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Supported Pd nanoparticle catalystsover Mg–Al mixed metal oxides derived from layered double hydroxideswere prepared by three different approaches, including coprecipitation,anion-exchange, and impregnation, in order to enhance the metal dispersionand thus facilitate the growth of uniform multiwalled carbon nanotubes(CNTs) via catalytic chemical vapor deposition of methane. The effectsof preparation methods for supported Pd catalysts on the morphologiesand microstructures of CNTs formed were investigated. The resultsrevealed that the characteristics of CNTs were strongly correlatedto the dispersion of active Pd species in the catalysts, and the structuraldefects and the diameter of CNTs were reduced with the increasingmetal dispersion. Especially, the anion-exchange route for preparationof supported Pd catalyst was appropriate for the growth of uniformbamboo-like CNTs with fewer defects, which could be contributed tothe presence of more uniform and smaller Pd0nanoparticleshighly dispersed over Mg–Al mixed-metal oxides. [ABSTRACT FROM AUTHOR]

The present work reported the synthesis of visible-light-inducedcobalt-doped zinc ferrite (Zn1-xCoxFe2O4) photocatalystsvia a facile reduction–oxidation route, which involved rapidreduction of Fe3+and Co2+cations in colloidmill reactor, followed by oxidation of iron and cobalt nuclei andstructural transformation under hydrothermal conditions. The structuraland optical properties of materials were characterized by powder X-raydiffraction (XRD), scanning electron microscopy (SEM), transmissionelectron microscopy (TEM), X-ray photoelectron spectroscopy (XPS),and UV–vis diffuse reflectance spectra. The results indicatedthat metallic Co and Fe nuclei could be obtained by reduction in thecolloid mill, and Zn1-xCoxFe2O4nanocrystals with uniformsize were successfully achieved. Furthermore, compared to ZnFe2O4, Zn1-xCoxFe2O4samples (x= 0.03, 0.1, 0.2) exhibited enhanced photocatalytic activity inthe degradation of methylene blue under visible light irradiation.Especially, the Zn0.8Co0.2Fe2O4sample had the highest photocatalytic activity, which wasmainly attributable to its smaller band edge. Since as-synthesizedZn–Co ferrites nanocrystals have the advantages of intrinsicchemical stability and magnetic property, it can be expected thatthey may have potential application in the field of industrial photodegradationof organic pollutants. [ABSTRACT FROM AUTHOR]

The in situ growth of Ni-containing layered double hydroxide(LDH)microcrystallites on microspherical γ-alumina support was carriedout through the surface activation of support followed by a homogeneouscoprecipitation process, and carbon nanomaterials were synthesizeddirectly over as-grown supported LDH samples via catalytic chemicalvapor deposition of acetylene. As compared to that prepared by theconventional impregnation, supported LDH samples calcined at 700 °Cpossessed higher metal dispersion, which was attributed to well-developedtwo-dimensional structure of LDH platelets uniformly grown on thesupport surface originating from the strong interaction between brucite-likelattices and support. Furthermore, the supported catalyst from NiAl-LDHcould catalyze the growth of regular carbon nanofibers, while anotherone from NiMgAl-LDH exhibited excellent catalytic performance forthe growth of uniform carbon nanotubes due to higher metal dispersionachieved by the separating effect of amorphous metal oxide (MgO andAl2O3) phases around Ni nanoparticles. As-synthesizedsupported Ni-based catalysts are promising for practical applicationsin the production of carbon nanostructures with uniform geometricshape. [ABSTRACT FROM AUTHOR]

Spinel-type zinc aluminate (ZnAl2O4) thin films with controlled surface microstructure on aluminum substrates were fabricated via a facile and effective in situ crystallization method without using any templates or surfactants. The surface microstructure of ZnAl2O4 films could be significantly controlled by varying the experimental conditions including concentration of reactants, crystallization temperature, and crystallization time. After surface modification, the specific topography of ZnAl2O4 films was beneficial to obtain surface hydrophobic or superhydrophobic properties. More importantly, compared to nanoparticle- and nanosword-assembled ZnAl2O4 films, nanorod-assembled ZnAl2O4 film provided a more effective barrier to aggressive species for aluminum substrates in a wide range of pH values; very low corrosion current density of the order of ∼10−19 A cm−12 could be achieved. A new contribution to the development of advanced coating system with ZnAl2O4 film materials that can be used in practical application for corrosion protection of aluminum materials is provided. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]

