MoS2基单原子催化剂的合成及其在电催化中的应用

电催化由于反应条件温和、反应速率较快等优势,在能源存储与转化、高值小分子合成等领域具有极大应用前景。因此,设计开发高效的电催化剂是推动电催化反应工业化的核心问题。二硫化钼(MoS₂)以其低成本、可调的电子性质和优异的化学稳定性,被认为是用于电催化的最有前景的候选材料之一。同时,单原子催化是一种功能强大、极具吸引力的技术,成本显著降低,且具有优异的催化活性。本文首先综述了MoS₂基单原子催化剂的制备策略,包括电化学沉积、湿化学浸渍、水热/溶剂热和氢气等离子体还原。其次,在此基础上重点介绍了相应催化剂在电催化领域的应用。最后,从单原子改性、机理研究、合成工艺三个方面讨论了新的研究方向和未来趋势,即制备多金属MoS₂基单原子催化剂,深度表征和计算澄清反应机理,开发绿色环保的合成工艺等。     

Synthesis of high-surface area mesoporous SiC with hierarchical porosity for use as catalyst support

Porous SiC with a hierarchical mesoporous structure is a promising material for high-performance catalytic systems because of its high thermal conductivity, high chemical inertness at high temperature, and oxidation resistance. Attempts to produce high-surface area hierarchical SiC have typically been made by using porous carbon as a template and reacting it with either Si or SiO₂ at high temperature under inert atmosphere. Because the reaction mechanism with Si involves a carbon dissolution step, and the reaction with SiO₂ is highly dependent on C-SiO₂ dispersion, the porous structure of the carbon template is not maintained, and the reaction yields nonporous SiC. In this work, mesoporous SiC has been synthesized using a novel hard-template methodology. SiC was prepared from hierarchical (mesoporous) silica which served as a solid template. Carbon deposition was done by Carbon Vapor Deposition (CVD) using CH₄ as carbon precursor, where different temperatures and reaction times were tested to optimize the carbon coating. The synthesized SiC retained 61 (118 m²/g) and 47% (0.3 cm³/g) of the BET surface area and the mesopore volume of the original SiO₂, which is 10 times higher than the retention reported for other template methods used to produce high surface area SiC.     

Surface-modified carbons as platinum catalyst support for PEM fuel cells

Carbon forms, such as activated carbon, carbon black, carbon nanofibers and nanotubes, can be used as support materials for precious metal catalysts used in fuel cell electrodes. This work first compares the ability of functionalized high surface area graphitic (carbon nanofibers) and amorphous (activated carbon) carbons to homogeneously support finely divided platinum catalyst particles, then contrasts the performance of platinum/carbon composite electrodes within a hydrogen fuel cell. Functionalization by concentrated acid treatment results in the creation of various oxygen carrying functionalities on the otherwise inert carbon surfaces. The degree of surface functionalization is found to be a function of the functionalization treatment strength. Chemical reduction of the platinum precursor complex using milder reducing agents in the temperature range of 75-85 °C, and using ethylene glycol at 140 °C yields the smallest platinum particle sizes observed in this study, a result confirmed by X-ray diffraction and transmission electron microscopy measurements. X-ray photoelectron spectroscopy measurements confirm the existence of platinum in primarily its metallic state on the functionalized carbon surfaces.     

Grubbs催化剂及其在聚合物基复合材料自修复中应用

对格拉布(Grubbs)催化剂的结构及特性,催化对双环戊二烯的开环复分解聚合反应及其在自修复聚合物基复合材料中的应用开拓,进行了扼要的综述。     

Synthesis of ZSM-5/SAPO-11 composite and its application in FCC gasoline hydro-upgrading catalyst

This article describes the synthesis, characterization and application of a novel aluminosilicate/silicoaluminophosphate composite zeolite ZSM-5/SAPO-11. The composite was synthesized by the in situ overgrowth of SAPO-11 on ZSM-5 and was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared (FT-IR) spectrometry, N₂ adsorption and infrared spectroscopy of adsorbed pyridine. The results were compared with those of the mechanical mixture composed of individual ZSM-5 and SAPO-11. In the mechanical mixture, the ZSM-5 phase was morphologically separate from the SAPO-11 phase, while the ZSM-5/SAPO-11 composite existed in a form of a core-shell structure, with the ZSM-5 phase as the core and the SAPO-11 phase as the shell. Compared with the mechanical mixture, the composite had more mesopores and moderate acidity distribution, which could accelerate the diffusion of substances and enhance the synergetic effect between Brönsted and Lewis acids. The comparison of the catalytic performances of the mechanical mixture and the composite-based Ni–Mo catalysts for FCC gasoline hydro-upgrading showed that, due to the above advantages of the composite, the corresponding catalyst yielded improved gasoline research octane number, high liquid yield, good desulfurization activity and lower coke amount and thus could be considered as a potential catalyst system for hydro-upgrading FCC gasoline.     

