User:Pei123/sandbox

peer review
For some reason, the figure you uploaded is not variable any more. The figure of carbon nanotube-supported catalysts will help people to understand better. Maybe you can upload a new one

Xieyuesmiling (talk) 20:56, 5 October 2011 (UTC)"Pear the ion (talk) 01:56, 6 October 2011 (UTC)" "Babie2011 (talk) 15:33, 6 October 2011 (UTC)"

General Public Summary
I think you should delete "General Public Summary" I didn’t see the title, so I assume your title is “carbon nanotube- supported catalyst”

The catalyst is a substance, usually used in small amounts relative to the reactants, that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. One or more kinds of catalysts can be loaded on another material with a high surface area, which serves as the support, to form a supported catalyst as a whole system. In a supported catalyst system, the significance of using the support are to disperse the active phase, to control the porous structure, to prevent sintering, to improve mechanical strength and to assist catalysis. There is a wide spectrum of supports ranging from conventional and most commonly alumina to novel various kinds of activated carbon. Synthesis methods and functions vary greatly due to different kinds of support and catalytic materials. I think you wrote too much information about the supports and catalysts. I would like to only keep "The catalyst is a substance, usually used in small amounts relative to the reactants, that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. One or more kinds of catalysts can be loaded on another material with a high surface area, which serves as the support, to form a supported catalyst as a whole system. Two conventional conventional and most commonly supports are alumina and silicon. By the way, you can use the IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "catalyst" as reference.

Carbon nanotubes supported catalyst (in bold) is a novel supported catalyst, using carbon nanotubes link as the support instead of the conventional alumina link or silicon link support. For CNTs, the exceptional physical properties as large specific surface areas, good electron conductivity incorporated with the relatively high oxidation stability and chemical inertness makes it a promising support material Suggested replacement: “The intrinsic properties of CNTs such as large specific surface areas, good electron conductivity and chemical inertness make them a promising support material for heterogeneous catalysts.”. As a reader, I prefer this paragraph as the first paragraph. I want to see "Carbon nanotubes supported catalyst is..." as the first sentence of the wiki page so I can immediately know what's this Wikipedia page about

The challenge is this the only challenge? or the biggest challenge or one of the biggest challenge? in making a supported nanoparticulate catalyst is to avoid agglomeration. This is achieved by the use of a poly-functional anchoring agent, and drying at a relatively low temperature. The examples describe the deposition link of palladium link and platinum link particles on activated carbon, using a polyacrylate anchor. Studies of adsorption link and precipitation chemistry reveal new molecular details of the extensive interactions between precursors and supports in an aqueous environment. Progress is being made in the use of chemical vapor deposition link for the synthesis of supported catalysts. Combinatorial techniques have made their first contributions to solid catalyst synthesis.

I think the third paragraph is too much information for a public summary. A public summary should be a brief description to the general audiences. It’s not necessary to keep it.

The following paragraph is my suggestion for the general public summary(it's just a rough draft): Carbon nanotube-supported catalyst is a novel supported catalyst, using carbon nanotubes as the support. The catalyst is a substance, usually used in small amounts relative to the reactants, that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. One or more kinds of catalysts can be loaded on another material with a high surface area, which serves as the support, to form a supported catalyst as a whole system. Two conventional supports are alumina or silicon. However, since the discovery of the CNTs by Iijima(S, Iijima nature,1991, 354,56), they have become a promising support material for heterogeneous catalysts due to their intrinsic properties such as large specific surface areas, good electron conductivity and chemical inertness. Then you can mention that CNTs supported catalyst= CNTs+ catalyst. These catalysts can grow on the CNTs sidewells or the end of the tubes(some very basic information). After that, mention the applications of these CNTs supported catalysts (for fuel cells, batteries and synthesis of a wide variety of chemicals in industries)( Gregory, G. W.; Craig, E. B.; Richard, G. C. (2006) “Metal Nanoparticles and Related Materials Supported on Carbon Nanotubes: Methods and Application”. Small 2 (2): 182-193.)

