Anomalous Role of Carbon in Pd-Catalyzed Selective Hydrogenation.

Carbonaceous species, including subsurface carbidic carbon and surface carbon, play crucial roles in heterogeneous catalysis. Many reports suggested the importance of subsurface carbon in the selective hydrogenation of alkynes over Pd-based catalysts. However, the role of surface carbon has been largely overlooked.

Improved Selectivity and Stability in Methane Dry Reforming by Atomic Layer Deposition on Ni-CeO-ZrO/AlO Catalysts.

Ni can be used as a catalyst for dry reforming of methane (DRM), replacing more expensive and less abundant noble metal catalysts (Pt, Pd, and Rh) with little sacrifice in activity. Ni catalysts deactivate quickly under realistic DRM conditions. Rare earth oxides such as CeO, or as CeO-ZrO-AlO (CZA), are supports that improve both the activity and stability of Ni DRM systems due to their redox activity.

Solvent-Free Depolymerization of Plastic Waste Enabled by Plastic-Catalyst Interfacial Engineering.

Depolymerization of condensation polymers by chemolysis often suffers from the large usage of solvents and homogeneous catalysts such as acids, bases, and metal salts. The catalytic efficiency of heterogeneous catalysts is largely constrained by the poor interfacial contact between solid catalysts and solid plastics below melting points. We report here our discovery of autogenous heterogeneous catalyst layer on polyethylene terephthalate surfaces during the generally believed homogeneous catalytic depolymerization process.

Elucidating the Roles of Amorphous Alumina Overcoat in Palladium-Catalyzed Selective Hydrogenation.

Amorphous alumina overcoats generated by atomic layer deposition (ALD) have been shown to improve the selectivity and durability of supported metal catalysts in many reactions. Several mechanisms have been proposed to explain the enhanced catalytic performance, but the accessibilities of reactants through the amorphous overcoats remain elusive, which is crucial for understanding reaction mechanisms. Here, we show that an AlO ALD overcoat is able to improve the alkene product selectivity of a supported Pd catalyst in acetylene (CH) hydrogenation.

Elucidating the surface compositions of Pd@Pt core-shell nanocrystals through catalytic reactions and spectroscopy probes.

The catalytic behaviors or properties of bimetallic catalysts are highly dependent on the surface composition, but it has been a grand challenge to acquire such information. In this work, we employ Pd@Pt core-shell nanocrystals with an octahedral shape and tunable Pt shell thickness as a model system to elucidate their surface compositions using catalytic reactions based upon the selective hydrogenation of butadiene and acetylene. Our results indicate that the surface of the core-shell nanocrystals changed from Pt-rich to Pd-rich when they were subjected to calcination under oxygen, a critical step involved in the preparation of many industrial catalysts.

Construction of Inverse Metal-Zeolite Interfaces via Area-Selective Atomic Layer Deposition.

The spatial confinement at metal-zeolite interfaces offers a powerful knob to steer the selectivity of chemical reactions on metal catalysts. However, encapsulating metal catalysts into small-pore zeolites remains a challenging task. Here, we demonstrate an inverse design of metal-zeolite interfaces, "" constructed by area-selective atomic layer deposition.

Critical Coupling of Visible Light Extends Hot-Electron Lifetimes for HO Synthesis.

Devices driven by above-equilibrium "hot" electrons are appealing for photocatalytic technologies, such as in situ HO synthesis, but currently suffer from low (<1%) overall quantum efficiencies. Gold nanostructures excited by visible light generate hot electrons that can inject into a neighboring semiconductor to drive electrochemical reactions. Here, we designed and studied a metal-insulator-metal (MIM) structure of Au nanoparticles on a ZnO/TiO/Al film stack, deposited through room-temperature, lithography-free methods.

A general synthesis approach for supported bimetallic nanoparticles via surface inorganometallic chemistry.

