In this study, magnetically nanoparticles of CuFe2O4@SiO2@PTMS@Tu@Ni(II) as novel and reusable catalyst were prepared. Synthesis of the Ni (II)‐nanocatalyst was carried out through the complexation of Ni(OAc)2·4H2O with the immobilized thiourea on silica‐layered CuFe2O4. The prepared nanocomposite system was then characterized using SEM, EDX, XRD, VSM, ICP‐OES, Raman, UV–Vis and FT‐IR analyses. Catalytic activity of the Ni(II)‐CuFe2O4 system was investigated towards rapid reduction of aromatic nitro compounds to arylamines with sodium borohydride as well as one‐pot reductive‐acetylation of nitroarenes to acetanilides with NaBH4/Ac2O system without the isolation of intermediate arylamines. All reactions were carried out in H2O within 3–7 min to afford the products arylamines/acetanilides in high to excellent yields. Reusability of the Ni(II)‐nanocatalyst was examined for seven consecutive cycles without the significant loss of the catalytic activity. 相似文献
In this study, the photocatalytic efficiency of anatase‐type TiO2 nanoparticles synthesized using the sol–gel low‐temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV–light‐assisted photo and NaBH4‐assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed‐bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH‐modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH‐modified Cu/TiO2 nanoparticles. 相似文献
Ni‐B and Ni‐B/CNTs amorphous alloy catalysts were prepared by chemical reduction and impregnation‐chemical reduction methods, respectively, and characterized by TEM, ICP, XPS, XRD, BET and CO chemisorption techniques. Their catalytic activities were evaluated in acetylene selective hydrogenation reaction. Based on characterizations, the effects of carbon nanotubes on Ni‐B amorphous alloy were attributed to both its structure effect, dispersing Ni‐B particles, leading to bigger surface area of active nickel and enhancing the thermal stability, and the electronic effect, resulting in electron‐rich nickel centers. Therefore, the superior thermal stability and acetylene selective hydrogenation activities of Ni‐B/CNTs to Ni‐B amorphous catalyst were obtained in the present study. 相似文献
A facile route to synthesize amorphous TiO2 nanospheres by a controlled oxidation and hydrolysis process without any structure‐directing agents or templates is presented. The size of the amorphous TiO2 nanospheres can be easily turned from 20 to 1500 nm by adjusting either the Ti species or ethanol content in the reaction solution. The phase structure of nanospheres can be controlled by hydrothermal treatment. The TiO2 nanospheres show excellent size‐dependent light‐scattering effects and can be structured into a light‐harvesting layer for dye‐sensitized solar cells with a quite high power conversion efficiency of 9.25 %. 相似文献
Neodymium is used as a promoter of Ni‐B/CNTs amorphous alloy catalyst to modify its catalytic properties. Ni‐B/CNTs and Ni‐Nd(5wt%)‐B/CNTs catalysts were prepared by the impregnation chemical reduction method. Their catalytic performances were examined in acetylene selective hydrogenation, which is a crucial step in industrial polymerization processes, with the aim of the complete elimination of alkynes from alkene feedstocks. Experiments showed that the latter exhibited higher acetylene hydrogenation activity but lower ethylene selectivity. Catalysts were characterized by ICP, CO‐chemisorption, XPS, XRD and H2‐TPD techniques. On the basis of characterizations, the modification of Nd on Ni‐B/CNTs catalyst was related to its geometric and electronic effects. 相似文献
Skeletal Ni catalysts were prepared from Ni–Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni–Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni30Zr70 alloy had a higher catalytic activity than that prepared from amorphous Ni40Zr60 and Ni50Zr50 alloys. The atomic arrangement of the Ni–Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni–Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface‐exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability. 相似文献
