Articles de revues : « Nanostructured catalytic supports »

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Ji, L., S. Tang, P. Chen, H. C. Zeng, J. Lin et K. L. Tan. « Effect of nanostructured supports on catalytic methane decomposition ». Pure and Applied Chemistry 72, n^o 1-2 (1 janvier 2000) : 327–31. http://dx.doi.org/10.1351/pac200072010327.

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Carbon deposition from catalytic methane decomposition has drawn increasing interest recently. Previously, we have found the carbon formation depends on the crystalline structure of the support, following the trend of Ni/CeO2 > Ni/CaO > Ni/MgO, because Ni supported on MgO is uniformly dispersed and can stabilize high-x CH x intermediates. We have also found that the addition of Pt can inhibit the carbon deposition on Co/Al2O3 because the alloying between Pt and Co results in the better dispersion of Co on the support. Furthermore, it was revealed that by judging the Ni/Mg molar ratio from 1 to 0.25 we could reduce the diameter of deposited carbon nanotubes from 20 to 12 nm, with substantially smaller production rate. All of these previous studies indicated that better dispersion of the supported metal would benefit the decreasing of carbon deposition. Here we present our recent investigation of the effect of support particle size on the carbon deposition. Three different types of 10 wt% Co/Al2O3 catalysts were prepared: Co on commercial Al2O3 (Cat 1), Co on sol-gel-processed Al2O3 (Cat 2), and sol-gel-made homogeneous Co-in-Al2O3 (Cat 3). TEM showed that the diameter of the Co3O4 particles in sol-gel Al2O3 is only around 6 nm, while it is 20-40 nm in the commercial catalyst. By using XRD and FTIR, Co was identified as crystalline Co3O4 in the as-prepared Cat 1 sample, CoAl2O4 in Cat 2, and amorphous Al2O3 in Cat 3, indicating the best dispersion in Cat 3. Methane CO2 reforming was studied on the three catalysts. Longer lifetime was measured for Cat 3 as compared to those on Cat 1 and Cat 2 (>20 h vs. 1 h). The support size effect is discussed.

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Rivera-Muñoz, Eric, Rafael Huirache-Acuña, Beatriz Millán-Malo, Rufino Nava, Barbara Pawelec et Cristina Loricera. « Crystallographic studies through HRTEM and XRD of MoS2nanostructures ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C512. http://dx.doi.org/10.1107/s205327331409487x.

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Mesoporous and silica-based SBA-15 and SBA-16 materials were used as supports of novel nanostructured ternary Co(Ni)-Mo-W hydrodesulphurization (HDS) catalysts. These materials have shown a high catalytic activity in HDS of dibenzothiophene (DBT) reactions, even much higher compared with commercial catalysts. An exploration was made on the structure of both the supports as well as on tri-metallic sulfide HDS catalysts. The sulfided catalysts were tested in the HDS of DBT performed in a batch reactor at 623 K and total pressure of 3.1 MPa. The calcined and fresh sulfide catalysts were characterized by a variety of techniques, such as N2 adsorption-desorption isotherms, Temperature-Programmed Desorption (TPD) of NH3, X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM). It has been found that both the morphology of the supports as its modification with varying amounts of phosphorus affect the catalytic activity of these nanostructured materials in HDS of DBT reactions. Furthermore, the nanostructures which correspond to the tri-metallic sulfided catalysts exhibit a typical morphology of MoS2 – 2H structure. The present work shows the microstructural study of these nanostructured materials, carried out from HRTEM images and XRD analysis. Both techniques, X–ray Diffractometry and High Resolution Transmission Electron Microscopy, play a fundamental role in the characterization of the microstructure of HDS catalytic nanomaterials, as well as in understanding the various phenomena involved, starting from the synthesis process unto the final performance of those materials.

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HERNÁNDEZ-PADRÓN, GENOVEVA, LAURA S. ACOSTA-TORRES, FERNANDO ROJAS-GONZÁLEZ et VÍCTOR M. CASTAÑO. « Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials ». Bulletin of Materials Science 35, n^o 7 (décembre 2012) : 1071–77. http://dx.doi.org/10.1007/s12034-012-0410-7.

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YING, J. Y. « ChemInform Abstract : Synthesis of Nanostructured Catalysts and Catalytic Supports ». ChemInform 26, n^o 42 (17 août 2010) : no. http://dx.doi.org/10.1002/chin.199542305.

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Krivoshapkina, Elena, Pavel Krivoshapkin et Aleksey Vedyagin. « Sol-Gel Synthesis of Nanostructured Alumina Supports for CO Oxidation Catalysts ». Materials Science Forum 917 (mars 2018) : 152–56. http://dx.doi.org/10.4028/www.scientific.net/msf.917.152.

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In present work, a new technique to prepare alumina nanoparticles and nanofibers using a sol-gel method was proposed. A solution combustion method was applied to form a nanostructured catalytically active layer of CuO–Co3O4–CeO2 on the surface of the alumina. The uniform distribution and fine dispersion of active components provide the appropriate activity of the catalysts obtained in a model reaction of CO oxidation. The morphology of nanostructured alumina was found to affect the catalytic behavior. Carbon monoxide conversion was observed at lower temperatures when alumina nanofibers were used as a catalyst support.

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Song, Wei, Peter Hildebrandt et Inez M. Weidinger. « Plasmonic Cu/CuCl/Cu2S/Ag and Cu/CuCl/Cu2S/Au Supports with Peroxidase-Like Activity : Insights from Surface Enhanced Raman Spectroscopy ». Zeitschrift für Physikalische Chemie 232, n^o 9-11 (28 août 2018) : 1541–50. http://dx.doi.org/10.1515/zpch-2018-1126.

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Abstract In the present study, we present nanostructured bimetallic Cu/CuCl/Cu2S/Au(Ag) supports that exhibit plasmonic electromagnetic field enhancement and peroxidase-like catalytic activity. The Cu2S component acts as the peroxidase-like catalyst, while the Au or Ag component provides the necessary light enhancement for surface enhanced Raman spectroscopic (SERS) studies of surface bound molecular reactants. As a test reaction the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in presence of H2O2 was investigated. The comparison of product evolution in solution measured by UV-Vis spectroscopy and on the surface measured via SERS is able to give more insight into the different steps involved in the overall catalysis.

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Sulman, Aleksandrina M., Valentina G. Matveeva et Lyudmila M. Bronstein. « Cellulase Immobilization on Nanostructured Supports for Biomass Waste Processing ». Nanomaterials 12, n^o 21 (27 octobre 2022) : 3796. http://dx.doi.org/10.3390/nano12213796.

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Nanobiocatalysts, i.e., enzymes immobilized on nanostructured supports, received considerable attention because they are potential remedies to overcome shortcomings of traditional biocatalysts, such as low efficiency of mass transfer, instability during catalytic reactions, and possible deactivation. In this short review, we will analyze major aspects of immobilization of cellulase—an enzyme for cellulosic biomass waste processing—on nanostructured supports. Such supports provide high surface areas, increased enzyme loading, and a beneficial environment to enhance cellulase performance and its stability, leading to nanobiocatalysts for obtaining biofuels and value-added chemicals. Here, we will discuss such nanostructured supports as carbon nanotubes, polymer nanoparticles (NPs), nanohydrogels, nanofibers, silica NPs, hierarchical porous materials, magnetic NPs and their nanohybrids, based on publications of the last five years. The use of magnetic NPs is especially favorable due to easy separation and the nanobiocatalyst recovery for a repeated use. This review will discuss methods for cellulase immobilization, morphology of nanostructured supports, multienzyme systems as well as factors influencing the enzyme activity to achieve the highest conversion of cellulosic biowaste into fermentable sugars. We believe this review will allow for an enhanced understanding of such nanobiocatalysts and processes, allowing for the best solutions to major problems of sustainable biorefinery.

