ">Figure 8
<p>Permeance of (<b>a</b>) He, Ν<sub>2</sub>, CO<sub>2</sub>, and CH<sub>4</sub> gases at 100 °C and (<b>b</b>) Ν<sub>2</sub> and CO<sub>2</sub> gases at 100 °C, through the CM5 membrane, as a function of the pressure.</p> Full article ">Figure 9
<p>Ideal selectivity values of the gas pairs (<b>a</b>) He/N<sub>2</sub> and (<b>b</b>) CO<sub>2</sub>/N<sub>2</sub>, with respect to the average values of He permeance for all Carbon/Vycor<sup>®</sup> membranes, that have been acquired over the entire feed pressure range applied.</p> Full article ">Figure 10
<p>(<b>a</b>) N<sub>2</sub> adsorption isotherms (at 77 K) for the CM1, CM4, and CM6 membranes and the PSD curves from the adsorption and desorption branch for (<b>b</b>) CM1, (<b>c</b>) CM4, and (<b>d</b>) CM6 of the respective adsorption isotherms, by NLDFT analysis for cylindrical silica pores.</p> Full article ">
11 pages, 2107 KiB  
Article
Laser-Assisted Growth of Carbon-Based Materials by Chemical Vapor Deposition
by Abiodun Odusanya, Imteaz Rahaman, Pallab Kumar Sarkar, Abdelrahman Zkria, Kartik Ghosh and Ariful Haque
C 2022, 8(2), 24; https://doi.org/10.3390/c8020024 - 26 Apr 2022
Cited by 1 | Viewed by 3323
Abstract
Carbon-based materials (CBMs) such as graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have received a great deal of attention in recent years due to their unique electronic, optical, thermal, and mechanical properties. CBMs have been grown using [...] Read more.
Carbon-based materials (CBMs) such as graphene, carbon nanotubes (CNT), highly ordered pyrolytic graphite (HOPG), and pyrolytic carbon (PyC) have received a great deal of attention in recent years due to their unique electronic, optical, thermal, and mechanical properties. CBMs have been grown using a variety of processes, including mechanical exfoliation, pulsed laser deposition (PLD), and chemical vapor deposition (CVD). Mechanical exfoliation creates materials that are irregularly formed and tiny in size. On the other hand, the practicality of the PLD approach for large-area high-quality CMB deposition is quite difficult. Thus, CVD is considered as the most effective method for growing CBMs. In this paper, a novel pulsed laser-assisted chemical vapor deposition (LCVD) technique was explored to determine ways to reduce the energy requirements to produce high quality CBMs. Different growth parameters, such as gas flow rate, temperature, laser energy, and deposition time were considered and studied thoroughly to analyze the growth pattern. CBMs are grown on Si and Cu substrates, where we find better quality CBM films on Cu as it aids the surface solubility of carbon. Raman spectroscopy confirms the presence of high-quality PyC which is grown at a temperature of 750 °C, CH4 gas flow rate of 20 sccm, a laser frequency of 10 Hz, and an energy density of 0.116 J/cm2 per pulse. It is found that the local pulsed-laser bombardment helps in breaking the carbon-hydrogen bonds of CH4 at a much lower substrate temperature than its thermal decomposition temperature. There is no significant change in the 2D peak intensity in the Raman spectrum with the further increase in temperature which is the indicator of the number of the graphene layer. The intertwined graphene flakes of the PyC are observed due to the surface roughness, which is responsible for the quenching in the Raman 2D signal. These results will provide the platform to fabricate a large area single layer of graphene, including the other 2D materials, on different substrates using the LCVD technique. Full article
(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)
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<p>Schematic diagram of the deposition process in the chamber.</p> Full article ">Figure 2
<p>Raman spectra of pristine high−quality graphene.</p> Full article ">Figure 3
<p>Raman spectra at a constant CH<sub>4</sub> flow rate at 10 sccm and different deposition temperatures.</p> Full article ">Figure 4
<p>(<b>a</b>–<b>o</b>) Raman spectra at constant CH<sub>4</sub> flow rate at 20 sccm with different deposition temperatures on Cu and Si substrates.</p> Full article ">Figure 4 Cont.
