•Sonogashira reaction can be realized by an efficient photocatalytic route over Pd/SiC catalyst.•The photo-generated electrons excited in SiC can quickly transfer to Pd nanoparticles.•The energetic electrons favor to facilitate the cleavage of carbon-halogen bond in aryl halides.•The final CC formation is achieved by the substitution reaction and reductive elimination.Sonogashira reaction of aryl halides with terminal alkynes can be realized by a visible-light-driven heterogeneous catalytic route using silicon carbide supported Pd nanoparticles as the catalyst under copper-, and ligand-free conditions. Under the irradiation of visible light, the photo-generated electrons excited in SiC can quickly transfer to Pd nanoparticles through the Mott-Schottky contact, and make them electron-rich. The electrons of Pd particles become energetic by absorbing the energy of visible light, and then transfer to halogen atoms to facilitate the cleavage of carbon-halogen bond in aryl halides. The final carbon-carbon formation is achieved by the substitution reaction and reductive elimination processes.Download high-res image (108KB)Download full-size image

CoS2/graphene composites fabricated by a facile hydrothermal method exhibit excellent photocatalytic performance for selective hydrogenation of nitroaromatics to the corresponding aniline employing molecular hydrogen as a reducing agent under visible light irradiation (400–800 nm). The rate constant of the composite catalyst for nitrobenzene hydrogenation can achieve as high as 35.50 × 10−3 min−1 with a selectivity of 100% toward the target product under mild conditions (30 °C and 0.25 MPa pressure of H2). The catalyst also shows high recyclability, and there is no decrease in the catalytic activity after five successive cycles. There exists a synergistic effect between the graphene support and the CoS2 particles: conductive graphene as the support can rapidly extract the photoexcited electrons and effectively suppress the recombination of photogenerated charges in CoS2 particles, and then improve the photocatalytic performance. The photocatalytic reduction of nitrobenzene over the CoS2/graphene catalyst to aniline occurs through the direct pathway in the presence of H2.

Highly selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with 2-propanol was achieved using SiC-supported Au nanoparticles as photocatalyst. The hydrogenation reached a turnover frequency as high as 487 h–1 with 100% selectivity for the production of alcohol under visible light irradiation at 20 °C. This high performance is attributed to a synergistic effect of localized surface plasmon resonance of Au NPs and charge transfer across the SiC/Au interface. The charged metal surface facilitates the oxidation of 2-propanol to form acetone, while the electron and steric effects at the interface favor the preferred end-adsorption of α,β-unsaturated aldehydes for their selective conversion to unsaturated alcohols. We show that this Au/SiC photocatalyst is capable of hydrogenating a large variety of α,β-unsaturated aldehydes to their corresponding unsaturated alcohols with high conversion and selectivity.

Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal–air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCo2O4 nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCo2O4 NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCo2O4 NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O2 to H2O in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.Keywords: electrocatalysis; graphene foam; mesoporous structure; NiCo2O4; oxygen reduction reaction

Fischer–Tropsch synthesis (FTS) converts carbon monoxide and hydrogen to liquid fuels and chemicals and is usually operated under high temperature ranges, which results in an evident increase of energy consumption and CO2 emission. A photocatalytic FTS route was proposed to efficiently harvest solar energy. Worm-like ruthenium nanostructures dispersed on graphene sheets can effectively catalyze FTS at mild conditions (150 °C, 2.0 MPa H2, and 1.0 MPa CO) under irradiation of visible light and achieve a catalytic activity as high as 14.4 molCO·molRu–1·h–1. The reaction rate of FTS can be enhanced by increasing the irradiation intensity or decreasing the irradiation wavelength. The work provides a green and efficient photocatalytic route for FTS.Keywords: Fischer−Tropsch synthesis; graphene; light-enhanced activity; photocatalysis; production distribution; worm-like ruthenium nanostructures

Herein, mesoporous Ni-doped Co3O4 nanowire (NW) arrays are reported as a highly efficient and low-cost catalyst for oxygen reduction reaction (ORR) in alkaline electrolyte. The Ni doping affords more electroactive sites and enhanced conductivity, and the mesoporous structure provides increased surface exposure, which may improve ion/electron transport and reduce charge transfer resistance. The NW arrays exhibit a high ORR activity with a four-electron transfer reaction in alkaline media, a half-wave potential of 0.86 V vs. RHE and a superior stability when compared to the commercial Pt (20 wt%)/C catalyst. Our results suggest that the mesoporous Ni-doped Co3O4 NW arrays could be a promising ORR catalyst for fuel cells and metal–air batteries.