Abstract: High-surface-area ZnAl2O4 with micro/mesoporous frameworks was synthesized via a facile one-pot solvothermal approach without using any surfactants or post-treatment. The results revealed that the textural properties of micro/mesoporous ZnAl2O4 were tuned by changing alcohol/water mixture solvents used in solvothermal synthesis and Ag nanoparticles were dispersed uniformly on the surface of ZnAl2O4 supports. Especially, the supported Ag catalyst on the microporous ZnAl2O4 synthesized in methanol/water solvent exhibited good catalytic performance for liquid phase selective hydrogenation of o-chloronitrobenzene to o-chloroaniline, owing to the high dispersion of Ag nanoparticles and the strong metal-support interaction. [Copyright &y& Elsevier]

Abstract: In this paper, we report on the three-dimensional nanostructured Cu2O/CuO films with controlled flower-like shapes using a direct crystallization approach in the presence of sodium borohydride without using any performed template, surfactant or oxidant. The microstructures and shapes of Cu2O/CuO architectures were investigated by field emission scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Three types of chrysanthemum-like, candock-like and dandelion-like CuO microstructures consisting of densely packed building blocks of nanobelts or nanoribbons were achieved by governing the concentrations of NaBH4. Possible growth mechanisms for the controlled organization of primary building units into three-dimensional flower-like architectures were proposed. After simple surface modification with sodium laurate, the resulting films displayed hydrophobic and even superhydrophobic properties owing to their special surface nano-/microstructures. [Copyright &y& Elsevier]

Nickel ferrite (NiFe2O4) films with macroporous frameworks are successfully fabricated on silicon substrates viaa novel template-assisted route. The fabrication approach mainly involves the formation of two-phase composite (desired nickel ferrite and nickel oxide phases) films by thermal conversion of Ni–Fe layered double hydroxide precursor films followed by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructural, magnetic and interfacial properties of the resulting films were characterized by means of X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results revealed that the microstructures (e.g.particle sizes and spacing among particles), magnetism and surface hydrophobic property of as-fabricated NiFe2O4films could be finely tuned by varying the composition of precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4films. Furthermore, the as-fabricated NiFe2O4films show tunable saturation magnetization varying from 36 to 55 emu/g and excellent surface hydrophobicity ranging from 139 to 152° after surface modification of films. We believe that such unique macroporous NiFe2O4films can open up new opportunities for a wide range of advanced applications. [ABSTRACT FROM AUTHOR]

Nickel ferrite (NiFe2O4) films with macroporous frameworks are successfully fabricated on silicon substrates viaa novel template-assisted route. The fabrication approach mainly involves the formation of two-phase composite (desired nickel ferrite and nickel oxide phases) films by thermal conversion of Ni–Fe layered double hydroxide precursor films followed by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructural, magnetic and interfacial properties of the resulting films were characterized by means of X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results revealed that the microstructures (e.g.particle sizes and spacing among particles), magnetism and surface hydrophobic property of as-fabricated NiFe2O4films could be finely tuned by varying the composition of precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4films. Furthermore, the as-fabricated NiFe2O4films show tunable saturation magnetization varying from 36 to 55 emu/g and excellent surface hydrophobicity ranging from 139 to 152° after surface modification of films. We believe that such unique macroporous NiFe2O4films can open up new opportunities for a wide range of advanced applications. [ABSTRACT FROM AUTHOR]