<p>(<b>a</b>–<b>o</b>) Raman spectra at constant CH<sub>4</sub> flow rate at 20 sccm with different deposition temperatures on Cu and Si substrates.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>f</b>) Raman spectra at different deposition times with a constant CH<sub>4</sub> flow rate of 20 sccm and 850 °C deposition temperature.</p> Full article ">Figure 6
<p>(<b>a</b>–<b>c</b>) Raman data plots showing the effect of: (<b>a</b>) no laser pulses; (<b>b</b>) laser incident spot; (<b>c</b>) laser non-incident spot on PyC deposition.</p> Full article ">
13 pages, 2296 KiB  
Article
On the Problem of “Super” Storage of Hydrogen in Graphite Nanofibers
by Yury S. Nechaev, Evgeny A. Denisov, Alisa O. Cheretaeva, Nadezhda A. Shurygina, Ekaterina K. Kostikova, Andreas Öchsner and Sergei Yu. Davydov
C 2022, 8(2), 23; https://doi.org/10.3390/c8020023 - 29 Mar 2022
Cited by 2 | Viewed by 2720
Abstract
This article is devoted to some fundamental aspects of “super” storage in graphite nanofibers (GNF) of “reversible” (~20–30 wt.%) and “irreversible” hydrogen (~7–10 wt.%). Extraordinary results for hydrogen “super” storage were previously published by the group of Rodriguez and Baker at the turn [...] Read more.
This article is devoted to some fundamental aspects of “super” storage in graphite nanofibers (GNF) of “reversible” (~20–30 wt.%) and “irreversible” hydrogen (~7–10 wt.%). Extraordinary results for hydrogen “super” storage were previously published by the group of Rodriguez and Baker at the turn of the century, which been unable to be reproduced or explained in terms of physics by other researchers. For the first time, using an efficient method of processing and analysis of hydrogen thermal desorption spectra, the characteristics of the main desorption peak of “irreversible” hydrogen in GNF were determined: the temperature of the highest desorption rate (Tmax = 914–923 K), the activation energy of the desorption process (Q ≈ 40 kJ mol−1), the pre-exponential rate constant factor (K0 ≈ 2 × 10−1 s−1), and the amount of hydrogen released (~8 wt.%). The physics of hydrogen “super” sorption includes hydrogen diffusion, accompanied by the “reversible” capture of the diffusant by certain sorption “centers”; the hydrogen spillover effect, which provides local atomization of gaseous H2 during GNF hydrogenation; and the Kurdjumov phenomenon on thermoelastic phase equilibrium. It is shown that the above-mentioned extraordinary data on the hydrogen “super” storage in GNFs are neither a mistake nor a mystification, as most researchers believe. Full article
(This article belongs to the Special Issue Carbon Materials for Physical and Chemical Hydrogen Storage)
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Full article ">Figure 1
<p>Processing (using the technique [<a href="#B20-carbon-08-00023" class="html-bibr">20</a>]) of thermal desorption (TDS) and thermogravimetric (TG) data from [<a href="#B5-carbon-08-00023" class="html-bibr">5</a>] for “super” desorption of “irreversible” hydrogen from GNF samples with a herringbone structure (see Figure 2 in [<a href="#B5-carbon-08-00023" class="html-bibr">5</a>]). (<b>a</b>) Fitting by three Gaussians (peaks ##1–3) of the TDS spectrum (β = 0.17 K s<sup>−1</sup>) for samples subjected to hydrogenation in gaseous H<sub>2</sub> (at 300 K, 11–4 MPa, 24 h); the red curve corresponds to the sum of three peaks. (<b>b</b>) Fitting by three Gaussians (peaks ##1–3) of the temperature derivative of the TG spectrum for samples subjected to hydrogenation in gaseous H<sub>2</sub> (at 300 K, 11–4 MPa, 24 h) and subsequent heating (β = 0.17 K/s) in He; the red curve corresponds to the sum of three peaks.</p> Full article ">Figure 2