A cathodic electrochemical method for the exfoliation of graphite to produce hydrogenated graphenic flakes is introduced. The resulting solutions consist of micrometer-sized and predominantly 1–4 layers thick hydrogenated graphenic flakes. In contrast to oxygenation, chemisorption of hydrogen avoids the formation of structural vacancy defects in the exfoliated flakes. Thermal desorption of hydrogen therefore results in graphenic flakes with a low defect density and consequently good electrical conductivity. Cathodic electrochemical exfoliation offers a remarkably simple and effective technique for the production of high quality graphene flakes and their hydrogenated relatives.

Graphene can stabilize metallic copper nanoparticles and enable them to exhibit excellent photocatalytic activity for aerobic oxidation of various primary and secondary amines into the corresponding imines. The copper nanoparticles stabilized on graphene absorb the energy of visible light via localized surface plasmon resonance, and produce energetic hot electrons that activate the reactants adsorbed on the surface of copper nanoparticles. The formation of imines involves selective oxygenation of amines to aldehydes and subsequent condensation with amines to form imines.

•Different crystalline and porous hierarchical carbon nitrides were prepared.•Photocatalytic activity in H2 evolution and dye degradation was compared.•Photo luminescence of carbon nitrides was studied in the picosecond range.•Catalytic activity correlates with crystallinity and the fluorescence intensity.•Low crystalline CN materials with large crystal size are not active!Graphitic carbon nitride materials with tri-s-triazine and s-triazine based structures were prepared by thermal condensation of melamine (CNT) and by solution reaction of cyanuric chloride with lithium nitride (CNS), respectively. An amphiphilic block copolymer-F68 was used as a soft template for the synthesis of mesoporous carbon nitride. The structural and photophysical properties of the as-prepared catalysts were characterized by X-ray powder diffraction, elemental analysis, N2-adsorption measurement, transmission electron microscopy, X-ray photoelectron spectroscopy, differential scanning calorimeter and UV–Vis absorption as well as time-resolved picosecond emission spectroscopy. The photocatalytic activity of the samples was evaluated by H2 evolution from water under visible light irradiation and the degradation of rose bengal (RB). The mesoporous CNT materials prepared with Pluronic F68 as template showed markedly higher activity compared to bulk carbon nitride, which can be attributed to its crystallinity, hierarchical porous structure and the enlarged surface area. The catalyst was relatively stable as proven by recycling experiments. Besides, the addition of H2O2 promoted the formation of active ·OH radicals and increased the activity of carbon nitride for photodegradation of rose bengal. The carbon nitrides prepared by solution reactions were of very poor activity both in photocatalytic water splitting and rose bengal degradation.

A novel C–Ni–SiC composite using sawtooth-like SiC as support and carbon as modified material was prepared by hydrothermal synthesis and thermochemical pyrolysis. As a supercapacitor electrode, it exhibits very high specific capacitance (1780 F g−1) and excellent cycling performance (>96% for 2500 cycles).

By using semiconductive SiC as the support, palladium exhibits a tremendous promotion of its intrinsic catalytic activity for the hydrogenation of furan derivatives at ambient temperature under visible light irradiation. The promotion in the catalytic activity results from the fact that the Mott–Schottky contact between SiC and Pd enhances the quick transfer of the photo-generated electrons from SiC to Pd nanoparticles.

Cu2O/graphene as a heterogeneous catalyst can effectively ignite and catalyze the Ullmann C–O cross-coupling of aryl iodides with phenols under mild conditions. The yield of diphenyl ether from the cross-coupling of phenol and iodobenzene can reach up to 96% at 150 °C in 3 h, and the turnover frequency can be as high as 1282 h−1. Meanwhile, the catalyst exhibits activity for varieties of C–O cross-coupling of aryl iodides, bromides and chlorides with phenol derivatives to form the corresponding aryl ethers.

SiC-supported Pt nanocatalyst was prepared by electrodeposition of Pt nanoparticles on the surface of high-surface-area SiC, which was fabricated by a versatile carbothermal reduction method. Characterization studies show that such synthesis protocol leads to well distribution of Pt nanoparticles, with a mean particle size of 2.9 nm on the support. This catalyst has been electrochemically characterized toward methanol oxidation, which exhibits higher catalytic activity, durability, and electrochemical active surface area than the electrodeposited Pt on multiwalled carbon nanotubes (MWCNTs). Further investigation reveals that the SiC-supported Pt also shows superior CO tolerance to Pt/MWCNTs. These results suggest that high-surface-area SiC could be a promising supporting material for constructing high-performance methanol oxidation electrocatalysts.