Tetravalent metal oxides, such as ceria and zirconia, are widely used as support materials in a broad range of heterogeneous catalytic processes. Herein, high-surface-area CeO 2 -ZrO 2 composite supports with micro/mesoprous structures were first fabricated successfully by a low temperature solution-phase method without the use of any additional templates and surfactants and resulting supported platinum nanoparticles were employed in liquid-phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, a key reaction for the production of important chemicals. It was found that the component of CeO 2 -ZrO 2 composites strongly influenced surface structures of catalysts, and consequently determined the nature of platinum species and the catalytic properties of catalysts. When platinum was dispersed on the CeO 2 -ZrO 2 composite with the Ce/Zr molar ratio of 1:1, a high cinnamyl alcohol yield of 89%, together with an extremely high turnover frequency value of 10423 h –1 , could be achieved without the use of additional alkali. Such high catalytic performance, which was superior to those of most known supported Pt-based catalysts previously reported, was mainly attributable to the synergism between electron-rich metallic Pt species and surface defects (i.e., Ce 3+ species and oxygen vacancies), thereby greatly promoting the chemisorption and activation of carbonyl group in cinnamaldehyde. Moreover, the porous network of CeO 2 -ZrO 2 composites is beneficial to the stabilization of Pt nanoparticles, thereby preventing the leaching and the growth of Pt particles in the course of reaction. This work offers a better understanding of the role of high-surface-area porous CeO 2 -ZrO 2 composite supports for highly efficient selective hydrogenation of α,β-unsaturated aldehydes in supported precious-metal-based catalysts. [ABSTRACT FROM AUTHOR]

Abstract: The gas-phase hydrogenation of dimethyl 1,4-cyclohexane dicarboxylate to 1,4-cyclohexane dimethanol (CHDM) was conducted on well-dispersed supported Cu/ZnO/ZrO2 catalysts. The results indicated that the structure and catalytic performance of resulting copper-based catalysts were profoundly affected by the addition of zirconium. Moreover, the as-synthesized catalyst with 35.0wt.% ZrO2 component was found to exhibit superior catalytic performance with a high CHDM yield of 96.8% to other catalysts, which should be mainly attributed to the significant dispersion effect of ZrO2 on the copper-containing species resulting in a higher metallic copper surface area as well as a larger number of Cu+ species. [Copyright &y& Elsevier]

Phenol production through the oxidation of cyclohexylbenzene (CHB) and the subsequent decomposition of tertiary hydroperoxide has attracted more and more attention. In this study, defective La 2- x CuO 4 perovskite-type oxide catalysts with tunable A-site deficient structures and abundant surface oxygen vacancies were developed for the liquid phase oxidation of CHB to produce cyclohexylbenzene-1-hydroperoxide (CHBHP). By tuning the amount of A-site La ions in the perovskite structure, more surface oxygen vacancies and Cu + species were formed in catalysts. The A-site-deficient La 1.9 CuO 4 catalyst achieved significant catalytic efficiency along with a high CHBHP yield of 27.6% at 48.6% CHB conversion under reaction conditions ( i.e. , 120 °C and 12 h), outperforming those of other transition metal-based catalysts previously reported in the literature. A series of structural characterization methods and catalytic reactions highlighted the crucial roles of surface oxygen vacancies and metal La and Cu ions in the oxidation process. It was revealed that metal ions favored CHB adsorption and activation, while surface oxygen vacancies facilitated the creation of active adsorbed oxygen species. The present study offers an opportunity for the future design of new high-efficiency heterogeneous catalyst systems for CHB oxidation to obtain phenol.

Currently, direct catalytic CO 2 hydrogenation to produce ethanol is an effective and feasible way for the resource utilization of CO 2 . However, constructing non-precious metal catalysts with satisfactory activity and desirable ethanol selectivity remains a huge challenge. Herein, we reported gallium-promoted CuCo-based catalysts derived from single-source Cu-Co-Ga-Al layered double hydroxide precursors. It was manifested that the introduction of Ga species could strengthen strong interactions between Cu and Co oxide species, thereby modifying their electronic structures and thus facilitating the formation of abundant metal-oxide interfaces ( i.e. , Cu 0 /Cu + -CoGaO x interfaces). Notably, the as-constructed Cu-CoGa catalyst with a Ga:Co molar ratio of 0.4 exhibited a high ethanol selectivity of 23.8% at a 17.8% conversion, along with a high space-time yield of 1.35 mmol EtOH ·g cat -1 ·h -1 for ethanol under mild reaction conditions ( i.e. , 220 °C, 3 MPa pressure), which outperformed most non-noble metal-based catalysts previously reported. According to the comprehensive structural characterizations and in situ diffuse reflectance infrared Fourier transform spectra of CO 2 /CO adsorption and CO 2 hydrogenation, it was unambiguously revealed that CH x could be formed at oxygen vacancies of defective CoGaO x species, while CO could be stabilized by Cu + species, and thus the catalytic synergistic role of Cu 0 /Cu + -CoGaO x interfacial sites promoted the generation of CH x and CO intermediates to participate in the CH x -CO coupling process and simultaneously inhibited alkylation reactions. The present work points out a promising new strategy for constructing CuCo-based catalysts with favorable interfacial sites for highly efficient CO 2 hydrogenation to produce ethanol.

