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Keywords = defect free graphene

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16 pages, 10306 KiB  
Article
Fabrication and Characterization of Flexible pH Sensors Based on Pulsed Laser-Ablated Graphene/MoS2 Interdigitated Electrodes
by Zhaochi Chen, Chengche Liu and Minh-Quang Tran
Nanomaterials 2025, 15(14), 1115; https://doi.org/10.3390/nano15141115 - 18 Jul 2025
Viewed by 432
Abstract
Point-of-care (POC) diagnostic technologies have become essential for the real-time monitoring and management of chronic wounds, where maintaining a moist environment and controlling pH levels are critical for effective healing. In this study, a flexible pH sensor based on a graphene/molybdenum disulfide (graphene/MoS [...] Read more.
Point-of-care (POC) diagnostic technologies have become essential for the real-time monitoring and management of chronic wounds, where maintaining a moist environment and controlling pH levels are critical for effective healing. In this study, a flexible pH sensor based on a graphene/molybdenum disulfide (graphene/MoS2) composite interdigitated electrode (IDE) structure was fabricated using pulsed laser ablation. The pH sensor, with an active area of 30 mm × 30 mm, exhibited good adhesion to the polyethylene terephthalate (PET) substrate and maintained structural integrity under repeated bending cycles. Precise ablation was achieved under optimized conditions of 4.35 J/cm2 laser fluence, a repetition rate of 300 kHz, and a scanning speed of 500 mm/s, enabling the formation of defect-free IDE arrays without substrate damage. The influence of laser processing parameters on the surface morphology, electrical conductivity, and wettability of the composite thin films was systematically characterized. The fabricated pH sensor exhibited high sensitivity (~4.7% change in current per pH unit) across the pH 2–10 range, rapid response within ~5.2 s, and excellent mechanical stability under 100 bending cycles with negligible performance degradation. Moreover, the sensor retained > 95% of its stable sensitivity after 7 days of ambient storage. Furthermore, the pH response behavior was evaluated for electrode structures with different pitches, demonstrating that structural design parameters critically impact sensing performance. These results offer valuable insights into the scalable fabrication of flexible, wearable pH sensors, with promising applications in wound monitoring and personalized healthcare systems. Full article
(This article belongs to the Special Issue Laser-Based Nano Fabrication and Nano Lithography: Second Edition)
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55 pages, 20925 KiB  
Review
Current Trends and Emerging Strategies in Friction Stir Spot Welding for Lightweight Structures: Innovations in Tool Design, Robotics, and Composite Reinforcement—A Review
by Suresh Subramanian, Elango Natarajan, Ali Khalfallah, Gopal Pudhupalayam Muthukutti, Reza Beygi, Borhen Louhichi, Ramesh Sengottuvel and Chun Kit Ang
Crystals 2025, 15(6), 556; https://doi.org/10.3390/cryst15060556 - 11 Jun 2025
Cited by 1 | Viewed by 1945
Abstract
Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships [...] Read more.
Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships between microstructure, properties, and performance under load. FSSW offers numerous benefits over traditional welding, particularly for joining both similar and dissimilar materials. Key process parameters, including tool design, rotational speed, axial force, and dwell time, are discussed for their impact on weld quality. Innovations in robotics are enhancing FSSW’s accuracy and efficiency, while numerical simulations aid in optimizing process parameters and predicting material behavior. The addition of nano/microparticles, such as carbon nanotubes and graphene, has further improved weld strength and thermal stability. This review identifies areas for future research, including refining robotic programming, using artificial intelligence for autonomous welding, and exploring nano/microparticle reinforcement in FSSW composites. FSSW continues to advance solid-state joining technologies, providing critical insights for optimizing weld quality in sheet material applications. Full article
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12 pages, 3584 KiB  
Article
The Coordination of Lanthanide Atoms with Stone–Wales Defects on Graphene: A Cluster DFT Analysis Using ECP Pseudopotentials
by Vladimir A. Basiuk and Elena V. Basiuk
Surfaces 2025, 8(2), 32; https://doi.org/10.3390/surfaces8020032 - 9 May 2025
Cited by 1 | Viewed by 554
Abstract
The main goal of the present study was to verify in detail whether the use of a cluster model for Stone–Wales (SW) defect-containing graphene (SWG) to study the adsorption of Ln atoms yields results similar to those previously obtained by employing a periodic [...] Read more.