CNT–Ni/SiC composites with three-dimensional hierarchical nanostructures were fabricated via in situ pyrolysis of methane to grow CNTs on a novel flake-like NiO/SiC material. The NiO/SiC was prepared by hydrothermally growing Ni(OH)2 on SiC. After calcination, Ni(OH)2 was converted to porous NiO flakes. During the methane pyrolysis, NiO was in situ converted to Ni nanoparticles, which acted as the catalyst for growing CNTs. Due to the combination of Ni nanoparticles, in situ grown CNTs and the SiC support, the CNT–Ni/SiC composites exhibit excellent catalytic activity and stability in electro-oxidation of methanol. The catalytic activity shows a dependence on the pyrolysis temperature of methane, and a pyrolysis temperature of 700 °C can lead to a mass activity of 10 A mg−1 Ni, which is about 15 times higher than that of the catalyst obtained from methane pyrolysis at 500 °C and about 4000 times higher than that of the original NiO/SiC catalyst.

A flower-like MoS2–SiC hybrid structure assembled from folded MoS2–SiC nanosheets can activate hydrogen evolution at a very low overpotential (0.04 V) and produce a large cathodic current, which compares favorably with that produced by a commercial 20 wt% Pt/C catalyst.

A carbon coated Co–SiC nanocomposite was fabricated via in situ pyrolysis of methane on a hierarchical Co3O4–SiC nanostructure, which was obtained by hydrothermal synthesis. By the reduction of methane, the Co3O4 was in situ converted to cobalt nanoparticles, and coated by carbon or filled in the CNTs. The as-prepared composite exhibits excellent microwave absorption performance in the frequency range of 2–18 GHz. When the match thickness is 1.8 mm, the composite has a reflection loss value below −10 dB in the range 12.2 to 18 GHz, which nearly covers the whole Ku-band (12–18 GHz). When the thickness is 2.6 mm, the reflection loss value below −10 dB distributes at 8.2–11.5 GHz, covering most of the X-band (8–12 GHz). Moreover, by further tuning the match thickness, the composite can selectively absorb some certain frequency bands of microwaves.

•SiC-graphene composites were prepared by a chemical grafting method.•The composites can catalytically split water under visible light irradiation.•C–Si bonds and heterojunctions were formed between SiC and graphene.•The C–Si bonds and heterojunctions are beneficial to split water.Chemically bonded SiC-graphene composites were prepared by a chemical grafting method. The Si–C bonds between SiC and graphene can form a heterojunction interface. The chemical bonding and the heterojunction interface are beneficial to the quick transfer of photogenerated electrons from SiC to graphene and thus avoiding the recombination with holes. As a result, the composites show an enhanced activity (more than 90%) for photocatalytic splitting of water under visible light irradiation.

Cuprous oxide (Cu2O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu2O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.

Bundle-like carbon nanofibers (CNFs) were prepared from methane decomposition over Ni nanoparticles supported by grooved SiC nanowires. In the bundle-like CNFs, several CNFs grow in a parallel mode and form a bundle of CNFs. Large loading of Ni and limited space of nanoscale grooves on the nanowires lead to aggregation of Ni nanoparticles in the nanoscale grooves. The aggregated Ni nanoparticles generate several CNFs, which close up each other and form the bundle-like CNFs. The bundle-like CNFs become curved due to the difference in growth rates of different CNFs.

β-SiC nanowires were synthesized by simple carbothermal reduction of a mixture composed of low-cost water glass and starch, and characterized by XRD, SEM, TEM, BET, UV–visible absorption, FT-IR spectrometer and X-ray photoelectron spectrometer. The results show that the β-SiC nanowires can absorb visible light and exhibit excellent photocatalytic hydrogen evolution performance from pure water under visible light irradiation. The hydrogen evolution rate can reach more than 60 μL/g·h. SiC nanowires by simple modification can greatly enhance the efficiency of H2 production. Average H2 production rate over the modified SiC is 76.1% higher than that of unmodified SiC. The enhanced H2 production is mainly due to stronger hydrophilic ability of the modified SiC. In addition, O2 is detectable in the experiment, indicating that water has been decomposed into H2 and O2.Highlights► β-SiC nanowires were synthesized using water glass and starch as raw materials. ► SiC nanowires can split water into hydrogen under visible light irradiation. ► SiC nanowires exhibit stable and efficient photocatalytic activity. ► The surface modification can greatly enhance the hydrogen production rate.

