Journal articles: 'Metal catalyst nanoparticles'

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Sasaki, Teruyoshi, Yusuke Horino, Tadashi Ohtake, Kazufumi Ogawa, and Yoshifumi Suzaki. "A Highly Efficient Monolayer Pt Nanoparticle Catalyst Prepared on a Glass Fiber Surface." Catalysts 10, no. 5 (April 25, 2020): 472. http://dx.doi.org/10.3390/catal10050472.

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Over the past few years, various nanoparticle-supported precious metal-based catalysts have been investigated to reduce the emission of harmful substances from automobiles. Generally, precious metal nanoparticle-based exhaust gas catalysts are prepared using the impregnation method. However, these catalysts suffer from the low catalytic activity of the precious metal nanoparticles involved. Therefore, in this study, we developed a novel method for preparing highly efficient glass fiber-supported Pt nanoparticle catalysts. We uniformly deposited a single layer of platinum particles on the support surface using a chemically adsorbed monomolecular film. The octane combustion performance of the resulting catalyst was compared with that of a commercial catalyst. The precious metal loading ratio of the proposed catalyst was approximately seven times that of the commercial catalyst. Approximately one-twelfth of the mass of the proposed catalyst exhibited a performance comparable to that of the commercial catalyst. Thus, the synthesis method used herein can be used to reduce the weight, size, and manufacturing cost of exhaust gas purification devices used in cars.

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Lindenthal, Lorenz, Raffael Rameshan, Harald Summerer, Thomas Ruh, Janko Popovic, Andreas Nenning, Stefan Löffler, Alexander Karl Opitz, Peter Blaha, and Christoph Rameshan. "Modifying the Surface Structure of Perovskite-Based Catalysts by Nanoparticle Exsolution." Catalysts 10, no. 3 (March 1, 2020): 268. http://dx.doi.org/10.3390/catal10030268.

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In heterogeneous catalysis, surfaces decorated with uniformly dispersed, catalytically-active (nano)particles are a key requirement for excellent performance. Beside standard catalyst preparation routines—with limitations in controlling catalyst surface structure (i.e., particle size distribution or dispersion)—we present here a novel time efficient route to precisely tailor catalyst surface morphology and composition of perovskites. Perovskite-type oxides of nominal composition ABO3 with transition metal cations on the B-site can exsolve the B-site transition metal upon controlled reduction. In this exsolution process, the transition metal emerges from the oxide lattice and migrates to the surface where it forms catalytically active nanoparticles. Doping the B-site with reducible and catalytically highly active elements, offers the opportunity of tailoring properties of exsolution catalysts. Here, we present the synthesis of two novel perovskite catalysts Nd0.6Ca0.4FeO3-δ and Nd0.6Ca0.4Fe0.9Co0.1O3-δ with characterisation by (in situ) XRD, SEM/TEM and XPS, supported by theory (DFT+U). Fe nanoparticle formation was observed for Nd0.6Ca0.4FeO3-δ. In comparison, B site cobalt doping leads, already at lower reduction temperatures, to formation of finely dispersed Co nanoparticles on the surface. These novel perovskite-type catalysts are highly promising for applications in chemical energy conversion. First measurements revealed that exsolved Co nanoparticles significantly improve the catalytic activity for CO2 activation via reverse water gas shift reaction.

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Zhang, Xiaolong, Shilei Jin, Yuhan Zhang, Liyuan Wang, Yang Liu, and Qian Duan. "One-Pot Facile Synthesis of Noble Metal Nanoparticles Supported on rGO with Enhanced Catalytic Performance for 4-Nitrophenol Reduction." Molecules 26, no. 23 (November 30, 2021): 7261. http://dx.doi.org/10.3390/molecules26237261.

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In this study, reduced graphene oxide (rGO)-supported noble metal (gold, silver, and platinum) nanoparticle catalysts were prepared via the one-pot facile co-reduction technique. Various measurement techniques were used to investigate the structures and properties of the catalysts. The relative intensity ratios of ID/IG in rGO/Au, rGO/Ag, rGO/Pt, and GO were 1.106, 1.078, 1.047, and 0.863, respectively. The results showed the formation of rGO and that noble metal nanoparticles were decorated on rGO. Furthermore, the catalytic activities of the designed nanocomposites were investigated via 4-nitrophenol. The catalysts were used in 4-nitrophenol reduction. The catalytic performance of the catalysts was evaluated using the apparent rate constant k values. The k value of rGO/Au was 0.618 min−1, which was higher than those of rGO/Ag (0.55 min−1) and rGO/Pt (0.038 min−1). The result proved that the rGO/Au catalyst exhibited a higher catalytic performance than the rGO/Ag catalyst and the rGO/Pt catalyst. The results provide a facile method for the synthesis of rGO-supported nanomaterials in catalysis.

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José-Yacamán, M., M. Marín-Almazo, and J. A. Ascencio. "High Resolution TEM Studies On Palladium, Rhodium Nanoparticles." Microscopy and Microanalysis 7, S2 (August 2001): 1100–1101. http://dx.doi.org/10.1017/s1431927600031573.

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The field of catalysis is one of the most important areas of the nano-sciences for many years. in deed the goal of having a catalyst, with the maximum active area exposed to a chemical reaction, has produced enormous amount of research in nanoparticles. Particularly, the metal nanoparticles study is a very important field in catalysis. Electron Microscopy is one of the techniques that have played a mayor role on studding nanoparticles. Since bright field images, dark field techniques, to the high-resolution atomic images of nanoparticles and more recently the High Angle Annular dark field images or Z-contrast. However this technique provides only indirect evidence of the atomic arrangements on the particles. High Resolution Electron Microscopy (HREM) still appears as a very powerful technique to study nanoparticles and their internal structure. Among the most interesting metals to study is the palladium, which acts for instance as excellent catalyst for hydrogenation of unsaturated hydrocarbons and has many other applications such as environmental catalysts.

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Biehler, Erik, Qui Quach, Clay Huff, and Tarek M. Abdel-Fattah. "Organo-Nanocups Assist the Formation of Ultra-Small Palladium Nanoparticle Catalysts for Hydrogen Evolution Reaction." Materials 15, no. 7 (April 6, 2022): 2692. http://dx.doi.org/10.3390/ma15072692.

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Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) to confirm the successful synthesis of ~3 nm palladium nanoparticles. The nanoparticles’ catalytic ability was explored via the hydrolysis reaction of sodium borohydride. The palladium nanoparticle catalyst performed best at 303 K at a pH of 7 with 925 μmol of sodium borohydride having an H2 generation rate of 1.431 mL min−1 mLcat−1. The activation energy of the palladium catalyst was calculated to be 58.9 kJ/mol.

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Patil, Siddappa A., Shivaputra A. Patil, and Renukadevi Patil. "Magnetic Nanoparticles Supported Carbene and Amine Based Metal Complexes in Catalysis." Journal of Nano Research 42 (July 2016): 112–35. http://dx.doi.org/10.4028/www.scientific.net/jnanor.42.112.

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Catalysis is one of the hottest research topics in chemistry. In recent years, metal complexes attracted great interest as catalysts towards various types of organic reactions. However, these catalysts, in most cases, suffer from the deficits during their recovery, recycling and the difficulty in separation of catalysts from the products. Therefore, the design and synthesis of recoverable and recyclable catalyst is very important aspect in catalysis. The aim of this review article is to highlight the speedy growth in the synthesis and catalytic applications of magnetic nanoparticles (Fe3O4, MNPs) supported N-heterocyclic carbene (NHC) and amine based metal complexes in various organic reactions. Furthermore, these catalysts can be easily separated from the reaction media with the external magnet and reused various times without a substantial loss of catalytic activity.

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Pisarek, Marcin, Piotr Kędzierzawski, Mariusz Andrzejczuk, Marcin Hołdyński, Anna Mikołajczuk-Zychora, Andrzej Borodziński, and Maria Janik-Czachor. "TiO2 Nanotubes with Pt and Pd Nanoparticles as Catalysts for Electro-Oxidation of Formic Acid." Materials 13, no. 5 (March 6, 2020): 1195. http://dx.doi.org/10.3390/ma13051195.