The main goal of the present study was to verify in detail whether the use of a cluster model for Stone–Wales (SW) defect-containing graphene (SWG) to study the adsorption of Ln atoms yields results similar to those previously obtained by employing a periodic model. We addressed this question by analyzing the optimized geometries of SWG + Ln complexes, their formation energies, and selected electronic parameters (in particular, the frontier orbital energies and atomic charges and spins). Within the frame of density functional theory, we used the computational methodology of the PBE-D2/DNP theoretical level using ECP pseudopotentials. The most important conclusion is that the use of a cluster model gives qualitatively similar results to those of the periodic model. While the corresponding plots of the dihedral angles θ versus the Ln atoms differ considerably, the two models have many common features in the trends of the bonding strength despite the use of two very different theoretical tools, namely periodic (plane waves) versus cluster calculations (localized basis sets). In comparing the results for SW defect-free and SW defect-containing cluster models, it is evident that SW defects serve as much more preferential adsorption sites compared to the conditions in the defect-free graphene model. Full article
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17 pages, 4655 KiB  
Article
Modification of Polyurethane/Graphene Oxide with Dielectric Barrier Plasma Treatment for Proper Coating Adhesion on Fiberglass
by Oscar Xosocotla, Bernardo Campillo, Horacio Martínez, María del Pilar Rodríguez-Rojas, Rafael Campos and Victoria Bustos-Terrones
Coatings 2025, 15(4), 411; https://doi.org/10.3390/coatings15040411 - 30 Mar 2025
Cited by 1 | Viewed by 639
Abstract
Wind turbine blades are made from fiberglass, whose faces are eroded due to environmental conditions. Polyurethane (PU) coatings are broadly used in several types of coatings due to their strong adhesion. However, their inferior mechanical properties limit their application on fiberglass. In this [...] Read more.
Wind turbine blades are made from fiberglass, whose faces are eroded due to environmental conditions. Polyurethane (PU) coatings are broadly used in several types of coatings due to their strong adhesion. However, their inferior mechanical properties limit their application on fiberglass. In this study, graphene oxide (GO) was modified through a dielectric barrier plasma (DBP) treatment at atmospheric pressure to improve the dispersion of GO in PU and increase its adhesion to fiberglass (GF) substrates, resulting in excellent adhesion properties of the PU/GO coating on fiberglass. Additionally, PU/GO coatings are crucial for preventing and protecting against erosion. The results obtained for the intensity ratio of the ID/IG peaks observed through Raman spectroscopy exhibited that the plasma treatment increased the defects in the GO structure through covalent and non-covalent interactions with the PU. Contact angle tests and surface free energy measurements indicated the deoxygenation of the GO structure, enhancing its dispersion in the PU matrix, as observed through XRD. The plasma treatment increased the PU/GO adhesion by 27.6% after 10 min of treatment, suggesting that more defects in the GO structure were correlated with greater adhesion strength. Full article
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11 pages, 5855 KiB  
Article
Graphene-Supported Cun (n = 5, 6) Clusters for CO2 Reduction Catalysis
by Yanling Guo, Lisu Zhang, Yanbo Zou, Xingguo Wang and Qian Ning
Nanomaterials 2025, 15(6), 445; https://doi.org/10.3390/nano15060445 - 15 Mar 2025
Viewed by 642
Abstract
In recent years, driven by the swift progress in nanotechnology and catalytic science, researchers in the field of physical chemistry have been vigorously exploring novel catalysts designed to enhance the efficiency and selectivity of a broad spectrum of chemical reactions. Against this backdrop, [...] Read more.