Silicon carbide supported nickel catalysts for CO methanation were prepared by impregnation method. The activity of the catalysts was tested in a fixed-bed reactor with a stream of H2/CO = 3 without diluent gas. The results show that 15 wt.% Ni/SiC catalyst calcined at 550 °C exhibits excellent catalytic activity. As compared with 15 wt.% Ni/TiO2 catalyst, the Ni/SiC catalyst shows higher activity and stability in the methanation reaction. The characterization results from X-ray diffraction and transmission electron microscopy suggest that no obvious catalyst sintering has occurred in the Ni/SiC catalyst due to the excellent thermal stability and high heat conductivity of SiC.Highlights► Ni/SiC catalyst exhibits high activity and stability for CO methanation. ► The performance of Ni/SiC catalyst is far better than commonly used Ni/TiO2. ► The merits result from excellent thermal stability and conductivity of SiC.

Silicon nitride supported nickel catalyst prepared by impregnation using nickel nitrate solution was employed for the carbon dioxide reforming of methane. The catalyst was tested at 800 °C under atmospheric pressure. The influences of Ni loading and calcination temperature on the catalytic performance were investigated. It was found that the nickel loading and calcination temperature strongly influenced the catalytic performance. Over the 7 wt. % Ni/Si3N4 catalyst calcined at 400 °C, the conversions of CH4 and CO2 can achieve 95% and 91%, respectively. Appropriate interaction between the metal and the basic support makes the catalyst more resistant to sintering and coking, and thus an excellent stability.

Fe@Pd, Fe@Pt, and Fe@Au core–shell nanoparticles supported by silicon carbide have been prepared by plasma sputtering deposition and employed as the catalyst for methane combustion. The core–shell catalysts exhibit higher activities than single metallic catalysts due to surface alloying effects. With the surface alloying of the core–shell nanoparticles, Pd–O and Pt–O bonds become weak because the increase of the electron cloud density around Pd and Pt atoms due to the electron transfer from surface Fe to Pd or Pt atoms. Therefore, the activities of Fe@Pd/SiC and Fe@Pt/SiC increase with the reaction time. The activity of Fe@Au/SiC keeps invariant in the reaction because the Fe@Au core–shell structure has high stability. Transmission electron microscopy and X-ray photoelectron spectroscopy results further confirm the structural evolution.

Pd–Au bimetallic nanoparticles supported by silicon carbide have been prepared by plasma sputtering deposition and employed as the catalyst for methane combustion. It is found that the bimetallic nanoparticles consist of tightly-coupled Pd and Au particles, which are neither Pd–Au alloyed nor core–shell structured. The catalytic activity increases with the Pd loading in the catalysts. When the temperature is higher than 520 °C, Pd catalysts have an obvious drop in the catalytic activity due to the decomposition of PdO. However, the introduction of Au can delay and weaken the drop. It is indicated that there exists a synergistic combination between Pd and Au: oxygen transfers from Pd to Au at a temperature lower than 520 °C and from Au to Pd at higher temperature. Transmission electron microscopy and X-ray photoelectron spectroscopy results further confirm the synergistic combination.

Macroscopic multi-branched tree-like carbon has been prepared by the chemical vapor deposition of camphor in argon using ferrocene as catalyst. The results show that the building blocks forming the carbon trees are carbon microspheres. Both the diameter of the tree branches and the size of the carbon microspheres become smaller with increasing ferrocene content. The ratio of tree branch diameter to carbon microsphere size is about 1.35, which is independent of the ferrocene content. Increasing the argon flow rate in the range of 500–2500 ml/min benefits the growth of carbon trees, and the most favorable argon flow rate is 2000–2500 ml/min. Increasing the reaction temperature in the range of 1000–1150 °C can enhance the coalescence of the carbon microspheres, and thus result in the carbon trees with smooth and straight branches.

By a simple carbothermal reduction method, β-SiC nanoparticles with different sizes were prepared from plastic wastes, water bottles and disposable boxes. These particles were characterized by X-ray diffraction, transmission electron microscopy, dynamic light scattering and so on. The SiC nanoparticles synthesized from water bottles mainly have dimensions in the range of 5–20 nm, while the nanoparticles synthesized from disposable boxes mainly have dimensions ranging from 30 to 70 nm. Compared with the large SiC nanoparticles, the SiC nanoparticles with smaller size have better reinforcement effect in epoxy resin composites.