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In the present work, the magnetron sputtering technique was used to prepare new catalysts of formic acid electrooxidation based on TiO2 nanotubes decorated with Pt (platinum), Pd (palladium) or Pd + Pt nanoparticles. TiO2 nanotubes (TiO2 NTs) with strictly defined geometry were produced by anodization of Ti foil and Ti mesh in a mixture of glycerol and water with ammonium fluoride electrolyte. The above mentioned catalytically active metal nanoparticles (NPs) were located mainly on the top of the TiO2 NTs, forming ‘rings’ and agglomerates. A part of metal nanoparticles decorated also TiO2 NTs walls, thus providing sufficient electronic conductivity for electron transportation between the metal nanoparticle rings and Ti current collector. The electrocatalytic activity of the TiO2 NTs/Ti foil, decorated by Pt, Pd and/or Pd + Pt NPs was investigated by cyclic voltammetry (CV) and new Pd/TiO2 NTs/Ti mesh catalyst was additionally tested in a direct formic acid fuel cell (DFAFC). The results so obtained were compared with commercial catalyst—Pd/Vulcan. CV tests have shown for carbon supported catalysts, that the activity of TiO2 NTs decorated with Pd was considerably higher than that one decorated with Pt. Moreover, for TiO2 NTs supported Pd catalyst specific activity (per mg of metal) was higher than that for well dispersed carbon supported commercial catalyst. The tests at DFAFC have revealed also that the maximum of specific power for 0.2 Pd/TiO2 catalyst was 70% higher than that of the commercial one, Pd/Vulcan. Morphological features, and/or peculiarities, as well as surface composition of the resulting catalysts have been studied by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and chemical surface analytical methods (X-ray photoelectron spectroscopy—XPS; Auger electron spectroscopy—AES).

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Ahmad, Mohamad M., Shehla Mushtaq, Hassan S. Al Qahtani, A. Sedky, and Mir Waqas Alam. "Investigation of TiO2 Nanoparticles Synthesized by Sol-Gel Method for Effectual Photodegradation, Oxidation and Reduction Reaction." Crystals 11, no. 12 (November 25, 2021): 1456. http://dx.doi.org/10.3390/cryst11121456.

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Metal oxide titanium dioxide (TiO2) nanoparticles were synthesized by using a simple and economical sol-gel method. The prepared nanoparticles were used to evaluate methylene blue dye degradation and as catalysts in the oxidation of benzaldehyde. The crystallite size of the titanium dioxide nanoparticle was 18.3 nm, which was confirmed by X-ray diffraction analysis. The spherical morphology was confirmed by scanning electron microscopy (SEM), and the elemental composition of the nanoparticle was found by energy dispersive X-ray (EDAX) analysis. The anatase form of the nanoparticle was confirmed by the bandgap 3.2 eV, which was measured using UV–DRS analysis. The bond between metal and oxygen was confirmed by the peaks at 485 and 606 cm–1 analyzed by Fourier transform infrared analysis (FTIR). The efficiency of the catalyst in dye degradation was 60.08, 68.38, and 80.89% with respect to 50, 75, and 100 mg catalyst weight. The yield % of benzoic acid was 94%, and the reduction efficiency against 4-nitrophenol was 98.44%.

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Gutiérrez, Yael, Dolores Ortiz, Rodrigo Alcaraz de la Osa, José M. Saiz, Francisco González, and Fernando Moreno. "Electromagnetic Effective Medium Modelling of Composites with Metal-Semiconductor Core-Shell Type Inclusions." Catalysts 9, no. 7 (July 22, 2019): 626. http://dx.doi.org/10.3390/catal9070626.

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The possibility of using light to drive chemical reactions has highlighted the role of photocatalysis as a key tool to address the environmental and energy issues faced by today’s society. Plasmonic photocatalysis, proposed to circumvent some of the problems of conventional semiconductor catalysis, uses hetero-nanostructures composed by plasmonic metals and semiconductors as catalysts. Metal-semiconductor core-shell nanoparticles present advantages (i.e., protecting the metal and enlarging the active sites) with respect to other hetero-nanostructures proposed for plasmonic photocatalysis applications. In order to maximize light absorption in the catalyst, it is critical to accurately model the reflectance/absorptance/transmittance of composites and colloids with metal-semiconductor core-shell nanoparticle inclusions. Here, we present a new method for calculating the effective dielectric function of metal-semiconductor core-shell nanoparticles and its comparison with existing theories showing clear advantages. Particularly, this new method has shown the best performance in the prediction of the spectral position of the localized plasmonic resonances, a key parameter in the design of efficient photocatalysts. This new approach can be considered as a useful tool for designing coated particles with desired plasmonic properties and engineering the effective permittivity of composites with core-shell type inclusions which are used in photocatalysis and solar energy harvesting applications.

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Kreitz, Bjarne, Aurina Martínez Arias, Jan Martin, Alfred Weber, and Thomas Turek. "Spray-Dried Ni Catalysts with Tailored Properties for CO2 Methanation." Catalysts 10, no. 12 (December 2, 2020): 1410. http://dx.doi.org/10.3390/catal10121410.

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A catalyst production method that enables the independent tailoring of the structural properties of the catalyst, such as pore size, metal particle size, metal loading or surface area, allows to increase the efficiency of a catalytic process. Such tailoring can help to make the valorization of CO2 into synthetic fuels on Ni catalysts competitive to conventional fossil fuel production. In this work, a new spray-drying method was used to produce Ni catalysts supported on SiO2 and Al2O3 nanoparticles with tunable properties. The influence of the primary particle size of the support, different metal loadings, and heat treatments were applied to investigate the potential to tailor the properties of catalysts. The catalysts were examined with physical and chemical characterization methods, including X-ray diffraction, temperature-programmed reduction, and chemisorption. A temperature-scanning technique was applied to screen the catalysts for CO2 methanation. With the spray-drying method presented here, well-organized porous spherical nanoparticles of highly dispersed NiO nanoparticles supported on silica with tunable properties were produced and characterized. Moreover, the pore size, metal particle size, and metal loading can be controlled independently, which allows to produce catalyst particles with the desired properties. Ni/SiO2 catalysts with surface areas of up to 40 m2 g−1 with Ni crystals in the range of 4 nm were produced, which exhibited a high activity for the CO2 methanation.

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Lemesh, N. V., and P. E. Strizhak. "Synthesis of multi-walled carbon nanotubes with controlled inner and outer diameters by ethylene decomposition over Ni/MgO and Co/MgO catalysts." Materials Science-Poland 36, no. 4 (December 1, 2018): 739–47. http://dx.doi.org/10.2478/msp-2018-0089.

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AbstractIn this work, multi-walled carbon nanotubes (MWCNTs) with significantly different mean diameters were produced by catalytic CVD over Ni and Co-based supported catalysts. Our results indicate that Ni nanoparticles in the Ni/MgO catalyst are responsible for controlling the inner diameters of the carbon nanotubes. Contrary, Co nanoparticles in the Co/MgO catalyst control the outer diameters of MWCNTs. The “base-growth” mechanism and smaller diameters of the MWCNTs grown on the Ni/MgO catalyst are associated with a strong metal-support interaction (SMSI) resulting from NixMg1−xO mixed oxide formation. The concept of the weak metal-support interaction (WMSI) between Co nanoparticles and MgO for the Co/MgO catalyst confirms the “tip-growth” mechanism of the MWCNTs.

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Ashmath, Shaik, Hyuk-Jun Kwon, Shaik Gouse Peera, and Tae Gwan Lee. "Solid-State Synthesis of Cobalt/NCS Electrocatalyst for Oxygen Reduction Reaction in Dual Chamber Microbial Fuel Cells." Nanomaterials 12, no. 24 (December 7, 2022): 4369. http://dx.doi.org/10.3390/nano12244369.

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Due to the high cost of presently utilized Pt/C catalysts, a quick and sustainable synthesis of electrocatalysts made of cost-effective and earth-abundant metals is urgently needed. In this work, we demonstrated a mechanochemically synthesized cobalt nanoparticles supported on N and S doped carbons derived from a solid-state-reaction between zinc acetate and 2-amino thiazole as metal, organic ligand in presence of cobalt (Co) metal ions ZnxCox(C3H4N2S). Pyrolysis of the ZnxCox(C3H4N2S) produced, Co/NSC catalyst in which Co nanoparticles are evenly distributed on the nitrogen and sulfur doped carbon support. The Co/NSC catalyst have been characterized with various physical and electrochemical characterization techniques. The Co content in the ZnxCox(C3H4N2S) is carefully adjusted by varying the Co content and the optimized Co/NSC-3 catalyst is subjected to the oxygen reduction reaction in 0.1 M HClO4 electrolyte. The optimized Co/NSC-3 catalyst reveals acceptable ORR activity with the half-wave potential of ~0.63 V vs. RHE in acidic electrolytes. In addition, the Co/NSC-3 catalyst showed excellent stability with no loss in the ORR activity after 10,000 potential cycles. When applied as cathode catalysts in dual chamber microbial fuel cells, the Co/NCS catalyst delivered satisfactory volumetric power density in comparison with Pt/C.

