Layered MoS2@graphene functionalized with nitrogen-doped graphene quantum dots as an enhanced electrochemical hydrogen evolution catalyst

Layered MoS₂@graphene functionalized with nitrogen-doped graphene quantum dots (MoS₂@NGQDs-GR) was obtained by one-pot hydrothermal method, as an enhanced electrochemical hydrogen evolution catalyst.     

Molybdenum-doped titanium dioxide supported low-Pt electrocatalyst for highly efficient and stable hydrogen evolution reaction

The Platinum(Pt)-based catalysts exhibit excellent catalytic performance for the hydrogen evolution reaction(HER) while suffering from poor stability due to the weak interaction between the carbon support and Pt.Herein,a molybdenum-doped titanium dioxide(Ti_(0.9)Mo_(0.1)O_2) supported low-Pt electrocatalyst with stronger interaction between catalyst and support is applied to tune the electrocatalytic performance of Pt.The Ti_(0.9)Mo_(0.1)O_2 support can not only tolerate the corrosion environment in the catalytic system,but also generate strong metal-support inte raction(SMSI) between the oxide and catalyst.A facile solvothermal method is used to prepare Ti_(0.9)Mo_(0.1)O_2 as support to anchor Pt nanoparticles.The 5% Pt supported on Ti_(0.9)Mo_(0.1)O_2 catalyst exhibits 4.4-fold mass activity(MA) at an overpotential of 50 mV and higher stability than 20% Pt/C with only 1/4 Pt loading.The SMSI between the Ti_(0.9)Mo_(0.1)O_2 and Pt prevents the Pt aggregation to achieve excellent stability,and hydrogen spillover effect in the interface between Pt and support benefits the hydrogen production process.This work presents a novel sight for the fabrication and design of oxide supported catalysts in various catalytic system by reasonably employing support effect.     

Polyaromatic-terminated iron(ii) clathrochelates as electrocatalysts for efficient hydrogen production in water electrolysis cells with polymer electrolyte membrane

1. Download : Download high-res image (182KB)
2. Download : Download full-size image

     

高效稳定的Al~(3+)偶联多层Eosin Y敏化TiO_2光催化制氢体系研究

通过Al3+偶联制备了多层EosinY敏化的TiO2催化剂,其光催化制氢性能优于Fe3+偶联的催化剂.在水体系、甲醇-水体系中,以三乙醇胺(TEOA)作电子给体,采用原位载Pt,考察了催化剂在可见光(λ420nm)下的制氢活性与稳定性.结果表明,含水0.5%(体积分数)的体系、载铂量为1.0%时,显示了较高的活性和良好的稳定性,20h的平均量子效率为20.5%,转换数为220.较高的活性和稳定性初步归结于Al3+水解趋势较Fe3+小,且催化剂在甲醇中比在水中更稳定,进一步的研究正在进行中.     

三维百合花状的CoNi2S4作为先进的双功能电催化剂用于氢析出和氧析出反应

为简化电解水催化剂的合成过程和优化电解水操作系统, 双功能电解水催化剂的研究, 特别是在碱性条件下同时具有优异催化氢析出和氧析出反应性能的双功能电催化剂的研究尤为重要. 其中, 过渡金属硫化物, 特别是 CoNi 硫化物, 被报道有与氢化酶类似的催化活性中心, 从而具有优异的催化氢析出和催化氧析出反应性能. 虽然有关对过渡金属硫化物的研究很多, 但主要集中在具有一维纳米线和二维纳米片形貌结构的过渡金属硫化物. 不幸的是, 这些形貌结构的过渡金属硫化物在电催化过程中容易聚集和受限于电荷传输能力. 三维纳米结构的材料具有较大的比表面积以分布更多的活性位点和拥有良好的电子传输能力, 所以, 开发三维纳米结构的过渡金属硫化物材料可能是改进其催化电解水性能的一个好途径. 本文采用简单的两步水热法, 通过硫化合成的 CoNi 前体得到了长于泡沫镍上的三维百合花状的 CoNi2S4(Co-Ni2S4/Ni). 它只需要 54 mV 的过电位即可获得 10 mA cm-2的催化氢析出反应电流, 是最好的碱性催化氢析出反应电极材料之一. 它在驱动 100 mA cm-2的催化氧析出反应电流时也只需要 328 mV 的过电位. 另外, 把 CoNi2S4/Ni 分别作为阴极和阳极组装成双电极碱性水电解槽时, 它只需要 1.56 V 的电压即可获取 10 mA cm-2的催化全电解水电流并具有良好的催化全电解水稳定性.扫描电子显微镜、透射电子显微镜和 N2吸脱附曲线测试结果表明, 该三维百合花状的 CoNi2S4/Ni 的表面粗糙度高和拥有多孔特性. 多孔结构的 CoNi2S4/Ni 可提供更多可接触的催化活性位点, 也有利于催化过程中的电解质和生成的气体的扩散与传递. 交流阻抗图谱测试结果表明, CoNi2S4/Ni 具有良好的电子传输能力. 另外, 不同于前期对尖晶石结构的硫化物 AB2S4的研究结果, XPS 结果表明, CoNi2S4/Ni 中含有 Niб+和 Sб-活性物种, 表明 CoNi2S4具有与活性氢化酶类似的活 性中心. Niδ+和 Sδ-可分别作为氢氧根和质子的接收体, 协助促进吸附的水分子的分离, 从而提高材料的催化性能. 所以, Niδ+和 Sδ-活性物种的出现, 大比表面积的三维百合花状多孔结构和良好的电荷传输能力等特性集合于 CoNi2S4/Ni 上使得CoNi2S4/Ni 具有优异的催化氢析出和催化氧析出反应性能.     