In a complex heterogeneous metal-catalyzed reaction process, unique cooperative effects between metal sites and surface-interface active sites, as well as favorable synergy between surface-interface active sites, can play crucial roles in improving their catalytic performances. In this work, a ZnO-modified Cu-based catalyst over defect-rich Pr 2 O 3 nanosheets for high-efficiency CO 2 hydrogenation to produce methanol was successfully constructed. It was demonstrated that an as-fabricated nanosheet-like Cu-based catalyst presented several structural advantages including the formation of highly dispersive Cu 0 sites and the coexistence of abundant defective Pr 3+ -V o -Pr 3+ structures (V o : oxygen vacancy) and interfacial Cu-O-Pr sites. Combining structural characterization and catalytic reaction results with density functional theory calculations, it was clearly unveiled that the synergy between surface defective structures and Cu-Pr 2 O 3 interfaces over the catalyst remarkably promoted the adsorption of CO 2 and CO intermediate, thus boosting the CO 2 hydrogenation simultaneously via both the formate intermediate pathway and the intense reverse water-gas shift reaction-derived CO hydrogenation pathway, along with a high space-time yield of methanol of 0.395 g MeOH ·g cat -1 ·h -1 under mild reaction conditions (260 °C and 3.0 MPa). The study provides a new strategy to construct high-performance Cu-based catalysts for high-efficiency CO 2 hydrogenation to produce methanol and a deep understanding of the promotional roles of synergy between surface-interface active sites in the CO 2 hydrogenation.

Currently, the catalytic transformation and utilization of biomass-derived compounds are of great importance to the alleviation of environmental problems and sustainable development. Among them, furfural alcohol derived from biomass resources has been found to be one of the most prospective biomass platforms for high-value chemicals and biofuels. Herein, high-surface-area ZrO 2 with abundant oxygen defects and surface acid-base sites was synthesized and used as a heterogeneous catalyst for the catalytic transfer hydrogenation of furfural into furfural alcohol using alcohol as a hydrogen donor. The as-synthesized ZrO 2 exhibited excellent catalytic performance with 98.2% FA conversion and 97.1% FOL selectivity, even comparable with that of a homogeneous Lewis acid catalyst. A series of characterization studies and experimental results revealed that acid sites on the surface of ZrO 2 could adsorb and activate the C[double bond, length as m-dash]O bond in furfural and base sites could facilitate the formation of alkoxide species. The synergistic effect of surface acid-base sites affords a harmonious environment for the reaction, which is crucial for catalytic transfer hydrogenation of furfural with high efficiency. Furthermore, the as-prepared ZrO 2 catalyst also exhibited a potential application for the efficient catalytic transfer hydrogenation of a series of biomass-derived carbonyl compounds.

