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A General Concurrent Template Strategy for Ordered Mesoporous Intermetallic Nanoparticles with Controllable Catalytic Performance.

ABSTRACT: We report a general concurrent template strategy for precise synthesis of mesoporous Pt-/Pd-based intermetallic nanoparticles with desired morphology and ordered mesostructure. The concurrent template not only supplies a mesoporous metal seed for re-crystallization growth of atomically ordered intermetallic phases with unique atomic stoichiometry but also provides a nanoconfinement environment for nanocasting synthesis of mesoporous nanoparticles with ordered mesostructure and rhombic dodecahedral morphology under elevated temperature. Using the selective hydrogenation of 3-nitrophenylacetylene as a proof-of-concept catalytic reaction, mesoporous intermetallic PtSn nanoparticles exhibited remarkably controllable intermetallic phase-dependent catalytic selectivity and excellent catalytic stability. This work provides a very powerful strategy for precise preparation of ordered mesoporous intermetallic nanocrystals for application in selective catalysis and fuel cell electrocatalysis.

SUBMITTER: Lv H

PROVIDER: S-EPMC9311168 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Highly ordered mesoporous silica film nanocomposites containing gold nanoparticles for the catalytic reduction of 4-nitrophenol.

Project description:We report that transparent mesostructured silica/gold nanocomposite materials with an interpore distance of 4.1 nm, as-synthesized from a templated sol-gel synthesis method using discotic trinuclear gold(I) pyrazolate complex, were successfully utilized for the fabrication of thin film mesoporous silica nanocomposites containing gold nanoparticles. The material exhibited a highly ordered hexagonal structure when subjected to a thermal hydrogen reduction treatment at 210 °C. In contrast, when the material was subjected to calcination as a heat treatment from 190 to 450 °C, the thin film nanocomposites showed an intense d 100 X-ray diffraction peak. Moreover, gold nanoparticles inside the thin film nanocomposites were confirmed by the presence of the d 111 diffraction peak at 2θ = 38.2°, a surface plasmon resonance peak between 500-580 nm, and the spherical shape observed in the transmission electron microscope images, as well as the visual change in color from pink to purple. Interestingly, by simply dipping the material into a reaction solution of 4-nitrophenol at room temperature, the highly ordered structure of the as-fabricated silica/gold nanoparticle thin film composite after thermal hydrogen reduction at 210 °C resulted in an improved catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol compared to the material calcined at 250 °C. Such catalytic activity is due to the presence of gold nanoparticles of smaller size in the silicate channels of the highly ordered mesoporous film nanocomposites.

| S-EPMC6633902 | biostudies-literature

Synthesis of mesoporous ceria using metal- and halogen-free ordered mesoporous carbon as a hard template.

Project description:Ordered mesoporous cerias were synthesised by employing metal- and halogen-free ordered mesoporous carbons (OMCs) as the hard templates in a 'nanocasting' procedure. TEM, small angle (SA) and wide angle (WA) XRD, and N2 physisorption analyses were used to characterise the templates, intermediates and ceria products and electron tomography (STEM-HAADF) was used to explore the 3D morphology of the ceria nanostructures grown within the carbon templates. This allowed the relationships between the structures of the OMC templates and the products to be considered in detail as two parameters were varied. These were: the method of impregnation of the ceria precursor; and the temperature of calcination of the OMC template. Of the four impregnation methods tested, the solid-liquid method was found to be the most successful. This gave a high quality product with the highest yield of uniform mesopores, and crystalline nanorods of ceria arrayed in clear long-range order, as viewed by TEM and determined in SA and WAXRD. The specific surface area and pore volume exhibited by this sample were 111 m2 g-1 and 0.39 cm3 g-1, respectively. 3D electron tomography reconstructions revealed the presence of a network of ordered, nanoscale, rod-like structures interlinked in a complex fashion. The effect of calcination temperature of the template on uptake of the ceria precursor during impregnation was studied by calcining OMCs at temperatures from 350 to 800 °C and using these as hard templates for the nanocasting of ceria. Of these, the carbon template calcined at 400 °C gave the highest quality product.

| S-EPMC9418743 | biostudies-literature

Sub-THz Vibrational Dynamics in Ordered Mesoporous Silica Nanoparticles.