In recent years, driven by the swift progress in nanotechnology and catalytic science, researchers in the field of physical chemistry have been vigorously exploring novel catalysts designed to enhance the efficiency and selectivity of a broad spectrum of chemical reactions. Against this backdrop, Cu clusters supported on defective graphene (Cun@GR, where n = 5, 6) function as two-dimensional nanocatalysts, demonstrating exceptional catalytic activity in the electrochemical reduction of carbon dioxide (CO2RR). A comprehensive investigation into the catalytic properties of these materials has been undertaken using density functional theory (DFT) calculations. By tailoring the configuration of Cun@GR, specific reduction products such as CH4 and CH3OH can be selectively produced. The product selectivity is quantitatively analyzed through free energy calculations. Remarkably, the Cu5@GR catalyst enables the electrochemical reduction of CO2 to CH4 with a significantly low overpotential of −0.31 eV. Furthermore, the overpotential of the hydrogen evolution reaction (HER) is higher than that of the conversion of CO2 to CH4; hence, the HER is unlikely to interfere and impede the efficiency of CH4 production. This study demonstrates that Cu5@GR offers low overpotential and high catalytic efficiency, providing a theoretical foundation for the design and experimental synthesis of composite nanocatalysts. Full article
(This article belongs to the Section 2D and Carbon Nanomaterials)
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14 pages, 4308 KiB  
Article
Microwave Plasma-Driven Synthesis of Graphene and N-Graphene at a Gram Scale
by Neli Bundaleska, Edgar Felizardo, Ana Dias, Ana Maria Ferraria, Ana Maria Botelho do Rego, Janez Zavašnik, Uros Cvelbar, Miroslav Abrashev, Jivko Kissovski, Amélia Almeida, Luís Lemos Alves, Bruno Gonçalves and Elena Tatarova
Processes 2025, 13(1), 196; https://doi.org/10.3390/pr13010196 - 12 Jan 2025
Viewed by 1471
Abstract
The large-scale microwave plasma synthesis of graphene and nitrogen-doped graphene with tailored structural properties, crucial for their successful usage applications, has been demonstrated. The developed atmospheric pressure plasma method offers several advantages, including the continuous production of high-quality, free-standing graphene without the use [...] Read more.
The large-scale microwave plasma synthesis of graphene and nitrogen-doped graphene with tailored structural properties, crucial for their successful usage applications, has been demonstrated. The developed atmospheric pressure plasma method offers several advantages, including the continuous production of high-quality, free-standing graphene without the use of chemicals, solvents, catalysts, or additional heating. This non-toxic process eliminates the need for vacuum systems while achieving high temperatures. The method enables the precise control over graphene’s properties, such as the layer number, defects, sheet size, uniformity, and functionality, as well as the doping type and configuration, by adjusting the plasma parameters. Protocols for the synthesis of specific nanostructures with a controlled structural quality, production rate, and chemical composition have been established using methane and methylamine as precursors. The comprehensive physicochemical characterization of the graphene and nitrogen-doped graphene was carried out using scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Full article
(This article belongs to the Special Issue Atmospheric Pressure Plasma Technologies and Applications)
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14 pages, 3865 KiB  
Article
Adsorption of Asymmetric and Linear Hazardous Gases on Graphene Oxides: Density Functional Study
by Yongju Kwon, Taeyang Kim, Jaemyeong Choi, Sangeon Lee, Sungmin Cha and Soonchul Kwon
C 2025, 11(1), 4; https://doi.org/10.3390/c11010004 - 2 Jan 2025
Viewed by 1103
Abstract
The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas [...] Read more.