Currently, the base-free aerobic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to produce 2,5-furandicarboxylic acid (FDCA) is attracting intense interest due to its prospects for the green, sustainable, and promising production of biomass-based aromatic polymers. Herein, we have developed a new Pt catalyst supported on nitrogen-doped-carbon-decorated CeO 2 (NC-CeO 2 ) for the aerobic oxidation of HMF in water without the addition of any homogeneous base. It was demonstrated that the small-sized Pt particles could be well dispersed on the surface of the hybrid NC-CeO 2 support, and the activity of the supported Pt catalyst depended strongly on the surface structure and properties of the catalysts. The as-fabricated Pt/NC-CeO 2 catalyst, with abundant surface defects, enhanced basicity, and favorable electron-deficient metallic Pt species, enabled an almost 100 % yield of FDCA in water with molecular oxygen (0.4 MPa) at 110 °C for 8 h without the addition of any homogeneous base, which is indicative of exceptional catalytic performance. Furthermore, this Pt/NC-CeO 2 catalyst also showed good stability and reusability owing to strong metal-support interactions. An understanding of the role of surface structural defects and basicity of the hybrid NC-CeO 2 support provides a basis for the rational design of high-performance and stable supported metal catalysts with practical applications in various transformations of biomass-derived compounds., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, nitrogen-doped carbon modified MgO-MgFe 2 O 4 (CN-MgFeO) magnetic composites were synthesized by a facile thermal decomposition of Mg-Fe layered double hydroxide (MgFe-LDH) and cyanamide mixture precursors. A series of comprehensive characterization studies including powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared of CO 2 adsorption, CO 2 -temperature programmed desorption, and X-ray photoelectron spectroscopy indicated that the introduction of cyanamide could finely tune the surface basicity of the resulting CN-MgFeO composites, especially surface strong Lewis basicity. Compared with CN-free MgFeO, the as-fabricated CN-MgFeO catalysts showed higher activity in the liquid-phase transesterification of tributyrin with methanol. Particularly, the CN-MgFeO composite prepared at a cyanamide/Mg molar ratio of 1.5 in the synthesis mixture gave a highest methylbutyrate yield of 80% after a reaction for 20 min. The high catalytic performance was attributable to the presence of a large amount of strong Lewis basic sites originating from highly dispersed basic MgO-MgFe 2 O 4 mixed metal oxides and CN component in the composite. What is more, such a cost-effective CN-MgFeO catalyst had the advantages of intrinsic magnetic properties and an excellent structural stability. We expect that they may have potential practical applications in the field of industrial production of biodiesels.

A facile and economical strategy to synthesize high surface area Mg-doped ZnAl 2 O 4 spinels is developed. These materials are employed as catalyst supports to prepare supported gold catalysts for the aerobic oxidation of benzyl alcohol by using molecular oxygen in the absence of additional alkali. The as-fabricated supported Au catalyst with the Mg/(Mg+Zn) molar ratio of 0.15 was found to show good catalytic activity with high benzaldehyde selectivity (>99 %) and a high turnover frequency of 5382 h -1 . The relationship between the surface properties of the supported Au catalysts and their catalytic performances reveals that the high catalytic efficiency is mainly attributable to surface cooperative effects between the abundant basic sites and favorable active Au species, including metallic Au and cationic Au δ+ ions. A possible mechanism for selective oxidation of benzyl alcohol is tentatively proposed. Moreover, the as-fabricated supported Au catalyst could be reused at least four times without significant loss of its catalytic performance. The present finding provides a new route for designing high-performance supported noble or non-noble metal catalysts by using high surface area ZnAl 2 O 4 -based spinels., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel three-dimensional (3D) rosette-like carbonate-type Mg-Al layered double hydroxide (MgAl-LDH) hierarchical microstructures were fabricated successfully by a surfactant-assisted coprecipitation method in the presence of hexamethylenetetramine as precipitant, and the morphology-dependent basic catalytic property was exploited. The morphologies of MgAl-LDH aggregates were diversified depending on the synthesis parameters including the type of precipitant, concentration of sodium stearate surfactant, and hydrothermal aging time. Specifically, the morphology of MgAl-LDH particles could change progressively from platelet-like aggregates to rosette-like microspheres with the increasing concentration of sodium stearate. A possible formation mechanism for special 3D flower-like MgAl-LDH microstructures was proposed based on the synergistic effect of precipitant with surfactant. Moreover, the resulting activated rosette-like MgAl-LDH, which was prepared through calcination-rehydration process, showed a higher catalytic activity in the transesterification of tributyrin with methanol, compared with that derived from the conventional platelet-like MgAl-LDH precursor, which was attributed to its higher specific basicity originating from multi-level hierarchical superstructure offering an advantage in contact with more exposed base sites., (Copyright © 2014 Elsevier Inc. All rights reserved.)