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Nyembe, Sanele, Gebhu Ndlovu, Poslet Shumbula, Richard Harris, Nosipho Moloto, and Lucky Sikhwivhilu. "Laser Assisted Catalytic Growth of Silicon Nanowires Using Gold and Nickel Catalysts." Journal of Nanoscience and Nanotechnology 21, no. 10 (October 1, 2021): 5260–65. http://dx.doi.org/10.1166/jnn.2021.19448.

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Laser assisted synthesis of silicon nanowires (SiNWs) was successfully achieved through the use of gold and nickel as catalysts. The diameter of the resulting SiNWs was found to be dependent on that of the catalyst in the case of gold catalyst. The gold catalysed silicon nanowires were unevenly curved and branched owing to the high kinetic energy possessed by gold nanoparticles (AuNPs) at relatively high processing temperature. The use of nickel as catalyst resulted in the formation of several SiNWs on a single nickel catalyst crystallite due to interconnection of the nickel metal crystallites at processing temperature. The morphology of SiNWs catalysed by both nickel and gold was controlled by optimising the laser energy during ablation.

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Oh, Kyung-Ryul, Sanil E. Sivan, Changho Yoo, Do-Young Hong, and Young Kyu Hwang. "Trimeric Ruthenium Cluster-Derived Ru Nanoparticles Dispersed in MIL-101(Cr) for Catalytic Transfer Hydrogenation." Catalysts 12, no. 9 (September 6, 2022): 1010. http://dx.doi.org/10.3390/catal12091010.

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The synthesis of highly dispersed metal nanoparticles supported on metal–organic frameworks has been widely studied as a means to provide high-performance heterogeneous catalysts. Here, a Ru-nanoparticles-supported MIL-101(Cr) catalyst was prepared via a diamine and oxo-centered trimeric ruthenium cluster ([Ru3(μ3-O)(μ-CH3COO)6(H2O)3]CH3COO), Ru3 cluster sequential grafting, followed by alcohol reduction. Ethylenediamine (ED) acted as the linker, coordinating with unsaturated sites on both MIL-101(Cr) and the Ru3 cluster to produce Ru3-ED-MIL-101(Cr), after which selective alcohol reduction process provided the Ru/ED-MIL-101(Cr) catalyst. The synthesized Ru/ED-MIL-101(Cr) catalyst contained small, finely dispersed Ru nanoparticles, and the structural integrity of ED-MIL-101(Cr) was maintained. The Ru/ED-MIL-101(Cr) catalyst was tested for the transfer hydrogenation of benzene using isopropanol as the hydrogen source, where it was shown to outperform other Ru-based catalysts.

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Hamzah, Noraini, Wan Nor Roslam Wan Isahak, Nadia Farhana Adnan, Nor Asikin Mohamad Nordin, Mohamad Bin Kassim, and Mohd Ambar Yarmo. "Catalytic Activity and Physical Properties of Nanoparticles Metal Supported on Bentonite for Hydrogenolysis of Glycerol." Advanced Materials Research 364 (October 2011): 211–16. http://dx.doi.org/10.4028/www.scientific.net/amr.364.211.

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Catalysts prepared from a variety of noble metal (Os, Ru, Pd and Au) supported on bentonite using impregnation method were studied and it found these series catalyst system gave different activity and selectivity. Among these catalysts, Os/bentonite and Ru/bentonite catalyst showed high activity in glycerol hydrogenolysis reaction at 150°C, 2.0 MPa initial hydrogen pressure for 7 hours. TEM analysis revealed that these nanometal particles catalyst have different in size and result showed that Os and Ru which have smaller average size in range 1-3 nm gave high activity which are 54.1% and 61.2% respectively. In contrast, less activity was obtained when using Pd/bentonite (29.0%) and Au/bentonite (27.8%) catalyst and TEM result showed that Pd and Au nanoparticles have large average particles size (8-10) nm. NH3-TPD analysis revealed that Ru/bentonite and Os/bentonite catalyst gave high total acidity and this behaviour contribute to high activity of the catalyst. This study revealed that size of nanoparticles and catalyst acidity play an important role in the activity and selectivity in glycerol hydrogenolysis reaction. These catalysts were also characterized by BET, XRD and XPS in order to get some physicochemical properties of the catalyst.

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Yakoumis, Iakovos, Εkaterini Polyzou, and Anastasia Maria Moschovi. "PROMETHEUS: A Copper-Based Polymetallic Catalyst for Automotive Applications. Part II: Catalytic Efficiency an Endurance as Compared with Original Catalysts." Materials 14, no. 9 (April 26, 2021): 2226. http://dx.doi.org/10.3390/ma14092226.

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PROMETHEUS catalyst, a copper-based polymetallic nano-catalyst has been proven to be suitable for automotive emission control applications. This novel catalyst consists of copper, palladium and rhodium nanoparticles as active phases, impregnated on an inorganic oxide substrate, CeO2/ZrO2 (75%, 25%). The aim of PROMETHEUS catalyst’s development is the substitution of a significant amount (85%) of Platinum Group Metals (PGMs) with copper nanoparticles while, at the same time, presenting high catalytic efficiency with respect to the commercial catalysts. In this work, an extensive investigation of the catalytic activity of full scale PROMETHEUS fresh and aged catalyst deposited on ceramic cordierites is presented and discussed. The catalytic activity was tested on an Synthetic Gas Bench (SGB) towards the oxidation of CO and CH4 and the reduction of NO. The loading of the washcoat was 2 wt% (metal content) on Cu, Pd, Rh with the corresponding metal ratio at 21:7:1. The concentration of the full-scale monolithic catalysts to be 0.032% total PGM loading for meeting Euro III standard and 0.089% for meeting Euro IV to Euro VIb standards. The catalytic activity of all catalysts was tested both in rich-burn (λ = 0.99) and lean-burn conditions (λ = 1.03).

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Ibraheem, Ibraheem J., Tareg A. Mandeel, A. D. Faisal, and Y. Al-Douri. "Thermal Degradation of Plastic Wastes (PP, LDPE) Using Metal Particles, Metal Oxides and Metal Nano Particles as a Catalyst." Advanced Materials Research 925 (April 2014): 359–63. http://dx.doi.org/10.4028/www.scientific.net/amr.925.359.

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Two different vacuum thermal degradation processes of plastic wastes materials: Poly Propylene (PP) and Low Density Poly Ethylene (LDPE) were conducted with homemade thermal degradation setup. The two processes were used 1-bulk metal particles,2-metal oxides (Fe,Ni,Fe2O3,NiO) and 3-metal nanoparticles (Fe and Ni) as a catalysts supported on feldspar clay respectively. The experimental results for both processes shows the presence of different products like liquid, wax, gas, and carbon. Our characterization was focused on the liquid product. The produced liquid was characterized by Fourier transform infra-red (FTIR) and Gas chromatography (GC) The octane number, cetane number, flash point, fire point, aniline point and some physical properties were also measured. The results indicated that the process with metal nanoparticles catalyst produces liquid much better properties compared to the other materials results used metal particles catalyst.

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Ju, Hyun, Jinho Park, Ilan Stern, and Seung Woo Lee. "Pyrochlore Oxide Decorated with Exsolved Metal Nanoparticles for Enhanced Water Splitting Reaction." ECS Meeting Abstracts MA2022-02, no. 50 (October 9, 2022): 2597. http://dx.doi.org/10.1149/ma2022-02502597mtgabs.

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Recently, we reported hybrid catalysts consist of metal nanoparticles on a metal oxide support for water splitting reaction, which is synthesized through an in situ exsolution process of metallic nanoparticles on pyrochlore oxide material.1,2 Specifically, we prepared Ni substituted lead ruthenate pyrochlore oxide (Pb2Ru1.6Ni0.4O6.5) via sol-gel crystallization and reduce the samples at different temperatures. Ni nanoparticles supported pyrochlore oxide catalyst significantly accelerate the conversion of Ni to NiOOH due to favorable electron transfer during the oxygen evolution reaction. The hybrid catalyst of pyrochlore oxide with NiRu alloy nanoparticles exhibits superior hydrogen evolution reaction performance, resulting from the bifunctional reaction mechanism, modified electronic structure, and efficient electron transport. Consequently, remarkable water electrolysis performance with superior long-term stability was obtained at the hybrid catalysts. References [1] S. W. Lee et al., Energy Environ. Sci., 2021, 14, 3053-3063. [2] S. W. Lee et al., Advanced Materials, 2019, 31, 1901977.

