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6 pages, 196 KiB

Open AccessEditorial

Recent Development of Nanomaterials for Chemical Engineering

by Meiwen Cao

Nanomaterials 2024, 14(5), 456; https://doi.org/10.3390/nano14050456 - 01 Mar 2024

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Abstract

There has been an explosive growth in research on nanomaterials since the late 1980s and early 1990s [...] Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

Research

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9 pages, 15591 KiB

Open AccessArticle

Phase Separation Prevents the Synthesis of VBi₂Te₄ by Molecular Beam Epitaxy

by Marieke Altena, Thies Jansen, Martina Tsvetanova and Alexander Brinkman

Nanomaterials 2024, 14(1), 87; https://doi.org/10.3390/nano14010087 - 28 Dec 2023

Viewed by 834

Abstract

Intrinsic magnetic topological insulators (IMTIs) have a non-trivial band topology in combination with magnetic order. This potentially leads to fascinating states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. One of the theoretically predicted IMTIs is VBi₂Te [...] Read more.

Intrinsic magnetic topological insulators (IMTIs) have a non-trivial band topology in combination with magnetic order. This potentially leads to fascinating states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. One of the theoretically predicted IMTIs is VBi₂Te₄, but experimental evidence of this material is lacking so far. Here, we report on our attempts to synthesise VBi₂Te₄ by molecular beam epitaxy (MBE). X-ray diffraction reveals that in the thermodynamic phase space reachable by MBE, there is no region where VBi₂Te₄ is stably synthesised. Moreover, scanning transmission electron microscopy shows a clear phase separation to Bi₂Te₃ and VTe₂ instead of the formation of VBi₂Te₄. We suggest the phase instability to be due to either the large lattice mismatch between VTe₂ and Bi₂Te₃ or the unfavourable valence state of vanadium. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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14 pages, 2966 KiB

Open AccessArticle

Synthesis and Evaluation of Peptide–Manganese Dioxide Nanocomposites as Adsorbents for the Removal of Strontium Ions

by Xingjie Lu, Zhen Liu, Wentao Wang, Xin Wang, Hongchao Ma and Meiwen Cao

Nanomaterials 2024, 14(1), 52; https://doi.org/10.3390/nano14010052 - 23 Dec 2023

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Abstract

In this study, a novel organic–inorganic hybrid material IIGK@MnO₂ (2-naphthalenemethyl-isoleucine-isoleucine-glycine-lysine@manganese dioxide) was designed as a novel adsorbent for the removal of strontium ions (Sr²⁺). The morphology and structure of IIGK@MnO₂ were characterized using TEM, AFM, XRD, and XPS. The [...] Read more.

In this study, a novel organic–inorganic hybrid material IIGK@MnO₂ (2-naphthalenemethyl-isoleucine-isoleucine-glycine-lysine@manganese dioxide) was designed as a novel adsorbent for the removal of strontium ions (Sr²⁺). The morphology and structure of IIGK@MnO₂ were characterized using TEM, AFM, XRD, and XPS. The results indicate that the large specific surface area and abundant negative surface charges of IIGK@MnO₂ make its surface rich in active adsorption sites for Sr²⁺ adsorption. As expected, IIGK@MnO₂ exhibited excellent adsorbing performance for Sr²⁺. According to the adsorption results, the interaction between Sr²⁺ and IIGK@MnO₂ can be fitted with the Langmuir isotherm and pseudo-second-order equation. Moreover, leaching and desorption experiments were conducted to assess the recycling capacity, demonstrating significant reusability of IIGK@MnO₂. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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30 pages, 9703 KiB

Open AccessArticle

Hexagonal Boron Nitride as Filler for Silica-Based Elastomer Nanocomposites

by Federica Magaletti, Gea Prioglio, Ulrich Giese, Vincenzina Barbera and Maurizio Galimberti

Nanomaterials 2024, 14(1), 30; https://doi.org/10.3390/nano14010030 - 21 Dec 2023

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Abstract

Two-dimensional hexagonal boron nitride (hBN) has attracted tremendous attention over the last few years, thanks to its stable structure and its outstanding properties, such as mechanical strength, thermal conductivity, electrical insulation, and lubricant behavior. This work demonstrates that hBN can also improve the [...] Read more.