The synthesis of ultrasmall supported bimetallic nanoparticles (between 1 and 3 nanometers in diameter) with well-defined stoichiometry and intimacy between constituent metals remains a substantial challenge. We synthesized 10 different supported bimetallic nanoparticles via surface inorganometallic chemistry by decomposing and reducing surface-adsorbed heterometallic double complex salts, which are readily obtained upon sequential adsorption of target cations and anions on a silica substrate. For example, adsorption of tetraamminepalladium(II) [Pd(NH) ] followed by adsorption of tetrachloroplatinate [PtCl ] was used to form palladium-platinum (Pd-Pt) nanoparticles.

Constructing Hierarchical Porous Zeolites via Kinetic Regulation.

Zeolites are crystalline inorganic solids with microporous structures, having widespread applications in the fields of catalysis, separation, adsorption, microelectronics, and medical diagnosis. A major drawback of zeolites is the mass transfer limitation due to the small size of the micropores (less than 1 nm). Numerous efforts have been dedicated to integrating mesopores with the microporous zeolite structures by using templating and/or destructive approaches.

Adhesion and Atomic Structures of Gold on Ceria Nanostructures: The Role of Surface Structure and Oxidation State of Ceria Supports.

We report an aberration-corrected electron microscopy analysis of the adhesion and atomic structures of gold nanoparticle catalysts supported on ceria nanocubes and nanorods. Under oxidative conditions, the as-prepared gold nanoparticles on the ceria nanocubes have extended atom layers at the metal-support interface. In contrast, regular gold nanoparticles and rafts are present on the ceria nanorod supports.

Microwave synthesis of microstructured and nanostructured metal chalcogenides from elemental precursors in phosphonium ionic liquids.

We describe a general approach for the synthesis of micro-/nanostructured metal chalcogenides from elemental precursors. The excellent solubility of sulfur, selenium, and tellurium in phosphonium ionic liquids promotes fast reactions between chalcogens and various metal powders upon microwave heating, giving crystalline products. This approach is green, universal, and scalable.

Fluorescence upconversion microbarcodes for multiplexed biological detection: nucleic acid encoding.

Fluoride rare-earth-doped upconversion microbarcodes have been successfully developed for multiplexed signaling and nucleic-acid encoding. This kind of novel barcode material can be used for rapid and sensitive analysis of nucleic acids and antigens, which would have many potential applications in clinical, food, and environment detection.

CO2-mediated synthesis of ZnO nanorods and their application in sensing ethanol vapor.

High-purity ZnO nanorods have been synthesized via a two-step route using zinc acetate as a precursor without any surfactant and additive. In this method, ZnCO3 fibers were first formed in the CO2-ethanol solution, which directed the formation of ZnO nanorods by subsequent treatment in KOH aqueous solution. The as-prepared nanorods were fully characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform Infrared spectroscopy.

Surfactant-free synthesis of Bi2Te3-Te micro-nano heterostructure with enhanced thermoelectric figure of merit.

An ideal thermoelectric material would be a semiconductor with high electrical conductivity and relatively low thermal conductivity: an "electron crystal, phonon glass". Introducing nanoscale heterostructures into the bulk TE matrix is one way of achieving this intuitively anomalous electron/phonon transport behavior. The heterostructured interfaces are expected to play a significant role in phonon scattering to reduce thermal conductivity and in the energy-dependent scattering of electrical carriers to improve the Seebeck coefficient.

Shape controlled synthesis of palladium nanocrystals by combination of oleylamine and alkylammonium alkylcarbamate and their catalytic activity.

The shape of Pd nanocrystals (NCs) can be controlled by combination of oleylamine (OAm) and alkylammonium alkylcarbamate (AAAC), and Pd spheres, tetrahedra and multipods have been synthesized. The multipods and tetrahedra are much more active than the spheres for hydrogenation reactions.

Arginine-mediated synthesis of highly efficient catalysts for transfer hydrogenations of ketones.