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Shah, Syed Shoaib Ahmad, Tayyaba Najam, Costas Molochas, Muhammad Altaf Nazir, Angeliki Brouzgou, Muhammad Sufyan Javed, Aziz ur Rehman, and Panagiotis Tsiakaras. "Nanostructure Engineering of Metal–Organic Derived Frameworks: Cobalt Phosphide Embedded in Carbon Nanotubes as an Efficient ORR Catalyst." Molecules 26, no. 21 (November 4, 2021): 6672. http://dx.doi.org/10.3390/molecules26216672.

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Heteroatom doping is considered an efficient strategy when tuning the electronic and structural modulation of catalysts to achieve improved performance towards renewable energy applications. Herein, we synthesized a series of carbon-based hierarchical nanostructures through the controlled pyrolysis of Co-MOF (metal organic framework) precursors followed by in situ phosphidation. Two kinds of catalysts were prepared: metal nanoparticles embedded in carbon nanotubes, and metal nanoparticles dispersed on the carbon surface. The results proved that the metal nanoparticles embedded in carbon nanotubes exhibit enhanced ORR electrocatalytic performance, owed to the enriched catalytic sites and the mass transfer facilitating channels provided by the hierarchical porous structure of the carbon nanotubes. Furthermore, the phosphidation of the metal nanoparticles embedded in carbon nanotubes (P-Co-CNTs) increases the surface area and porosity, resulting in faster electron transfer, greater conductivity, and lower charge transfer resistance towards ORR pathways. The P-Co-CNT catalyst shows a half-wave potential of 0.887 V, a Tafel slope of 67 mV dec−1, and robust stability, which are comparatively better than the precious metal catalyst (Pt/C). Conclusively, this study delivers a novel path for designing multiple crystal phases with improved catalytic performance for energy devices.

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Huang, Tiefan, Guan Sheng, Priyanka Manchanda, Abdul H. Emwas, Zhiping Lai, Suzana Pereira Nunes, and Klaus-Viktor Peinemann. "Cyclodextrin polymer networks decorated with subnanometer metal nanoparticles for high-performance low-temperature catalysis." Science Advances 5, no. 11 (November 2019): eaax6976. http://dx.doi.org/10.1126/sciadv.aax6976.

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The synthesis of support materials with suitable coordination sites and confined structures for the controlled growth of ultrasmall metal nanoparticles is of great importance in heterogeneous catalysis. Here, by rational design of a cross-linked β-cyclodextrin polymer network (CPN), various metal nanoparticles (palladium, silver, platinum, gold, and rhodium) of subnanometer size (<1 nm) and narrow size distribution are formed via a mild and facile procedure. The presence of the metal coordination sites and the network structure are key to the successful synthesis and stabilization of the ultrasmall metal nanoparticles. The as-prepared CPN, loaded with palladium nanoparticles, is used as a heterogeneous catalyst and shows outstanding catalytic performance in the hydrogenation of nitro compounds and Suzuki-Miyaura coupling reaction under mild conditions. The CPN support works synergistically with the metal nanoparticles, achieving high catalytic activity and selectivity. In addition, the catalytic activity of the formed catalyst is controllable.

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Rout, Lipeeka, Prashanth Rengasamy, Basanti Ekka, Aniket Kumar, and Priyabrat Dash. "Supported Bimetallic AgSn Nanoparticle as an Efficient Photocatalyst for Degradation of Methylene Blue Dye." Nano 10, no. 04 (June 2015): 1550059. http://dx.doi.org/10.1142/s1793292015500599.

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We report the synthesis of TiO 2-supported monometallic Ag , Sn and bimetallic AgSn nanoparticle catalysts prepared using sol–gel method via a rational nanoparticle encapsulation route. The samples were thoroughly characterized by ultraviolet-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) with image mapping and Brunauer–Emmett–Teller (BET) surface area analyzer. The supported bimetallic AgSn catalyst had the anatase structure, surface area of 50 m2/g and 2.6 ± 0.6 nm particle size. The efficiency of the catalysts was evaluated on photodegradation of methylene blue (MB) dye under visible light. The photocatalytic activity of MB was significantly enhanced in the presence of bimetallic AgSn nanoparticles (NPs) as compared to individual metal nanoparticles. Reusability study of the photocatalyst showed that the catalyst can be reused upto 5 runs with minimal loss in activity. Kinetic study revealed that the degradation reaction follows a pseudo first-order pathway.

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da Cunha, Tairan, Alberto Maulu, Jérôme Guillot, Yves Fleming, Benoit Duez, Damien Lenoble, and Didier Arl. "Design of Silica Nanoparticles-Supported Metal Catalyst by Wet Impregnation with Catalytic Performance for Tuning Carbon Nanotubes Growth." Catalysts 11, no. 8 (August 17, 2021): 986. http://dx.doi.org/10.3390/catal11080986.

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The catalytic activity of cobalt and iron nanoparticles for the growth of carbon nanotubes (CNTs) was studied by a specific reproducible and up-scalable fabrication method. Co and Fe catalysts were deposited over SiO2 nanoparticles by a wet-impregnation method and two different annealing steps were applied for the catalyst formation/activation. The samples were calcined at an optimal temperature of 450 °C resulting in the formation of metal oxide nano-islands without the detection of silicates. Further reduction treatment (700 °C) under H2 successfully converted oxide nanoparticles to Co and Fe metallic species. Furthermore, the catalytic efficiency of both supported-metal nanoparticles at 2 and 5% in weight of silica was evaluated through the growth of CNTs. The CNT structure, morphology and size dispersion were tailored according to the metal catalyst concentration.

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Takabatake, Moe, and Ken Motokura. "Montmorillonite-based heterogeneous catalysts for efficient organic reactions." Nano Express 3, no. 1 (March 1, 2022): 014004. http://dx.doi.org/10.1088/2632-959x/ac5ac3.

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Abstract In this review, we give a brief overview of recently developed montmorillonite-based heterogeneous catalysts used for efficient organic reactions. Cation-exchanged montmorillonite catalysts, metal catalysts supported on montmorillonite, and an interlayer design used for selective catalysis are introduced and discussed. In traditional syntheses, homogeneous acids and metal salts were used as catalysts, but the difficulty in separation of catalysts from products was a bottleneck when considering industrialization. The use of solid heterogeneous catalysts is one of the major solutions to overcome this problem. Montmorillonite can be used as a heterogeneous catalyst and/or catalyst support. This clay material exhibits strong acidity and a stabilizing effect on active species, such as metal nanoparticles, due to its unique layered structure. These advantages have led to the development of montmorillonite-based heterogeneous catalysts. Acidic montmorillonite, such as proton-exchanged montmorillonite, exhibits a high catalytic activity for the activation of electrophiles, such as alcohols, alkenes, and even alkanes. The montmorillonite interlayer/surface also functions as a good support for various metal species used for oxidation and carbon-carbon bond forming reactions. The use of an interlayer structure enables selective reactions and the stabilization of catalytically active species.

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Sooknoi, Tawan, Siriya Jiamesakul, Sitthisuntron Supothina, Angkhana Jaroenworaluck, Thammarat Panyathanmaporn, and Kannikar Juengsuwattananon. "G-1 Metal-loaded Titanium Dioxide Nanoparticles as Oxidation Catalyst(Session: Titanium Oxide)." Proceedings of the Asian Symposium on Materials and Processing 2006 (2006): 126–27. http://dx.doi.org/10.1299/jsmeasmp.2006.126.

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Koji, Hirofumi, Yuji Kusumoto, Akimitsu Hatta, and Hiroshi Furuta. "Formation of Thermally Stable, High-Areal-Density, and Small-Diameter Catalyst Nanoparticles via Intermittent Sputtering Deposition for the High-Density Growth of Carbon Nanotubes." Nanomaterials 12, no. 3 (January 24, 2022): 365. http://dx.doi.org/10.3390/nano12030365.