Background
I think the background section is great.It does provide sufficient background to place the topic in the context of the field of materials science

Catalyst supports and supported catalysts
Catalysts are widely used in various chemical reactions. The activity, stability, selectivity, and regeneration ability are the most important properties to be considered in catalyst design. Maybe you can combine the first and second paragraphs

Catalysts can be loaded on catalyst supports, which can improve specific properties such as mechanical strength, distribution, stablity, catalytical reactivity and selectivity of catalysts. The definition of the support will be broad, including granular, powdered, colloidal, coprecipitated, extruded, pelleted, spherical, wires, honeycombs, and skeletal supports such as diatomaceous earth. My suggested replacement is: The catalyst supports can improve specific properties such as mechanical strength, distribution, stablity, catalytical reactivity and selectivity of catalysts. The definition of the support will be broad: there are granular, powdered, colloidal, coprecipitated, extruded, pelleted, spherical, wires, honeycombs, and skeletal supports. cross out "such as diatomaceous earth“ Catalyst supports can be either inert or active in reactions. The ensemble of the catalyst and its support can be regarded as an entirety: supported catalyst.

The supports were considered as merely were only considered as carriers on which the catalytic metal or oxide was disposed as broadly and uniformly as possible in pre-1940 publications. But over the years, a better understanding of the cofunctioning of catalyst catalysts and their supports has been achieved. It was recognized that the support was actually a promoter in many cases. In Catalysis (Berkman et al. 1940), the difference between a promoter and a support is described as the difference in quantity: when the support exceeds the quantity of the catalyst, it becomes a support; otherwise it is a promoter. This was a simplistic view, but implied the recognition even at this early date that the support was a catalytic component in the broadly construed catalytic composition.

An early purpose of the support was to obtain a solid granular material link where catalytic component could be coated, deriving a hard and stable structure to withstand disintegration under gas or liquid flows. Another purpose of loading noble metal on supports is to dilute precious metals in a large volume. Some supports serve as a stabilizer link to prevent agglomeration of lower-melting-point materials. A further use for the support was as a reservoir for semimolten salts.

After many experiments about alumina I think you only link the words the first time you mention them. Well, I'm not sure, please double check. , it has been recognized that catalyst supported on the different species of alumina have different catalytic properties. In the same time frame, observations were made that the catalyst and the support were sometimes cooperating to produce two simultaneous and mutually beneficial reactions. This was called the dual-functioning catalyst and was observed in hydrodenitrogenation, hydrodesulfurization, and reforming catalysts, to name a few.

Traditional carbon materials as supports
Carbon is a ubiquitous element that forms millions of compounds ranging from simple carbon monoxide link to highly complex enzymes. Regarding to its elemental form, although no catalytic properties can be ascribed to diamond link, graphite is known to be an active catalyst in some oxidation reactions. Graphitic carbon is also used as a support material on which other catalytic entities may be dispersed in order to increase the surface area they expose to the chemical reactants.

The uses of graphite, carbon black and activated charcoal manufactured annually as catalyst support are relatively few. The major catalytic use of charcoal and carbon blacks is the support of metals, and charcoals are sometimes used to support compounds such as sulfides link and halides link. Some graphite is used to support metals, but the most important feature of graphite is its ability to form intercalates, which are the catalysts for some hydrogenation, dehydrogenation, isomerization, alkylation, hydrodealkylation, polymerization and ammonia formation reactions. For charcoal and carbon black-supported metals with various industrial uses, the methods of manufacture can be divided into three broad groups depending on the catalytic metal: wet impregnation, hydrolysis impregnation and chemical vapor deposition (CVD).

Properties
Many textbooks describe carbon nanotubes (CNTs) in simple terms as tubular structures made entirely of rolled-up layers of graphene, with diameters ranging from about one nanometer to tens of nanometers and length up to centimeters. In general, CNTs possess large specific surface areas resulting from hollow geometry, which also makes CNTs extremely attractive as supports for heterogeneous catalysts. Another advantage of CNTs is the relatively high oxidation stability supported by their structural integrity and chemical inertness. In addition, CNTs have exceptional physical properties     including electrical, mechanical and thermal properties, which are important factors for catalyst supports. CNTs can be either metallic or semiconductive, depending on their helicity and diameter, and can affect charge transfer processes. CNTs possess a very large Young's modulus, as well as a great tensile strength, thus their flexibility makes them potentially suitable for applications in composite materials. CNTs also have good thermal conductivitity, which helps to hinder the growth of small nanoparticles during postannealing treatments, and stabilize new phases.