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Costa, João M. Cunha Bessa da, José R. Monteiro Barbosa, João Restivo, Carla A. Orge, Anabela Nogueira, Sérgio Castro-Silva, Manuel F. Ribeiro Pereira et Olívia S. Gonçalves Pinto Soares. « Engineering of Nanostructured Carbon Catalyst Supports for the Continuous Reduction of Bromate in Drinking Water ». C 8, n^o 2 (22 mars 2022) : 21. http://dx.doi.org/10.3390/c8020021.

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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.

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Deligen, Si Qin, et Bao Agula. « Preparation, Characterization and Catalytic Properties of Nanostructured Mesoporous Au/CeO₂ ». Applied Mechanics and Materials 778 (juillet 2015) : 144–47. http://dx.doi.org/10.4028/www.scientific.net/amm.778.144.

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The mesoporous CeO2were prepared via a surfactant-assisted method of nanoparticle assembly, CTAB was used as surfactant. The mesoporous CeO2were used as the supports for preparingxAu/CeO2catalysts by the chemical reduction method, and the catalytic activities of the total oxidation of propane were studied. The prepared catalysts were characterized by XRD, TEM and N2adsorption techniques. The content of Au can affect the catalytic properties of thexAu/CeO2catalysts. 4Au/CeO2exhibited the highest catalytic activity in propane complete oxidation with theT100of 420 °C.

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Carretero-González, J., J. M. Benito López, M. A. Rodríguez Barbero, I. Rodríguez Ramos et A. Guerrero Ruiz. « Development of Nanostructured Catalytic Membranes for Partial Benzene Hydrogenation to Cyclohexene ». Journal of Nanoscience and Nanotechnology 7, n^o 12 (1 décembre 2007) : 4391–401. http://dx.doi.org/10.1166/jnn.2007.903.

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Novel nanostructured catalytic membranes (NCMs) have been prepared by ruthenium deposition (Ru3(CO)12 wet-impregnation) within the porous framework of different tubular porous supports modified and unmodified with microporous glassy-carbon (GC) material. The aim of this work is to investigate the influence of the transport mechanism, layer distribution, textural properties, surface composition and metallic phase distribution of each type of NCMs on the partial benzene hydrogenation to cyclohexene performance in gas phase, operating under through-flow mode in a membrane reactor. Two types of glass (Vycor®) and ceramic (Cordierite-Alumina) supports with different layer distribution, have been used to prepared the NCMs. The modified and unmodified with GC membranes have been characterised by gas permeability measurements. High resolution-scanning electron microscopy (HR-SEM) and energy dispersive X-ray spectroscopy (EDS) have been realised to evidence GC deposition and to analyse the ruthenium nanoparticles distribution along the porous membranes section, respectively. An attempt to correlate the membrane characterization results and the catalytic results has been carried out.

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Mendoza-Nieto, J. A., K. D. Tejeda-Espinosa, I. Puente-Lee, C. Salcedo-Luna et T. Klimova. « Nanostructured SBA-15 Materials as Appropriate Supports for Active Hydrodesulfurization Catalysts Prepared from HSiW Heteropolyacid ». MRS Proceedings 1479 (2012) : 77–82. http://dx.doi.org/10.1557/opl.2012.1601.

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ABSTRACTA series of NiW catalysts supported on SBA-15-type materials modified with Al, Ti or Zr were prepared and tested in simultaneous hydrodesulfurization (HDS) of two model compounds: dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Catalysts were prepared by incipient wetness impregnation of SBA-type materials (pure silica SBA-15, Al-SBA-15, Ti-SBA-15 or Zr-SBA-15) using Keggin-type heteropolyacid H4SiW12O40 as active phase precursor and nickel nitrate. Nominal composition of the catalysts was 19 wt.% of WO3 and 3 wt.% of NiO. The supports and catalysts were characterized by SEM-EDX, N2physisorption, small-angle and powder XRD, UV-Vis DRS, TPR and HRTEM. It was shown that a good dispersion of Al, Ti and Zr species on the SBA-15 surface was reached. The characteristic structure of the SBA-15 support was preserved in all supports and NiW catalysts. Addition of metal atoms (Al, Ti, Zr) on the SBA-15 surface prior to catalysts’ preparation improved dispersion of Ni and W oxide species in calcined catalysts. HRTEM characterization of sulfided catalysts showed that the dispersion of NiW active phase was also better on metal-containing SBA-15 supports than on the pure silica one. All NiW catalysts supported on metal-containing SBA-15 materials showed an outstanding catalytic performance in HDS of both model compounds used (DBT and 4,6-DMDBT). A good correlation was found between the dispersion of sulfided NiW active phase and catalytic activity results. The highest HDS activity was obtained with the NiW catalyst supported on Zr-containing SBA-15 molecular sieve, which makes it a promising catalytic system for ultra-deep hydrodesulfurization of diesel fuel.

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Matoh, Lev, Boštjan Žener, Tina Skalar et Urška Lavrenčič Štangar. « Synthesis of Nanostructured TiO2 Microparticles with High Surface Area ». Catalysts 11, n^o 12 (11 décembre 2021) : 1512. http://dx.doi.org/10.3390/catal11121512.

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Hydrothermal reactions represent a simple and efficient method for the preparation of nanostructured TiO2 particles that could be of interest as photocatalysts or catalytic supports. Although the particle size is in the range of 2–5 µm, the nanostructures composing the particles ensure a large specific surface area with values above 100 m2/g. The effects of the different synthesis parameters on the morphology, photocatalytic activity, and stability of the prepared material were studied. The surface morphology of the prepared TiO2 powders was studied by scanning electron microscopy (SEM). To further characterize the samples, the specific surface area for different morphologies was measured and the photocatalytic activity of the prepared powders was tested by degrading model pollutants under UV irradiation. The results show that the initial morphology had little effect on the photocatalytic properties. On the other hand, the final calcination temperature significantly increased the degradation rates, making it comparable to that of P25 TiO2 (particle size 20–30 nm).

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Ferrara, Marcello, Michele Melchionna, Paolo Fornasiero et Manuela Bevilacqua. « The Role of Structured Carbon in Downsized Transition Metal-Based Electrocatalysts toward a Green Nitrogen Fixation ». Catalysts 11, n^o 12 (15 décembre 2021) : 1529. http://dx.doi.org/10.3390/catal11121529.

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Electrocatalytic Nitrogen Reduction Reaction (NRR) to ammonia is one of the most recent trends of research in heterogeneous catalysis for sustainability. The stark challenges posed by the NRR arise from many factors, beyond the strongly unfavored thermodynamics. The design of efficient heterogeneous electrocatalysts must rely on a suitable interplay of different components, so that the majority of research is focusing on development of nanohybrids or nanocomposites that synergistically harness the NRR sequence. Nanostructured carbon is one of the most versatile and powerful conductive supports that can be combined with metal species in an opportune manner, so as to guide the correct proceeding of the reaction and boost the catalytic activity.

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Guan, Yejun, D. A. J. Michel Ligthart, Özlem Pirgon-Galin, Johannis A. Z. Pieterse, Rutger A. van Santen et Emiel J. M. Hensen. « Gold Stabilized by Nanostructured Ceria Supports : Nature of the Active Sites and Catalytic Performance ». Topics in Catalysis 54, n^o 5-7 (8 février 2011) : 424–38. http://dx.doi.org/10.1007/s11244-011-9673-2.