<p>Processing (in the first-order reaction approximation) of kinetic data from [<a href="#B4-carbon-08-00023" class="html-bibr">4</a>] on the change in hydrogen pressure in the working chamber during “super” adsorption of “reversible” hydrogen (at a temperature of about 300 K) for three samples of graphite nanofibers with a “herringbone” structure.</p> Full article ">Figure 3
<p>Processing of thermodynamic and kinetic data from [<a href="#B10-carbon-08-00023" class="html-bibr">10</a>] on the “super” sorption of “reversible” hydrogen (~15 wt.%) for GNF samples with a “plate” structure (see <a href="#carbon-08-00023-f004" class="html-fig">Figure 4</a>) subjected to hydrogenation (24 h) in gaseous molecular hydrogen (at a pressure of 12 MPa and a temperature of 300 K) and subsequent dehydrogenation with a decrease in hydrogen pressure to 0.1 MPa: (<b>a</b>) processing of adsorption data in the approximation of the sorption isotherm of the Henry–Langmuir type [<a href="#B17-carbon-08-00023" class="html-bibr">17</a>]; (<b>b</b>) processing of thermal desorption data in the first-order reaction approximation.</p> Full article ">Figure 4
<p>A micrograph of graphite nanofibers [<a href="#B11-carbon-08-00023" class="html-bibr">11</a>] subjected to hydrogenation (24 h) in gaseous molecular hydrogen at a pressure of 12 MPa and a temperature of 300 K to a content of “reversible” hydrogen of ~17 wt.%. The sizes of lenticular nanocavities in one of the nanofibers are shown, which are necessary for estimating (see works [<a href="#B2-carbon-08-00023" class="html-bibr">2</a>,<a href="#B17-carbon-08-00023" class="html-bibr">17</a>,<a href="#B18-carbon-08-00023" class="html-bibr">18</a>,<a href="#B24-carbon-08-00023" class="html-bibr">24</a>]) the volume of such nanocavities and the density of “reversible” hydrogen localized in them.</p> Full article ">Figure 5
<p>Approximation by two Gaussians of the thermal desorption spectrum (kinetic curves 0.08 wt.% and 0.02 wt.% from Figure 18 in [<a href="#B13-carbon-08-00023" class="html-bibr">13</a>]) for sample #3 GNF with a herringbone structure (Table 3 in [<a href="#B13-carbon-08-00023" class="html-bibr">13</a>]), subjected to the action of gaseous molecular hydrogen at a pressure of 13 MPa and subsequent heating from 293 K (β = 0.10 K s<sup>−1</sup>) to a stop and isothermal holding at 1173 K.</p> Full article ">
15 pages, 497 KiB  
Review
A Review of Embodied Carbon in Landscape Architecture. Practice and Policy
by Anastasia Nikologianni, Theodoros Plowman and Benjamin Brown
C 2022, 8(2), 22; https://doi.org/10.3390/c8020022 - 26 Mar 2022
Cited by 5 | Viewed by 4437
Abstract
This paper aims to discuss the importance of the climate crisis and embodied carbon in the landscape architecture sector. The study was carried out in a multiprofessional team with the collaboration of the Landscape Institute (LI) Chartered Body of Landscape Architecture, UK, and [...] Read more.