An efficient homogeneous gold(I) catalyst for N-alkylation of amines with alcohols by hydrogen autotransfer

A new and highly efficient homogeneous [Ph₃PAuCl]/AgOTf catalytic system was developed in N-alkylation reaction of primary amines with alcohols through a hydrogen autotransfer process. This Au(I) catalytic system shows excellent selectivity for mono-alkylation of primary amines with benzyl alcohol under moderate temperature of 100 °C (only secondary amines as product). The possible mechanism of this hydrogen autotransfer reaction with the catalytic system was proposed.     

Bis-chelate tetracarbene palladium(II) complex as an efficient and recyclable catalyst precursor for Heck reaction

A homoleptic Pd(II) complex with two chelating di-N-heterocyclic carbene (NHC) ligands has been synthesized and its square planar molecular geometry has been determined by X-ray diffraction analysis. The complex proved to be an efficient catalyst having exceedingly high turnover number and good reusability in Heck reaction.     

消化污泥负载稳定高效非均相光Fenton催化材料的制备及性能优化(英文)

近年来,随着我国经济飞速发展和城市人口快速增长,城市污水排放量不断增加,市政污泥产生量也随之增大.市政污泥含有大量有毒有害物质,如寄生虫卵、致病菌、有机污染物和重金属等,若不进行妥善处理处置将会对环境造成严重的二次污染.传统的污泥处理处置方法如卫生填埋、露天堆放和土地利用等已经无法满足日趋严格的污泥处理处置标准,研发新的污泥资源化利用方法具有重要的环境意义和经济价值.本课题组前期以铁盐为前驱体通过简单步骤制备了以市政污泥为载体,污泥中的重金属为可见光光敏剂,铁氧化物为活性中心的稳定高效非均相光Fenton催化剂.此催化剂在制备过程中虽然已经充分利用了市政污泥中的所有成分,但是其中部分可生化的有机大分子物质在制备过程中被直接燃烧或碳化,从而造成能源流失和浪费.为了更加充分利用市政污泥中的有机物,在制备稳定高效催化剂的同时尽可能多地回收能源和资源,本文在前期研究基础上进行了如下改进和优化:(1)采用市政污泥厌氧消化后的消化污泥为载体,通过厌氧消化手段将其中可生化的有机物转化为沼气,相对于直接用市政污泥制备催化剂,减少了能量流失,更具有经济效益和环境意义;(2)通过改变焙烧温度(250,350,450,550,650和750°C)、铁盐类型((NH4)_2Fe(SO_4)_2,FeSO_4,FeCl_3和Fe(NO_3)_3)和铁盐添加量(0,0.5,1.0,1.5,2.0和3.0 mol/L)对所制得催化材料的性能进行优化.利用红外光谱、X射线衍射、扫描电子显微镜和电感耦合等离子体质谱法等手段对所制备光Fenton反应催化剂结构进行了表征.结果表明,以消化污泥为原料制备的催化材料具有多孔和较高的比表面积,保证了在反应过程中催化剂与H2O2和被降解物质充分接触.样品中Fe含量较高,主要是以α-Fe2O3或无定形铁化合物形式存在,并通过Si–O–Fe键结合在污泥载体上,从而保证了催化剂较多的活性位点和较高的稳定性,因此所制材料可用作稳定高效的光Fenton反应催化剂.以偶氮染料罗丹明B为模式污染物评价了所制催化剂对污染物的降解效果.结果表明,在焙烧温度和铁盐添加量一定时,以亚铁盐(即(NH4)_2Fe(SO_4)_2和FeSO_4)为前驱体所制催化剂性能明显优于以铁盐(FeCl_3和Fe(NO_3)_3)为前驱体的催化剂;以(NH4)_2Fe(SO_4)_2为前驱体且其添加量为1 mol/L,焙烧温度为350 oC时所制FAS-1-350催化剂具有较高的降解速率(0.308±0.016 min.1)和较低的Fe~(2+)溶出率(0.94±0.24 mg/L).在紫外光照射下FAS-1-350重复使用6次,其催化性能没有明显降低,证实该样品结构稳定,可重复利用,具有良好的应用前景.     