The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas sensor materials by modifying the surface with their chemical and structural stability. In order to understand the mechanisms of graphene and graphene oxides for adsorbing the hazardous gases, we classified the four gases (H2S, NH3, HF and COS) with their phases (two asymmetric and two linear), and conducted density functional theory calculations to determine the adsorption affinity, which represents the binding energy, bond distance, energy charge (Mulliken and Hirshfeld methods) and band gap between the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital). The results showed that introducing a functional group enhanced the binding energy with a narrowed band gap in asymmetric gas adsorption (H2S and NH3), while the results of the linear gases (HF and COS) showed lowered binding energy with a narrowed band gap. It is judged that the oxygen functional groups can narrow the band gap by introducing localized states between the valence and conduction bands or by forming new hybrid states through interactions with all the gases. However, from the differences in the phases, the linear gases stably interacted with a defect-free, porous and flat structure like with π–π interactions. In short, the theoretical findings confirm that the oxidation functional groups narrowed the band gap with a local interaction; however, linear gases showed enhanced binding energies with pristine graphene, which highlights the importance of surface material selection dependent on the target gases. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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11 pages, 2901 KiB  
Article
Using a Single-Atom FeN4 Catalyst on Defective Graphene for the Efficient Reduction of NO to Alanine: A Computational Study
by Yu Tian, Xiaoxi Yuan, Zexuan Guo, Jingyao Liu, Tingting Zhao and Zhongmin Su
Catalysts 2024, 14(12), 876; https://doi.org/10.3390/catal14120876 - 30 Nov 2024
Viewed by 1149
Abstract
The use of a single-atom FeN4 catalyst on defective graphene (Fe-NC) has recently emerged as an effective method for the synthesis of amino acids. Herein, we investigated the mechanism of alanine formation on FeN4-doped graphene using comprehensive density [...] Read more.
The use of a single-atom FeN4 catalyst on defective graphene (Fe-NC) has recently emerged as an effective method for the synthesis of amino acids. Herein, we investigated the mechanism of alanine formation on FeN4-doped graphene using comprehensive density functional theory (DFT) computations. The alanine formation reaction begins with the activation of NO molecules on the surface, followed by their reaction with hydrogen atoms provided in the system. The computational results show that NO molecules can be effectively activated on Fe-NC, facilitating the subsequent alanine formation at a relatively lower potential. The potential-limiting step in alanine production involves either the formation of HNO* or HNOH* intermediates on Fe-NG, as the free energy changes (ΔG) in these two elementary steps are nearly equivalent. Notably, the formation of HNO* exhibits a higher activation energy (Ea) compared to HNOH* formation. This study provides valuable insights into the C–N coupling reaction and the mechanism of amino acid synthesis on single-atom catalysts. Full article
(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)
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14 pages, 3952 KiB  
Article
Investigating Layered Topological Magnetic Materials as Efficient Electrocatalysts for the Hydrogen Evolution Reaction under High Current Densities
by Sanju Gupta, Hanna Świątek, Mirosław Sawczak, Tomasz Klimczuk and Robert Bogdanowicz
Catalysts 2024, 14(10), 676; https://doi.org/10.3390/catal14100676 - 1 Oct 2024
Cited by 1 | Viewed by 1267
Abstract
Despite considerable progress, high-performing durable catalysts operating under large current densities (i.e., >1000 mA/cm2) are still lacking. To discover platinum group metal-free (PGM-free) electrocatalysts for sustainable energy, our research involves investigating layered topological magnetic materials (semiconducting ferromagnets) as highly efficient electrocatalysts [...] Read more.