Two-dimensional hexagonal boron nitride (hBN) has attracted tremendous attention over the last few years, thanks to its stable structure and its outstanding properties, such as mechanical strength, thermal conductivity, electrical insulation, and lubricant behavior. This work demonstrates that hBN can also improve the rheological and mechanical properties of elastomer composites when used to partially replace silica. In this work, commercially available pristine hBN (hBN-p) was exfoliated and ball-mill treated in air for different durations (2.5, 5, and 10 h milling). Functionalization occurred with the -NH and -OH groups (hBN-OH). The functional groups were detected using Fourier-Transform Infrared pectroscopy (FT-IR) and were estimated to be up to about 7% through thermogravimetric analysis. The presence of an increased amount of oxygen in hBN-OH was confirmed using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy. (SEM-EDS). The number of stacked layers, estimated using WAXD analysis, decreased to 8–9 in hBN-OH (10 h milling) from about 130 in hBN-p. High-resolution transmission electron microscopy (HR-TEM) and SEM-EDS revealed the increase in disorder in hBN-OH. hBN-p and hBN-OH were used to partially replace silica by 15% and 30%, respectively, by volume, in elastomer composites based on poly(styrene-co-butadiene) from solution anionic polymerization (S-SBR) and poly(1,4-cis-isoprene) from Hevea Brasiliensis (natural rubber, NR) as the elastomers (volume (mm³) of composites released by the instrument). The use of both hBNs in substitution of 30% of silica led to a lower Payne effect, a higher dynamic rigidity, and an increase in E′ of up to about 15% at 70 °C, with similar/lower hysteresis. Indeed, the composites with hBN-OH revealed a better balance of tan delta (higher at low temperatures and lower at high temperatures) and better ultimate properties. The functional groups reasonably promote the interaction of hBN with silica and with the silica’s coupling agent, sulfur-based silane, and thus promoted the interaction with the elastomer chains. The volume of the composite, measured using a high-pressure capillary viscometer, increased by about 500% and 400% after one week of storage in the presence of hBN-p and hBN-OH. Hence, both hBNs improved the processability and the shelf life of the composites. Composites obtained using hBN-OH had even filler dispersion without the detachments of the filler from the elastomer matrix, as shown through TEM micrographs. These results pave the way for substantial improvements in the important properties of silica-based composites for tire compounds, used to reduce rolling resistance and thus the improve environmental impacts. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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12 pages, 10179 KiB

Open AccessArticle

Dissolution Reaction and Surface Modification of UICC Amosite in Mimicked Gamble’s Solution: A Step towards Filling the Gap between Asbestos Toxicity and Its Crystal Chemical Features

by Alessandro Pacella, Paolo Ballirano, Maria Cristina Di Carlo, Marzia Fantauzzi, Antonella Rossi, Elisa Nardi, Cecilia Viti, Lorenzo Arrizza, Antonella Campopiano, Annapaola Cannizzaro, Andrea Bloise and Maria Rita Montereali

Nanomaterials 2023, 13(22), 2933; https://doi.org/10.3390/nano13222933 - 12 Nov 2023

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Abstract

This study focuses on the dissolution process and surface characterization of amosite fibres following interaction with a mimicked Gamble’s solution at a pH of 4.5 and T = 37 °C, up to 720 h. To achieve this, a multi-analytical approach was adopted, and [...] Read more.

This study focuses on the dissolution process and surface characterization of amosite fibres following interaction with a mimicked Gamble’s solution at a pH of 4.5 and T = 37 °C, up to 720 h. To achieve this, a multi-analytical approach was adopted, and the results were compared to those previously obtained on a sample of asbestos tremolite and UICC crocidolite, which were investigated under the same experimental conditions. Combining surface chemical data obtained by XPS with cation release quantified by ICP-OES, an incongruent behaviour of the fibre dissolution was highlighted for amosite fibres, similarly to asbestos tremolite and UICC crocidolite. In particular, a preferential release of Mg and Ca from the amphibole structure was observed, in agreement with their Madelung site energies. Notably, no Fe release from amosite fibres was detected in our experimental conditions (pH of 4.5 and atmospheric pO₂), despite the occurrence of Fe(II) at the M(4) site of the amphibole structure, where cations are expected to be rapidly leached out during mineral dissolution. Moreover, the oxidation of both the Fe centres initially present on the fibre surface and those promoted from the bulk, because of the erosion of the outmost layers, was observed. Since biodurability (i.e., the resistance to dissolution) is one of the most important toxicity parameters, the knowledge of the surface alteration of asbestos possibly occurring in vivo may help to understand the mechanisms at the basis of its long-term toxicity. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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12 pages, 2627 KiB