Gold microspheres with hierarchical structure/conducting polymer composite film: Preparation, characterization and application as catalyst

Monodisperse gold microspheres with novel hierarchical structure and their composite integrated with a conducting film obtained from a new conducting copolymer, poly(acrylonitrile-co-vinyl acetate) -graft- poly(3,4-ethylenedioxythiophene), have been successfully prepared in one step via the in-situ reduction of AuCl₄^- on the conducting film surface. The morphology and structure of the as-prepared composite film are characterized, and its catalytic effect on reduction of p-nitrophenol is investigated. By controlling the concentration of HAuCl₄ and the conductivity (or PEDOT content) of P(AN-co-VA)-g-PEDOT copolymer film, the amount and the size of gold microspheres can be effectively adjusted. It is suggested that the side poly(3,4-ethylenedioxythiophene) chains of the conducting copolymer play both reducing and structure-directing roles during the formation of Au microspheres with hierarchical structure.     

Immobilization of dendrimer-encapsulated platinum nanoparticles on pretreated carbon-fiber surfaces and their application for oxygen reduction

This paper reports the successful preparation of catalytic electrodes based on carbon-fiber paper modified with dendrimer-encapsulated platinum nanoparticles. The metallic nanoparticles were first synthesized from solution within generation-four hydroxyl-terminated PAMAM dendrimers, which serve as a carrier for their subsequent immobilization on the solid substrates. The carbon-fiber surfaces were activated by means of three alternative anodic pretreatments and then loaded with the dendrimer-metal nanocomposites by cycling of the carbon-electrode potential. The degree of oxidation of the carbon surface affects the anchoring of the dendritic material, the coverage of which is indicated by the electroactive area of the encapsulated platinum. The modified carbon-fiber surfaces pretreated by cyclic polarization are found to be electrocatalytic for the oxygen reduction reaction, presenting a good exchange-current density at low platinum loading.     

In-situ synthesis of MCM-41 on ceramic membranes and its application in transesterification as catalyst support for p-toluenesulfonic acid

In this study, a new kind of solid acid catalyst p-toluenesulfonic acid/MCM-41/ceramic membrane was synthesized by in situ synthesis and impregnation method, which has shown its favorable catalytic activity, as verified in the transesterification and catalyst characterization. The catalyst was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. The transesterification of palm oil and methanol results showed that p-toluenesulfonic acid/MCM-41/ceramic membrane had the highest catalytic activity with immersing p-toluenesulfonic acid solution concentration of 0.15 mol/L. Different operation parameters of the transesterification of palm oil with methanol, such as catalyst amount, catalytic mass ratio, reaction time, reaction temperature and methanol/palm oil molar ratio were investigated. Under the optimum conditions of 4 % of fresh catalyst (catalytic mass ratio is 4.37 %), 80 min of reaction time, reaction temperature of 120 °C and methanol to palm oil molar ratio of 12:1, a relatively high fatty acid methyl ester yield of 95.6 % was obtained.     

Synthesis and characterization of polypyrrole‐platinum composite for use as electrode material

Synthesis and characterization of polypyrrole (PPy) supported platinum by a simple method is reported in this study. The porous structure of PPy and its tendency for doping with acids prompted us to utilize this property to incorporate platinum by adsorption followed by reduction on the PPy matrix. Dispersed platinum electro catalyst on the conducting PPy support provides favorable reaction site for redox reactions in electrochemical devices such as hydrox fuel cell. The mesoporous matrix of PPy as revealed by FESEM could facilitate effective contact between the reactant gases and electro catalyst. The cauliflower like structure of the PPy matrix could enhance the electrochemical active surface area of the catalyst. The composite material is characterized by cyclic voltammetry (CV), polarization study, four probe technique, density and porosity study. The CV highlights the use of PPy‐Pt hybrid as a capacitor and the Tafel plot infers on the high exchange current density of the hybrid material. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Fabrication of polyoxometallate-modified gold nanoparticles and their utilization as supports for dispersed platinum in electrocatalysis