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We report the formation of thermally stable catalyst nanoparticles via intermittent sputtering deposition to prevent the agglomeration of the nanoparticles during thermal chemical vapor deposition (CVD) and for the high-density growth of carbon nanotubes (CNTs). The preparation of high-areal-density and small-diameter catalyst nanoparticles on substrates for the high-density growth of CNTs is still a challenging issue because surface diffusion and Ostwald ripening of the nanoparticles induce agglomeration, which results in the low-density growth of large-diameter CNTs during high-temperature thermal CVD. Enhancing the adhesion of nanoparticles or suppressing their diffusion on the substrate to retain a small particle diameter is desirable for the preparation of thermally stable, high-areal-density, and small-diameter catalyst nanoparticles. The intermittent sputtering method was employed to deposit Ni and Fe metal nanoparticles on a substrate for the synthesis of high-areal-density CNTs for Fe nanoparticle catalyst films. The metal particles deposited via intermittent sputtering with an interval time of over 30 s maintained their areal densities and diameters during the thermal CVD process in a vacuum for CNT synthesis. An interval of over 30 s was expected to oxidize the metal particles, which resulted in thermal stability during the CVD process. The intermittent sputtering method is thus a candidate process for the preparation of thermally stable catalyst films for the growth of a high density of long CNTs, which can be combined with the present CNT production process.

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Kolasinski, Kurt W. "Metal-Assisted Catalytic Etching (MACE) for Nanofabrication of Semiconductor Powders." Micromachines 12, no. 7 (June 30, 2021): 776. http://dx.doi.org/10.3390/mi12070776.

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Electroless etching of semiconductors has been elevated to an advanced micromachining process by the addition of a structured metal catalyst. Patterning of the catalyst by lithographic techniques facilitated the patterning of crystalline and polycrystalline wafer substrates. Galvanic deposition of metals on semiconductors has a natural tendency to produce nanoparticles rather than flat uniform films. This characteristic makes possible the etching of wafers and particles with arbitrary shape and size. While it has been widely recognized that spontaneous deposition of metal nanoparticles can be used in connection with etching to porosify wafers, it is also possible to produced nanostructured powders. Metal-assisted catalytic etching (MACE) can be controlled to produce (1) etch track pores with shapes and sizes closely related to the shape and size of the metal nanoparticle, (2) hierarchically porosified substrates exhibiting combinations of large etch track pores and mesopores, and (3) nanowires with either solid or mesoporous cores. This review discussed the mechanisms of porosification, processing advances, and the properties of the etch product with special emphasis on the etching of silicon powders.

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Librando, Ivy L., Abdallah G. Mahmoud, Sónia A. C. Carabineiro, M. Fátima C. Guedes da Silva, Francisco J. Maldonado-Hódar, Carlos F. G. C. Geraldes, and Armando J. L. Pombeiro. "Heterogeneous Gold Nanoparticle-Based Catalysts for the Synthesis of Click-Derived Triazoles via the Azide-Alkyne Cycloaddition Reaction." Catalysts 12, no. 1 (December 31, 2021): 45. http://dx.doi.org/10.3390/catal12010045.

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A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC reaction, additional robust catalytic systems complementary to the copper catalyzed AAC remain in high demand. Herein, Au nanoparticles supported on Al2O3, Fe2O3, TiO2 and ZnO, along with gold reference catalysts (gold on carbon and gold on titania supplied by the World Gold Council) were used as catalysts for the AAC reaction. The supported Au nanoparticles with metal loadings of 0.7–1.6% (w/w relative to support) were able to selectively obtain 1,4-disubstituted-1,2,3-triazoles in moderate yields up to 79% after 15 min, under microwave irradiation at 150 °C using a 0.5–1.0 mol% catalyst loading through a one-pot three-component (terminal alkyne, organohalide and sodium azide) procedure according to the “click” rules. Among the supported Au catalysts, Au/TiO2 gave the best results.

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Lindenthal, Lorenz, Richard Buchinger, Hedda Drexler, Florian Schrenk, Thomas Ruh, and Christoph Rameshan. "Exsolution Catalysts—Increasing Metal Efficiency." Encyclopedia 1, no. 1 (February 25, 2021): 249–60. http://dx.doi.org/10.3390/encyclopedia1010023.

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Exsolution catalysts are perovskite oxide-based materials that can exsolve catalytically active dopant elements as nanoparticles covering the surface, while the perovskite backbone can act as a stable support material. Thus, under proper conditions, a highly catalytically active and stable catalyst surface can be achieved. For many catalytic materials, precious metals or non-abundant elements play a key role in high catalytic activity. As these elements are often expensive or their supply is ecologically and ethically problematic, the replacement, or at the least reduction in the necessary amount used, is a common aim of current research. One strategy to do so is utilizing exsolution catalysts, as the active elements can be very selectively exsolved, and hence only very small doping amounts are sufficient for excellent results. This approach enables catalyst design with very high active metal efficiency.

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Glaspell, Garry, Victor Abdelsayed, Khaled M. Saoud, and M. Samy El-Shall. "Vapor-phase synthesis of metallic and intermetallic nanoparticles and nanowires: Magnetic and catalytic properties." Pure and Applied Chemistry 78, no. 9 (January 1, 2006): 1667–89. http://dx.doi.org/10.1351/pac200678091667.

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In this paper, we present several examples of the vapor-phase synthesis of intermetallic and alloy nanoparticles and nanowires, and investigate their magnetic and catalytic properties. In the first example, we report the vapor-phase synthesis of intermetallic aluminide nanoparticles. Specifically, FeAl and NiAl nanoparticles were synthesized via laser vaporization controlled condensation (LVCC) from their bulk powders. The NiAl nanoparticles were found to be paramagnetic at room temperature, with a blocking temperature of approximately 15 K. The FeAl nanoparticles displayed room-temperature ferromagnetism. In the second example, we report the vapor-phase synthesis of cobalt oxide nanoparticle catalysts for low-temperature CO oxidation. The incorporation of Au and Pd nanoparticles into the cobalt oxide support leads to significantly improved catalytic activity and stability of the binary catalyst systems. Finally, we report the synthesis of nanowires of Ge, Mg, Pd, and Pt using the vapor-liquid-solid (VLS) method where the vapor-phase growth of the wire is catalyzed using a proper metal catalyst present in the liquid phase.

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Zebardasti, Ali, Mohammad Dekamin, and Esmail Doustkhah. "The Isocyanurate-Carbamate-Bridged Hybrid Mesoporous Organosilica: An Exceptional Anchor for Pd Nanoparticles and a Unique Catalyst for Nitroaromatics Reduction." Catalysts 11, no. 5 (May 12, 2021): 621. http://dx.doi.org/10.3390/catal11050621.

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Hybridisation of mesoporous organosilicas (MO) to reinforce the surface capability in adsorption and stabilisation of noble metal nanoparticles is of great attention in generating/supporting noble metal within their matrices and transforming them into efficient heterogeneous catalysts. Here, we used a unique hybrid of organic-inorganic mesoporous silica in which pore profile pattern was similar to the well-known mesoporous silica, SBA-15 for catalysis. This hybrid mesoporous organosilica was further engaged as a support in the synthesis and stabilisation of Pd nanoparticles on its surface, and then, the obtained Pd-supported MO was employed as a heterogeneous green catalyst in the conversion of aqueous p-nitrophenol (PNP) to p-aminophenol (PAP) at room temperature with efficient recyclability.

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31

Ruzicka, Jan-Yves, David P. Anderson, Sally Gaw, and Vladimir B. Golovko. "Platinum-Ruthenium Nanoparticles: Active and Selective Catalysts for Hydrogenation of Phenylacetylene." Australian Journal of Chemistry 65, no. 10 (2012): 1420. http://dx.doi.org/10.1071/ch12219.

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Bimetallic metal nanoparticles are often more catalytically active than their monometallic counterparts, due to a so-called ‘synergistic effect’. Atomically precise ruthenium-platinum clusters have been shown to be active in the hydrogenation of phenylacetylene to styrene (a reaction of importance to the polymer industry). However, the synthesis of these clusters is generally complex, and cannot be modified to produce clusters with differing metal compositions or ratios. Hence, any truly systematic study of compositional effects using such clusters is hindered by the inaccessibility of certain metal ratios. In this study, a series of larger bimetallic ruthenium-platinum colloids of varying metal ratios was synthesised in solution and immobilised on silica. Catalytic activity was evaluated by hydrogenation of phenylacetylene to styrene. Both bimetallic and monometallic colloids were active catalysts for the hydrogenation of phenylacetylene to styrene and further to ethylbenzene. Of those studied, a catalyst composed of 73 % platinum-27 % ruthenium (by moles) showed the highest activity. This suggests that synergistic effects play an important role in the catalysis of this reaction. To our knowledge this is the first systematic study of ruthenium-platinum nanoparticle catalytic activity on this reaction.