Open AccessArticle

Machine Learning-Assisted Large-Area Preparation of MoS₂ Materials

by Jingting Wang, Mingying Lu, Yongxing Chen, Guolin Hao, Bin Liu, Pinghua Tang, Lian Yu, Lei Wen and Haining Ji

Nanomaterials 2023, 13(16), 2283; https://doi.org/10.3390/nano13162283 - 09 Aug 2023

Viewed by 1143

Abstract

Molybdenum disulfide (MoS₂) is a layered transition metal-sulfur compound semiconductor that shows promising prospects for applications in optoelectronics and integrated circuits because of its low preparation cost, good stability and excellent physicochemical, biological and mechanical properties. MoS₂ with high quality, [...] Read more.

Molybdenum disulfide (MoS₂) is a layered transition metal-sulfur compound semiconductor that shows promising prospects for applications in optoelectronics and integrated circuits because of its low preparation cost, good stability and excellent physicochemical, biological and mechanical properties. MoS₂ with high quality, large size and outstanding performance can be prepared via chemical vapor deposition (CVD). However, its preparation process is complex, and the area of MoS₂ obtained is difficult to control. Machine learning (ML), as a powerful tool, has been widely applied in materials science. Based on this, in this paper, a ML Gaussian regression model was constructed to explore the growth mechanism of MoS₂ material prepared with the CVD method. The parameters of the regression model were evaluated by combining the four indicators of goodness of fit (r2), mean squared error (MSE), Pearson correlation coefficient (p) and p-value (p_val) of Pearson’s correlation coefficient. After comprehensive comparison, it was found that the performance of the model was optimal when the number of iterations was 15. Additionally, feature importance analysis was conducted on the growth parameters using the established model. The results showed that the carrier gas flow rate (Fr), molybdenum sulfur ratio (R) and reaction temperature (T) had a crucial impact on the CVD growth of MoS₂ materials. The optimal model was used to predict the size of molybdenum disulfide synthesis under 185,900 experimental conditions in the simulation dataset so as to select the optimal range for the synthesis of large-size molybdenum disulfide. Furthermore, the model prediction results were verified through literature and experimental results. It was found that the relative error between the prediction results and the literature and experimental results was small. These findings provide an effective solution to the preparation of MoS₂ materials with a reduction in the time and cost of trial and error. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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22 pages, 1198 KiB

Open AccessArticle

Synthesis of Composites for the Removal of F^- Anions

by Adriana Saldaña-Robles, Javier Antonio Arcibar-Orozco, Luz Rocío Guerrero-Mosqueda, César Eduardo Damián-Ascencio, Alfredo Marquez-Herrera, Miguel Corona, Armando Gallegos-Muñoz and Sergio Cano-Andrade

Nanomaterials 2023, 13(16), 2277; https://doi.org/10.3390/nano13162277 - 08 Aug 2023

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Abstract

This work presents the synthesis of amine and ferrihydrite functionalized graphene oxide for the removal of fluoride from water. The synthesis of the graphene oxide and the modified with amine groups is developed by following the modified Hummer’s method. Fourier transform infrared spectrometry, [...] Read more.

