Highly dispersed MoO(x) on carbon nanotube as support for high performance Pt catalyst towards methanol oxidation

HPMo self-assembly on carbon nanotubes followed by decomposition is used to fabricate highly dispersed MoO(x)/CNTs as a support for high performance of a Pt catalyst towards methanol oxidation.     

Pt decorating PdCu/C as highly effective electrocatalysts for methanol oxidation

In this study, a low-cost and high performance catalyst Pt decorating PdCu/C (Pt–PdCu/C) for methanol oxidation is prepared by a new two-stage route. TEM and XRD examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface areas. Catalytic activity and stability for the oxidation of methanol are studied by cyclic voltammetry and chronoamperometry. High electrocatalytic activities and good stabilities could be attributed to the synergistic effect between Pt and PdCu.     

Controllable synthesis of grain boundary-enriched Pt nanoworms decorated on graphitic carbon nanosheets for ultrahigh methanol oxidation catalytic activity

Although one-dimensional Pt nanocrystals have long been regarded as ideal electrode catalysts for fuel cells,the synthetic techniques commonly involve the use o...     

Magnetically modified nanogold-biosilica composite as an effective catalyst for CO oxidation

The temperature-dependent biosynthesis of gold nanoparticles (AuNP) using diatom cells of Diadesmis gallica was successfully performed. The resulting biosynthesis product was a bionanocomposite containing AuNP (app. 20 nm) subsequently anchored on the silica surface of diatomaceous frustules. As-prepared nanogold-biosilica composite was tested as catalyst in the oxidation of carbon monoxide using gas chromatograph with thermal conductivity detector. For catalytic activity enhancement, bionanocomposite was magnetically modified by ferrofluid using two different methods, i.e., with and without the use of methanol. The oxidation of CO at 300 °C was 58–60% in the presence of nanogold-biosilica composites. CO conversion at 300 °C was only 15% over magnetically responsive sample modified in the presence of methanol. On the other hand, complete CO conversion was reached over direct (without methanol) magnetically modified nanogold-biosilica composite at 330 °C (GHSV = 60 l g⁻¹ h⁻¹). Our results show, that the type of magnetic modification can influence the catalytic activity of bionanocomposite. The best catalytic effect in CO conversion established direct magnetically modified nanogold-biosilica composite.     

Nanostructured Pt supported on cocoon-derived carbon as an efficient electrocatalyst for methanol oxidation

Development of suitable supports has been proven as an important preparation process for high active catalysts of fuel cell. In this work, a carbon material was prepared by pyrolyzing cocoons with ferric chloride as activator, and then Pt nanoparticles (ca. 50 wt.%) were deposited on its surface. The characteristics of X-ray diffraction and transmission electron microscopy showed that the face-centered cubic structured Pt nanoparticles with nano-sized crystals interconnected each other via grain boundaries were formed on the surface of pyrolyzed cocoons. Afterwards, electrochemical results demonstrate that the nanostructured Pt supported on this support exhibits higher catalytic activity and CO tolerance than Pt nanoparticles supported on Vulcan carbon for methanol oxidation reaction.     

Molybdate sulfonic acid: preparation, characterization, and application as an effective and reusable catalyst for octahydroxanthene-1,8-dione synthesis

Molybdate sulfonic acid (MSA) as a highly efficient catalyst was synthesized and employed for the synthesis of octahydroxanthene-1,8-dione derivatives. MSA efficiently catalyzed condensation of a wide range of aryl aldehydes and cyclohexane-1,3-diones to obtain octahydroxanthene-1,8-diones. It was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), and FT-IR spectroscopy. This catalyst can be recovered and reused several times in other reactions maintaining its high activity. This novel and green method is very cheap and has many advantages such as excellent yields, the use of recoverable and eco-friendly catalysts, and a simple work-up procedure.     

Single-Cu-atoms anchored on 3D macro-porous carbon matrix as efficient catalyst for oxygen reduction and Pt co-catalyst for methanol oxidation

Single metal atoms immobilized on a carbon substrate are of great potential for enhancing the catalytic activities for oxygen reduction and methanol oxidation reactions（ORR/MOR） owing to the maximized atom utilization. Herein, single copper atoms（SCAs） are loaded on macro-porous nitrogen-doped carbon（Cu-NC） derived from zeolitic imidazolate framework-8（ZIF-8）, which are used as catalysts for ORR and Pt-supports for MOR. For ORR, the catalyst marked as Cu-NC-3 exhibits a higher peak potential of ...     

Palladium/graphitic carbon nitride catalyst for selective oxygen transfer in Wacker oxidation

Nanoscaled palladium particles supported on graphitic carbon nitride (Pd⁰/g-C₃N₄) is prepared to improve the oxygen transfer in Wacker oxidation via chemical reduction method. From the analysis of FT-IR, XRD, SEM, TEM, XPS and ICP, Pd⁰ particles are firmly combined with g-C₃N₄ layers, and sub-surface ones occupy most of the components. It is worth mentioning that graphene oxide (GO), which is completely recyclable without further pollution, can be used as a ‘solid weak acid’ taking the place of H₂SO₄ and CF₃COOH. Under the optimization conditions, as many as 46 kinds of olefins are transferred into corresponding products with satisfactory yields, and o-methyl styrene gets the highest yield of 94%. After five times of recycling experiment, the yield of acetophenone only decreases by about 7.0% in the uniform reaction process. In virtue of former research results and molecular electrostatic potential, a possible mechanism is put forward to explain the catalytic process.     

