Design Of Nanocatalysts Research Articles

Mimicking nature's strategies for the design of nanocatalysts

Recent developments in bionanotechnology have produced a knowledge pool that enables the fabrication, functionalization, and activation of inorganic nanostructures. Continued progress in this field has led to advances in inorganic nanomaterial control, providing for the generation of catalysts that operate under biologically influenced conditions of temperature, pressure, and solvent. Outlined in this Perspective are a selection of catalysts active for a variety of reactions including C–C coupling, chemical reduction, electrocatalysis, and bond cleavage reactions, where a combination of both the inorganic core and biological surface work in concert to achieve the final functionality. By fully understanding the total structure/function relationship of these bio-inspired nanomaterials, new catalytic structures could be designed using biological principles that are energy neutral, eco-friendly, and selective, all of which represent grand challenges in light of the current global condition.

Highly branched Pt–Ni nanocrystals enclosed by stepped surface for methanol oxidation

Integrated design of nanocatalysts with a preferential surface atomic arrangement, composition, and overall morphology will provide great opportunities to enhance their catalytic activity and durability. In this work, Pt–Ni bimetallic nanobundles (NBs) with branched morphology and stepped surfaces have been prepared by a seed-based diffusion method. For methanol oxidation, the Pt–Ni NBs possess 3.6-fold the activity of conventional Pt nanoparticles (NPs), likely due to the high-density surface atomic steps and the presence of surface Ni species. With the aggregation resistant starlike morphology, the Pt–Ni NBs pertain 55% of initial peak current density after 4000 cycles, while conventional Pt NPs maintain only 10% of that.

RhPt 이종금속 나노입자의 크기 및 조성 제어를 통한 촉매 활성도에 관한 연구

This study shows that catalytic activity of bimetallic RhPt nanoparticle arrays under CO oxidation can be tuned by varying the size and composition of nanoparticles. The tuning of size of RhPt nanoparticles was achieved by changing concentration of rhodium and platinum precursors in one-step polyol synthesis. Two-dimensional RhPt bimetallic nanoparticle arrays in different size and composition were prepared through Langmuir-Blodgett thin film technique. CO oxidation was carried out on these two-dimensional nanoparticle arrays, revealing higher activity on the smaller nanoparticles compared to the bigger nanoparticles. X-ray photoelectron spectroscopy (XPS) results indicate the preferential surface segregation of Rh compared to Pt on the smaller nanoparticles, which is consistent with the thermodynamic analysis. Because the catalytic activity is associated with differences in the rates of <TEX>$O_2$</TEX> dissociative adsorption between Pt and Rh, this paper suppose that the surface segregation of Rh on the smaller bimetallic nanoparticles is responsible for the higher catalytic activity in CO oxidation. This result suggests a control mechanism of catalytic activity via synthetic approaches of colloid nanoparticles, with possible application in rational design of nanocatalysts.

Design of Nanocatalysts for Green Hydrogen Production from Bioethanol

Bioethanol is an interesting feedstock that may be used for hydrogen production by steam or autothermal reforming. However, the impurities (heavy alcohols, esters, acids, N compounds) contained in the raw feedstock require a costly purification, as they have a dramatic impact on catalyst activity and stability. Thus, a method that can utilize the raw feedstock without severe degradation of the catalyst would be desirable. In this Minireview, the composition of bioethanol from first and second generation biomass, the reactions involved in the catalytic ethanol steam reforming process and the design of catalysts adapted for hydrogen production from a real bioethanol feed are surveyed.

Size effect of RhPt bimetallic nanoparticles in catalytic activity of CO oxidation: Role of surface segregation

We show that catalytic activity of bimetallic Rh 0.5Pt 0.5 nanoparticle arrays under CO oxidation can be tuned by varying the size of nanoparticles. The tuning of size of RhPt nanoparticles was achieved by changing the concentration of rhodium and platinum precursors in one-step polyol synthesis. We obtained two dimensional Rh 0.5Pt 0.5 bimetallic nanoparticle arrays in size between 5.7 nm and 11 nm. CO oxidation was carried out on these two-dimensional nanoparticle arrays, revealing higher activity on the smaller nanoparticles compared to the bigger nanoparticles. X-ray photoelectron spectroscopy (XPS) results indicate the preferential surface segregation of Rh compared to Pt on the smaller nanoparticles, which is consistent with our thermodynamic analysis. Because the catalytic activity is associated with differences in the rates of O 2 dissociative adsorption between Pt and Rh, we suppose that the surface segregation of Rh on the smaller bimetallic nanoparticles is responsible for the higher catalytic activity in CO oxidation. This result suggests a control mechanism of catalytic activity via synthetic approaches for colloid nanoparticles, with possible application in rational design of nanocatalysts.