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Holade, Yaovi, Claudia Morais, Karine Servat, Teko W. Napporn et K. Boniface Kokoh. « Enhancing the available specific surface area of carbon supports to boost the electroactivity of nanostructured Pt catalysts ». Phys. Chem. Chem. Phys. 16, n^o 46 (2014) : 25609–20. http://dx.doi.org/10.1039/c4cp03851g.

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Magro, Massimiliano, Davide Baratella, Andrea Venerando, Giulia Nalotto, Caroline R. Basso, Simone Molinari, Gabriella Salviulo, Juri Ugolotti, Valber A. Pedrosa et Fabio Vianello. « Enzyme Immobilization on Maghemite Nanoparticles with Improved Catalytic Activity : An Electrochemical Study for Xanthine ». Materials 13, n^o 7 (10 avril 2020) : 1776. http://dx.doi.org/10.3390/ma13071776.

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Generally, enzyme immobilization on nanoparticles leads to nano-conjugates presenting partially preserved, or even absent, biological properties. Notwithstanding, recent research demonstrated that the coupling to nanomaterials can improve the activity of immobilized enzymes. Herein, xanthine oxidase (XO) was immobilized by self-assembly on peculiar naked iron oxide nanoparticles (surface active maghemite nanoparticles, SAMNs). The catalytic activity of the nanostructured conjugate (SAMN@XO) was assessed by optical spectroscopy and compared to the parent enzyme. SAMN@XO revealed improved catalytic features with respect to the parent enzyme and was applied for the electrochemical studies of xanthine. The present example supports the nascent knowledge concerning protein conjugation to nanoparticle as a means for the modulation of biological activity.

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Saffari, Nafiseh Sadat, Behzad Aghabarari, Masoumeh Javaheri, Ali Khanlarkhani et Maria Victoria Martinez-Huerta. « Transforming Waste Clamshell into Highly Selective Nanostructured Catalysts for Solvent Free Liquid Phase Oxidation of Benzyl Alcohol ». Catalysts 12, n^o 2 (27 janvier 2022) : 155. http://dx.doi.org/10.3390/catal12020155.

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High yield production of benzaldehyde in the solvent-free oxidation of benzyl alcohol by using green catalysts is highly desirable. In this work, calcium hydroxide derived from waste clamshell was used as low-cost and environmentally friendly catalyst support (CaSUP) for Pd and V nanoparticles. The physicochemical properties of the catalysts were analyzed using X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic oxidation of benzyl alcohol to benzaldehyde was studied in a liquid phase reaction by using H2O2 as an oxidizing agent. The effects of catalyst loading, the molar ratio of hydrogen peroxide to benzyl alcohol, temperature and reaction duration were investigated. In the optimized conditions, Pd nanoparticles supported on clamshell-derived supports displayed excellent catalytic conversion (88%) and selectivity to benzaldehyde (89%). Furthermore, the catalyst can be effectively reused without a significant loss in its activity and selectivity. The high yield and stability can be related to the structural and basic properties of the catalyst. These results provide important insights into the benzyl alcohol oxidation process for industrial applications.

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Ochoa, Elba, Daniel Torres, José Luis Pinilla et Isabel Suelves. « Nanostructured Carbon Material Effect on the Synthesis of Carbon-Supported Molybdenum Carbide Catalysts for Guaiacol Hydrodeoxygenation ». Energies 13, n^o 5 (5 mars 2020) : 1189. http://dx.doi.org/10.3390/en13051189.

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The impact of using different nanostructured carbon materials (carbon nanofibers, carbon nanotubes, graphene oxide and activated carbon) as a support for Mo2C-based catalysts on the hydrodeoxygenation (HDO) of guaiacol was studied. To optimise the catalyst preparation by carbothermal hydrogen reduction (CHR), a thermogravimetric study was conducted to select the optimum CHR temperature for each carbon material, considering both the crystal size of the resulting β-Mo2C particles and the extent of the support gasification. Subsequently, catalysts were prepared in a fixed bed reactor at the optimum temperature. Catalyst characterization evidenced the differences in the catalyst morphology as compared to those prepared in the thermogravimetric study. The HDO results demonstrated that the carbon nanofiber-based catalyst was the one with the best catalytic performance. This behaviour was attributed to the high thermal stability of this support, which prevented its gasification and promoted a good evolution of the crystal size of Mo species. This catalyst exhibited well-dispersed β-Mo2C nanoparticles of ca. 11 nm. On the contrary, the other supports suffered from severe gasification (60–70% wt. loss), which resulted in poorer HDO efficiency catalysts regardless of the β-Mo2C crystal size. This exhibited the importance of the carbon support stability in Mo2C-based catalysts prepared by CHR.

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Naef, Noah U., et Stefan Seeger. « Silicone Nanofilament Support Layers in an Open-Channel System for the Fast Reduction of Para-Nitrophenol ». Nanomaterials 11, n^o 7 (24 juin 2021) : 1663. http://dx.doi.org/10.3390/nano11071663.

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Chemical vapor phase deposition was used to create hydrophobic nanostructured surfaces on glass slides. Subsequently, hydrophilic channels were created by sputtering a metal catalyst on the channels while masking the outside. The surface tension gradient between the hydrophilic surface in the channels and the outside hydrophobicity formed the open-channel system. The reduction of para-nitrophenol (PNP) was studied on these devices. When compared to nanostructure-free reference systems, the created nanostructures, namely, silicone nanofilaments (SNFs) and nano-bagels, had superior catalytic performance (73% and 66% conversion to 55% at 0.5 µL/s flow rate using 20 nm platinum) and wall integrity; therefore, they could be readily used multiple times. The created nanostructures were stable under the reaction conditions, as observed with scanning electron microscopy. Transition electron microscopy studies of platinum-modified SNFs revealed that the catalyst is present as nanoparticles ranging up to 13 nm in size. By changing the target in the sputter coating unit, molybdenum, gold, nickel and copper were evaluated for their catalytic efficiency. The relative order was platinum < gold = molybdenum < nickel < copper. The decomposition of sodium borohydride (NaBH4) by platinum as a concurrent reaction to the para-nitrophenol reduction terminates the reaction before completion, despite a large excess of reducing agent. Gold had the same catalytic rate as molybdenum, while nickel was two times and copper about four times faster than gold. In all cases, there was a clear improvement in catalysis of silicone nanofilaments compared to a flat reference system.

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Isaeva, Vera I., Vladimir V. Chernyshev, Vadim V. Vergun, Danil A. Arkhipov, Grigory S. Deyko, Lev M. Glukhov, Gennady I. Kapustin, Olga P. Tkachenko et Leonid M. Kustov. « The Impact of Functionality and Porous System of Nanostructured Carriers Based on Metal–Organic Frameworks of UiO-66-Type on Catalytic Performance of Embedded Au Nanoparticles in Hydroamination Reaction ». Catalysts 13, n^o 1 (6 janvier 2023) : 133. http://dx.doi.org/10.3390/catal13010133.

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New methods for the preparation of metal–organic frameworks UiO-66 and NH2-UiO-66 with a hierarchical porous structure were developed using the MW-assisted technique under atmospheric pressure. The synthesized nanostructured meso-UiO-66 and meso-NH2-UiO-66 matrices were utilized as Au nanoparticle carriers. The resulting Au@meso-UiO-66 and Au@NH2-UiO-66 nanohybrids were studied in the reaction of phenylacetylene hydroamination with aniline into imine ([phenyl-(1-phenylethylydene)amine]) for the first time. Their catalytic behavior is significantly determined by a combination of factors, such as a small crystal size, micro–mesoporous structure, and functionality of the UiO-66 and NH2-UiO-66 carriers, as well as a high dispersion of embedded gold nanoparticles. The Au@meso-UiO-66 and Au@NH2-UiO-66 nanocatalysts demonstrate high activities (TOF), with conversion and selectivity values over 90. This excellent catalytic performance is comparable or even better than that demonstrated by heterogeneous systems based on conventional inorganic and inorganic supports known from the literature.