Polyoxometalate-modified carbon nanotubes: new catalyst support for methanol electro-oxidation

A new catalyst support, polyoxometalate-modified carbon nanotubes, is presented in this paper through the chemisorption between polyoxometalate and carbon. Pt and Pt-Ru nanoparticles were electrochemically deposited on polyoxometalate-modified carbon nanotubes electrodes, and their electrocatalytic properties for methanol electro-oxidation are investigated in detail. Due to the unique electrical properties of carbon nanotubes and the excellent redox properties and the high protonic conductivity of polyoxometalate, for the similar deposition charge of Pt and Pt-Ru catalysts, 1.4 times larger exchange current density, 1.5 times higher specific activity, and better cycle stabilities can be obtained at polyoxometalate-modified carbon nanotube electrodes as compared to the electrodes without polyoxometalate modification. These results show that polyoxometalate-modified carbon nanotubes as a new catalyst support have good potential application in direct methanol fuel cells.     

Supported ruthenium catalyst as an effective catalyst for selective oxidation of toluene

The investigation comprised an evaluation of the use of the catalyst 1%Ru/TiO₂ in the liquid-phase conversion of toluene to benzyl alcohol and benzaldehyde. Transmission electron microscopy (TEM) and N₂ adsorption-desorption isotherms were deployed to delineate the properties of the supported catalysts. The findings indicated a good catalytic performance by 1%Ru/TiO₂ under green reaction conditions. This performance was deemed a consequence of the spread and loading of Ru on the TiO₂. The reaction conditions such as temperature, reaction time, type of support, catalyst preparation method, and activating quantity) were optimized to achieve superior reaction parameters. Catalyst produced via sol-immobilization has higher activity than the one prepared with the wet-impregnation method, which lead to a transformation rate of up to 9.5%, with the selectivity for benzyl alcohol at 92%.     

Green and facile synthesis of Pt/{PW12-GN} composite film and its electrocatalytic activity for methanol oxidation

In this paper, H₃PW₁₂O₄₀ (PW₁₂)-functionalized graphene nanosheets (PW₁₂-GNs) were prepared using a green and facile method via a UV-irradiated photoreduction process, in which PW₁₂ was directly deposited on the GNs as a reductant and also as an anionic stabilizer. The as-prepared water-dispersive PW₁₂-GN composite is used as matrices for electrodeposition of the interesting orchidlike Pt nanoclusters in situ. The PW₁₂-GN composite was characterized by transmission electron microscopy (TEM) and cyclic voltammetry (CV). It was shown that the electrochemical properties of PW₁₂ were maintained in PW₁₂-GNs. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) confirmed that Pt had been deposited on the PW₁₂-GN composite surface. Field emission scanning electron microscopy (FE-SEM) showed that the interesting orchidlike Pt nanoparticles were uniformly immobilized on the surface of the {PW₁₂-GN} composite film. Cyclic voltammetry and chronoamperometric curves were used to study the electrocatalytic activity of Pt/{PW₁₂-GN} regarding methanol oxidation in 0.5 M H₂SO₄. It is worthy of note that the Pt/{PW₁₂-GN} composite film-modified electrode presents a high catalytic activity (j?=?353 mA mg^?1) and better tolerance of CO towards methanol electrooxidation.     

In situ synthesis of Pt/carbon nanofiber nanocomposites with enhanced electrocatalytic activity toward methanol oxidation

Pt/carbon nanofiber (Pt/CNF) nanocomposites were facilely synthesized by the reduction of hexachloroplatinic acid (H(2)PtCl(6)) using formic acid (HCOOH) in aqueous solution containing electrospun carbon nanofibers at room temperature. The obtained Pt/CNF nanocomposites were characterized by TEM and EDX. The Pt nanoparticles could in situ grow on the surface of CNFs with small particle size, high loading density, and uniform dispersion by adjusting the concentration of H(2)PtCl(6) precursor. The electrocatalytic activities of the Pt/CNF nanocomposites were also studied. These Pt/CNF nanocomposites exhibited higher electrocatalytic activity toward methanol oxidation reaction compared with commercial E-TEK Pt/C catalyst. The results presented may offer a new approach to facilely synthesize direct methanol fuel cells (DMFCs) catalyst with enhanced electrocatalytic activity and low cost.     

Synthesis of coin-like hollow carbon and performance as Pd catalyst support for methanol electrooxidation

The coin-like hollow carbon (CHC) has been synthesized by only using ethanol as the carbon source with a novel Mg/NiCl₂ catalytic system via a facile solvothermal method for the first time. The CHC synthesized at optimized conditions shows an average thickness of less than 154 nm and the coin diameter of 1–3 μm. The CHC is characterized by SEM, TEM, XRD and electrochemical techniques. Pd on CHC (denotes as Pd/CHC) electrocatalysts are prepared for methanol oxidation in alkaline media. The Pd/CHC electrocatalyst gives a mass activity of 2930 A g⁻¹ Pd for methanol oxidation against 870 A g⁻¹ Pd on Pd/C electrocatalyst. One main reason for the higher mass activity of the Pd/CHC is the higher electrochemical active surface area (EASA) of the Pd/CHC.     