This paper aims to discuss the importance of the climate crisis and embodied carbon in the landscape architecture sector. The study was carried out in a multiprofessional team with the collaboration of the Landscape Institute (LI) Chartered Body of Landscape Architecture, UK, and experts in the field. Using the expertise and knowledge of professionals as well as existing landscape examples and pioneering tools on carbon, this review paper focuses on the importance of low/net-zero carbon landscapes for our cities and regions and the ways in which these can contribute to the broader health and wellbeing of our communities. Examining the current situation on carbon methodologies and the latest knowledge on carbon calculations through a landscape lens, the paper explores why embodied carbon is important for open spaces/landscapes and the necessary policies to support a more efficient implementation of these concepts. The intensity of recent environmental challenges demands action. This review highlights the need for holistic approaches that integrate embodied carbon calculations on large-scale landscape design. Using the innovative example of the Pathfinder App, a carbon calculation tool, as well as other similar software, this paper argues that more steps are needed towards the calculation and adaptation of CO2 emissions resulting from design, construction and materials in landscape schemes. The low availability of carbon calculation tools, specially developed for landscape schemes, is a major concern for the profession as it creates several issues with the sustainable development of the landscape projects as well as fragmented policies that exclude spatial and open spaces. Even though carbon calculation and embodied carbon are being calculated in buildings or materials, it is a relatively new area when it comes to land, the landscape and open and green space, and therefore, this study will present and discuss some of the pioneering carbon calculation tools focusing on landscape projects. Full article
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<p>Example of a scorecard with the use of the Pathfinder tool, demonstrating the embodied and sequestered carbon over 50 years. Source: CMG Architects.</p> Full article ">
18 pages, 1793 KiB  
Article
Engineering of Nanostructured Carbon Catalyst Supports for the Continuous Reduction of Bromate in Drinking Water
by João M. Cunha Bessa da Costa, José R. Monteiro Barbosa, João Restivo, Carla A. Orge, Anabela Nogueira, Sérgio Castro-Silva, Manuel F. Ribeiro Pereira and Olívia S. Gonçalves Pinto Soares
C 2022, 8(2), 21; https://doi.org/10.3390/c8020021 - 22 Mar 2022
Cited by 3 | Viewed by 3533
Abstract
Recent works in the development of nanostructured catalysts for bromate reduction in drinking water under hydrogen have highlighted the importance of the properties of the metallic phase support in their overall performance. Since most works in catalyst development are carried out in powder [...] Read more.
Recent works in the development of nanostructured catalysts for bromate reduction in drinking water under hydrogen have highlighted the importance of the properties of the metallic phase support in their overall performance. Since most works in catalyst development are carried out in powder form, there is an overlooked gap in the correlation between catalyst support properties and performance in typical continuous applications such as fixed bed reactors. In this work, it is shown that the mechanical modification of commercially available carbon nanotubes, one of the most promising supports, can significantly enhance the activity of the catalytic system when tested in a stirred tank reactor, but upon transition to a fixed bed reactor, the formation of preferential pathways for the liquid flow and high pressure drops were observed. This effect could be minimized by the addition of an inert filler to increase the bed porosity; however, the improvement in catalytic performance when compared with the as-received support material was not retained. The operation of the continuous catalytic system was then optimized using a 1 wt.% Pd catalyst supported on the as-received carbon nanotubes. Effluent and hydrogen flow rates as well as catalyst loadings were systematically optimized to find an efficient set of parameters for the operation of the system, regarding its catalytic performance, capacity to treat large effluent flows, and minimization of catalyst and hydrogen requirements. Experiments carried out in the presence of distilled water as a reaction medium demonstrate that bromate can be efficiently removed from the liquid phase, whereas when using a real water matrix, a tendency for the deactivation of the catalyst over time was more apparent throughout 200 flow passages over the catalytic bed, which was mostly attributed to the competitive adsorption of inorganic matter on the catalyst active centers, or the formation of mineral deposits blocking access to the catalyst. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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<p>Schematic representation of the reactor system used for reduction of bromate in continuous mode.</p> Full article ">Figure 2