This work presents the synthesis of amine and ferrihydrite functionalized graphene oxide for the removal of fluoride from water. The synthesis of the graphene oxide and the modified with amine groups is developed by following the modified Hummer’s method. Fourier transform infrared spectrometry, X-ray, Raman spectroscopy, thermogravimetric analysis, surface charge distribution, specific surface area and porosity, adsorption isotherms, and the van’t Hoff equation are used for the characterization of the synthesized materials. Results show that the addition of amines with ferrihydrite generates wrinkles on the surface layers, suggesting a successful incorporation of nitrogen onto the graphene oxide; and as a consequence, the adsorption capacity per unit area of the materials is increased. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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12 pages, 5959 KiB

Open AccessArticle

Study on Oxygen Evolution Reaction of Ir Nanodendrites Supported on Antimony Tin Oxide

by Yu-Chun Chiang, Zhi-Hui Pu and Ziyi Wang

Nanomaterials 2023, 13(15), 2264; https://doi.org/10.3390/nano13152264 - 07 Aug 2023

Cited by 1 | Viewed by 1079

Abstract

In this study, the iridium nanodendrites (Ir NDs) and antimony tin oxide (ATO)-supported Ir NDs (Ir ND/ATO) were prepared by a surfactant-mediated method to investigate the effect of ATO support and evaluate the electrocatalytic activity for the oxygen evolution reaction (OER). The nano-branched [...] Read more.

In this study, the iridium nanodendrites (Ir NDs) and antimony tin oxide (ATO)-supported Ir NDs (Ir ND/ATO) were prepared by a surfactant-mediated method to investigate the effect of ATO support and evaluate the electrocatalytic activity for the oxygen evolution reaction (OER). The nano-branched Ir ND structures were successfully prepared alone or supported on ATO. The Ir NDs exhibited major diffraction peaks of the fcc Ir metal, though the Ir NDs consisted of metallic Ir as well as Ir oxides. Among the Ir ND samples, Ir ND2 showed the highest mass-based OER catalytic activity (116 mA/mg at 1.8 V), while it suffered from high degradation in activity after a long-term test. On the other hand, Ir ND2/ATO had OER activity of 798 mA/mg, and this activity remained >99% after 100 cycles of LSV and the charge transfer resistance increased by less than 3 ohm. The enhanced durability of the OER mass activities of Ir ND2/ATO catalysts over Ir NDs and Ir black could be attributed to the small crystallite size of Ir and the increase in the ratio of Ir (III) to Ir (IV), improving the interactions between the Ir NDs and the ATO support. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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16 pages, 25703 KiB

Open AccessArticle

Facile Preparation of SrZr_1-xTi_xO₃ and SrTi_1-xZr_xO₃ Fine Particles Assisted by Dehydration of Zr⁴⁺ and Ti⁴⁺ Gels under Hydrothermal Conditions

by José Remigio Quiñones-Gurrola, Juan Carlos Rendón-Angeles, Zully Matamoros-Veloza, Jorge López-Cuevas, Roberto Pérez-Garibay and Kazumichi Yanagisawa

Nanomaterials 2023, 13(15), 2195; https://doi.org/10.3390/nano13152195 - 28 Jul 2023

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Abstract

In recent decades, perovskite-type compounds (ABB′O₃) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO₃–SrTiO₃ was conducted under hydrothermal conditions in [...] Read more.

In recent decades, perovskite-type compounds (ABB′O₃) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO₃–SrTiO₃ was conducted under hydrothermal conditions in a KOH (5 M) solution at 200 °C for 4 h under a constant stirring speed of 130 rpm. The precursors employed were SrSO₄ powder (<38 μm size) and coprecipitated hydrous gels of Zr(OH)₄•9.64 H₂O (Zr-gel) and Ti(OH)₄•4.5H₂O (Ti-gel), which were mixed according to the stoichiometry of the SrZr_1-xTi_xO₃ in the compositional range of 0.0 > x > 100.0 mol% Ti⁴⁺. The XRD results revealed the formation of two crystalline phases rich in Zr⁴⁺, an orthorhombic structured SrZr_0.93Ti_0.07O₃ and a cubic structured SrZr_0.75Ti_0.25O₃ within the compositional range of 0.1–0.5 mol of Ti⁴⁺. A cubic perovskite structured solid solution, SrTi_1-xZr_xO₃, was preferentially formed within the compositional range of 0.5 > x > 0.1 mol% Ti⁴⁺. The SrZrO₃ and SrZr_0.93Ti_0.07O₃-rich phases had particle sizes averaging 3 μm with a cubic morphology. However, a remarkable reduction in the particle size occurred on solid solutions prepared with hydrous Ti-gel over contents of 15 mol% Ti⁴⁺ in the reaction media, resulting in the formation of nanosized particle agglomerates with a cuboidal shape self-assembled via a 3D hierarchical architecture, and the sizes of these particles varied in the range between 141.0 and 175.5 nm. The limited coarsening of the particles is discussed based on the Zr-gel and Ti-gel dehydration capability differences that occurred under hydrothermal processing. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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19 pages, 9316 KiB