Nanoditches from selective etching of periodically twinned SiC nanowires were employed to hinder the migration and coalescence of Pd nanoparticles supported on the nanowires, and thus to improve their catalytic stability for total combustion of methane. The results show that the etched Pd/SiC catalyst can keep the methane conversion of almost 100% while the unetched one has an obvious decline in the catalytic activity from 100 to 82% after ten repeated reaction cycles. The excellent catalytic stability originates from the limitation of the nanoditches to the migration and growth of Pd nanoparticles.

The Monte Carlo method has been used to simulate the kinetic oscillations during partial oxidation of methane under nonisothermal conditions. The oscillatory behavior can be found with the selected parameters by using oxide formation and removal model. From the simulation, the temperature variation during the reaction synchronizes well with the oscillations of product formation rates, and also with the rates of oxide formation and reduction processes. Compared with the isothermal simulation results, the oscillations under the nonisothermal conditions are observed to have a slightly shorter period, lower maximum carbon coverage and higher nickel oxide coverage.

Branched carbon structures were formed by a chemical vapor deposition of toluene using ferrocene as a catalyst precursor and thiophene as a promoter. The effects of sulfur on the carbon products were investigated by SEM, XRD, and EDX. Results show that the product microstructure changes from tree-like to worm-like when the thiophene volume fraction in the toluene increases from 0.01 to 1%. The carbon trees consist of long, straight, and well-developed branches, while the worm carbons are composed of short and curled fibers. There is no obvious difference in d002, La and Lc for the two products.

The Monte Carlo method is employed to study the kinetics of catalytic partial oxidation of methane to syngas on nickel catalyst. Using the Langmuir–Hinshelwood mechanism, self-sustained reaction rate oscillations can be observed under suitable conditions. Further analysis reveals that the rate oscillations are caused by the repetitive oxidation and reduction cycles of nickel surface, which result in a transformation of the formation mechanism of carbon monoxide from the reaction between C and O to the direct reduction of nickel oxide. The conditions for generating the self-sustained oscillations are investigated, and the regular oscillations are found for the diffusion parameter Ndif > 50 and the lattice size L ⩾ 90.

A simplified Monte Carlo model was proposed to simulate the oscillatory behavior during catalytic partial oxidation of methane. Using the Langmuir-Hinshelwood mechanism, the oscillatory behavior was observed in both reaction rates and coverages of adsorbed species. The influence of oxidation and reduction of the catalyst surface on the oscillations was investigated, and the analysis showed that the fast oxidation and slow reduction of the catalyst surface resulted in the oscillatory behavior.

Crystalline Si3N4 thin nanobelts have been synthesized via direct nitridation of Si powders without using any catalyst. The purified Si3N4 sample was characterized by X-ray diffraction, high-resolution transmission electron microscopy, energy dispersion X-ray spectrum, and Fourier transform infrared spectroscopy. The results show that the sample mainly consists of Si3N4 thin nanobelts with a width of 100–500 nm and a length of several microns. The infrared adsorptions of the nanobelts exhibit obvious red shift compared with those of Si3N4 nanowires. The growth of the nanobelts follows the vapor–solid mechanism.

Carbon trees, quite different from those previously reported, have been produced by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor. The influences of formation conditions such as catalyst mass, toluene flow rate, and reaction time on the tree growth and morphology have been investigated. The yield of carbon trees is greatly affected by catalyst quantity. A lower toluene flow rate (50–100 ml/min) or shorter reaction time (10–30 min) leads to trees with thinner (several microns) and filamentous branches, while a higher toluene flow rate (greater than 200 ml/min) or longer reaction time (60–120 min) produces thicker (tens of microns) and spherical branches. Results suggest that the morphology of the carbon trees can be adjusted by varying the reaction conditions.

Monte Carlo method was employed to investigate the filling process of nickel into carbon nanotubes. According to the simulation, nickel atoms around a nanotube firstly aggregated into clusters at the two ends of the tube. Then, the nickel clusters entered the tube, diffused along the tube axis and coalesced into a continuous structure. When the nanotube diameter was larger than 0.76 nm, the continuous nickel structure could transform into an ordered fashion with several concentric layers. By analyzing the radial distribution function, the encapsulated nickel displayed some different features in the microstructure compared to its bulk form.The filling process of carbon nanotubes consists of the formation, deformation, diffusion and coalescence of nickel clusters.