CNTs are tough and tensile, owning good electron conductivity and chemical inertness. Therefore they become unique and ideal templates for nanoparticle immobilization, allowing the construction of designed nanoarchitectures that are extremely attractive as supports for heterogeneous catalysts and related technologies.



Preparation of carbon nanotubes
CNTs are generally produced by four main techniques: arc discharge, laser ablation, molten salt intercalation, and chemical vapor deposition. Since as-produced CNTs contain a variety of impurities such as graphene fragments, amorphous carbon, fullerenes and metal catalyst particles which interfere with most of the desired properties and biocompatibility of CNTs, they need to be purified, separated and functionalized before being used in hybrid materials. Furthermore, uniform and stable dispersions of CNTs are required in many applications, but pristine single-walled CNTs (SWCNTs) are insoluble in most solvents, leading to aggregation between individual tubes. We also want to separate CNTs based on whether they are semiconducting or metallic.

The production of CNTs has become easier and cheaper by the years, and the quality of as-prepared CNTs has improved since the contaminated impurities are concerned. Thus, the major challenge will be the development of methods to improve the uniformity in lengths, diameters and chirality of CNTs. CNTs has great potential as an important bridge connecting the molecular realm and the macroscopic world.

Preparations
In order to get a CNTs supported catalyst, the first thing is to load the catalytic materials onto CNTs. A variety of synthesis strategies for the CNT/metal nanoparticle hybrids can be categorized as ex situ and in situ techniques.

Ex situ approaches
Ex situ approaches utilize different interactions, such as covalent interactions, noncovalent interactions, π-π stacking link and electrostatic interactions.

Covalent interactions, for instance, amide link bonds, are used to attach function group terminated inorganic nanoparticles link to acid treated CNTs. Au nanoparticles, among the most frequently used materials because of their excellent potential in biosensing and other medical application, have been linked to acid-terminated CNTs by aminothiols, bifunctional thiols or thioether bonds. The advantage of hydrophilic metal oxides such as MnO2 subscript, MgO , TiO2 subscript and Zr(SO4)2 subscript is that they can be attached to the carboxyl groups without linking agent, but the interactions are weak and result in nonuniform distribution.

Nanoparticles can also be attached to pristine CNTs via noncovalent interactions such as van der Waals interactions, hydrogen bonding, π-π stacking, and electrostatic interactions. The surfactant sodium dodecylsulfate (SDS) can be used to decorate multi-walled carbon nanotubes (MWCNTs) with nanoparticles of pure Pt, EuF3 subscript , TbF3 subscript and SiO2 subscript  particles. The use of hydrophobic capping agents, for example, octanethiols and dodecanethiols, provides another route which can control both coverage and morphology of the hybrid materials by modifying the length and functionality of the chains. A similar approach is to utilize the delocalized π electrons of CNTs and those in aromatic organic compounds modified with polar group terminated alkyl chains   , and its main advantage is the lasting absorption of pyrene link compounds on CNTs, providing greater solubility, continues dispersibility and enhanced charge transfer from nanoparticles to CNTs. For electrostatic approach, which is simple and feasible, the deposition of ionic polyelectrolytes to attract charged nanoparticles is the most common route.

In situ approaches
Inorganic compounds can also be directly formed on CNTs surface, with a better control of dispersion. For in situ synthesis directly on the CNT surface, techniques including electrochemical techniques, sol-gel process, hydrothermal and aerosol techniques and gas-phase deposition are used.

Electrochemistry enables effective control over nucleation and growth of noble metals and alloys. Metal nanoparticles are obtained via reduction of metal complexes by electrons, and the size of the metal nanoparticles and their coverage on the sidewalls of CNTs can be controlled by various electrochemical deposition parameters including nucleation potential and deposition time.