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Bronikowski, Michael J., and Melissa King. "Rhenium and Molybdenum as Diffusion Inhibitors in Catalytic Metal Particles for growth of Ultra-Long Carbon Nanotubes (CNTs)." MRS Advances 5, no. 31-32 (2020): 1697–704. http://dx.doi.org/10.1557/adv.2020.162.

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ABSTRACTBulk production by Chemical Vapor Deposition (CVD) of ultra-long Carbon Nanotubes (CNTs) with lengths greater than several centimeters is desirable for materials applications, but is not presently feasible. A principal reason for this limitation is cessation of CNT growth due to erosion of the nano-sized catalyst particles from which the CNTs nucleate and grow: at elevated CVD growth temperatures, atoms of catalytic metal detach and diffuse away from the particles, resulting in erosion and eventual deactivation of the particles. Recently, a novel idea was introduced to slow this diffusion and erosion by including heavy refractory metals with the catalyst metals in the nanoparticles. Here are presented recent and ongoing investigations into this method. The metal system investigated uses iron as catalyst and rhenium as diffusion inhibitor. Results show that inclusion of Re in the catalyst particles will substantially increase the catalysts particle lifetimes, and hence the growth time of the CNTs produced. These results are compared to previous results obtained using the iron/molybdenum system of catalyst/inhibitor.

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Konsolakis, Michalis, and Maria Lykaki. "Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review." Catalysts 11, no. 4 (March 31, 2021): 452. http://dx.doi.org/10.3390/catal11040452.

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The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

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Bulyarskiy S.V., L'vov P. E., Pavlov A. A., and Terentyev A.V. "Formation of catalyst nanoparticles for the growth of carbon nanotubes during annealing of amorphous Co-Zr-O films." Physics of the Solid State 64, no. 11 (2022): 1777. http://dx.doi.org/10.21883/pss.2022.11.54697.394.

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The formation of nanosized catalyst particles for the growth of carbon nanotubes can be carried out during the crystallization of amorphous films consisting of two metals, one of which has higher free energy of the oxide. During annealing in the presence of oxygen, this metal is oxidized with the reduction of the second metal, which leads to the formation of nanoparticles embedded in the oxide of the first metal. This the process has been experimentally and theoretically studied by the example of the formation of cobalt nanoparticles on the surface of amorphous Co-Zr-O films as a result of the decomposition of a supersaturated solid solution and mechanical stresses arising during the oxidation of zirconium. We have proposed a mechanism for the formation of catalyst nanoparticles and phenomenological model of this process developed on the basis of the phase-field theory. Keywords: carbon nanotubes, nanoparticles of catalyst, phase transitions, decomposition of supersaturated solid solutions.

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35

Albano, Gianluigi, Antonella Petri, and Laura Antonella Aronica. "Palladium Supported on Bioinspired Materials as Catalysts for C–C Coupling Reactions." Catalysts 13, no. 1 (January 16, 2023): 210. http://dx.doi.org/10.3390/catal13010210.

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In recent years, the immobilization of palladium nanoparticles on solid supports to prepare active and stable catalytic systems has been deeply investigated. Compared to inorganic materials, naturally occurring organic solids are inexpensive, available and abundant. Moreover, the surface of these solids is fully covered by chelating groups which can stabilize the metal nanoparticles. In the present review, we have focused our attention on natural biomaterials-supported metal catalysts applied to the formation of C–C bonds by Mizoroki–Heck, Suzuki–Miyaura and Sonogashira reactions. A systematic approach based on the nature of the organic matrix will be followed: (i) metal catalysts supported on cellulose; (ii) metal catalysts supported on starch; (iii) metal catalysts supported on pectin; (iv) metal catalysts supported on agarose; (v) metal catalysts supported on chitosan; (vi) metal catalysts supported on proteins and enzymes. We will emphasize the effective heterogeneity and recyclability of each catalyst, specifying which studies were carried out to evaluate these aspects.

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León-Gutiérrez, Yasna, and Galo Cárdenas-Triviño. "Catalyst characterization Ni-Sn nanoparticles supported in Al₂O₃ and MgO: Acetophenone hydrogenation." Nanomaterials and Nanotechnology 12 (January 2022): 184798042211321. http://dx.doi.org/10.1177/18479804221132128.

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Monometallic and bimetallic Ni and Sn catalysts were prepared in different ratios by the Solvated Metal Atom Dispersed (SMAD) method for the catalytic hydrogenation of acetophenone to 1-phenylethanol. The preparation of the catalysts was carried out by evaporation of Ni and Sn metal atoms and subsequent co-deposition at 77 K using 2- isopropanol as solvent on alumina and magnesium oxide as supports. X-ray photoelectron spectroscopy (XPS) analysis showed a high percentage of nickel atoms in zero valence, while the tin phases were founded in reduced and oxidized form. The average size of the nanoparticles measured by transmission electron microscopy (TEM) ranged from 8 to 15 nm while the metal dispersion on the surface measured by hydrogen chemisorption ranged from 0.07% for Ni1% Sn0.3%/MgO to 3.2% for Ni5%/MgO. Thermogravimetric analysis shows that γ-Al2O3 catalysts exhibit higher thermal stability than MgO catalysts. The catalysis results showed that the best support is MgO reaching 66% conversion in Ni5% Sn0.5%/MgO catalyst.

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Matus, E. V., L. M. Khitsova, O. S. Efimova, S. A. Yashnik, N. V. Shikina, and Z. R. Ismagilov. "Preparation of Carbon Nanotubes with Supported Metal Oxide Nanoparticles: Effect of Metal Precursor on Thermal Decomposition Behavior of the Materials." Eurasian Chemico-Technological Journal 21, no. 4 (December 18, 2019): 303. http://dx.doi.org/10.18321/ectj887.

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To develop new catalysts based on carbon nanomaterials with supported metal oxide nanoparticles for oxidative transformations of sulfur compounds, a series of metal oxide nanoparticle-decorated carbon nanotubes (MOx/CNTs) were prepared by incipient wetness impregnation at a variation of the active metal type (M = Ce, Mo, Cu). The thermal decomposition of bulk and CNT supported metal precursors used in the preparation of MOx/CNTs was analyzed under inert atmosphere employing several thermoanalytical techniques (thermogravimetry, differential thermogravimetry and differential scanning calorimetry) coupled with mass spectrometry. The thermolysis parameters of the bulk and supported metal precursors were compared and the effect of CNT support on the decomposition pattern of compounds was elucidated. It was established that the decomposition of metal precursors supported on CNTs was started and completed at temperatures of 15‒25 and 25‒70 °C lower, respectively, compared with the bulk active metal precursor. The enhancement of CNT support stability against thermal degradation is observed in the following row of metal cations: Ce < Cu < Мо < pristine and metal anions of precursor: nitrate < chloride < sulfate. The optimal mode of thermal treatment of catalyst and appropriate active metal precursors were selected for advanced synthesis of nanosized MOx/CNT catalyst.

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Capelli, Sofia, Stefano Cattaneo, Marta Stucchi, Bart D. Vandegehuchte, Alessandro Chieregato, Alberto Villa, and Laura Prati. "The Nature of Active Sites in the Pd/C-Catalyzed Hydrogenation/Hydrodeoxygenation of Benzaldehyde." Catalysts 12, no. 3 (February 22, 2022): 251. http://dx.doi.org/10.3390/catal12030251.

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Hydrogenations and hydrodeoxygenations represent two of the most important reactions in the production of both bulk and fine chemicals. Despite the wide and long use of metal-based catalysts for this reaction, there is still some uncertainty with respect to the properties governing the catalyst activity. Using the hydrogenation of benzaldehyde as a model reaction, in this paper, we disclose the dominant parameters determining catalyst activity of Pd nanoparticles supported on a carbonaceous material (carbon nanoplates, GNP). In particular, several operating parameters of the catalyst synthesis were varied in order to obtain materials with differences in such physico-chemical properties as nanoparticle size, Pd oxidation state and Pd surface exposure. A linear correlation between catalyst activity and the amount of surface Pd(0) atoms was found; this dependence, maintained after catalyst recycling, pointed out the nature of the active site of the Pd/GNP catalyst represented by exposed Pd(0) species.