Tungsten trioxide nanorods were prepared at 453 K by the hydrothermal treatment of aqueous tungstic acid sol, which was obtained by sodium tungstate solution passing through a strongly acidic ion-exchange resin in its proton form. The composition and morphology evolution of the nanorods were investigated by means of scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and X-ray diffraction. The results show that all as-prepared samples mainly consist of hexagonal tungsten trioxide and tungsten trioxide one-third hydrate. With the extension of treatment time, the sample morphology will undergo an evolution in the sequence of nanorod, bundle-like and irregular shapes.

X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the effects of reaction conditions (catalysts, reaction temperature and time) on the crystalline phases and morphologies of the carbothermal reaction products in the sol-gel synthesis of Si3N4 nanowires. The results showed that Si3N4 nanowires could be obtained with high yield by using xerogel, which produced a mixture with 5% (w) Fe after carbonization, with a controlling reaction temperature and time of 1300 °C and 10 h, respectively. The products obtained by using different additives had different crystalline phases. The content of additives also influenced the morphologies of the products. With increasing the reaction temperature or extending the reaction time, the products underwent a phase transformation of SiOx→Si2N2O→Si3N4. In the presence of metals, Si3N4 nanowires were produced with the help of the vapor-liquid-solid mechanism.

Biomorphic porous silicon carbide was successfully prepared by spontaneous infiltration of melted silicon into a carbon template derived from natural millet at 1600 °C for 2 h. The purified SiC sample was characterized by X-ray diffraction, scanning electron microscopy and mercury intrusion. The results suggest that the sample mainly consists of β-SiC and perfectly replicates the microstructure and morphology of the carbon template. The SiC sample has a mean pore diameter of 93 μm and a specific surface area of 30 m2/g, and both of them are very similar to those of the carbon template, 87 μm and 55 m2/g, respectively. The surface fractal dimension is 2.72 for the SiC sample and 2.76 for the template by analyzing the mercury intrusion data.

Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000–1200 °C and a carrier gas flow rate of 1000–2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies.

Silicon nitride nanowires and nanotudes were synthesized from a binary sol–gel route, in which tetraethoxysilane (TEOS) and phenolic resin were used to prepare a carbonaceous silica xerogel and ferric nitrate was employed as additive. Raw Si3N4 product was obtained by heating the xerogel at 1300 °C for 10 h in nitrogen flow (200 ml/min). The Si3N4 sample after purification was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersion X-ray (EDX) spectrum and selected area electron diffraction (SEAD). The results showed that the sample mainly consisted of α-Si3N4 nanowires with a few of nanotubes. Both the nanowires and nanotubes have a diameter of 30–100 nm and a length of hundreds microns. Liquid droplets were also found at the tip of the nanowires, and this indicated that the growth of the nanowires and nanotubes followed the vapor–liquid–solid (VLS) mechanism.

The bamboo-like silicon carbide nanofibers were synthesized by the carbothermal reduction of the carbonaceous silicon xerogel containing lanthanum nitrate. The xerogel was heated to 1300 °C in argon flow in a horizontally tubular reactor and produced as-synthesized sample. The as-synthesized sample was then heated in air at 700 °C for removal of the residual carbon and treated by nitric acid and then hydrofluoric acid for elimination of the unreacted silica and other impurities. The purified product was characterized by XRD, SEM, TEM and HRTEM. The results indicated that the product was bamboo-like β-SiC nanofibers with a diameter of 40–100 nm and a length of tens to hundreds of micrometers and had planar stacking faults perpendicular to the fiber axis.

Coalescence kinetics of free and supported Ag, Cu, Ni and Pd clusters was studied by the Monte Carlo method with the Lennard-Jones plus Axilrod-Teller potential. A coalescence temperature was defined to characterize the coalescence of small metal clusters. The dependence of the cluster shape evolution on temperature and different stages during coalescence were studied. Firstly, neighboring clusters contacted each other through diffusion, and then neck regions formed between two neighboring clusters. Afterward the coalescing clusters deformed and finally relaxed to a new equilibrium shape. From the different shape evolution stages, it was found that the cluster growth followed the diffusion and coalescence mechanism, and the coalescence temperature was dependent not only on the cluster size but also on the average binding energy of the metal clusters.