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Bykov, Alexey V., Galina N. Demidenko, Linda Zh Nikoshvili et Lioubov Kiwi-Minsker. « Hyper-Cross-Linked Polystyrene as a Stabilizing Medium for Small Metal Clusters ». Molecules 26, n^o 17 (31 août 2021) : 5294. http://dx.doi.org/10.3390/molecules26175294.

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Among different polymers nanostructured cross-linked aromatics have the greatest potential as catalytic supports due to their exceptional thermal and chemical stability and preservation of the active phase morphology. This work studies the ability of hyper-cross-linked polystyrene (HPS) to stabilize small Pdn and Ptn (n = 4 or 9) clusters. Unrestricted DFT calculations were carried out for benzene (BZ) adsorption at the BP level of theory using triple-zeta basis sets. The adsorption of BZ rings (stepwise from one to four) was found to result in noticeable gain in energy and stabilization of resulting adsorption complexes. Moreover, the interaction of metal clusters with HPS micropores was also addressed. For the first time, the incorporation of small clusters in the HPS structure was shown to influences its geometry resulting in the stabilization of polymer due to its partial relaxation.

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Islam, Md Aminul, M. Anwarul Kabir Bhuiya et M. Saidul Islam. « A Review on Chemical Synthesis Process of Platinum Nanoparticles ». Asia Pacific Journal of Energy and Environment 1, n^o 2 (31 décembre 2014) : 103–16. http://dx.doi.org/10.18034/apjee.v1i2.215.

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Nanoparticles are key components in the advancement of future energy technologies; thus, strategies for preparing nanoparticles in large volume by techniques that are cost-effective are required. In the substitution of fossil-fuels by renewable energy resources, nanometersized particles play a key role for synthesizing energy vectors from varying and heterogeneous biomass feedstocks. They are extensively used in reformers for the production of hydrogen from solid, liquid, or gaseous energy carriers. Catalyst activities depend critically on their size-dependent properties. Nanoparticles are further indispensable as electrocatalysts in fuel cells and other electrochemical converters. The desire to increase the activity per unit area, and decrease the necessary amount of the expensive catalytic standard, It is clear that performance and commercialization of fuel cells depend on electrode materials performance. The application of pt nanomaterials as an electrode in the field of fuel cell has become a new, growing area of interest in recent years. We review chemical process for synthesis of pt nanoparticles. Recent developments in syntheses process of pure & mixed platinum nanoparticles has briefly reviewed specifically for applications in fuel cells. As the physicochemical properties of noble-metal nanostructures are strongly dependent upon shape and size, the development of reliable synthesis methods for the production of nanocrystals with well-defined size and morphology have been discussed briefly. The role of nanostructured supports for the nanoparticles, such as ordered mesoporous carbon, dendrimer have also discussed. And size of the nanoparticles obtained in deferent process and their temperature dependence has also discussed briefly.

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Kostuch, Aldona, Pawel J. Kulesza, Anna Wadas, Beata Dembinska, Iwona A. Rutkowska, Kinga Zdunek, Enrico Negro, Vito Di Noto et Keti Vezzu. « Enhancement of Activity Low-Pt-Content O₂-Reduction Catalysts through Formation of Hybrid Systems with Sub-Stoichiometric Cerium Oxide Nanostructures ». ECS Meeting Abstracts MA2022-01, n^o 49 (7 juillet 2022) : 2069. http://dx.doi.org/10.1149/ma2022-01492069mtgabs.

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Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, under such condition, O2-reduction reaction (ORR) often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Recent studies have demonstrated that the rational design of a catalytic system is based on nanostructures of platinum, or carbon-supported platinum (Pt/C), and metal oxide (MOx). By combining the catalytic properties of both components, such hybrid Pt-MOx catalysts are capable of tuning of the activity and durability of Pt. Due to strong interactions of MOx with Pt catalytic nanoparticles leading to the improved activity and durability during ORR, certain nanostructured metal oxides are considered as co-catalysts or active components of supports. The existence of specific interactions between MOx and noble metal (Pt) nanoparticles should improve the stability and activity of the metal catalytic sites due to modification of the Pt electronic structure and diminishing of the oxo (OH) species adsorption on Pt surface, thus promoting centers for the adsorption of oxygen and the cleavage of O=O bonds. The interactions mentioned above would also facilitate dispersion of Pt, inhibit their detachment and further aggregation, and, consequently, prevent or decrease their degradation during the fuel cell operation [1]. The catalytic activity of substoichiometric ceria, CeOx (where x < 2) additive results from its unique structure, presence of oxygen vacancies, and other features resulting from the 4f-electronic configuration of cerium. While the oxygen defects are likely to serve as active oxygen adsorption sites, the mixed-valent CeIII/CeIV redox sites should permit the electron shuffling within the lattice of oxygen vacancies and enhancing the ORR activity. The formation of oxygen-defects is accompanied by the localization of electrons left behind in Ce 4f states, thus leading to the formation of CeIII species capable of elongating and reducing the O–O bond strength of the adsorbed O2 molecule; consequently, by increasing the relative ratio of CeIII-to-CeIV, the ORR electrocatalytic activity can be improved [1]. Therefore, in the present study, we consider the intentionally reduced CeOx nanostructured components through subjecting them to high-temperature pretreatment in the presence of argon gas admixed with hydrogen. It is reasonable to expect that, the increased population of CeIII sites on the surfaces of the pretreated ceria particles would stabilize the neighboring active Pt-metal centers, exhibit reductive interactions toward Pt-oxo species, and to improve durability of the catalytic materials. Thus the boundary formed between the Pt-metal and CeOx-metal oxide should facilitate inhibition of the Pt oxide formation by the CeOx layer. Furthermore, our recent studies clearly show that, in the presence of ceria, the oxidative degradation of carbon carriers is also largely decreased. Finally, cerium oxide is known to act as the oxidative scavenger for free radicals such as hydroxyl (HO•) and hydroperoxyl (HOO•), which, once generated, would otherwise lead to the formation of undesirable hydrogen peroxide. Sub-stoichiometric CeOx is capable of rapidly switching between CeIII and CeIV oxidation states, thus inducing the decomposition of both radicals and peroxides. The above observation seems to be very helpful when it comes to designing highly active and durable ORR catalysts containing low platinum loadings. [1] A.Kostuch, I.A. Rutkowska, B. Dembinska, A. Wadas, E. Negro, K. Vezzù, V. Di Noto, P.J. Kulesza, Molecules 26 (2021) 5147. Acknowledgements: This work was supported by the National Science Center (Poland) under Opus Project (2018/29/B/ST5/02627) and under auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

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Rilievo, Graziano, Alessandro Cecconello, Simone Molinari, Andrea Venerando, Lavinia Rutigliano, Gayathri T. Govardhan, Dinusha H. Kariyawasam et al. « Acidic Shift of Optimum pH of Bovine Serum Amine Oxidase upon Immobilization onto Nanostructured Ferric Tannates ». International Journal of Molecular Sciences 23, n^o 20 (12 octobre 2022) : 12172. http://dx.doi.org/10.3390/ijms232012172.