Ammonia-treated activated carbon as support of Ru-Ba catalyst for ammonia synthesis

Ammonia-treated activated carbon has been studied as a support of Ru-Ba catalyst for ammonia synthesis. It is shown that the introduction of nitrogen leads to a decrease of ammonia synthesis activity for the catalysts with a low Ba/Ru molar ratio, while no significant changes are obtained for the catalysts with a high Ba/Ru molar ratio, confirming that electronegative impurities suppress the activity in ammonia synthesis and consume part of the promoters. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of Zr-containing FSM-16 as an effective support for Co catalyst in the Fischer-Tropsch synthesis

Zr⁴⁺ ions have been introduced into the framework of FSM-16 using a sol-gel method at Si/Zr ≥ 200 (molar ratio). Co/Zr-FSM-16 showed high CO conversion and a high selectivity for C₅₊ hydrocarbons in the Fischer-Tropsch synthesis due to the high surface area of FSM-16 and the isomorphously substituted Zr⁴⁺ as a co-catalyst.     

Microwave-assisted synthesis of Pt-WC/TiO2 in ionic liquid and its application for methanol oxidation

Tungsten carbide/titanium oxide (WC/titanium dioxide (TiO₂)) particles are prepared by microwave-assisted heating in conjunction with ionic liquid and the subsequent reduction–carbonization. The platinum particles are loaded on the WC/TiO₂ to prepare Pt-WC/TiO₂. The electrocatalytic performances of the Pt-WC/TiO₂ toward methanol oxidation are evaluated by cyclic voltammetry, chronoamperometry, and the CO stripping tests. It is found that electrocatalytic activity of Pt-WC/TiO₂ is enhanced by adding ionic liquid (IL) during sample preparation. The results indicate that better performance toward methanol oxidation and higher tolerance to CO are achieved with an optimal addition of 1.5 ml 1-methyl-imidazoliumtetr-afluoroborate for preparing Pt-WC/TiO₂. To investigate the function of IL, the phase structure and morphology of samples at different stages during preparation are examined by X-ray diffraction and transmission electron microscopy. Ionic liquid is found to act as not only a good solvent offering the excellent microwave absorption, but also a structure-directing agent to control the morphology and structure of sample, which affect the activity of the final catalysts.     

Ultrasonic assisted polyol synthesis of highly dispersed Pt/MWCNT electrocatalyst for methanol oxidation

A novel chemical method based on ultrasonic assisted polyol synthesis for the fabrication of highly dispersed Pt nanoparticles on multi-walled carbon nanotubes (MWCNTs) was developed. The simple and green method took only about 10 min at ambient temperature. The structure and chemical nature of the resulting Pt/MWCNT composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS). The results showed that the prepared Pt nanoparticles were uniformly dispersed on the MWCNT surface. The mean size of Pt nanoparticles was about 2.8 nm. Electrochemical properties of Pt/MWCNT electrode for methanol oxidation were examined by cyclic voltammetry (CV) and excellent electrocatalytic activities could be observed. The possible formation mechanism of Pt/MWCNTs was also discussed.     

Preparation and characterization of Cu (II) Schiff base complex functionalized boehmite nanoparticles and its application as an effective catalyst for oxidation of sulfides and thiols

The synthesis, characterization, and evaluation of a Schiff base Cu (II) complex functionalized boehmite nanoparticles (Cu-complex-boehmite) as a new catalyst for oxidation of sulfides and thiols in the presence of hydrogen peroxide with complete selectivity and high conversion under solvent-free and mild reaction conditions were reported. Characterization of the catalyst was performed with various physicochemical methods. This effective catalyst was evaluated in terms of activity and reusability. It indicated high catalytic activity, good recoverability and reusability, and supplied the corresponding products in high yields and short reaction times. In addition, it shows notable advantages such as simplicity of operation, heterogeneous nature, easy work up, and it could be used at least eight times with no significant loss of its activity.     

Surface modified Pt/C as a methanol tolerant oxygen reduction catalyst for direct methanol fuel cells

A new procedure has been successfully developed by which PtN_x/C is synthesized to enhance methanol tolerance while maintaining a high catalytic activity for the oxygen-reduction reaction (ORR). The nitrogen-modified Pt surface, which is prepared using a chelating agent followed by heat treatment, exhibits considerable selectivity toward the ORR in the presence of methanol. The high methanol tolerance could be attributed to the suppression of methanol adsorption resulting from the modification of the Pt surface with nitrogen. A direct methanol fuel-cell (DMFC) test showed that a power density of up to 120 m W cm⁻² was generated when PtN_x/C was used as the cathode catalyst (1 mg cm⁻²) in 6 M methanol and oxygen at 70 °C.