Open AccessEditor’s ChoiceArticle

In Situ Ultra-Small- and Small-Angle X-ray Scattering Study of ZnO Nanoparticle Formation and Growth through Chemical Bath Deposition in the Presence of Polyvinylpyrrolidone

by Karina Abitaev, Petia Atanasova, Joachim Bill, Natalie Preisig, Ivan Kuzmenko, Jan Ilavsky, Yun Liu and Thomas Sottmann

Nanomaterials 2023, 13(15), 2180; https://doi.org/10.3390/nano13152180 - 26 Jul 2023

Viewed by 1184

Abstract

ZnO inverse opals combine the outstanding properties of the semiconductor ZnO with the high surface area of the open-porous framework, making them valuable photonic and catalysis support materials. One route to produce inverse opals is to mineralize the voids of close-packed polymer nanoparticle [...] Read more.

ZnO inverse opals combine the outstanding properties of the semiconductor ZnO with the high surface area of the open-porous framework, making them valuable photonic and catalysis support materials. One route to produce inverse opals is to mineralize the voids of close-packed polymer nanoparticle templates by chemical bath deposition (CBD) using a ZnO precursor solution, followed by template removal. To ensure synthesis control, the formation and growth of ZnO nanoparticles in a precursor solution containing the organic additive polyvinylpyrrolidone (PVP) was investigated by in situ ultra-small- and small-angle X-ray scattering (USAXS/SAXS). Before that, we studied the precursor solution by in-house SAXS at T = 25 °C, revealing the presence of a PVP network with semiflexible chain behavior. Heating the precursor solution to 58 °C or 63 °C initiates the formation of small ZnO nanoparticles that cluster together, as shown by complementary transmission electron microscopy images (TEM) taken after synthesis. The underlying kinetics of this process could be deciphered by quantitatively analyzing the USAXS/SAXS data considering the scattering contributions of particles, clusters, and the PVP network. A nearly quantitative description of both the nucleation and growth period could be achieved using the two-step Finke–Watzky model with slow, continuous nucleation followed by autocatalytic growth. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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27 pages, 5191 KiB

Open AccessArticle

Enhanced Degradation of Methyl Orange and Trichloroethylene with PNIPAm-PMMA-Fe/Pd-Functionalized Hollow Fiber Membranes

by Rollie Mills, Cameron Tvrdik, Andrew Lin and Dibakar Bhattacharyya

Nanomaterials 2023, 13(14), 2041; https://doi.org/10.3390/nano13142041 - 10 Jul 2023

Viewed by 1331

Abstract

Trichloroethylene (TCE) is a prominent groundwater pollutant due to its stability, widespread contamination, and negative health effects upon human exposure; thus, an immense need exists for enhanced environmental remediation techniques. Temperature-responsive domains and catalyst incorporation in membrane domains bring significant advantages for toxic [...] Read more.

Trichloroethylene (TCE) is a prominent groundwater pollutant due to its stability, widespread contamination, and negative health effects upon human exposure; thus, an immense need exists for enhanced environmental remediation techniques. Temperature-responsive domains and catalyst incorporation in membrane domains bring significant advantages for toxic organic decontamination. In this study, hollow fiber membranes (HFMs) were functionalized with stimuli-responsive poly-N-isopropylacrylamide (PNIPAm), poly-methyl methacrylate (PMMA), and catalytic zero-valent iron/palladium (Fe/Pd) for heightened reductive degradation of such pollutants, utilizing methyl orange (MO) as a model compound. By utilizing PNIPAm’s transition from hydrophilic to hydrophobic expression above the LCST of 32 °C, increased pollutant diffusion and adsorption to the catalyst active sites were achieved. PNIPAm-PMMA hydrogels exhibited 11.5× and 10.8× higher equilibrium adsorption values for MO and TCE, respectively, when transitioning from 23 °C to 40 °C. With dip-coated PNIPAm-PMMA-functionalized HFMs (weight gain: ~15%) containing Fe/Pd nanoparticles (d_p~34.8 nm), surface area-normalized rate constants for batch degradation were determined, resulting in a 30% and 420% increase in degradation efficiency above 32 °C for MO and TCE, respectively, due to enhanced sorption on the hydrophobic PNIPAm domain. Overall, with functionalized membranes containing superior surface area-to-volume ratios and enhanced sorption sites, efficient treatment of high-volume contaminated water can be achieved. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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16 pages, 3375 KiB