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Protein–nanoparticle hybrids represent entities characterized by emerging biological properties that can significantly differ from those of the parent components. Herein, bovine serum amine oxidase (i.e., BSAO) was immobilized onto a magnetic nanomaterial constituted of surface active maghemite nanoparticles (i.e., SAMNs, the core), surface-modified with tannic acid (i.e., TA, the shell), to produce a biologically active ternary hybrid (i.e., SAMN@TA@BSAO). In comparison with the native enzyme, the secondary structure of the immobilized BSAO responded to pH variations sensitively, resulting in a shift of its optimum activity from pH 7.2 to 5.0. Conversely, the native enzyme structure was not influenced by pH and its activity was affected at pH 5.0, i.e., in correspondence with the best performances of SAMN@TA@BSAO. Thus, an extensive NMR study was dedicated to the structure–function relationship of native BSAO, confirming that its low activity below pH 6.0 was ascribable to minimal structural modifications not detected by circular dichroism. The generation of cytotoxic products, such as aldehydes and H2O2, by the catalytic activity of SAMN@TA@BSAO on polyamine oxidation is envisaged as smart nanotherapy for tumor cells. The present study supports protein–nanoparticle conjugation as a key for the modulation of biological functions.

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Papakonstantinou, Georgios D., Jelena M. Jaksic, Diamantoula Labou, Angeliki Siokou et Milan M. Jaksic. « Spillover Phenomena and Its Striking Impacts in Electrocatalysis for Hydrogen and Oxygen Electrode Reactions ». Advances in Physical Chemistry 2011 (19 janvier 2011) : 1–22. http://dx.doi.org/10.1155/2011/412165.

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The core subject of the present paper represents the interrelated spillover (effusion) phenomena both of the primary oxide and the H-adatoms, their theory and practice, causes, appearances and consequences, and evidences of existence, their specific properties, and their alterpolar equilibria and kinetic behavior, structural, and resulting catalytic, and double layer charging features. The aim is to introduce electron conductive and d-d interactive individual and composite (mixed valence) hypo-d-oxide compounds, of increased altervalent capacity, or their suboxides (Magnéli phases), as the interactive catalytic supports and therefrom provide (i) the strong metal-support interaction (SMSI) catalytic effect and (ii) dynamic spillover interactive transfer of primary oxides (M-OH) and free effusional H-adatoms for further electrode reactions and thereby advance the overall electrocatalytic activity. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. In fact, altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and then spontaneously pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H0.35WO3 Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured-type electrocatalysts, even of mixed-valence hypo-d-oxide structures (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C), have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron conductivity, and nonexchanged initial pure monobronze spillover and catalytic properties. Such a unique electrocatalytic system, as the striking target issue of the present paper, has been shown to be the superior for substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The main target of the present thorough review study has been to throw some specific insight light on the overall spillover phenomena and their effects in electrocatalysis of oxygen and hydrogen electrode reactions from diverse angles of view and broad contemporary experimental methods and approaches (XPS, FTIR, DRIFT, XRD, potentiodynamic spectra, UHRTEM).

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Plankensteiner, Nina, Stanley Bus, Anna Staerz, Cole Smith et Philippe M. Vereecken. « High Surface Area 3D Copper Nanowire Networks for High-Throughput Electrochemical CO₂ Reduction ». ECS Meeting Abstracts MA2022-02, n^o 22 (9 octobre 2022) : 928. http://dx.doi.org/10.1149/ma2022-0222928mtgabs.

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An attractive solution towards net-zero carbon emission is the electrocatalytic CO2 reduction with its ability to convert the greenhouse gas CO2 with renewable electricity and appropriate catalytic materials to useful chemicals and fuels to store energy. Depending on the number of electrons transferred a variety of oxygenates and hydrocarbons can be obtained. Among used catalytic materials, such as metals, alloys or composites, copper has shown the unique property to electrocatalytically convert CO2 into a wide variety of valuable C2+ products such as ethylene or alcohols. Apart from the high potential to reshape our carbon economy the electrocatalytic CO2 reduction is still in its early development stage compared to the more mature water electrolysis, with high-throughput operation at practical current densities as well as long-term stability of the catalysts being only scarcely demonstrated. Additionally, selectivity towards high-value (beyond C1) products using copper catalysts has proven to be challenging and many research efforts are directed towards improving product selectivity. For this purpose, mainly nanostructured porous Cu electrodes either based on randomly ordered nanoparticles loaded on porous (carbon-based) supports or low-surface area metal foams, meshes or felts with high porosity are commonly used. While the former electrode architecture typically shows poor long-term stability with often weak adhesion between the nanoparticles and the porous support, the latter electrodes have a low electrochemical surface area and hence are not suitable for high-throughput CO2 reduction at high current densities. In this work we present novel high-surface area porous copper electrodes, so-called copper nanomeshes, that are regular 3D-networks of interconnected Cu nanowires. These unique few µm-thin electrodes show a large surface area enhancement (compared to planar Cu) by a factor of ~80, while providing a high porosity of ~70% together with sufficient mechanical stability, an important aspect towards their practical implementation in electrocatalytic flow cells. Cu nanomesh electrodes with a thickness of 4µm were fabricated through electrochemically plating in 3D-porous anodic aluminum oxide templates and show a mixed surface texture of (111), (100) and (110) Cu. We demonstrate the high potential toward high-throughput CO2 electrolysis of these novel electrodes in comparison to planar copper electrodes in various CO2-containing electrolyte solutions. The CO2 reduction product analysis showed a significant difference in selectivity between planar (polycrystalline or with preferential 111 or 200 texture) and the polycrystalline Cu nanomesh electrodes with CO or C2H4 as major reduction products depending on the potential applied. The beneficial effect of the high electrochemical surface area was demonstrated by a significant increase in the current density on the nanostructured Cu electrodes. Additionally, we characterized the copper nanomesh electrodes before, during and after CO2 reduction with complementary techniques to gain insights on the reaction mechanism and on the electrode stability. Figure 1

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Li, Huan Ying, Shu Li Bai, Wen Ping Jia et Fang Li. « The Preparation and Characterization of Carbon Nanostructures Catalyst and its Catalytic Activity ». Advanced Materials Research 418-420 (décembre 2011) : 629–32. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.629.

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In this work, the constructing of different carbon nanostructures materials were studied, and the single-structure and pure surface of carbon nanostructures were employed to as catalyst support and the morphology and structure of different carbon nanostructures-based catalysts were investigated. NO catalytic reduction was used as a probe reaction to investigate the catalytic properties of different carbon nanostructures materials and how the controlling of carbon nanostructures would affect its catalytic functions. The results show that vanadium was molecularly anchored on the surface of carbon nanostructures and the mesh-carbon nanotubes as a support show a high catalytic activity.

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Woitassek, Dennis, José G. Moya-Cancino, Yangyang Sun, Yefan Song, Dennis Woschko, Stefan Roitsch et Christoph Janiak. « Sweet, Sugar-Coated Hierarchical Platinum Nanostructures for Easy Support, Heterogenization and Separation ». Chemistry 4, n^o 4 (30 septembre 2022) : 1147–60. http://dx.doi.org/10.3390/chemistry4040078.

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Metal nanoparticles are increasingly gaining interest in the field of heterogeneous catalysis. Here, we present a novel strategy for synthesizing sugar-coated platinum nanostructures (SC-Pt-NS) from the carbohydrates sucrose and D(-)-fructose. In the synthesis from a mixture of H2PtCl6·6H2O, the carbohydrate in an ionic liquid (IL) yielded primary particles of a homogeneous average size of ~10 nm, which were aggregated to hierarchical Pt nanostructures of ~40–65 nm and surrounded or supported by the carbohydrate. These sugar-coated platinum nanostructures present a facile way to support and heterogenize nanoparticles, avoid leaching and enable easier separation and handling. The catalytic activity of the SC-Pt-NS was shown in the hydrosilylation test reaction of phenylacetylene with triethylsilane, where very high turnover frequency (TOF) values of up to 87,200 h−1 could be achieved, while the platinum metal leaching into the product was very low.