Controlled coammonolysis of elementalkylamides in aprotic organic solvents at low temperatures have been shown to result in the formation of polyazanes. The synthetic procedure developed may be addressed as “sol‐gel‐route in the ammono system”. Pyrolysis of these novel polymer precursors gave access to multinary nitrides. For the model systems Si(NHMe)4/B(NMe2)3, Si(NHMe)4/Ti(NMe2)4, and Si(NHMe)4/Ta(NMe2)5 polymeric boro‐, titano and tantalosilazanes were obtained. Pyrolysis in ammonia at 1000 °C yielded amorphous silicon boron nitride, silicon titanium nitride and silicon tantalum nitride powders; further heating of the nitride powders at 1500 °C in nitrogen atmosphere led to the formation of partly crystalline composites of α‐Si3N4 and amorphous silicon boron nitride for the Si/B/N system, a composite of finely dispersed TiN and amorphous silicon titanium nitride for the Si/Ti/N system, and crystalline TaN and amorphous silicon nitride for the Si/Ta/N system. Furthermore, the structure and pyrolysis chemistry of the polymeric intermediates, as well as the morphology of the pyrolysis products, were studied by NMR, MAS‐NMR, FT‐IR, DTA‐TG‐MS, XRD, SEM, EDX and elemental analyses. 相似文献
Thin film of amorphous tungsten‐doped cobalt oxide (W:CoO) was successfully grown on a conducting electrode via an electrochemical oxidation process employing a [Co(WS4)2]2? deposition bath. The W:CoO catalyst displays an attractive performance for the oxygen evolution reaction in an alkaline solution. In an NaOH solution of pH 13, W:CoO operates with a moderate onset overpotential of 230 mV and requires 320 mV overpotential to generate a catalytic current density of 10 mA cm?2. A low Tafel slope of 45 mV decade?1 was determined, indicating a rapid O2‐evolving kinetics. The as‐prepared W:CoO belongs to the best cobalt oxide‐based catalysts ever reported for the oxygen evolution (OER) reaction. 相似文献
A nanostructured organic–inorganic framework, hexagonal NH2‐MIL‐88B, has been prepared through a facile one‐pot reflux reaction and then it was characterized using various techniques. The as‐prepared sample with high specific surface area (414 m2 g?1) showed excellent adsorption for 2,4,6‐trinitrophenol (TNP) in the liquid phase. Detailed studies of the adsorption kinetics, adsorption mechanism, adsorption isotherm, activation energy and various thermodynamic parameters were conducted. The adsorption mechanism of NH2‐MIL‐88B for TNP may be ascribed to hydrogen bond interaction, and the complexation between ─OH in TNP and unsaturated Fe(III) on the surface of NH2‐MIL‐88B. The maximum adsorption capacity of NH2‐MIL‐88B for TNP based on the Langmuir isotherm was 163.66 mg g?1. The as‐prepared NH2‐MIL‐88B adsorbent seems to be a promising material in practice for TNP removal from aqueous solution. 相似文献
We report a NaOH‐mediated NaBH4 reduction method for the synthesis of mono‐, bi‐, and tri‐thiolate‐protected Au25 nanoclusters (NCs) with precise control of both the Au core and thiolate ligand surface. The key strategy is to use NaOH to tune the formation kinetics of Au NCs, i.e., reduce the reduction ability of NaBH4 and accelerate the etching ability of free thiolate ligands, leading to a well‐balanced reversible reaction for rapid formation of thermodynamically favorable Au25 NCs. This protocol is facile, rapid (≤3 h), versatile (applicable for various thiolate ligands), and highly scalable (>1 g Au NCs). In addition, bi‐ and tri‐thiolate‐protected Au25 NCs with adjustable ratios of hetero‐thiolate ligands were easily obtained. Such ligand precision in molecular ratios, spatial distribution and uniformity resulted in richly diverse surface landscapes on the Au NCs consisting of multiple functional groups such as carboxyl, amine, and hydroxy. Analysis based on NMR spectroscopy revealed that the hetero‐ligands on the NCs are well distributed with no ligand segregation. The unprecedented synthesis of multi‐thiolate‐protected Au25 NCs may further promote the practical applications of functional metal NCs. 相似文献
Hierarchical flowerlike β‐Ni(OH)2 superstructures composed of intermeshed nanoflakes are synthesized by hydrothermal treatment with a mixed solution of C2H4(NH2)2, NaOH, and Ni(NO3)2. The as‐prepared β‐Ni(OH)2 superstructures could be easily changed into NiO superstructures without great morphology change by calcination at 400 °C for 5 h. Furthermore, the TiO2 nanoparticles can be homogeneously deposited on the surface of NiO superstructures by dispersing β‐Ni(OH)2 powders in Ti(OC4H9)4–C2H5OH mixed solution and then vaporizing to remove the ethanol at 100 °C, and finally calcination at 400 °C for 5 h. The prepared NiO/TiO2p–n junction superstructures show much higher photocatalytic activity for photocatalytic degradation of p‐chlorophenol aqueous solution than conventional TiO2 powders and NiO superstructures prepared under the same experimental conditions. An obvious enhancement in the photocatalytic activity can be related to several factors, including formation of hierarchical porous structures, dispersion of TiO2 particles on the surface of NiO superstructures, and production of a p–n junction. Further results show that NiO/TiO2 composite superstructures can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and re‐used, compared with conventional powder photocatalysts. After many recycling experiments for the photodegradation of p‐chlorophenol, the NiO/TiO2 composite sample does not exhibit any great activity loss, confirming that NiO/TiO2 sample is stable and not photocorroded. 相似文献