The usefulness of Keggin-type anions (PMo₁₂O₄₀³⁻) as both reducing, capping and activating agents during synthesis of polyoxometallate-modified gold nanoparticles is demonstrated here. Fabrication of gold nanoparticles stabilized with monolayer-type films of inorganic polyoxometallates (e.g. phosphododecamolybdates), Au-PMo₁₂, was achieved by treating an aqueous solution of gold precursor (HAuCl₄) with a solution of the partially reduced heteropolyblue molybdate. The choice of temperature strongly affected morphology and size of the resulting Au nanoparticles. The presence of strongly adsorbed molybdate-agents on surfaces of gold nanoparticles was evident from the independent infrared (FTIR by reflectance) and voltammetric experiments. Interfacial polymolybdate anions on Au prevent the particle agglomeration and support formation of the stable colloidal Au-PMo₁₂ solutions. They are colored due to existence of the plasmonic effect. The Au-PMo₁₂ nanoparticles typically had 30–40 nm diameters, and they were used as supports or carriers for dispersed catalytic platinum nanoparticles (of ca. 7–8 nm diameters). Polyoxometallates (PMo₁₂O₄₀³⁻) existing on gold surfaces could also interact with neighboring platinum centers thus acting as “linking” agents facilitating dispersion of Pt nanoparticles. Further, the phosphomolybdate adsorbates (on Au supports) are also likely to activate Pt sites (e.g. by providing reactive hydroxy groups) towards more efficient electrocatalytic oxidation of ethanol both under voltammetric and chronoamperometric conditions.     

CeO2的制备及其在催化剂载体中的应用研究进展

概述了 CeO₂的制备方法对其性能的影响以及CeO2在催化剂载体中的运用,指出 CeO₂独特的储放氧性能使其在氧化反应、甲醇裂解、重整及变换反应和氮氧化物的还原等反应过程中呈现了良好的载体功能;溶胶-凝胶法以及超临界干燥等方法可以制备大比表面积的载体 CeO₂。制约载体 CeO₂工业应用的因素在于其机械强度和耐热性。     

高性能PtNi合金催化剂构筑及其对甲醇电催化

以多壁碳纳米管（CNTs）为载体，H2PtCl6·6H2O为铂源、Ni(NO3)2·6H2O为镍源，硼氢化钠和乙二醇为还原剂，采用一锅法制备了一种PtNi/CNTs合金电催化剂。采用XRD、SEM、TEM、HR-TEM、XPS、ICP-OES和Raman对催化剂结构进行表征。采用循环伏安法（CV）、计时安培法（i-t）和CO溶出曲线法评价了催化剂的电化学活性与稳定性。结果表明，PtNi/CNTs对甲醇电催化氧化（MOR）反应具有优异的电催化性能，峰值电流和稳态电流分别是商业Pt/C的5.89倍和38.97倍，同时，PtNi/CNTs还表现出良好的稳定性，主要归因于碳纳米管独特的结构与双金属合金的协同效应。     

ZrO2-Al2O3催化剂载体的制备及应用

ZrO₂-Al₂O₃复合载体具有独特的性能，当其作为催化剂载体时，可通过与活性组分的相互作用改变活性组分的分散状态及活性相结构，从而改善催化剂的催化性能。介绍了ZrO₂-Al₂O₃复合载体的制备以及组织结构、物相、表面酸性和与活性组分的相互作用等性能，并重点介绍了其在加氢脱硫反应中的应用。     

A novel 12-molybdovanadate nanocluster: Synthesis,structure investigation and its application as an efficient heterogeneous sulfoxidation catalyst

Tetraethylammonium salt of a new Keggin-type 12-molybdovanadate nanocluster, [(C₂H₅)₄N]₄[VMo₁₂O₄₀] (1) was synthesized via reaction between sodium tungstate, ammonium vanadate and tetraethylammonium bromide in acidic medium. Compound 1 was characterized by X-ray crystallography, FT-IR, UV–Vis and cyclic voltammetry and then applied as an efficient heterogeneous catalyst to oxidation of various organosulfides to sulfoxides with H₂O₂ at room temperature with 81–100% conversion and 60–99% selectivity. Nanocluster 1 was also shown to display excellent recyclability – it can be reused more than 10 times.     

Synthesis of a graft copolymer from an ozonized polycarbonate and its application as a compatibilizer

The polycarbonate (PC)/polystyrene (PS) blend is an immiscible system. The use of copolymers as compatibilizers in blends is one approach that is being developed within the larger field of polymer alloys. In this study, PC was ozonized to create peroxides and hydroperoxides on the polymer chain. These functional groups under heating conditions were used to initiate the radical polymerization of styrene (vinyl monomers) to give graft copolymers. The first part of this study was dedicated to the examination of the kinetics of the styrene polymerization initiated by an ozonized PC. However, the structure of the graft copolymers was confirmed by IR spectroscopy, and the molecular weight of the PS graft chain was determined by gel permeation chromatography. The compatibilized bends were prepared by melt blending in an internal mixer. The morphologies of the PC/PS/graft copolymer blend were examined by transmission electron microscopy and were finer than those of an uncompatibilized blend. The tensile properties of these blends were also investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of nanoporous platinum thin films and application as hydrogen sensor