Sol-gel process is a versatile, solution-based process which can produce ceramic and glass materials in various forms. . Generally, this process starts with metal salts or metal organic compounds which go through a series of hydrolysis link and condensation link reactions to form a colloidal or polymeric sol. The sol is converted to gel upon aging, and subsequent drying under supercritical conditions converts the gel into aerogel. This is a cheap and low-temperature technique which exquisitely controls chemical composition and allows lowest concentration of dopants. But the disadvantage is that the product typically contains an amorphous phase and requires crystallization link and postannealing steps.

Hydrothermal techniques are developed in recent years. The hydrothermal method typically enables the formation of crystalline particles or films without postannealing and calcinations. Furthermore, the forced crystallization enables the formation of inorganic nanowires and nanorods.

In addition, there are various gas-phase deposition methods to prepare CNT-inorganic materials. Among the most common methods to produce inorganic nanomaterials, chemical   and physical    vapor depositions show excellent control over the size, shape and uniformity. They enable deposition of thin, continuous films on carbon substrates without damaging the 3D intergrity. Other physical techniques such as sputtering   and pulsed laser deposition (PLD), as well as chemical methods like atomic layer deposition (ALD)  , are alternatives for CNT-inorganic hybrids preparation.

Applications
I am not sure "applications" is the correct word to describe the content below. it sounds different "categories" of the carbon nanotube-support catalysts to me

Although at an early stage of research, CNTs as supports of metal-nanoparticle catalysts as transition metals Ru, Co, Ag, Pt, Pd, and Au add special light to many catalysis reaction in many fields such as batteries link, flat panel displays, and chemical sensors. This sentence is awkward, esp "add special light."Please rewrite it. In organic synthesis like Heck reaction or Fischer–Tropsch synthesis, CNTs supported Pd or Co catalysts are applied to improve catalytic activity or to optimize experimental conditions. For the selective catalytic reduction of NOx with hydrocarbons, CNTs supported Pt–Rh catalyst displays higher NOx reduction activity.

Particularly, with hydrogen carbon-based fuel reserves rapidly running out, fuel cell link and battery application of CNT-supported metal nanoparticles catalysts is an active area of research. For example, catalytic hydrogenation of CO2 subscript to produce methanol link has been considered as one of the most economical and effective ways to chemically fix huge amount of emitted CO2 subscript to improve climate conditions. In hydrogenation of CO2 subscript, CNTs supported Pd catalyst is favored because of its considerable activity and selectivity.

Nevertheless, further optimization in design is required for the development of these applications from laboratory devices to industrial prototypes. The control of the interface and the morphology and phase composition of the catalysts, as well as the type and quality of CNTs, remains a big challenge. Reproducibility is another problem, and a better understanding of the relationship between structures and properties is also in need.

Carbon nanotube-supported Pd catalyst
In the catalysts of Heck reaction, precious metal palladium was the most used active component. Supported palladium catalysts possessed many advantages, such as high catalytic activity, good stability, easy separation and satisfactory reusability compared with the traditional homogeneous Pd(OAc)2 subscript, PdCl2 subscript catalysts in Heck reaction.

In experiment part, addition of chemical reductant is used to promote the dispersion of palladium nanoparticles due to the agglomeration of palladium nanoparticles. CNT was CNTs were used as the carrier materials and two carbon nanotube supported palladium catalysts were prepared using chemical reduction and without reductant as a comparison.



Carbon nanotube-supported Pd-metal catalyst
I want to know the alloy is made of Pd and what metal. Please provide some examples, like Pd-Ru? Formic acid is a non-toxic and non-explosive liquid at room temperature. It has shown potential applications in small portable fuel cell applications due to its low toxicity, facility of storage, handling and primarily high energy density. Carbon supported palladium you mean Pd metal? catalysts have played a very important role in DFAFC (direct formic acid fuel cell) catalyst research in recent years, showing good activity along with the potential for more efficient palladium metal utilization and lower metal loadings.