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Khan, Il Son, Adrian Ramirez, Genrikh Shterk, Luis Garzón-Tovar, and Jorge Gascon. "Bimetallic Metal-Organic Framework Mediated Synthesis of Ni-Co Catalysts for the Dry Reforming of Methane." Catalysts 10, no. 5 (May 25, 2020): 592. http://dx.doi.org/10.3390/catal10050592.

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Dry reforming of methane (DRM) involves the conversion of CO2 and CH4, the most important greenhouse gases, into syngas, a stoichiometric mixture of H2 and CO that can be further processed via Fischer–Tropsch chemistry into a wide variety of products. However, the devolvement of the coke resistant catalyst, especially at high pressures, is still hampering commercial applications. One of the relatively new approaches for the synthesis of metal nanoparticle based catalysts comprises the use of metal-organic frameworks (MOFs) as catalyst precursors. In this work we have explored MOF-74/CPO-27 MOFs as precursors for the synthesis of Ni, Co and bimetallic Ni-Co metal nanoparticles. Our results show that the bimetallic system produced through pyrolysis of a Ni-Co@CMOF-74 precursor displays the best activity at moderate pressures, with stable performance during at least 10 h at 700 °C, 5 bar and 33 L·h−1·g−1.

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Zhang, Yuchen, Jianhui Zhang, Zongcheng Liu, Yiyi Wu, Yu Lv, Yadian Xie, and Huanjiang Wang. "Alloying Iron into Palladium Nanoparticles for an Efficient Catalyst in Acetylene Dicarbonylation." Nanomaterials 12, no. 21 (October 28, 2022): 3803. http://dx.doi.org/10.3390/nano12213803.

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Motivated by the prominent catalytic performance and durability of nanoalloy catalysts, the Pd-based bimetallic nanoalloy catalysts were prepared using an aqueous reduction method. The Fe-Pd bimetallic nanoalloy catalyst (nano-Fe/Pd) demonstrated 98.4% yield and 99.7% selectivity for the unsaturated 1,4-dicarboxylic acid diesters. Moreover, the inductively coupled plasma (ICP) analysis shows that the Pd leaching of the catalyst can be effectively suppressed by alloying Fe atoms into the Pd crystal lattice for acetylene dicarbonylation. The detailed catalyst structure and morphology characterization demonstrate that introducing Fe into the Pd nanoparticles tunes the electronic–geometrical properties of the catalyst. Theoretical calculations indicate that the electrons of Fe transfer to Pd in the nano-Fe/Pd catalyst, enhancing activation of the C≡C bond in acetylene and weakening CO absorption capacity on catalyst surfaces. Alloying Fe into the Pd nanocatalyst effectively inhibits active metal leaching and improves catalyst activity and stability under high-pressure CO reactions.

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Wang, Jingzhen, Kaijie Mu, Xuedong Zhao, Dianliang Luo, Xiaodi Yu, Wenpeng Li, Jie Chu, Jing Yang, and Qinzheng Yang. "Uniform Distribution of Pd on GO-C Catalysts for Enhancing the Performance of Air Cathode Microbial Fuel Cell." Catalysts 11, no. 8 (July 22, 2021): 888. http://dx.doi.org/10.3390/catal11080888.

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Metal, as a high-performance electrode catalyst, is a research hotspot in the construction of a high-performance microbial fuel cell (MFC). However, metal catalyst nanoparticles and their dispersed carriers are prone to aggregation, producing catalytic electrodes with inferior qualities. In this study, Pd is uniformly dispersed on the graphene framework supported by carbon black to form nanocomposite catalysts (Pd/GO-C catalysts). The effect of the palladium loading amount in the catalyst on the catalytic performance of the air cathode was further studied. The optimized metal loading afforded a reduced resistance and improved accessibility of Pd particles for the ORR. The maximum current output of the 0.250 Pd (mg/cm2) MFC was 1645 mA/m2, which is 4.2-fold higher than that of the carbon paper cathode. Overall, our findings provide a novel protocol for the preparation of high-efficient ORR catalyst for MFCs.

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Hamedi Shokrlu, Y., and T. Babadagli. "In-Situ Upgrading of Heavy Oil/Bitumen During Steam Injection by Use of Metal Nanoparticles: A Study on In-Situ Catalysis and Catalyst Transportation." SPE Reservoir Evaluation & Engineering 16, no. 03 (July 29, 2013): 333–44. http://dx.doi.org/10.2118/146661-pa.

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Summary Studies on the application of transition-metal catalysts for heavy-oil or bitumen in-situ upgrading were conducted in the absence of a porous medium, mainly measuring the characteristics of heavy oil in reaction with metal ions at static conditions with the help of a magnetic stirrer. Metal species in ionic form are not soluble in oil phase. Therefore, metal particles, as inhomogeneous catalysts, are considered in this paper. Furthermore, dynamic tests in porous media are needed to clarify the injection possibility of the metal particles and their effect on in-situ upgrading of heavy oil. Injection of metal particles may deteriorate the recovery process by damaging porous media because of attractive forces such as van der Waals and electrostatic forces between particles and porous rock. A better understanding of these forces and their importance in the retention of particles is required. In this paper, the catalysis effect of pure nanometer-sized nickel during steam-injection application was compared with that of an industrial catalyst such as micron-sized Raney nickel. The changes in the viscosity, refractive index, and asphaltene content were measured after each test to analyze the catalysis effects. Nickel nanoparticles showed a better catalysis compared with Raney nickel. The approximate optimum concentration of the catalysts was determined. Then, the catalysis effect of nickel nanoparticles was studied in the presence of sandpack as a porous medium. The results showed accelerated catalysis in presence of the sands. Also, nickel nanoparticles improved the oil recovery factor. The next phase of this paper studies the injectivity and transport of nickel particles. The injected suspension was stabilized by use of xanthan gum polymer and ultrasonication. The effect of solution pH, which controls the magnitude of the repulsive electrostatic forces, was clarified. Stabilization of the metal particles’ suspension was studied at different pH values through zeta-potential measurements. Also, the zeta potential of the recovered suspensions was studied to confirm the stability of the suspension during travel through the porous medium. Depending on the size, particles carry different charges and have different settling velocities. Therefore, the stabilization pH and dispersant concentration were different from one sample to another. The results of the injectivity tests confirmed the lower retention and better injectivity of nanoparticles in comparison with micron-sized particles.

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Kim, Youngjin, A. Anto Jeffery, Jiho Min, and Namgee Jung. "Modulating Catalytic Activity and Durability of PtFe Alloy Catalysts for Oxygen Reduction Reaction Through Controlled Carbon Shell Formation." Nanomaterials 9, no. 10 (October 19, 2019): 1491. http://dx.doi.org/10.3390/nano9101491.

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Demand on synthetic approaches to high performance electrocatalyst with enhanced durability is increasing for fuel cell applications. In this work, we present a facile synthesis of carbon shell-coated PtFe nanoparticles by using acetylacetonates in metal precursors as carbon sources without an additional polymer coating process for the carbon shell formation. The carbon shell structure is systematically controlled by changing the annealing conditions such as the temperature and gas atmosphere. PtFe catalysts annealed at 700 °C under H2-mixed N2 gas show much higher oxygen reduction reaction (ORR) activity and superior durability compared to a Pt catalyst due to the ultrathin and porous carbon shells. In addition, when increasing the annealing temperature, the carbon shells encapsulating the PtFe nanoparticles improves the durability of the catalysts due to the enhanced crystallinity of the carbon shells. Therefore, it is demonstrated that the developed hybrid catalyst structure with the carbon shells not only allows the access of reactant molecules to the active sites for oxygen reduction reaction but also prevents the agglomeration of metal nanoparticles on carbon supports, even under harsh operating conditions. The proposed synthetic approach and catalyst structure are expected to provide more insights into the development of highly active and durable catalysts for practical fuel cell applications.

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Mao, H., Y. Liao, J. Ma, S. L. Zhao, and F. W. Huo. "Water-soluble metal nanoparticles stabilized by plant polyphenols for improving the catalytic properties in oxidation of alcohols." Nanoscale 8, no. 2 (2016): 1049–54. http://dx.doi.org/10.1039/c5nr07897k.

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We successfully synthesized amphiphilic platinum nanoparticle catalyst (BWT-Pt) by using black wattle tannin (BWT) as the stabilizer, which prevented the Pt nanoparticles from aggregating and leaching during the catalytic reactions. The resultant catalyst exhibited high activity and cycling stability in the oxidation of alcohols.