Open AccessArticle

Bimetallic AgPt Nanoalloys as an Electrocatalyst for Ethanol Oxidation Reaction: Synthesis, Structural Analysis, and Electro-Catalytic Activity

by Fabian Mares-Briones, América Higareda, Jose Luis Lopez-Miranda, Rubén Mendoza-Cruz and Rodrigo Esparza

Nanomaterials 2023, 13(8), 1396; https://doi.org/10.3390/nano13081396 - 18 Apr 2023

Cited by 3 | Viewed by 1570

Abstract

In the present work, the chemical synthesis of AgPt nanoalloys is reported by the polyol method using polyvinylpyrrolidone (PVP) as a surfactant and a heterogeneous nucleation approach. Nanoparticles with different atomic compositions of the Ag and Pt elements (1:1 and 1:3) were synthesized [...] Read more.

In the present work, the chemical synthesis of AgPt nanoalloys is reported by the polyol method using polyvinylpyrrolidone (PVP) as a surfactant and a heterogeneous nucleation approach. Nanoparticles with different atomic compositions of the Ag and Pt elements (1:1 and 1:3) were synthesized by adjusting the molar ratios of the precursors. The physicochemical and microstructural characterization was initially performed using the UV-Vis technique to determine the presence of nanoparticles in suspension. Then, the morphology, size, and atomic structure were determined using XRD, SEM, and HAADF-STEM techniques, confirming the formation of a well-defined crystalline structure and homogeneous nanoalloy with an average particle size of less than 10 nm. Finally, the cyclic voltammetry technique evaluated the electrochemical activity of bimetallic AgPt nanoparticles supported on Vulcan XC-72 carbon for the ethanol oxidation reaction in an alkaline medium. Chronoamperometry and accelerated electrochemical degradation tests were performed to determine their stability and long-term durability. The synthesized AgPt (1:3)/C electrocatalyst presented significative catalytic activity and superior durability due to the introduction of Ag that weakens the chemisorption of the carbonaceous species. Thus, it could be an attractive candidate for cost-effective ethanol oxidation compared to commercial Pt/C. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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23 pages, 7089 KiB

Open AccessEditor’s ChoiceArticle

Nitrogen-Doped Graphene Oxide as Efficient Metal-Free Electrocatalyst in PEM Fuel Cells

by Adriana Marinoiu, Mircea Raceanu, Elena Carcadea and Mihai Varlam

Nanomaterials 2023, 13(7), 1233; https://doi.org/10.3390/nano13071233 - 30 Mar 2023

Cited by 4 | Viewed by 2169

Abstract

Nitrogen-doped graphene is currently recognized as one of the most promising catalysts for the oxygen reduction reaction (ORR). It has been demonstrated to act as a metal-free electrode with good electrocatalytic activity and long-term operation stability, excellent for the ORR in proton exchange [...] Read more.

Nitrogen-doped graphene is currently recognized as one of the most promising catalysts for the oxygen reduction reaction (ORR). It has been demonstrated to act as a metal-free electrode with good electrocatalytic activity and long-term operation stability, excellent for the ORR in proton exchange membrane fuel cells (PEMFCs). As a consequence, intensive research has been dedicated to the investigation of this catalyst through varying the methodologies for the synthesis, characterization, and technologies improvement. A simple, scalable, single-step synthesis method for nitrogen-doped graphene oxide preparation was adopted in this paper. The physical and chemical properties of various materials obtained from different precursors have been evaluated and compared, leading to the conclusion that ammonia allows for a higher resulting nitrogen concentration, due to its high vapor pressure, which facilitates the functionalization reaction of graphene oxide. Electrochemical measurements indicated that the presence of nitrogen-doped oxide can effectively enhance the electrocatalytic activity and stability for ORR, making it a viable candidate for practical application as a PEMFC cathode electrode. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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9 pages, 1697 KiB