Monte Carlo method was applied to simulate the oscillatory behavior during partial oxidation of methane under non-isothermal condition. The simulation was performed to examine the influences of heat transfer constant and particle size on the kinetic oscillation. The oscillatory period and amplitude were observed to increase with the increase of heat transfer constant. The increase of catalyst particle size was found to result in short oscillatory period and more or less regular oscillations combined with the formation of oxide down to L = 100.

Ni/SiC and La2O3 modified Ni/SiC were prepared by impregnation method and used as the catalysts for methanation of CO2. The modified Ni/SiC shows better catalytic activity and stability than pure Ni/SiC. XRD and TPR results indicate that La2O3 can effectively restrain the growth of NiO nanoparticles, improve the dispersion of NiO and strengthen the interaction between NiO and SiC. XPS result suggests that La2O3 can change the electron environment surrounding Ni atoms and thus reactant CO2 on the Ni atoms can be activated more easily.La2O3 modification can enhance the metal–support interaction and thus stabilize nickel nanoparticles on the support. Therefore Ni–La/SiC catalyst exhibits high activity and excellent durability for CO2 methanation.Download full-size imageHighlights► Ni/SiC and La2O3 modified Ni/SiC catalysts were prepared by impregnation method. ► La2O3 modified Ni/SiC exhibits higher activity and durability in CO2 methanation. ► The improved catalytic behavior results from the high dispersion of nickel species.

The performances of different promoters (CeO2, ZrO2 and Ce0.5Zr0.5O2 solid solution) modified Pd/SiC catalysts for methane combustion are studied. XRD and XPS results showed that Zr4+ could be incorporated into the CeO2 lattice to form Zr0.5Ce0.5O2 solid solution. The catalytic activities of Pd/CeO2/SiC and Pd/ZrO2/SiC are lower than that of Pd/Zr0.5Ce0.5O2/SiC. The Pd/Zr0.5Ce0.5O2/SiC catalyst can ignite the reaction at 240 °C and obtain a methane conversion of 100% at 340 °C, and keep 100% methane conversion after 10 reaction cycles. These results indicate that active metallic nanoparticles are well stabilized on the SiC surface while the promoters serve as oxygen reservoir and retain good redox properties.The performances of different promoters (CeO2, ZrO2 and Ce0.5Zr0.5O2 solid solution) modified Pd/SiC catalysts for methane combustion are studied. The catalytic activities of Pd/SiC, Pd/CeO2/SiC and Pd/ZrO2/SiC are lower than that of Pd/Zr0.5Ce0.5O2/SiC. The Pd/Zr0.5Ce0.5O2/SiC catalyst can ignite the reaction at 240 °C and obtain a methane conversion of 100% at 340 °C, and keep 100% methane conversion after 10 reaction cycles. These indicate that active metallic nanoparticles are well stabilized on the SiC surface while the promoters serve as oxygen reservoir and retain good redox properties.Download full-size imageResearch Highlights► The Pd/Zr0.5Ce0.5O2/SiC catalyst can ignite the reaction at 240oC and obtain a methane conversion of 100% at 340oC, and keep 100% methane conversion after 10 reaction cycles. ► The catalytic activities of Pd/SiC, Pd/CeO2/SiC and Pd/ZrO2/SiC are lower than that of Pd/Zr0.5Ce0.5O2/SiC. ► XRD and XPS results reveal that Zr4+ is incorporated into the CeO2 lattice to form Zr0.5Ce0.5O2 solid solution. ►

Herein, mesoporous Ni-doped Co3O4 nanowire (NW) arrays are reported as a highly efficient and low-cost catalyst for oxygen reduction reaction (ORR) in alkaline electrolyte. The Ni doping affords more electroactive sites and enhanced conductivity, and the mesoporous structure provides increased surface exposure, which may improve ion/electron transport and reduce charge transfer resistance. The NW arrays exhibit a high ORR activity with a four-electron transfer reaction in alkaline media, a half-wave potential of 0.86 V vs. RHE and a superior stability when compared to the commercial Pt (20 wt%)/C catalyst. Our results suggest that the mesoporous Ni-doped Co3O4 NW arrays could be a promising ORR catalyst for fuel cells and metal–air batteries.