<p>Dimensionless bromate concentration during semi-batch hydrogen reduction over 1 wt.% Pd catalysts on different carbon supports. (H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C<sub>0</sub> (BrO<sub>3</sub><sup>−</sup>) = 200 ppb, 0.125 g<sub>CAT</sub> L<sup>−1</sup>).</p> Full article ">Figure 3
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalysts 1 wt.% Pd/MWCNT-O, 1 wt.% Pd/MWCNT@N and 1 wt.% Pd/MWCNT-BM mixed with 0.500 mm carborundum under H<sub>2</sub>. (Q = 5 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 4
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under different H<sub>2</sub> flow rates. (Q = 5 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 5
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub> using different feed flow rates of water containing bromate. (200 mg<sub>CAT</sub>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>-</sup>) = 200 ppb).</p> Full article ">Figure 6
<p>Bromate concentration (ppb) during continuous hydrogen reduction using different catalyst loadings of 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub>. (Q = 5 mL min<sup>−1</sup>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 7
<p>Dimensionless bromate concentration during semi-batch hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-BM using different types of water. (H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C<sub>0</sub> (BrO<sub>3</sub><sup>−</sup>) = 200 ppb, 0.125 g<sub>CAT</sub> L<sup>−1</sup>).</p> Full article ">Figure 8
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub> using distilled water and water from a water treatment plant. (Q = 7.8 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, H<sub>2</sub> = 12.5 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">
13 pages, 2014 KiB  
Article
Chemical Reduction of GO: Comparing Hydroiodic Acid and Sodium Borohydride Chemical Approaches by X-ray Photoelectron Spectroscopy
by Wei Liu and Giorgio Speranza
C 2022, 8(2), 20; https://doi.org/10.3390/c8020020 - 22 Mar 2022
Cited by 3 | Viewed by 3145
Abstract
The efficiency of two wet chemical processes based on hydroiodic acid (HI) and sodium borohydride (NaBH4) used to reduce graphene oxide (GO) have been studied. At this aim, the oxygen abundance of reduced graphene oxide (rGO) was studied as a function [...] Read more.
The efficiency of two wet chemical processes based on hydroiodic acid (HI) and sodium borohydride (NaBH4) used to reduce graphene oxide (GO) have been studied. At this aim, the oxygen abundance of reduced graphene oxide (rGO) was studied as a function of the reductant concentration. A number of rGO samples were produced and their chemical compositions were studied using X-ray photoelectron spectroscopy. The analyses show that the reduction of the oxygen concentration proceeds non-linearly. At the beginning, when pristine GO is utilized a higher extent of reduction is obtained. The oxygen concentration decreases from ~32% to 10.5% by increasing the HI concentration to 0.24 M. A steeper reduction was observed for NaBH4, where the oxygen concentration lowers to ~13.6% using just 50 mg of NaBH4. Next, reduction reactions performed with increasing amounts of reductants in aqueous suspensions show a progressive saturation effect, indicating a limit in the final oxygen concentration. We obtained a residual oxygen concentration of 5.3% using 7.58 M of HI and 8.6% with 1200 mg of NaBH4. The chemical analysis highlights that the reduction of the oxygen concentration in rGO samples is mainly derived from the cleavage of C-OH bonds and the next reconstruction of C-C bonds. Full article
(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)
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<p>(<b>A</b>) Wide spectra of rGO samples synthesized using HI at increasing concentrations. The wide spectrum of GO is plotted as a reference. (<b>B</b>) Wide spectra of rGO samples synthesized using NaBH<sub>4</sub> at increasing concentrations. All the spectra are normalized to the C 1s intensities to highlight O 1s variations and shifted along the <span class="html-italic">Y</span> axis to better show the spectral features. The main spectral components are indicated in both figures.</p> Full article ">Figure 2
<p>(<b>A</b>) C 1s and (<b>B</b>) O 1s core-lines of the S_H2 sample reported together with their peak fitting.</p> Full article ">Figure 3
<p>(<b>A</b>) C 1s and (<b>B</b>) O 1s core-lines of the S_N3 sample reported together with their peak fitting.</p> Full article ">Figure 4
<p>Trend of the total oxygen concentrations (blue) and of the concentration of oxygen derived from the C1s fit and carbon oxidized fit components of carbon (red) in rGO reduced using HI (<b>A</b>) or NaBH<sub>4</sub> (<b>B</b>).</p> Full article ">Figure 5
<p>(<b>A</b>) Model of the chemical reaction occurring between oxygen-containing aromatic groups and HI; (<b>B</b>) progression of carbonyl group reduction until the complete depletion of B–H bonds and boron oxidation.</p> Full article ">
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