Despite considerable progress, high-performing durable catalysts operating under large current densities (i.e., >1000 mA/cm2) are still lacking. To discover platinum group metal-free (PGM-free) electrocatalysts for sustainable energy, our research involves investigating layered topological magnetic materials (semiconducting ferromagnets) as highly efficient electrocatalysts for the hydrogen evolution reaction under high current densities and establishes the novel relations between structure and electrochemical property mechanisms. The materials of interest include transition metal trihalides, i.e., CrCl3, VCl3, and VI3, wherein a structural unit, the layered structure, is formed by Cr (or V) atoms sandwiched between two halides (Cl or I), forming a tri-layer. A few layers of quantum crystals were exfoliated (~50−60 nm), encapsulated with graphene, and electrocatalytic HER tests were conducted in acid (0.5M H2SO4) and alkaline (1M KOH) electrolytes. We find a reasonable HER activity evolved requiring overpotentials in a range of 30–50 mV under 10 mA cm−2 and 400−510 mV (0.5M H2SO4) and 280−500 mV (1M KOH) under −1000 mA cm−2. Likewise, the Tafel slopes range from 27 to 36 mV dec−1 (Volmer–Tafel) and 110 to 190 mV dec−1 (Volmer–Herovsky), implying that these mechanisms work at low and high current densities, respectively. Weak interlayer coupling, spontaneous surface oxidation, the presence of a semi-oxide subsurface (e.g., O–CrCl3), intrinsic Cl (or I) vacancy defects giving rise to in-gap states, electron redistribution (orbital hybridization) affecting the covalency, and sufficiently conductive support interaction lowering the charge transfer resistance endow the optimized adsorption/desorption strength of H* on active sites and favorable electrocatalytic properties. Such behavior is expedited for bi-/tri-layers while exemplifying the critical role of quantum nature electrocatalysts with defect sites for industrial-relevant conditions. Full article
(This article belongs to the Section Catalysis for Sustainable Energy)
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14 pages, 1387 KiB  
Article
Corrosion Resistance of Atomically Thin Graphene Coatings on Single Crystal Copper
by Md Mahmudul Hasan, Ramesh Devadig, Pawan Sigdel, Alexey Lipatov, Recep Avci, Bharat K. Jasthi and Venkataramana Gadhamshetty
Coatings 2024, 14(6), 656; https://doi.org/10.3390/coatings14060656 - 22 May 2024
Cited by 1 | Viewed by 2597
Abstract
Designing minimally invasive, defect-free coatings based on conformal graphene layers to shield metals from both abiotic and biotic forms of corrosion is a persistent challenge. Single-layer graphene (SLG) grown on polycrystalline copper (PC-Cu) surfaces often have inherent defects, particularly at Cu grain boundaries, [...] Read more.
Designing minimally invasive, defect-free coatings based on conformal graphene layers to shield metals from both abiotic and biotic forms of corrosion is a persistent challenge. Single-layer graphene (SLG) grown on polycrystalline copper (PC-Cu) surfaces often have inherent defects, particularly at Cu grain boundaries, which weaken their barrier properties and worsen corrosion through grain-dependent mechanisms. Here, we report that an SLG grown via chemical vapor deposition (CVD) on Cu (111) single crystal serves as a high-performance coating to lower corrosion by nearly 4–6 times (lower than bare Cu (111)) in abiotic (sulfuric acid) and microbiologically influenced corrosion (MIC) environments. For example, the charge transfer resistance for SLG/Cu (111) (3.95 kΩ cm2) was 2.5-fold higher than for bare Cu (111) (1.71 kΩ cm2). Tafel analysis corroborated a reduced corrosion current (42 ± 3 µA cm−2) for SLG/Cu (111) compared to bare Cu (111) (115 ± 7 µA cm−2). These findings are consistent with the results based on biofilm measurements. The SLG/Cu (111) reduced biofilm formation by 3-fold compared to bare Cu (111), increasing corrosion resistance, and effectively mitigating pitting corrosion. The average depths of the pits (3.4 ± 0.6 µm) for SLG/Cu (111) were notably shallower than those of bare Cu (111) (6.5 ± 1.2 µm). Surface analysis of the corrosion products corroborated these findings, with copper sulfide identified as a major component across both surfaces. The absence of grain boundaries in Cu (111) resulted in high-quality SLG manifesting higher barrier properties compared to SLG on PC-Cu. Our findings show promise for using the presented strategy for developing durable graphene coatings against diverse forms of corrosion. Full article
(This article belongs to the Special Issue Wear-Resistance and Corrosion-Resistance Coatings)
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11 pages, 2246 KiB  
Article
Monitoring Aging Effects in Graphite Bisulfates by Means of Raman Spectroscopy
by Carlo Camerlingo, Marcella Salvatore and Gianfranco Carotenuto
Coatings 2024, 14(1), 101; https://doi.org/10.3390/coatings14010101 - 12 Jan 2024
Cited by 1 | Viewed by 1327
Abstract
Graphite bisulfate (GBS) compounds consist of graphite layers intercalated by HSO4 ions and H2SO4 molecules. Owing to electrostatic interactions with the graphene plane, HSO4 ions cause point defects in the graphite’s crystalline structure, while H2 [...] Read more.