Mn-MOF@Pi composite: synthesis,characterisation and an efficient catalyst for the Knoevenagel condensation reaction

We have synthesised new Mn-MOF@Pi composite by encapsulation of piperidine in desolvated Mn-MOF and investigated its catalytic performance in Knoevenagel condensation reaction. The newly developed composite is compatible with various aromatic aldehydes and converting them to the desired Knoevenagel condensation products in good yields and selectivity. Furthermore, composite Mn-MOF@Pi is reusable and shows good catalytic activity than native MOF.     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

Novel cyclometallated Pd(II) and Pt(II) complexes with indole derivatives and their use as catalysts in Heck reaction

Several palladacycle and platinacycle complexes have been prepared from easily available or naturally occurring indole derivatives, such as gramine and related compounds. Dimeric complexes were obtained with Pd(OAc)₂, while Pt(DMSO)₂Cl₂ mainly afforded monomeric structures. A notable feature of these reactions was the formation of new M-C bonds between Pd or Pt and C-2 and C-3 of the indole ring. With ligands like 2-(2′-pyridyl)-1H-indoles, N-N metallacycles were generated instead: in fact new C-M bonds with the C-3 position could only form if N-substituted indoles were used. The reactivity of Pd dimeric complexes with PPh₃, sym-collidine and DMAP was explored to obtain monomeric complexes. Three such compounds were prepared, one of which was characterized by X-ray diffraction. Metathetical reactions were carried out to effect a ligand exchange replacing OAc with halide ions, with the aim to synthesize μ-Cl and μ-Br bridged structures. Turning to the synthesis of hetaryl complexes, functionalization of the C-2 position on the indole ring was achieved. These complexes were prepared by substitution reactions starting from gramine and/or its alkylammonium salts.     

以葡萄糖为电子给体光催化还原水制氢的研究

以葡萄糖为电子给体,研究了在M/TiO2(M=Pt,Pd,Au,Rh)催化剂上光催化还原水生成氢气的反应.重点考察了体系(或溶液)中溶解的气体和溶液的pH值对析氢速率的影响.实验结果表明,四种催化剂均能够有效地催化以葡萄糖为电子给体的光催化还原水制氢反应.溶液中溶解的一氧化碳和氧气对放氢反应有负面影响,析氢的最佳pH值约为5.本文还对可能的氧化反应机理进行了讨论,葡萄糖很可能经葡萄糖醛酸被氧化.     

Electrochemical performance of grown layer of Ni(OH)2 on nickel foam and treatment with phosphide and selenide for efficient water splitting

Active nanocomposites synthesized by the electrochemical approach play a vital role in energy generation, conversion, and storage technologies. Recently, scientists began to explore the use of earth-rich transition metal-based materials to replace precious metal-based catalysts. Transition metals (TMs) based nickel (Ni) and their pnictides compounds such as phosphides and selenides exhibit good activity for hydrogen evaluation reaction (HER) and the entire water electrolysis process. In this study, we first prepared Ni(OH)₂ and grown its layer on Ni foam (NF) and treated it with selenide (Se) and phosphide (P) then nickel-based selenide-phosphide catalyst (Ni–P–Se) was prepared by simultaneous selenization and phosphidation process for the first time. The as-obtained composite was then analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), elemental mapping and transmission electron microscope (TEM) means to study the composition, structure, and micro-morphology of materials. Furthermore, we also observed electrocatalytic water splitting activity using electrochemical cell. The results of electrochemical tests depicted that the selenization and phosphidation treatments significantly enhanced the electrocatalytic HER activity of the starting materials. The overpotentials required for Ni–P–Se to reach 10 ?mA ?cm^?2 and 100 ?mA ?cm^?2 were only 242 ?mV and 282 ?mV. The Tafel slope of Ni–P–Se is 151 ?mV dec^?1, which is lower than that of nickel phosphide, selenide, and hydroxide indicating that selenide-phosphide enhances the HER reaction kinetics of the material, which in turn increases hydrogen output rate as compared with previous studies.     