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Synthesis of uniform ordered mesoporous TiO2 microspheres with controllable phase junctions for efficient solar water splitting.

Project description:As a benchmark photocatalyst, commercial P25-TiO2 has been widely used for various photocatalytic applications. However, the low surface area and poorly porous structure greatly limit its performance. Herein, uniform ordered mesoporous TiO2 microspheres (denoted as Meso-TiO2-X; X represents the rutile percentage in the resultant microspheres) with controllable anatase/rutile phase junctions and radially oriented mesochannels are synthesized by a coordination-mediated self-assembly approach. The anatase/rutile ratio in the resultant microspheres can be facilely adjusted as desired (rutile percentage: 0-100) by changing the concentration of hydrochloric acid. As a typical one, the as-prepared Meso-TiO2-25 microspheres have a similar anatase/rutile ratio to commercial P25. But the surface area (78.6 m2 g-1) and pore volume (0.39 cm3 g-1) of the resultant microspheres are larger than those of commercial P25. When used as the photocatalyst for H2 generation, the Meso-TiO2-25 delivers high solar-driven H2 evolution rates under air mass 1.5 global (AM 1.5 G) and visible-light (? > 400 nm), respectively, which are significantly larger than those of commercial P25. This coordination-mediated self-assembly method paves a new way toward the design and synthesis of high performance mesoporous photocatalysts.

| S-EPMC6368211 | biostudies-literature

Pt incorporated mesoporous carbon spheres: controllable structure with enhanced catalytic activity and stability.

Project description:We report a simple synthesis process to prepare well-dispersed Pt nanoparticles incorporated in mesoporous carbon spheres. By manipulating the relative ratio of Pt precursor and resorcinol-formaldehyde resin (RF), Pt/carbon composites with different morphologies and Pt content were achieved. The as-prepared Pt/C composite materials show higher catalytic activity and reusability for the reduction of 4-nitrophenol (4-NP) than the Pt deposited commercial activated carbon (Pt/AC), which can be ascribed to the high dispersion of Pt nanoparticles in the carbon spheres.

| S-EPMC9079855 | biostudies-literature

Atomically ordered non-precious Co<sub>3</sub>Ta intermetallic nanoparticles as high-performance catalysts for hydrazine electrooxidation.

Project description:Nano-ordered intermetallic compounds have generated great interest in fuel cell applications. However, the synthesis of non-preciousearly transition metal intermetallic nanoparticles remains a formidable challenge owing to the extremely oxyphilic nature and very negative reduction potentials. Here, we have successfully synthesized non-precious Co3Ta intermetallic nanoparticles, with uniform size of 5 nm. Atomic structural characterizations and X-ray absorption fine structure measurements confirm the atomically ordered intermetallic structure. As electrocatalysts for the hydrazine oxidation reaction, Co3Ta nanoparticles exhibit an onset potential of -0.086 V (vs. reversible hydrogen electrode) and two times higher specific activity relative to commercial Pt/C (+0.06 V), demonstrating the top-level performance among reported electrocatalysts. The Co-Ta bridge sites are identified as the location of the most active sites thanks to density functional theory calculations. The activation energy of the hydrogen dissociation step decreases significantly upon N2H4 adsorption on the Co-Ta bridge active sites, contributing to the significantly enhanced activity.

| S-EPMC6778194 | biostudies-literature

Influence of Molecular Weight on Structure and Catalytic Characteristics of Ordered Mesoporous Carbon Derived from Lignin.