Graphite bisulfate (GBS) compounds consist of graphite layers intercalated by HSO4 ions and H2SO4 molecules. Owing to electrostatic interactions with the graphene plane, HSO4 ions cause point defects in the graphite’s crystalline structure, while H2SO4 molecules are free to move via diffusion in the spaces between the adjacent graphite sheets and segregate to form linear defects. In the present work, we report the results of our investigation using Raman spectroscopy on the temporal evolution of such defects on selected GBS samples over 84 months. Two characteristic lengths correlated with the average distance between defects have been estimated and their evolution with aging was investigated. The results show a decrease in the density of point-like defects after aging, regardless of the pristine structural configuration of the GBS samples, revealing a structural instability. This study can provide significant information for the technological development of industrial processes aimed to produce expanded graphite based on GBS precursors, where the aging of GBS is known to influence the efficiency and quality. Full article
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14 pages, 3718 KiB  
Article
In Situ Synthesis of Doped Bio-Graphenes as Effective Metal-Free Catalysts in Removal of Antibiotics: Effect of Natural Precursor on Doping, Morphology, and Catalytic Activity
by Maryam Afsharpour, Lugain Radmanesh and Chuanxi Yang
Molecules 2023, 28(20), 7212; https://doi.org/10.3390/molecules28207212 - 22 Oct 2023
Cited by 1 | Viewed by 1521
Abstract
Wastewater contaminated with antibiotics is a major environmental challenge. The oxidation process is one of the most common and effective ways to remove these pollutants. The use of metal-free, green, and inexpensive catalysts can be a good alternative to metal-containing photocatalysts in environmental [...] Read more.
Wastewater contaminated with antibiotics is a major environmental challenge. The oxidation process is one of the most common and effective ways to remove these pollutants. The use of metal-free, green, and inexpensive catalysts can be a good alternative to metal-containing photocatalysts in environmental applications. We developed here the green synthesis of bio-graphenes by using natural precursors (Xanthan, Chitosan, Boswellia, Tragacanth). The use of these precursors can act as templates to create 3D doped graphene structures with special morphology. Also, this method is a simple method for in situ synthesis of doped graphenes. The elements present in the natural biopolymers (N) and other elements in the natural composition (P, S) are easily placed in the graphene structure and improve the catalytic activity due to the structural defects, surface charges, increased electron transfers, and high absorption. The results have shown that the hollow cubic Chitosan-derived graphene has shown the best performance due to the doping of N, S, and P. The Boswellia-derived graphene shows the highest surface area but a lower catalytic performance, which indicates the more effective role of doping in the catalytic activity. In this mechanism, O2 dissolved in water absorbs onto the positively charged C adjacent to N dopants to create oxygenated radicals, which enables the degradation of antibiotic molecules. Light irradiation increases the amount of radicals and rate of antibiotic removal. Full article
(This article belongs to the Special Issue Advanced Oxidation Processes for Degradation of Antibiotics in Water)
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20 pages, 9641 KiB  
Article
Carbon Gels–Green Graphene Composites as Metal-Free Bifunctional Electro-Fenton Catalysts
by Lilian D. Ramírez-Valencia, Esther Bailón-García, Adriana I. Moral-Rodríguez, Francisco Carrasco-Marín and Agustín F. Pérez-Cadenas
Gels 2023, 9(8), 665; https://doi.org/10.3390/gels9080665 - 17 Aug 2023
Cited by 15 | Viewed by 3915
Abstract
The Electro-Fenton (EF) process has emerged as a promising technology for pollutant removal. However, the EF process requires the use of two catalysts: one acting as an electrocatalyst for the reduction of oxygen to H2O2 and another Fenton-type catalyst for [...] Read more.