Skeletal Ni catalysts were prepared from an amorphous Ni40Zr60 alloy (a‐NiZr) by heating at various temperatures under vacuum, followed by the selective extraction of Zr moieties by an HF treatment. Each sample was characterized by various spectroscopic methods, and the catalytic performance was tested in the hydrogenation of 1‐octene. The differences in preparation temperatures of a‐NiZr strongly affected the catalytic performance of the obtained catalysts, whereby those prepared from heated a‐NiZr in the pre‐crystallization state exhibited higher catalytic activity. Especially, moderate thermal treatment of a‐NiZr at a temperature slightly lower than that for its crystallization, that is, ~573 K, resulted in a significant enhancement of the catalytic activity. Such prepared skeletal Ni catalyst can also be used efficiently for hydrogen generation from aqueous hydrazine. 相似文献
The imine condensation reaction of 5,5′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)diisophthalaldehyde with cyclohexanediamine resulted in a shape‐persistent multifunctional tubular organic cage (MTC1). It exhibits selective fluorescence sensing towards divalent Pd ions with a very low detection limit (38 ppb), suggesting effective complexation between these two species. Subsequent reduction of MTC1 and Pd(OAc)2 with NaBH4 afforded a cage‐supported catalyst with well‐dispersed ultrafine Pd nanoparticles (NPs) in a narrow size distribution (1.9±0.4 nm), denoted as Pd@MTC1‐1/5. Such ultrafine Pd NPs in Pd@MTC1‐1/5, in cooperation with photocatalytically active MTC1, enable efficient sequential reactions involving visible light‐induced aerobic hydroxylation of 4‐nitrophenylboronic acid to 4‐nitrophenol and the following hydride reduction with NaBH4. This is the first example of a multifunctional organic cage capable of sensing, directing nanoparticle growth, and catalyzing sequential reactions. 相似文献
Novel dual molecular‐ and ion‐recognition responsive poly(N‐isopropylacrylamide‐co‐benzo‐12‐crown‐4‐acrylamide) (PNB12C4) linear copolymers with benzo‐12‐crown‐4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ‐cyclodextrin (γ‐CD) and Na+. The presence of γ‐CD induces the lower critical solution temperature (LCST) of PNB12C4 copolymer to shift to a higher value due to the formation of 1:1 γ‐CD/B12C4 host‐guest inclusion complexes, while Na+ causes a negative shift in LCST due to the formation of 2:1 “sandwich” B12C4/Na+ host‐guest complexes. Regardless of the complexation order, when γ‐CD and Na+ coexist with PNB12C4, competitive complexation actions of B12C4 as both guest and host units toward γ‐CD and Na+ finally form equilibrium 2:2:1 γ‐CD/B12C4/Na+ composite complexes, and the final LCST values of PNB12C4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB12C4‐based smart materials in various applications.
We report the synthesis and characterization of new NixRu1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni2+ and Ru3+ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni0.74Ru0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni0.74Ru0.26 alloy catalyst was measured to be approximately 37 kJ mol?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol?1) and Ru NPs (≈49 kJ mol?1), and for Ni@Ru (≈44 kJ mol?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal. 相似文献
In this work, for the first time, a cobalt carbonate hydroxide (Co(CO3)0.5(OH)?0.11 H2O) nanowire array on Ti mesh (CHNA/Ti) was applied to drive the dehydrogenation of alkaline NaBH4 solution for on‐demand hydrogen production. Compared with other nanostructured Co‐based catalyst systems, CHNA/Ti can be activated more quickly and separated easily from fuel solutions. This self‐supported cobalt salt nanowire array catalyst works as an efficient and robust 3D catalyst for the hydrolysis reaction of NaBH4 with a hydrogen generation rate of 4000 mL min?1 gCo?1 and a low apparent activation energy of 39.78 kJ mol?1 and offers an attractive system for on‐demand hydrogen generation. 相似文献