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Xamidov, Anvar, Farhodjon Hoshimov, Shavkat Mamatkulov, Khakimjan Butanov, Mirakhmat Yunusov et Olim Ruzimuradov. « Catalytic Activity of Ni, Co, Mo Supported Anodic Aluminum Oxide Nanocomposites ». Bulletin of Chemical Reaction Engineering & ; Catalysis 15, n^o 3 (10 novembre 2020) : 845–52. http://dx.doi.org/10.9767/bcrec.15.3.8480.845-852.

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Nanostructured catalysts based on porous aluminum oxide (PAO) and some 3d metals, such as: nickel, cobalt, and molybdenum, have been obtained by anodic oxidation and impregnation. The synthesis of porous aluminum oxide with a highly ordered pore structure with pore sizes of 50 nm and a thickness of 50 µm is carried out by the method of two-stage anodic oxidation. The catalysts are obtained by impregnation of 3d metals into nanosized pores of aluminum oxide. The obtained catalysts based on nickel and porous Al2O3 are studied by scanning electron microscopy (SEM-EDX). The results of SEM-EDX analysis shows that a spongy structure with filament sizes of 100 nanometers containing particles of 3d metals formed on the surface of the aluminum oxide matrix. The results are presented on the activity of nickel and heterogenic cobalt and molybdenum nanoparticles in the reaction of hydrogenation of hexene to hexane. The results show that the yield temperature of the hexane is decreased and the yield of hexane is observed at 200 °C with Ni/Al2O3 catalysts, and a similar yield of hexane mass is achieved at temperatures higher than 250 °C with Co-Mo/Al2O3 and traditional nickel catalysts on kieselguhr. Copyright © 2020 BCREC Group. All rights reserved

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Kang, Bowen, Tingting Zhang, Lei Yan, Chengxiang Gou, Zihe Jiang, Min Ji, Li Chen, Zhenglong Zhang, Hairong Zheng et Hongxing Xu. « Local controllability of hot electron and thermal effects enabled by chiral plasmonic nanostructures ». Nanophotonics 11, n^o 6 (2 février 2022) : 1195–202. http://dx.doi.org/10.1515/nanoph-2021-0780.

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Abstract The control of hot electron (HE) and thermal effects induced by plasmonic nanostructures has recently attracted considerable attention. When illuminated by light with different circular polarization states, the circular dichroism signal of molecules adsorbed by plasmonic chiral nanostructures can control HE and thermal effects. These effects have the potential to enhance reaction rates and to change selectivity patterns in photothermal catalysis. Here, we propose an aluminum L-shaped chiral nanostructure system in which HE and thermal effects can be controlled in different regions of the nanostructure by changing the chirality of the excitation light. A large difference of 12.75% in the HE effect but a virtually identical thermal effect can be achieved in different regions of the nanostructure by selecting the appropriate probed region, while a large thermal effect difference of 65.67% but a virtually identical HE effect can be achieved in one region of the nanostructure by changing the polarization state of the excitation light. In addition, the HE and thermal chiral selectivity effects of double L-shaped nanostructures are investigated as these structures can be more easily controlled during asymmetric chiral growth and crystallization. This work combined with plasmonic chirality is beneficial for quantifying HE and thermal effects in photochemical reactions and provides theoretical support for designing catalysts and optimizing plasmonic platforms. Additionally, the local controllability of HE and thermal effects plays an essential role in high-resolution photochemical reactions, especially in single-molecule photochemical reactions.

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Duan, Sibin, Zhe Du, Hongsheng Fan et Rongming Wang. « Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications ». Nanomaterials 8, n^o 11 (17 novembre 2018) : 949. http://dx.doi.org/10.3390/nano8110949.

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Platinum-based nanomaterials have attracted much interest for their promising potentials in fields of energy-related and environmental catalysis. Designing and controlling the surface/interface structure of platinum-based nanomaterials at the atomic scale and understanding the structure-property relationship have great significance for optimizing the performances in practical catalytic applications. In this review, the strategies to obtain platinum-based catalysts with fantastic activity and great stability by composition regulation, shape control, three-dimension structure construction, and anchoring onto supports, are presented in detail. Moreover, the structure-property relationship of platinum-based nanomaterials are also exhibited, and a brief outlook are given on the challenges and possible solutions in future development of platinum-based nanomaterials towards catalytic reactions.

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Lisovski, Oleg, Sergei Piskunov, Dmitry Bocharov, Yuri Zhukovskii, Janis Kleperis, Ainars Knoks et Peteris Lesnicenoks. « CO2 and CH2 Adsorption on Copper-Decorated Graphene : Predictions from First Principle Calculations ». Crystals 12, n^o 2 (28 janvier 2022) : 194. http://dx.doi.org/10.3390/cryst12020194.

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Single-layer graphene decorated with monodisperse copper nanoparticles can support the size and mass-dependent catalysis of the selective electrochemical reduction of CO2 to ethylene (C2H4). In this study, various active adsorption sites of nanostructured Cu-decorated graphene have been calculated by using density functional theory to provide insight into its catalytic activity toward carbon dioxide electroreduction. Based on the results of our calculations, an enhanced adsorption of the CO2 molecule and CH2 counterpart placed atop of Cu-decorated graphene compared to adsorption at pristine Cu metal surfaces was predicted. This approach explains experimental observations for carbon-based catalysts that were found to be promising for the two-electron reduction reaction of CO2 to CO and, further, to ethylene. Active adsorption sites that lead to a better catalytic activity of Cu-decorated graphene, with respect to general copper catalysts, were identified. The atomic configuration of the most selective CO2 toward the reduction reaction nanostructured catalyst is suggested.

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Chellasamy, Velu, et Ramasamy Manoharan. « The Role of Nanostructured Active Support Materials in Electrocatalysis of Direct Methanol Fuel Cell Reactions ». Materials Science Forum 710 (janvier 2012) : 709–14. http://dx.doi.org/10.4028/www.scientific.net/msf.710.709.

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The necessity for developing oxidation–resistant noncarbon catalyst support materials for use in the electrode/electrolyte interface of proton exchange membrane (PEM) based direct methanol fuel cells (DMFCs) is emphasized. A great deal of attention is currently being paid to nanostructured catalytic and support materials for electrocatalysing both anodic methanol oxidation reaction (MOR) and cathodic oxygen reduction reaction (ORR). The performances of various nanostructured transition metal oxides have been reviewed. Mn3O4 nanorods have been synthesized by us and their performances for electrocatalysing the MOR with Pd catalyst are discussed. A model explaining how nanostructured active support materials can extract active oxygen atoms required for complete oxidation of methanol from the electrolyte and supply to the adjacent catalytic sites has been proposed.

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An, Jing, Galong Li, Yifan Zhang, Tingbin Zhang, Xiaoli Liu, Fei Gao, Mingli Peng, Yuan He et Haiming Fan. « Recent Advances in Enzyme-Nanostructure Biocatalysts with Enhanced Activity ». Catalysts 10, n^o 3 (18 mars 2020) : 338. http://dx.doi.org/10.3390/catal10030338.

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Owing to their unique physicochemical properties and comparable size to biomacromolecules, functional nanostructures have served as powerful supports to construct enzyme-nanostructure biocatalysts (nanobiocatalysts). Of particular importance, recent years have witnessed the development of novel nanobiocatalysts with remarkably increased enzyme activities. This review provides a comprehensive description of recent advances in the field of nanobiocatalysts, with systematic elaboration of the underlying mechanisms of activity enhancement, including metal ion activation, electron transfer, morphology effects, mass transfer limitations, and conformation changes. The nanobiocatalysts highlighted here are expected to provide an insight into enzyme–nanostructure interaction, and provide a guideline for future design of high-efficiency nanobiocatalysts in both fundamental research and practical applications.