The Electro-Fenton (EF) process has emerged as a promising technology for pollutant removal. However, the EF process requires the use of two catalysts: one acting as an electrocatalyst for the reduction of oxygen to H2O2 and another Fenton-type catalyst for the generation of ·OH radicals from H2O2. Thus, the search for materials with bifunctionality for both processes is required for a practical and real application of the EF process. Thus, in this work, bifunctional electrocatalysts were obtained via doping carbon microspheres with Eco-graphene, a form of graphene produced using eco-friendly methods. The incorporation of Eco-graphene offers numerous advantages to the catalysts, including enhanced conductivity, leading to more efficient electron transfer during the Electro-Fenton process. Additionally, the synthesis induced structural defects that serve as active sites, promoting the direct production of hydroxyl radicals via a 3-electron pathway. Furthermore, the spherical morphology of carbon xerogels enhances the accessibility of the reagents to the active sites. This combination of factors results in the effective degradation of Tetracycline (TTC) using metal-free catalysts in the Electro-Fenton process, achieving up to an impressive 83% degradation without requiring any other external or additional catalyst. Full article
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8 pages, 5356 KiB  
Article
Graphene Oxide Membranes: Controlled Laser Reduction for Sensing Applications
by Aiden Rowley, Yijing Stehle, Luke Kilby and Caleb Bashant
C 2023, 9(3), 74; https://doi.org/10.3390/c9030074 - 30 Jul 2023
Cited by 6 | Viewed by 2382
Abstract
Reduced graphene oxide (rGO) has attracted attention as an active electrode material for flexible electrochemical devices due to its high electric conductivity and large surface area. Compared to other reduction processes, laser reduction is a precise, low-cost, and chemical-free process that is directly [...] Read more.
Reduced graphene oxide (rGO) has attracted attention as an active electrode material for flexible electrochemical devices due to its high electric conductivity and large surface area. Compared to other reduction processes, laser reduction is a precise, low-cost, and chemical-free process that is directly applied to graphene oxide (GO) membranes. This study aims to develop rGO through laser irradiation for application as electrodes in thin flexible electrochemical sensors. Laser irradiation parameters will be optimized to achieve reduction of a low oxygen to carbon (O/C) ratio and surface impedance. The influence of humidity on the impedance of rGO electrodes will be studied. The observed instability of the rGO electrode is related to incomplete reduction and oxygenated defects involved in reduction. Partially removed oxygenated functional groups not only influence the impedance of the electrode but make it sensitive to the humidity of the working environment. The result provides references for GO’s laser reduction optimization, demonstrates the potential of applying rGO as an electrode in sensing applications, but also reveals the limitation of applying the laser reduced rGO electrode in a non-constant humidity environment. Full article
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16 pages, 6377 KiB  
Article
Effect of Carbon Nanoparticles on the Porous Texture of ι-Carrageenan-Based N-Doped Nanostructured Porous Carbons and Implications for Gas Phase Applications
by Samantha K. Samaniego Andrade, Alfréd Menyhárd, Szilvia Klébert, Miklós Mohai, Balázs Nagy and Krisztina László
C 2023, 9(3), 68; https://doi.org/10.3390/c9030068 - 12 Jul 2023
Cited by 3 | Viewed by 2592
Abstract
S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. [...] Read more.
S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. The porous textures were characterized by N2 (−196.15 °C) and CO2 (0 °C) isotherms. The best GO- and CNT-added carbons had an apparent surface area of 1780 m2/g and 1170 m2/g, respectively, compared to 1070 m2/g for the CNP-free matrix. Analysis of the Raman spectra revealed that CNT was more efficient in introducing new defects than GO. Based on XPS, the carbon samples contain 2–4.5 at% nitrogen and 1.1 at% sulfur. The Dubinin–Radushkevich (DR) and Henry models were used to assess the strength of the interactions between various gases and the surface. The N2/H2 and CO2/CH4 selectivities were estimated with ideal adsorbed solution theory (IAST). While the CNPs, particularly GO, had a remarkable influence on the porous texture and affected the surface chemistry, their influence on the separation selectivity of these gases was more modest. Full article
(This article belongs to the Special Issue Carbons for Health and Environmental Protection)
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