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres supported palladium complex as an efficient catalyst for Heck reaction

<正>Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres synthesized by suspension polymerization were used as supports for palladium catalyst.The results showed the novel magnetic catalyst can promote Heck reaction of aryl halides with acrylic acid efficiently without an inert atmosphere.In addition,the novel catalyst can be conveniently recovered by applying an external magnet and reused at least five times without significant loss of its activity.     

Synthesis,interaction with double-helical DNA and biological activity of new Pt(II) and Pd(II) complexes with phenylglycine

The mononuclear palladium(II) (1) and platinum(II) (2) complexes containing phenylglycine have been synthesized and characterized by elemental analysis, IR spectra, and ¹H NMR spectra. The structure of 1 was determined by X-ray diffractometry. The interaction between the complexes and fish sperm DNA (FS-DNA), adenosine-5′-triphosphate (ATP), and adenine (Ade) were investigated by UV absorption spectra, the interaction mode of the complex binding to DNA was studied by fluorescence spectra and viscometry. The results indicate that the two complexes have different binding affinities to DNA, complex 2 > complex 1. Gel electrophoresis assay demonstrates that the two complexes have the ability to cleave pBR322 plasmid DNA. Cytotoxicity experiments were carried out toward four different cancer cell lines, and 1 shows lower inhibitory efficiency than 2, consistent with the binding affinities towards DNA.     

Copper(I) complex covalently anchored on graphene oxide as an efficient and recyclable catalyst for Sonogashira reaction

In this study, the organosilane‐functionalized graphene oxide as a stabilizer was prepared by a facile one‐step silylation approach. [Cu(PPh₃)₃Cl] complex was successfully immobilized onto the graphene oxide surface through coordination interaction with organosilane ligand spacers. The supported catalyst showed enhanced catalytic performance toward Sonogashira reaction of aryl halides with phenylacetylene in water solvent compared with the homogeneous analogues, and it could be readily recycled and reused several times without discernible loss of its activity.     

Multi-wall carbon nanotube supported tungsten hexacarbonyl: an efficient and reusable catalyst for epoxidation of alkenes with hydrogen peroxide

Highly efficient epoxidation of alkenes with H₂O₂ catalyzed by tungsten hexacarbonyl supported on multi-wall carbon nanotubes (MWCNTs) modified with 1,2-diaminobenzene is reported. The prepared catalyst, [W(CO)₆@DAB-MWCNT], was characterized by elemental analysis, scanning electron microscopy, FT-IR, and diffuse reflectance UV-Vis spectroscopic methods. The prepared catalyst was applied as an efficient catalyst for green epoxidation of alkenes with hydrogen peroxide in CH₃CN. This heterogeneous metal carbonyl catalyst showed high stability and reusability in epoxidation without loss of its catalytic activity.     

Mn(III)-porphyrin/graphene oxide nanocomposite as an efficient catalyst for the aerobic oxidation of hydrocarbons

In this study, manganese porphyrin was grafted on the surface of graphene oxide nanosheets via covalent bonding to produce a heterogeneous catalyst. The prepared nanocomposite was characterized using X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. Atomic absorption spectroscopy was also used to determine the amount of the loaded catalyst. The catalytic efficiency of the immobilized Mn-porphyrin was investigated for the aerobic oxidation of alkenes and saturated alkanes in acetone under mild reaction conditions. The prepared heterogenized catalyst displays superior catalytic performance as compared to the homogeneous catalyst. Moreover, the excellent turnover number (more than 31,767) achieved for the oxidation of styrene indicates the high longevity of the supported catalyst. The catalyst structure is preserved well after the oxidation reaction and is simply reused at least five times, without any significant loss of the catalytic efficiency.     

Aluminium(III) trifluoromethanesulfonate as an efficient catalyst for the intramolecular hydroalkoxylation of unactivated olefins: experimental and theoretical approaches

The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.