Design of Novel Structured Gold Nanocatalysts

Small gold nanoparticles dispersed on certain oxide supports exhibit unprecedented catalytic activities in low-temperature CO oxidation, and gold catalysts show a great potential for selective oxidation or hydrogenation of organic substrates. Nevertheless, most gold catalysts (e.g., Au/TiO2, Au/Al2O3, Au/Fe2O3, Au/SiO2, Au/CeO2) have been prepared by loading gold on unmodified or modified solid supports through traditional synthesis methodologies (e.g., deposition precipitation, wet impregnation), therefore having simple metal-on-support structures and metal–support interactions. The current Perspective highlights some recent progress in the design of novel structured gold nanocatalysts, including unsupported or supported core–shell or yolk–shell structures, gold nanoparticles encapsulated in an inorganic matrix, postmodified gold catalysts, gold-based alloy catalysts, and gold catalysts with additional interfacial sites (or metal oxide components) carried to supports or formed in situ on supports. The objective of most of these studies was to demonstrate synthetic protocols by testing the catalytic performance of the prepared catalysts in simple probe reactions, and the focus was more on materials synthesis than on catalytic reactions or reaction mechanisms. These novel structured gold catalysts will certainly bring new opportunities for studying their performance in various catalytic reactions, the nature of active sites, reaction mechanisms, and correlations between structure and catalytic properties.

Nanotechnology in Agriculture: Propagating, Perpetuating, and Protecting Life

Natural agricultural production is an open system, both energy and matters are exchanged freely in this system involving interactions of geosphere (especially pedosphere), biosphere, and atmosphere. Agriculture provides crops for food and industry, fiber, fuel, auto-fuel and drugs. On one hand it faces ever escalating food prices and farmer’s suicides, and on the other hand input use efficiency is low. Present agricultural practices have made harvests toxic, mother’s milk a poison, and breathing-air venom. In this background, nanotechnology brings new hope. Nanotechnology is an interdisciplinary venture-field that converge science, engineering, and agriculture and food systems into one. The Environmental Protection Agency of the US has defined nanotechnology as the understanding and control of matter at dimensions of roughly 1-100 nm, where unique physical properties make novel applications possible. The triple problems of agriculture – over-dependence on supplementary irrigation, vulnerability to climate, and poor input and energy conversion to products – can be solved by using nanotechnology, provided agricultural scientists seek a chance to try and cooperate with scientists of kindred disciplines. Nanotechnology is new to agriculture; a ventured field of less than a decade old. But, already success has been achieved for manufacturing nano-pesticides and nano-fertilizer, in disease elimination in poultry, in food packaging, use of agricultural waste, nanosensors, precision agricultural practices, and in livestock and fisheries. Nanotechnology holds the potential to revolutionize agriculture and food systems in the areas of nano-fertilizers, pesticide career, microfluidics, BioMEMS, nucleic acid bioengineering, smart treatment delivery systems, nanobioprocessing, bioanalytical nanosensors, nanomaterials, bioselective surfaces, environmental processing, pathogen detection, plant/animal production, biosecurity, molecular and cellular biology, protection of the environment through the reduction and conversion of agricultural materials into valuable products, design and development of new nanocatalysts to convert vegetable oils into biobased fuels and biodegradable industrial solvents, and in controlled ecological life support system, to name a few.

Nanotechnology in Agriculture: Propagating, Perpetuating, and Protecting Life

AbstractNatural agricultural production is an open system, both energy and matters are exchanged freely in this system involving interactions of geosphere (especially pedosphere), biosphere, and atmosphere. Agriculture provides crops for food and industry, fiber, fuel, auto-fuel and drugs. On one hand it faces ever escalating food prices and farmer’s suicides, and on the other hand input use efficiency is low. Present agricultural practices have made harvests toxic, mother’s milk a poison, and breathing-air venom. In this background, nanotechnology brings new hope. Nanotechnology is an interdisciplinary venture-field that converge science, engineering, and agriculture and food systems into one. The Environmental Protection Agency of the US has defined nanotechnology as the understanding and control of matter at dimensions of roughly 1-100 nm, where unique physical properties make novel applications possible. The triple problems of agriculture – over-dependence on supplementary irrigation, vulnerability to climate, and poor input and energy conversion to products – can be solved by using nanotechnology, provided agricultural scientists seek a chance to try and cooperate with scientists of kindred disciplines. Nanotechnology is new to agriculture; a ventured field of less than a decade old. But, already success has been achieved for manufacturing nano-pesticides and nano-fertilizer, in disease elimination in poultry, in food packaging, use of agricultural waste, nanosensors, precision agricultural practices, and in livestock and fisheries. Nanotechnology holds the potential to revolutionize agriculture and food systems in the areas of nano-fertilizers, pesticide career, microfluidics, BioMEMS, nucleic acid bioengineering, smart treatment delivery systems, nanobioprocessing, bioanalytical nanosensors, nanomaterials, bioselective surfaces, environmental processing, pathogen detection, plant/animal production, biosecurity, molecular and cellular biology, protection of the environment through the reduction and conversion of agricultural materials into valuable products, design and development of new nanocatalysts to convert vegetable oils into biobased fuels and biodegradable industrial solvents, and in controlled ecological life support system, to name a few.