Palladium-hydrotalcite catalysts were prepared by immobilizing Pd(2+) on hydrotalcite (HT) via an amino acid, arginine (Arg), followed by reduction with NaBH(4) at room temperature. The resulting composite was characterized by different techniques. X-ray photoelectron spectroscopy analysis showed that the loaded Pd on hydrotalcite mainly existed in the form of Pd(0), and distributed uniformly on the support with particle size around 4 nm, as confirmed by transmission electron microscopy examination.

The immobilization of glycidyl-group-containing ionic liquids and its application in CO2 cycloaddition reactions.

Covalent immobilization of glycidyl-group-containing ionic liquids (ILs) on organic and inorganic supports with functional surfaces was achieved, based on the fact that the glycidyl group can actively react with almost all nucleophilic, electrophilic, neutral, and free-radical species. By using polymer spheres with amino- and carboxyl-group-functionalized surfaces as organic supports and silicas (including SBA15 and silica gel) with amino groups attached as inorganic supports, the ionic liquid 1-glycidyl-butylimidazolium chloride was successfully grafted onto these polymer and silica supports, respectively, through reactions between the glycidyl group in the IL and the polar groups on the support surfaces. The resultant samples were examined by transmission electron microscopy, solid-state (13)C NMR spectroscopy, IR spectroscopy, and ion chromatography.

Study on the anatase to rutile phase transformation and controlled synthesis of rutile nanocrystals with the assistance of ionic liquid.

We developed a route to synthesize rutile TiO(2) nanocrystals (NCs) with the assistance of 1-butyl-3-methylimidazolium chloride (bmim(+)Cl(-)). The phase transformation from anatase to rutile phase was investigated, and a simple model to describe the phase transformation process was proposed considering that the nucleation and growth of rutile phase were determined by the aggregation manner of anatase NCs and Ostwald ripening process, respectively. It was demonstrated that the surfactant-like nature of the IL used was crucial for controlling the crystallization process via controlling the aggregation manner of the NCs.

Dispersion of graphene sheets in ionic liquid [bmim][PF6] stabilized by an ionic liquid polymer.

Dispersion of graphene sheets in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was successfully achieved with the aid of a polymerized ionic liquid (PIL).

Shape and size controlled synthesis of anatase nanocrystals with the assistance of ionic liquid.

We report an ionic liquid (IL) assisted hydrothermal method to synthesize anatase TiO(2) nanocrystals (NCs), in which TiCl(4) was used as precursor, 1-butyl-3-methylimidazolium chloride (bmim(+)Cl(-)) as IL, and F(-) or SO(4)(2-) ions as phase transformation inhibitor. The surfactant-like nature of IL was found to play a key role in controlling the crystallization process via controlling the aggregation manner of the NCs. The fine-tuning abilities of the operating parameters of the bmim(+)Cl(-)/TiCl(4)/H(2)O system facilitated the controlling over the shape and size of TiO(2) NCs.

p-Aminophenylacetic acid-mediated synthesis of monodispersed titanium oxide hybrid microspheres in ethanol solution.

Monodispersed TiO2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA). The effects of the APA:TTIP molar ratio, water content, reaction time and reaction temperature on the morphology of the resultant spheres were investigated. The products were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction.

In situ controllable loading of ultrafine noble metal particles on titania.

Herein we present a novel and facile approach to controllably load ultrafine noble metal nanoparticles on titania through in situ redox reaction between the reductive titanium(III) oxide support and metal salt precursors in aqueous solution. A series of noble metal/TiO(2) nanocomposites with uniform metal dispersion, tunable metal particle size, and narrow metal particle size distribution were obtained.

The dispersion of carbon nanotubes in water with the aid of very small amounts of ionic liquid.

Multiwalled carbon nanotubes can be dispersed stably in water with the aid of a very small amount of 1-aminoethyl-3-methylimidazolium bromide ([C(2)NH(2)mim][Br]) or 1-(2-aminoethyl) pyridinium bromide ([C(2)NH(2)py][Br]).