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Guo, Jia, Xiaoming Mu, Shihao Song, Yanwei Ren, Kai Wang, and Zunming Lu. "Preparation of Ag0 Nanoparticles by EDM Method as Catalysts for Oxygen Reduction." Metals 11, no. 9 (September 20, 2021): 1491. http://dx.doi.org/10.3390/met11091491.

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At present, platinum-based catalysts are the best cathode catalysts, but due to their high prices, they are difficult to use widely. Under alkaline conditions, silver is a better low-cost substitute. Here, a physical preparation method—electrical discharge machining (EDM)—is used to prepare Ag0 nanoparticles. The method is simple and has a high yield. The diameter of prepared nanoparticles is about 30 nm and the nanoparticle surface is rich in defects. These defects enhance the adsorption of O2. In addition, defects can cause tensile strain on the silver catalyst, causing the d-band center of silver to move upward. The defects and the upward shift of the d-band center jointly improve the adsorption energy and catalytic performance of Ag0. This work provides a new method for the engineering construction of surface defects and the preparation of metal catalysts.

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Zeynalov, N. A., U. A. Mammadova, A. F. Isazade, N. T. Shikhverdiyeva, Ch M. Seidova, H. F. Aslanova, N. T. Rahimli, K. J. Hasanova, and E. H. Babayev. "SYNTHESIS AND STUDY OF THE STRUCTURE OF Pd AND Mn NANOPARTICLES IN THE PRESENCE OF POLYVINYLPYRROLIDONE." Chemical Problems 20, no. 2 (2022): 145–53. http://dx.doi.org/10.32737/2221-8688-2022-2-145-153.

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Poly-N-vinylpyrrolidone is widely used among synthetic polymers due to its non-toxicity and solubility in water and other organic solvents. Complex compounds with metals and non-metals find widespread application in various fields of industry and medicine. The purpose of this study is to synthesize metal-polymer complexes for obtaining a new type of catalyst. Poly-N-vinylpyrrolidone was first dissolved in water and then re-mixed with the addition of the PdCl2 salt. A reducing agent was added to the solution, and finally the resulting substance was established by means of a binder. The same process was typical for MnCl2 salt. Complexes obtained studied by various research methods (FTIR, XRD, SEM, UV-Vis). Proceeding from the results of the research methods, we can say that the construction process was successful and the metal nanoparticles settled on the surface and inside the polymer. The obtained complex compounds are intended to be used as catalysts

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Rankin, Rees, and Tamara Lozano. "Adsorption Energy Shifts for Oxygen and Hydroxyl on 4-atom Metal-Decorated Graphene Catalysts Via Solvation, pH, and Substrate Dopants: Effects on ORR Activity." Metals 9, no. 2 (February 14, 2019): 227. http://dx.doi.org/10.3390/met9020227.

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Recent literature results have highlighted the role of small transition metal and intermetallic nanoparticles supported on graphene as catalysts for many key applications in energy and commodity chemicals industries. Specifically, metal nanoparticle catalysts down to sizes of 4 and even 1 (single atom catalysts) on graphene have been studied for the Oxygen Reduction Reaction (ORR). A recent study showed that 4-atom transition metal intermetallic nanoparticles (NP) on graphene (metal-decorated graphene (MDG)) even generate a predictive Volcano Plot for ORR activity. Initial results from that study were not completely explained, and an expanded analysis and discussion built from that work is presented in this manuscript. Specifically, in this new work, the original Volcano Plot for 4-atom MDG NP catalysts for the ORR is analyzed for its counter-intuitive thermodynamic inversion between the rate limiting steps of O* hydrogenation and OH* hydrogenation. The Volcano Plot is then further studied for dependence on solvent correction energy, system pH, and with an initial probe on the sensitivity of descriptor values on doping of the graphene support via B and N atoms. Recommendations for optimum 4-atom MDG NP catalyst operation for the ORR are provided, and directions for future work and study are provided.

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Campos, Cristian H., Bruno F. Urbano, Cecilia C. Torres, and Joel A. Alderete. "A Novel Synthesis of Gold Nanoparticles Supported on Hybrid Polymer/Metal Oxide as Catalysts for p-Chloronitrobenzene Hydrogenation." Journal of Chemistry 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/7941853.

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This contribution reports a novel preparation of gold nanoparticles on polymer/metal oxide hybrid materials (Au/P[VBTACl]-M metal: Al, Ti or Zr) and their use as heterogeneous catalysts in liquid phase hydrogenation of p-chloronitrobenzene. The support was prepared by in situ radical polymerization/sol gel process of (4-vinyl-benzyl)trimethylammonium chloride and 3-(trimethoxysilyl)propyl methacrylate in conjunction with metal-alkoxides as metal oxide precursors. The supported catalyst was prepared by an ion exchange process using chloroauric acid (HAuCl4) as gold precursor. The support provided the appropriate environment to induce the spontaneous reduction and deposition of gold nanoparticles. The hybrid material was characterized. TEM and DRUV-vis results indicated that the gold forms spherical metallic nanoparticles and that their mean diameter increases in the sequence, Au/P[VBTACl]-Zr > Au/P[VBTACl]-Al > Au/P[VBTACl]-Ti. The reactivity of the Au catalysts toward the p-CNB hydrogenation reaction is attributed to the different particle size distributions of gold nanoparticles in the hybrid supports. The kinetic pseudo-first-order constant values for the catalysts in the hydrogenation reaction increases in the order, Au/P[VBTACl]-Al > Au/P[VBTACl]-Zr > Au/P[VBTACl]-Ti. The selectivity for all the catalytic systems was greater than 99% toward the chloroaniline target product. Finally the catalyst supported on the hybrid with Al as metal oxide could be reused at least four times without loss in activity or selectivity for the hydrogenation of p-CNB in ethanol as solvent.

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Wetchasat, Piraya, Saros Salakhum, Thidarat Imyen, Duangkamon Suttipat, Wannaruedee Wannapakdee, Marisa Ketkaew, Anittha Prasertsab, Pinit Kidkhunthod, Thongthai Witoon, and Chularat Wattanakit. "One-Pot Synthesis of Ultra-Small Pt Dispersed on Hierarchical Zeolite Nanosheet Surfaces for Mild Hydrodeoxygenation of 4-Propylphenol." Catalysts 11, no. 3 (March 5, 2021): 333. http://dx.doi.org/10.3390/catal11030333.

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The rational design of ultra-small metal clusters dispersed on a solid is of crucial importance in modern nanotechnology and catalysis. In this contribution, the concept of catalyst fabrication with a very ultra-small size of platinum nanoparticles supported on a hierarchical zeolite surface via a one-pot hydrothermal system was demonstrated. Combining the zeolite gel with ethylenediaminetetraacetic acid (EDTA) as a ligand precursor during the crystallization process, it allows significant improvement of the metal dispersion on a zeolite support. To illustrate the beneficial effect of ultra-small metal nanoparticles on a hierarchical zeolite surface as a bifunctional catalyst, a very high catalytic performance of almost 100% of cycloalkane product yield can be achieved in the consecutive mild hydrodeoxygenation of 4-propylphenol, which is a lignin-derived model molecule. This instance opens up perspectives to improve the efficiency of a catalyst for the sustainable conversion of biomass-derived compounds to fuels.

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Chen, Chao, Yang Liu, Tusheng He, and Changan Tian. "Hexagonal sheet Ag and Ag nanoparticle inside 3D-TiO₂ NTAs decorated Ti gauze by electrodeposition." Journal of Physics: Conference Series 2390, no. 1 (December 1, 2022): 012035. http://dx.doi.org/10.1088/1742-6596/2390/1/012035.

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Abstract Noble metal nanoparticles have attracted extensive attention by many researchers because of their optical, electrical and magnetic advantages. Half hexagon sheet Ag and Ag nanoparticles inside 3D-TiO2 nanotube arrays (NTAs) on Ti gauze was firstly synthesized by electrodeposition. The addition has a great influence on the morphology of Ag. When Ag hexagonal side length reached a maximum of 2 μm for 20 pluses, hexagonal Ag would transform oval Sphere with depositional pulses continuing increases, Ag nanoparticle inside 3D-TiO2 NTAs also were found, and the Ag modified NTAs for 20 pulses with the best photo-catalytic activity degraded methyl orange (MO) under solar light irradiation. Due to 3D-TiO2 NTAs supporting Ag catalyst, which is a benefit for recycling after the catalyst. This work is expected to provide a fundamental guide for the design of novel morphology catalysts on Ti gauze, which is conducive to recycling.

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Journal articles on the topic 'Metal catalyst nanoparticles'

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