Open AccessCommunication

Hydrophilic Surface Modification of Amorphous Hydrogenated Carbon Nanocomposite Films via Atmospheric Oxygen Plasma Treatment

by Algirdas Lazauskas, Mindaugas Andrulevičius, Brigita Abakevičienė, Dalius Jucius, Viktoras Grigaliūnas, Asta Guobienė and Šarūnas Meškinis

Nanomaterials 2023, 13(6), 1108; https://doi.org/10.3390/nano13061108 - 20 Mar 2023

Cited by 1 | Viewed by 1447

Abstract

Herein we investigated hydrophilic surface modification of SiO_x containing amorphous hydrogenated carbon nanocomposite films (DLC:SiO_x) via the use of atmospheric oxygen plasma treatment. The modified films exhibited effective hydrophilic properties with complete surface wetting. More detailed water droplet contact angle [...] Read more.

Herein we investigated hydrophilic surface modification of SiO_x containing amorphous hydrogenated carbon nanocomposite films (DLC:SiO_x) via the use of atmospheric oxygen plasma treatment. The modified films exhibited effective hydrophilic properties with complete surface wetting. More detailed water droplet contact angle (CA) measurements revealed that oxygen plasma treated DLC:SiO_x films maintained good wetting properties with CA of up to 28 ± 1° after 20 days of aging in ambient air at room temperature. This treatment process also increased surface root mean square roughness from 0.27 nm to 1.26 nm. Analysis of the surface chemical states suggested that the hydrophilic behavior of DLC:SiO_x treated with oxygen plasma is attributed to surface enrichment with C–O–C, SiO₂, and Si–Si chemical bonds as well as significant removal of hydrophobic Si–CH_x functional groups. The latter functional groups are prone to restoration and are mainly responsible for the increase in CA with aging. Possible applications of the modified DLC:SiO_x nanocomposite films could include biocompatible coatings for biomedical applications, antifogging coatings for optical components, and protective coatings to prevent against corrosion and wear. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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21 pages, 13881 KiB

Open AccessArticle

Ag Catalysts Supported on CeO₂, MnO₂ and CeMnO_x Mixed Oxides for Selective Catalytic Reduction of NO by C₃H₆

by Eleonora La Greca, Tamara S. Kharlamova, Maria V. Grabchenko, Luca Consentino, Daria Yu Savenko, Giuseppe Pantaleo, Lidiya S. Kibis, Olga A. Stonkus, Olga V. Vodyankina and Leonarda Francesca Liotta

Nanomaterials 2023, 13(5), 873; https://doi.org/10.3390/nano13050873 - 26 Feb 2023

Cited by 2 | Viewed by 1480

Abstract

In the present study CeO₂, MnO₂ and CeMnO_x mixed oxide (with molar ratio Ce/Mn = 1) were prepared by sol-gel method using citric acid as a chelating agent and calcined at 500 °C. The silver catalysts (1 wt.% Ag) [...] Read more.

In the present study CeO₂, MnO₂ and CeMnO_x mixed oxide (with molar ratio Ce/Mn = 1) were prepared by sol-gel method using citric acid as a chelating agent and calcined at 500 °C. The silver catalysts (1 wt.% Ag) over the obtained supports were synthesized by the incipient wetness impregnation method with [Ag(NH₃)₂]NO₃ aqueous solution. The selective catalytic reduction of NO by C₃H₆ was investigated in a fixed-bed quartz reactor using a reaction mixture composed of 1000 ppm NO, 3600 ppm C₃H₆, 10 vol.% O₂, 2.9 vol.% H₂ and He as a balance gas, at WHSV of 25,000 mL g⁻¹ h⁻¹.The physical-chemical properties of the as-prepared catalysts were studied by several characterization techniques, such as X-ray fluorescence analysis, nitrogen adsorption/desorption, X-ray analysis, Raman spectroscopy, transmission electron microscopy with analysis of the surface composition by X-ray energy dispersive spectroscopy and X-ray photo-electron spectroscopy. Silver oxidation state and its distribution on the catalysts surface as well as the support microstructure are the main factors determining the low temperature activity in NO selective catalytic reduction. The most active Ag/CeMnO_x catalyst (NO conversion at 300 °C is 44% and N₂ selectivity is ~90%) is characterized by the presence of the fluorite-type phase with high dispersion and distortion. The characteristic “patchwork” domain microstructure of the mixed oxide along with the presence of dispersed Ag⁺/Ag_n^δ+ species improve the low-temperature catalyst of NO reduction by C₃H₆ performance compared to Ag/CeO₂ and Ag/MnO_x systems. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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15 pages, 2753 KiB