Project description:Bio-renewable lignin has been used as a carbon source for the preparation of porous carbon materials. Nevertheless, up to now, there are few studies about the influence of molecular weight of lignin on the structure and morphology of the ordered mesoporous carbon. Here, we synthesized the ordered mesoporous carbon derived from different molecular weights of lignin and Pluronic F127. Fortunately, we found that molecular weight is an important factor for obtaining highly ordered channels, high specific surface area, and ordered mesoporous carbon. More importantly, the narrow well-defined mesoporous channel could exert a spatial restriction effect to some extent, which can serve as nanoreactors for efficient reactions and enhance catalytic performance. The highly ordered mesoporous carbon from lignin is a good candidate for Fischer-Tropsch synthesis catalyst supports.

| S-EPMC6641423 | biostudies-literature

New route toward building active ruthenium nanoparticles on ordered mesoporous carbons with extremely high stability.

Project description:Creating highly active and stable metal catalysts is a persistent goal in the field of heterogeneous catalysis. However, a real catalyst can rarely achieve both of these qualities simultaneously due to limitations in the design of the active site and support. One method to circumvent this problem is to fabricate firmly attached metal species onto the voids of a mesoporous support formed simultaneously. In this study, we developed a new type of ruthenium catalyst that was firmly confined by ordered mesoporous carbons through the fabrication of a cubic Ia3d chitosan-ruthenium-silica mesophase before pyrolysis and silica removal. This facile method generates fine ruthenium nanoparticles (ca. 1.7?nm) that are homogeneously dispersed on a mesoporous carbonaceous framework. This ruthenium catalyst can be recycled 22 times without any loss of reactivity, showing the highest stability of any metal catalysts; this catalyst displays a high activity (23.3?mol(LA)h(-1)g(metal)(-1)) during the catalytic hydrogenation of levulinic acid (LA) when the metal loading is 6.1?wt%. Even at an ultralow loading (0.3?wt%), this catalyst still outperforms the most active known Ru/C catalyst. This work reveals new possibilities for designing and fabricating highly stable and active metal catalysts by creating metal sites and mesoporous supports simultaneously.

| S-EPMC3971394 | biostudies-literature

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Project description:The precise synthesis of fine-sized nanoparticles is critical for realizing the advantages of nanoparticles for various applications. We developed a technique for preparing finely controllable sizes of gold nanoparticles (Au NPs) on a silica template, using the seed-mediated growth and interval dropping methods. These Au NPs, embedded on silica nanospheres (SiO2@Au NPs), possess peroxidase-like activity as nanozymes and have several advantages over other nanoparticle-based nanozymes. We confirmed their peroxidase activity; in addition, factors affecting the activity were investigated by varying the reaction conditions, such as concentrations of tetramethyl benzidine and H2O2, pH, particle amount, reaction time, and termination time. We found that SiO2@Au NPs are highly stable under long-term storage and reusable for five cycles. Our study, therefore, provides a novel method for controlling the properties of nanoparticles and for developing nanoparticle-based nanozymes.

| S-EPMC8508978 | biostudies-literature

Influence of spatial configurations on electromagnetic interference shielding of ordered mesoporous carbon/ordered mesoporous silica/silica composites.

Project description:Ordered mesoporous carbons (OMCs), obtained by nanocasting using ordered mesoporous silicas (OMSs) as hard templates, exhibit unique arrangements of ordered regular nanopore/nanowire mesostructures. Here, we used nanocasting combined with hot-pressing to prepare 10 wt% OMC/OMS/SiO2 ternary composites possessing various carbon mesostructure configurations of different dimensionalities (1D isolated CS41 carbon nanowires, 2D hexagonal CMK-3 carbon, and 3D cubic CMK-1 carbon). The electric/dielectric properties and electromagnetic interference (EMI) shielding efficiency (SE) of the composites were influenced by spatial configurations of carbon networks. The complex permittivity and the EMI SE of the composites in the X-band frequency range decreased for the carbon mesostructures in the following order: CMK-3-filled > CMK-1-filled > CS41-filled. Our study provides technical directions for designing and preparing high-performance EMI shielding materials. Our OMC-based silica composites can be used for EMI shielding, especially in high-temperature or corrosive environments, owing to the high stability of the OMC/OMS fillers and the SiO2 matrix. Related shielding mechanisms are also discussed.

| S-EPMC3832851 | biostudies-other

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