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Jin, Rongchao. « The impacts of nanotechnology on catalysis by precious metal nanoparticles ». Nanotechnology Reviews 1, n^o 1 (1 janvier 2012) : 31–56. http://dx.doi.org/10.1515/ntrev-2011-0003.

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AbstractThis review article focuses on the impacts of recent advances in solution phase precious metal nanoparticles on heterogeneous catalysis. Conventional nanometal catalysts suffer from size polydispersity. The advent of nanotechnology has significantly advanced the techniques for preparing uniform nanoparticles, especially in solution phase synthesis of precious metal nanoparticles with excellent control over size, shape, composition and morphology, which have opened up new opportunities for catalysis. This review summarizes some recent catalytic research by using well-defined nanoparticles, including shape-controlled nanoparticles, high index-faceted polyhedral nanocrystals, nanostructures of different morphology (e.g., core-shell, hollow, etc.), bi- and multi-metallic nanoparticles, as well as atomically precise nanoclusters. Such well-defined nanocatalysts provide many exciting opportunities, such as identifying the types of active surface atoms (e.g., corner and edge atoms) in catalysis, the effect of surface facets on catalytic performance, and obtaining insight into the effects of size-induced electron energy quantization in ultra-small metal nanoparticles on catalysis. With well-defined metal nanocatalysts, many fundamentally important issues are expected to be understood much deeper in future research, such as the nature of the catalytic active sites, the metal-support interactions, the effect of surface atom arrangement, and the atomic origins of the structure-activity and the structure-selectivity relationships.

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Sarigamala, Karthik Kiran, Shobha Shukla, Alexander Struck et Sumit Saxena. « Graphene-Based Coronal Hybrids for Enhanced Energy Storage ». Energy Material Advances 2021 (20 février 2021) : 1–15. http://dx.doi.org/10.34133/2021/7273851.

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Functional materials with designer morphologies are anticipated to be the next generation materials for energy storage applications. In this manuscript, we have developed a holistic approach to enhance the surface area and hence the properties of nanostructures by synthesizing coronal nanohybrids of graphene. These nanohybrids provide distinctive advantages in terms of performance and stability over vertically stacked nanocomposites reported in literature. Various double hydroxide materials self-assembled as coronal lamellae on graphene shells have been synthesized and systematically studied. These coronal nanohybrids result in about a threefold increase in energy storage capacity as compared to their traditionally synthesized nanocomposite counterparts. The 3D graphene-based nanofibrils in the synthesized coronal nanohybrids provide mechanical support and connect the nodes of the double hydroxide lattices to inhibit restacking. Complex morphologies such as coronal nanostructures increase the interaction surface of the nanostructure significantly. Such an approach is also expected to bring a paradigm shift in development of functional materials for various applications such as sensors, energy storage, and catalysis.

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Zhang, Xiaolong, Lei Chen, Yang Liu et Qian Duan. « Preparation of Reduced-Graphene-Oxide-Supported CoPt and Ag Nanoparticles for the Catalytic Reduction of 4-Nitrophenol ». Catalysts 11, n^o 11 (5 novembre 2021) : 1336. http://dx.doi.org/10.3390/catal11111336.

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Composite nanostructure materials are widely used in catalysis. They exhibit several characteristics, such as the unique structural advantage and the synergism among their components, which significantly enhances their catalytic performance. In this work, CoPt nanoparticles and reduced-graphene-oxide-based nanocomposite catalysts (rGO/CoPt, rGO/CoPt/Ag) were prepared by using a facile co-reduction strategy. The crystalline structure, morphology, composition, and optical characteristics of the CoPt nanoparticles, rGO/CoPt nanocomposite, and rGO/CoPt/Ag nanocomposite catalysts were investigated by a set of techniques. The ID/IG value of the rGO/CoPt/Ag nanocomposite is 1.158, higher than that of rGO/CoPt (1.042). The kinetic apparent rate constant, k, of the rGO/CoPt/Ag nanocomposite against 4-nitrophenol (4-NP) reduction is 5.306 min−1, which is higher than that of CoPt (0.495 min−1) and rGO/CoPt (1.283 min−1). The normalized rate constant, knor, of the rGO/CoPt/Ag nanocomposite is 56.76 min−1mg−1, which is higher than some other catalytic materials. The rGO/CoPt/Ag nanocomposite shows a significantly enhanced catalytic performance when compared to CoPt nanoparticles and the rGO/CoPt nanocomposite, which may confirm that the novel rGO/CoPt/Ag nanocomposite is a promising catalyst for the application of catalytic fields.

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Gamal, Ahmed, Kamel Eid, Muftah H. El-Naas, Dharmesh Kumar et Anand Kumar. « Catalytic Methane Decomposition to Carbon Nanostructures and COx-Free Hydrogen : A Mini-Review ». Nanomaterials 11, n^o 5 (6 mai 2021) : 1226. http://dx.doi.org/10.3390/nano11051226.

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Catalytic methane decomposition (CMD) is a highly promising approach for the rational production of relatively COx-free hydrogen and carbon nanostructures, which are both important in multidisciplinary catalytic applications, electronics, fuel cells, etc. Research on CMD has been expanding in recent years with more than 2000 studies in the last five years alone. It is therefore a daunting task to provide a timely update on recent advances in the CMD process, related catalysis, kinetics, and reaction products. This mini-review emphasizes recent studies on the CMD process investigating self-standing/supported metal-based catalysts (e.g., Fe, Ni, Co, and Cu), metal oxide supports (e.g., SiO2, Al2O3, and TiO2), and carbon-based catalysts (e.g., carbon blacks, carbon nanotubes, and activated carbons) alongside their parameters supported with various examples, schematics, and comparison tables. In addition, the review examines the effect of a catalyst’s shape and composition on CMD activity, stability, and products. It also attempts to bridge the gap between research and practical utilization of the CMD process and its future prospects.

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Cringoli, Maria Cristina, Siglinda Perathoner, Paolo Fornasiero et Silvia Marchesan. « Carbon Nanostructures Decorated with Titania : Morphological Control and Applications ». Applied Sciences 11, n^o 15 (24 juillet 2021) : 6814. http://dx.doi.org/10.3390/app11156814.

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Nanostructured titania (TiO2) is the most widely applied semiconducting oxide for a variety of purposes, and it is found in many commercial products. The vast majority of uses rely on its photo-activity, which, upon light irradiation, results in excited states that can be used for diverse applications. These range from catalysis, especially for energy or environmental remediation, to medicine—in particular, to attain antimicrobial surfaces and coatings for titanium implants. Clearly, the properties of titania are enhanced when working at the nanoscale, thanks to the increasingly active surface area. Nanomorphology plays a key role in the determination of the materials’ final properties. In particular, the nucleation and growth of nanosized titania onto carbon nanostructures as a support is a hot topic of investigation, as the nanocarbons not only provide structural stability but also display the ability of electronic communication with the titania, leading to enhanced photoelectronic properties of the final materials. In this concise review, we present the latest progress pertinent to the use of nanocarbons as templates to tailor nanostructured titania, and we briefly review the most promising applications and future trends of this field.

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Wang, Xu, Lin-Ying Du, Meng Du, Chao Ma, Jie Zeng, Chun-Jiang Jia et Rui Si. « Catalytically active ceria-supported cobalt–manganese oxide nanocatalysts for oxidation of carbon monoxide ». Physical Chemistry Chemical Physics 19, n^o 22 (2017) : 14533–42. http://dx.doi.org/10.1039/c7cp02004j.

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Fraile, José M., José I. García, Clara I. Herrerías, José A. Mayoral et Elísabet Pires. « Enantioselective catalysis with chiral complexes immobilized on nanostructured supports ». Chem. Soc. Rev. 38, n^o 3 (2009) : 695–706. http://dx.doi.org/10.1039/b806643b.