Open AccessArticle

Life Cycle Assessment as Support Tool for Development of Novel Polyelectrolyte Materials Used for Wastewater Treatment

by George Barjoveanu, Carmen Teodosiu, Irina Morosanu, Ramona Ciobanu, Florin Bucatariu and Marcela Mihai

Nanomaterials 2023, 13(5), 840; https://doi.org/10.3390/nano13050840 - 23 Feb 2023

Cited by 4 | Viewed by 1176

Abstract

This life cycle assessment (LCA) study focused on comparing the environmental performances of two types of synthesis strategies for polyethyleneimine (PEI) coated silica particles (organic/inorganic composites). The classic layer-by-layer and the new approach (one-pot coacervate deposition) were the two synthesis routes that were [...] Read more.

This life cycle assessment (LCA) study focused on comparing the environmental performances of two types of synthesis strategies for polyethyleneimine (PEI) coated silica particles (organic/inorganic composites). The classic layer-by-layer and the new approach (one-pot coacervate deposition) were the two synthesis routes that were tested for cadmium ions removal from aqueous solutions by adsorption in equilibrium conditions. Data from the laboratory scale experiments for materials synthesis, testing, and regeneration, were then fed into a life cycle assessment study so that the types and values of environmental impacts associated with these processes could be calculated. Additionally, three eco-design strategies based on material substitution were investigated. The results point out that the one-pot coacervate synthesis route has considerably lower environmental impacts than the layer-by-layer technique. From an LCA methodology point of view, it is important to consider material technical performances when defining the functional unit. From a wider perspective, this research is important as it demonstrates the usefulness of LCA and scenario analysis as environmental support tools for material developers because they highlight environmental hotspots and point out the environmental improvement possibilities from the very early stages of material development. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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Noble Metals Functionalized on Graphene Oxide Obtained by Different Methods—New Catalytic Materials

by Mihaela Iordache, Anisoara Oubraham, Ioan-Sorin Sorlei, Florin Alexandru Lungu, Catalin Capris, Tudor Popescu and Adriana Marinoiu

Nanomaterials 2023, 13(4), 783; https://doi.org/10.3390/nano13040783 - 20 Feb 2023

Cited by 5 | Viewed by 2276

Abstract

In recent years, research has focused on developing materials exhibiting outstanding mechanical, electrical, thermal, catalytic, magnetic and optical properties such as graphene/polymer, graphene/metal nanoparticles and graphene/ceramic nanocomposites. Two-dimensional sp² hybridized graphene has become a material of choice in research due to the [...] Read more.

In recent years, research has focused on developing materials exhibiting outstanding mechanical, electrical, thermal, catalytic, magnetic and optical properties such as graphene/polymer, graphene/metal nanoparticles and graphene/ceramic nanocomposites. Two-dimensional sp² hybridized graphene has become a material of choice in research due to the excellent properties it displays electrically, thermally, optically and mechanically. Noble nanomaterials also present special physical and chemical properties and, therefore, they provide model building blocks in modifying nanoscale structures for various applications, ranging from nanomedicine to catalysis and optics. The introduction of noble metal nanoparticles (NPs) (Au, Ag and Pd) into chemically derived graphene is important in opening new avenues for both materials in different fields where they can provide hybrid materials with exceptional performance due to the synergistical result of the specific properties of each of the materials. This review presents the different synthetic procedures for preparing Pt, Ag, Pd and Au NP/graphene oxide (GO) and reduced graphene oxide (rGO) composites. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering (Volume II))

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