A nanoporous platinum (np-Pt) thin film based hydrogen sensor was fabricated and studied. The np-Pt thin films were fabricated through a method of chemical dealloying and coarsening starting from a CuPt alloy. The alloy thin films of Cu_xPt_1?x were deposited by sputtering copper and platinum at the same time. The dealloying process completely removed the copper from the film. We demonstrate a method to control the porosity of np-Pt by a method of coarsening. Scanning electron microscopy confirmed the presence of porosity with size ranging from a few nanometers to tens of nanometers. A sensor device with four electrodes was fabricated on the np-Pt thin films using a stainless steel mask and by sputtering copper. The electrical characteristics of the sensor exhibit marked sensitivity or current changes in the presence of hydrogen. The results demonstrate that np-Pt thin films configured as a gas sensor have high sensitivity to hydrogen.     

Synthesis and characterization of a bisbenzotriazole derivative and its application in PVC as an ultraviolet absorber

A novel ultraviolet (UV) absorber, 5,5′‐disulfide‐bis[2‐(2‐hydroxy‐3,5‐di‐tert‐butylphenyl)‐2Hbenzotriazole] (DSBHTBB) was synthesized. Its structure was characterized by FTIR, NMR, UV, FABMS, and elemental analysis. In comparison with the common commercial benzotriazole UV absorbers, the absorption maximum of DSBHTBB (364 nm) is red shifted by about 20 nm, and the molar extinction coefficient (56,800, in CHCl₃) is much greater. With those properties the bisbenzotriazole could be applied as an efficient UV absorber for the protection of polymeric materials and sensitive skin from longer‐wavelength (near‐visible) ultraviolet light. The experimental results showed that DSBHTBB can greatly inhibit the discoloration under irradiation of poly (vinyl chloride) (PVC) containing an organic antimony stabilizer. J. VINYL ADDIT. TECHNOL., 13:195–200, 2007. © 2007 Society of Plastics Engineers     

Electro-synthesis of novel nanostructured PEDOT films and their application as catalyst support

Poly(3,4-ethylenedioxythiophene) (PEDOT) films doped with nitric and chlorine ions have been electrochemically deposited simply by a one-step electrochemical method in an aqueous media in the absence of any surfactant. The fabricated PEDOT films were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results indicate that the hierarchical structured PEDOT film doped with nitric ions displays a 'lunar craters' porous morphology consisting of PEDOT nano-sheets with a thickness of less than 2 nm. The effect of counter ions on the electro-polymerization, the electrochemistry, and the morphology of the polymer film was studied. Compared with PEDOT film doped with nitric acid, PEDOT film deposited in the presence of chlorine ions shows irregular morphology and less electrochemical activity. The specific nanostructure of the polymer was further studied as catalyst support for platinum nanoparticles to methanol electro-oxidation.     

Synthesis of novel CuS with hierarchical structures and its application in lithium-ion batteries

Novel sphere-like CuS hierarchical structures are fabricated by solvothermal approach without any surfactant and template. SEM and TEM characterizations show that the CuS sphere-like structures are composed of tens to hundreds of well-arranged and self-assembled nanoplates with a thickness of about 20 nm. The effects of dosage of CuCl₂•6H₂O, temperature and reaction time on the morphology of the products are systematically investigated and the results indicate that the CuS sphere-like hierarchical structures can only be obtained under certain experimental conditions. The possible formation mechanism of the CuS hierarchical structures is proposed. In addition, the possibility of using CuS as the electrode material for lithium ion batteries is studied.     

Synthesis and characterization of Ti(Tbse)2 and its application as a catalyst for ROP of rac‐Lactide

A novel bis(3,5‐di‐ tert‐butylsalicylaldehyde‐co‐ethanolamine) titanium(IV) complex (Ti(Tbse)₂) was synthesized and structurally characterized. The X‐ray diffraction results showed that the titanium ion was bonded with two 3,5‐di‐tert‐butylsalicylaldehyde‐co‐ethanolamine ligands (Tbse ligands) in O,N,O‐tridentate mode. Experimental results revealed that the Ti(Tbse)₂ complex could efficiently catalyze the ring‐opening polymerization (ROP) of rac‐lactide and showed a well‐controlled manner at 160 °C, and the polymers obtained had a controlled molecular weight and low polydispersity indices. Kinetic studies showed that the polymerization reaction was second order in monomer concentration and first order in catalyst concentration, and the apparent activation energy (E_a = 77.0 kJ mol^?1) and frequency factor (A = 3.3 × 10¹¹) were obtained according to the Arrhenius equation. ¹³C nuclear magnetic resonance spectra and thermogravimetric and differential scanning calorimetry analysis indicated that the polylactide was essentially a heterotactic and thermally stable polymer. Copyright © 2012 Society of Chemical Industry