Morphology‐Dependent Interactions of ZnO with Cu Nanoparticles at the Materials’ Interface in Selective Hydrogenation of CO2 to CH3OH

A good face: The (002) polar facet of platelike ZnO nanoparticles gives a much stronger electronic interaction with Cu nanoparticles than other facets (see picture; CB=conductance band; VB=valence band) and shows higher selectivity in the catalytic hydrogenation of CO2 to methanol. This finding provides the basis for the rational design of new nanocatalysts for CO2 hydrogenation.

Nanoalloying in real time. A high resolution STEM and computer simulation study

Bimetallic nanoparticles constitute a promising type of catalysts, mainly because their physical and chemical properties may be tuned by varying their chemical composition, atomic ordering, and size. Today, the design of novel nanocatalysts is possible through a combination of virtual lab simulations on massive parallel computing and modern electron microscopy with picometre resolution on one hand, and the capability of chemical analysis at the atomic scale on the other. In this work we show how the combination of theoretical calculations and characterization can solve some of the paradoxes reported about nanocatalysts: Au–Pd bimetallic nanoparticles. In particular, we demonstrate the key role played by adsorbates, such as carbon monoxide (CO), on the structure of nanoalloys. Our results imply that surface condition of nanoparticles during synthesis is a parameter of paramount importance.

Structural and Chemical Properties of Gold Rare Earth Disilicide Core−Shell Nanowires

Clear understanding of the relationship between electronic structure and chemical activity will aid in the rational design of nanocatalysts. Core-shell Au-coated dysprosium and yttrium disilicide nanowires provide a model atomic scale system to understand how charges that transfer across interfaces affect other electronic properties and in turn surface activities toward adsorbates. Scanning tunneling microscopy data demonstrate self-organized growth of Au-coated DySi₂ nanowires with a nanometer feature size on Si(001), and Kelvin probe force microscopy data measure a reduction of work function that is explained in terms of charge transfer. Density functional theory calculations predict the preferential adsorption site and segregation path of Au adatoms on Si(001) and YSi₂. The chemical properties of Au-YSi₂ nanowires are then discussed in light of charge density, density of states, and adsorption energy of CO molecules.

First-principles calculations on the role of Ni-doping in Cu n clusters: From geometric and electronic structures to chemical activities towards CO 2

First-principles calculations have been applied to investigate the role of Ni-doping in modifying the geometric and electronic structures of Cu n clusters ( n = 1 – 12 ), and the chemical activity of clusters towards CO 2. The results reveal that Ni-doping introduces a significant modulation of the electronic structures, such as the density of states, HOMO–LUMO gaps and the d-band centers, which dominate their chemical activities towards CO 2 adsorption. Our findings contribute valuable information for high efficient Cu–Ni alloy nano-catalyst design.

Synthesis, characterization and catalytic activity of highly ordered hexagonal and cubic composite monoliths

Design of nanocatalysts for efficient heterogeneous catalytic systems is needed to high ingredients for environmental cleanup of organic pollutant species. Here, well-defined order NiO–silica monolithic catalysts with hexagonal P6mm and cubic Pm3n mesostructures were successfully fabricated by using an instant direct-templating method of lyotropic and microemulsion phases of Brij 76 (C 18H 37(OCH 2CH 2) 10OH, C 18EO 10). Ordered hexagonal P6mm NiO/HOM-2 monoliths could be fabricated in lyotropic system of Brij 76 at phase composition domains of TMOS/Brij 76 (50 wt%). However, periodically ordered cubic Pm3n NiO-supported monoliths were synthesized in microemulsion system formed by addition of C 12-alkane to the hexagonal phase domains. This synthetic strategy also revealed that the NiO particles were well-dispersed into the silicate pore surface matrices of mesostructures. Monolithic NiO–silica composites with 2D hexagonal and 3D cubic geometries and with large particle morphologies show promise to act as catalysts. The current study revealed evidence of the advantages of nanoscale pore geometry and shape, and particle morphology of the supported silica monoliths in the design of nanocatalysts that can efficiently enhance the catalytic functionality in terms of stability, reversibility and reactivity. Furthermore, a key finding in our study was that 2D hexagonal and 3D cubic mesostructured NiO–silica catalysts retained the specific activity towards the oxidation reaction even after several regeneration/reuse cycles. Significant study of the mechanistic cyclization of the organic reactant using the density functional (DFT) calculations provided evidence of the key components of conformations of the functional model during the formation of the oxidation product.