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Zhu, Yuhua, Yuan Yao, Zhu Luo, Chuanqi Pan, Ji Yang, Yarong Fang, Hongtao Deng et al. « Nanostructured MoO3 for Efficient Energy and Environmental Catalysis ». Molecules 25, n^o 1 (19 décembre 2019) : 18. http://dx.doi.org/10.3390/molecules25010018.

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This paper mainly focuses on the application of nanostructured MoO3 materials in both energy and environmental catalysis fields. MoO3 has wide tunability in bandgap, a unique semiconducting structure, and multiple valence states. Due to the natural advantage, it can be used as a high-activity metal oxide catalyst, can serve as an excellent support material, and provide opportunities to replace noble metal catalysts, thus having broad application prospects in catalysis. Herein, we comprehensively summarize the crystal structure and properties of nanostructured MoO3 and highlight the recent significant research advancements in energy and environmental catalysis. Several current challenges and perspective research directions based on nanostructured MoO3 are also discussed.

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Yin, S. M., J. J. Duanmu, Y. H. Zhu, Y. F. Yuan, S. Y. Guo, J. L. Yang, Z. H. Ren et G. R. Han. « Investigation on CO catalytic oxidation reaction kinetics of faceted perovskite nanostructures loaded with Pt ». RSC Advances 7, n^o 10 (2017) : 6102–7. http://dx.doi.org/10.1039/c6ra24713j.

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Perovskite lead titanate nanostructures with specific {111}, {100} and {001} facets exposed, have been employed as supports to investigate the crystal facet effect on the growth and CO catalytic activity of Pt nanoparticles.

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Konopka, Daniel, Svitlana Pylypenko, Timothy Ward et Plamen Atanassov. « Nanostructured Mesoporous NbRuyOz as a Catalytic Support for Fuel Cells ». ECS Transactions 19, n^o 27 (18 décembre 2019) : 117–25. http://dx.doi.org/10.1149/1.3265875.

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Ochoa-Fernández, Esther, De Chen, Zhixin Yu, Bård Tøtdal, Magnus Rønning et Anders Holmen. « Carbon nanofiber supported Ni catalyst : Effects of nanostructure of supports and catalyst preparation ». Catalysis Today 102-103 (mai 2005) : 45–49. http://dx.doi.org/10.1016/j.cattod.2005.02.005.

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Wang, Shaozhen, Biao Zang, Qiang Zhang, Hui Zhang, Liping Qu et Hongqi Chen. « Self-Supported Dendritic Pd Nanostructures : Surfactant-Free Synthesis and Their Superior Activity for Methanol Electro-Oxidation ». Nano 14, n^o 06 (juin 2019) : 1950073. http://dx.doi.org/10.1142/s1793292019500735.

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This paper reports a surfactant-free synthesis of clean-surface dendritic Pd nanostructures. The key of this synthetic strategy was using ethanol as a reductant to directly reduce Pd(OH)2. In terms of electrocatalytic methanol oxidation in alkaline media, the clean-surface and self-supported Pd nanostructures are beneficial to a high catalytic performance, including superior electrocatalytic activity and stability. The as-prepared dendritic Pd shows 2.57 and 4.39 times higher specific activity than palladium nanoparticles and a commercial Pd/C catalyst, respectively. Furthermore, we demonstrated that the clean-surface nanoparticles exhibit higher performance than that of the surfactant-capped Pd nanostructures for methanol electro-oxidation. Therefore, the dendritic Pd nanostructures are potential candidates as the efficient electrode material in fuel cells.

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Verma, Sahil, Sumit Sinha-Ray et Suman Sinha-Ray. « Electrospun CNF Supported Ceramics as Electrochemical Catalysts for Water Splitting and Fuel Cell : A Review ». Polymers 12, n^o 1 (19 janvier 2020) : 238. http://dx.doi.org/10.3390/polym12010238.

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With the per capita growth of energy demand, there is a significant need for alternative and sustainable energy resources. Efficient electrochemical catalysis will play an important role in sustaining that need, and nanomaterials will play a crucial role, owing to their high surface area to volume ratio. Electrospun nanofiber is one of the most promising alternatives for producing such nanostructures. A section of key nano-electrocatalysts comprise of transition metals (TMs) and their derivatives, like oxides, sulfides, phosphides and carbides, etc., as well as their 1D composites with carbonaceous elements, like carbon nanotubes (CNTs) and carbon nanofiber (CNF), to utilize the fruits of TMs’ electronic structure, their inherent catalytic capability and the carbon counterparts’ stability, and electrical conductivity. In this work, we will discuss about such TM derivatives, mostly TM-based ceramics, grown on the CNF substrates via electrospinning. We will discuss about manufacturing methods, and their electrochemical catalysis performances in regards to energy conversion processes, dealing mostly with water splitting, the metal–air battery fuel cell, etc. This review will help to understand the recent evolution, challenges and future scopes related to electrospun transition metal derivative-based CNFs as electrocatalysts.

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Zambrzycki, Christian, Runbang Shao, Archismita Misra, Carsten Streb, Ulrich Herr et Robert Güttel. « Iron Based Core-Shell Structures as Versatile Materials : Magnetic Support and Solid Catalyst ». Catalysts 11, n^o 1 (7 janvier 2021) : 72. http://dx.doi.org/10.3390/catal11010072.

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Core-shell materials are promising functional materials for fundamental research and industrial application, as their properties can be adapted for specific applications. In particular, particles featuring iron or iron oxide as core material are relevant since they combine magnetic and catalytic properties. The addition of an SiO2 shell around the core particles introduces additional design aspects, such as a pore structure and surface functionalization. Herein, we describe the synthesis and application of iron-based core-shell nanoparticles for two different fields of research that is heterogeneous catalysis and water purification. The iron-based core shell materials were characterized by transmission electron microscopy, as well as N2-physisorption, X-ray diffraction, and vibrating-sample magnetometer measurements in order to correlate their properties with the performance in the target applications. Investigations of these materials in CO2 hydrogenation and water purification show their versatility and applicability in different fields of research and application, after suitable individual functionalization of the core-shell precursor. For design and application of magnetically separable particles, the SiO2 shell is surface-functionalized with an ionic liquid in order to bind water pollutants selectively. The core requires no functionalization, as it provides suitable magnetic properties in the as-made state. For catalytic application in synthesis gas reactions, the SiO2-stabilized core nanoparticles are reductively functionalized to provide the catalytically active metallic iron sites. Therefore, Fe@SiO2 core-shell nanostructures are shown to provide platform materials for various fields of application, after a specific functionalization.

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Xu, Zaixiang, Yuzhen Zhu, Lijie Bai, Qingqing Lang, Wenli Hu, Chunxiao Gao, Shuxian Zhong et Song Bai. « Chemical etching of graphene-supported PdPt alloy nanocubes into concave nanostructures for enhanced catalytic hydrogen production from alkaline formaldehyde aqueous solution ». Inorganic Chemistry Frontiers 4, n^o 10 (2017) : 1704–13. http://dx.doi.org/10.1039/c7qi00421d.

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Graphene-supported PdPt concave nanostructures with different degrees of concavity were synthesized by etching PdPt nanocubes for enhanced catalytic hydrogen production from alkaline formaldehyde aqueous solution.

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Vlaicu, Alexandru, Gabriel Vasilievici, Adrian Radu, Simona Ghimis et Sanda Velea. « Mesoporous SBA-15-Based Materials for Catalytic Hydroprocessing Reaction of Microalgal Biomass ». Proceedings 57, n^o 1 (11 novembre 2020) : 44. http://dx.doi.org/10.3390/proceedings2020057044.

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