CNT–Ni/SiC composites with three-dimensional hierarchical nanostructures were fabricated via in situ pyrolysis of methane to grow CNTs on a novel flake-like NiO/SiC material. The NiO/SiC was prepared by hydrothermally growing Ni(OH)2 on SiC. After calcination, Ni(OH)2 was converted to porous NiO flakes. During the methane pyrolysis, NiO was in situ converted to Ni nanoparticles, which acted as the catalyst for growing CNTs. Due to the combination of Ni nanoparticles, in situ grown CNTs and the SiC support, the CNT–Ni/SiC composites exhibit excellent catalytic activity and stability in electro-oxidation of methanol. The catalytic activity shows a dependence on the pyrolysis temperature of methane, and a pyrolysis temperature of 700 °C can lead to a mass activity of 10 A mg−1 Ni, which is about 15 times higher than that of the catalyst obtained from methane pyrolysis at 500 °C and about 4000 times higher than that of the original NiO/SiC catalyst.

Graphene can stabilize metallic copper nanoparticles and enable them to exhibit excellent photocatalytic activity for aerobic oxidation of various primary and secondary amines into the corresponding imines. The copper nanoparticles stabilized on graphene absorb the energy of visible light via localized surface plasmon resonance, and produce energetic hot electrons that activate the reactants adsorbed on the surface of copper nanoparticles. The formation of imines involves selective oxygenation of amines to aldehydes and subsequent condensation with amines to form imines.

By using semiconductive SiC as the support, palladium exhibits a tremendous promotion of its intrinsic catalytic activity for the hydrogenation of furan derivatives at ambient temperature under visible light irradiation. The promotion in the catalytic activity results from the fact that the Mott–Schottky contact between SiC and Pd enhances the quick transfer of the photo-generated electrons from SiC to Pd nanoparticles.

A novel C–Ni–SiC composite using sawtooth-like SiC as support and carbon as modified material was prepared by hydrothermal synthesis and thermochemical pyrolysis. As a supercapacitor electrode, it exhibits very high specific capacitance (1780 F g−1) and excellent cycling performance (>96% for 2500 cycles).

Cuprous oxide (Cu2O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu2O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.

Cu2O/graphene as a heterogeneous catalyst can effectively ignite and catalyze the Ullmann C–O cross-coupling of aryl iodides with phenols under mild conditions. The yield of diphenyl ether from the cross-coupling of phenol and iodobenzene can reach up to 96% at 150 °C in 3 h, and the turnover frequency can be as high as 1282 h−1. Meanwhile, the catalyst exhibits activity for varieties of C–O cross-coupling of aryl iodides, bromides and chlorides with phenol derivatives to form the corresponding aryl ethers.

A flower-like MoS2–SiC hybrid structure assembled from folded MoS2–SiC nanosheets can activate hydrogen evolution at a very low overpotential (0.04 V) and produce a large cathodic current, which compares favorably with that produced by a commercial 20 wt% Pt/C catalyst.

CoS2/graphene composites fabricated by a facile hydrothermal method exhibit excellent photocatalytic performance for selective hydrogenation of nitroaromatics to the corresponding aniline employing molecular hydrogen as a reducing agent under visible light irradiation (400–800 nm). The rate constant of the composite catalyst for nitrobenzene hydrogenation can achieve as high as 35.50 × 10−3 min−1 with a selectivity of 100% toward the target product under mild conditions (30 °C and 0.25 MPa pressure of H2). The catalyst also shows high recyclability, and there is no decrease in the catalytic activity after five successive cycles. There exists a synergistic effect between the graphene support and the CoS2 particles: conductive graphene as the support can rapidly extract the photoexcited electrons and effectively suppress the recombination of photogenerated charges in CoS2 particles, and then improve the photocatalytic performance. The photocatalytic reduction of nitrobenzene over the CoS2/graphene catalyst to aniline occurs through the direct pathway in the presence of H2.

A carbon coated Co–SiC nanocomposite was fabricated via in situ pyrolysis of methane on a hierarchical Co3O4–SiC nanostructure, which was obtained by hydrothermal synthesis. By the reduction of methane, the Co3O4 was in situ converted to cobalt nanoparticles, and coated by carbon or filled in the CNTs. The as-prepared composite exhibits excellent microwave absorption performance in the frequency range of 2–18 GHz. When the match thickness is 1.8 mm, the composite has a reflection loss value below −10 dB in the range 12.2 to 18 GHz, which nearly covers the whole Ku-band (12–18 GHz). When the thickness is 2.6 mm, the reflection loss value below −10 dB distributes at 8.2–11.5 GHz, covering most of the X-band (8–12 GHz). Moreover, by further tuning the match thickness, the composite can selectively absorb some certain frequency bands of microwaves.