The mechanism of formic acid electrooxidation on Pt and select Pt-group metal surfaces in acid solution follows the so-called dual pathways dehydrogenation and dehydration. Multi-walled carbon nanotubes (MWCNTs) have been used as the support of the cathode electrocatalyst and showed a better performance in DEFCs (direct ethanol fuel cells) due to the higher nanoparticle dispersion than that electrocatalysts supported on carbon black.



Carbon nanotube-supported Pd-metal-oxide catalyst
Hydrogenation of carbon dioxide has been considered as one of the most economical and effective ways to chemically fix huge amount of emitted CO2 link subscript. Supported Pd-metal-oxide catalysts have also been found to exhibit considerable activity and selectivity for hydrogenation of CO2 subscript. to methanol, and the supporter has significant effect on the performance of the catalyst.

MWCNT- supported Pd–ZnO catalysts for CO2 subscript. hydrogenation to methanol played dual roles as a catalyst supporter and a promoter. It could reversibly adsorb a greater amount of hydrogen, which would be in favor of generating a micro-environment with higher concentration of active H-adspecies at the surface of the functioning catalyst, thus increasing the rate of surface hydrogenation reactions.Those advantages introduce much better performance for highly effective and selective formation of methanol from CO2 hydrogenation.

Carbon nanotubes supported platinum catalyst
you mean "Carbon nanotube-supported Pt catalyst" as you use chemical symbols of the metals above. Be consistent Direct ethanol fuel cells (DEFC) and direct methanol fuel cells (DMFC) are efficient, silent and clean energy conversion systems producing electricity via electrochemical reactions. They are expected to provide a power source for portable electronic devices, such as mobile phones, laptop computers and other advanced mobile electronic devices. A successful commercialization of DMFC or DEFC is very much dependent on the activity of their electrocatalysts. With respect to the electrocatalytic efficiency, Pt catalysts are considered to be indispensible and are the most effective catalysts for alchohol oxidation. Pt is often alloyed or combined with a second precious or non-precious metal(like "Ru, Rh, Sn, Pb, Sb, Ni,etc.), which are referred to as bimetallic catalysts, to enhance its electrochemical activity and its tolerance to poisoning reaction intermediates by the so-called byfunctional or ligand mechanisms.

As a kind of electrocatalyst support, CNTs have shown better corrosion-resistance than other catalyst supports such as carbon black under operational conditions. Besides, CNTs not only enjoy have? a highly electrochemically accessible surface area but can also offer a remarkable electronic conductivity due to its multi-wall structure, which properties render it a competitive electrocatalyst support for Pt-catalyst.

It has been found that the electrochemical activity of different Pt-catalysts follows the order of Pt-WO3/CNT > Pt-Ru/E-TEK-Vulcan > Pt/CNT > Pt/E-TEK-Vulcan > bulkplatinum. The higher electrochemichal response of CNT based materials has been correlated to the higher available electroactive surface area.

Carbon nanotubes supported cobalt nanoparticles catalyst
again, "Co" catalyst The Fischer–Tropsch synthesis (FTS) process has shown to be catalyzed by certain transition metals, with Co, Fe, and Ru presenting the highest activity. Among them, cobalt catalysts are the preferred catalysts for FTS based on natural gas because of their high activity for FTS, high selectivity to linear hydrocarbons, low activity for the water gas shift (WGS) reaction, more stable toward deactivation by water (a by product of the FTS reaction), and low cost compared to RuActivated space between Ru and activated? carbon has many advantages if utilized as FTS catalyst support (resistance to acidic or basic media, stable at high temperatures, etc.) Using carbon nanotubes as cobalt catalyst support was found to cause the reduction temperature of cobalt oxide species to shift to lower temperatures. The strong metal-support interactions are reduced to a large extent and the reducibility of the catalysts improved significantly. CNT aided in well dispersion of metal clusters and average cobalt clusters size decreased. Results are presented showing that the hydrocarbon yield obtained by inventive CNT supported cobalt catalyst is surprisingly much larger than that obtained from cobalt on alumina supports.