炭负载Pd/Ce双金属催化剂对Heck反应的催化性能

通过简便的方法制备了炭负载Pd/Ce双金属催化剂,利用Pd/Ce双金属催化剂的协同效应提高催化剂对Heck反应的催化效率。 以碘苯与丙烯酸的Heck芳基化反应为模型反应,研究了反应条件对催化剂催化性能的影响。 结果显示,在反应温度为130 ℃,反应时间为5 h,N,N-二甲基甲酰胺(DMF)作为溶剂和三丁胺(Bu₃N)作为碱的条件下,炭负载Pd/Ce双金属催化剂对丙烯酸和碘苯的Heck芳基化反应具有良好的催化性能,产率达到70%以上。 另外,该催化剂属于非均相催化剂,催化剂易与反应溶液分离;也可以重复利用,使用3次反应产率仍达到66.9%,显示了炭负载Pd/Ce双金属催化剂良好的催化活性。     

碳负载钯催化剂对Heck反应的催化性能

研究了钯碳催化剂对芳基卤和取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应的催化性能.结果表明:在反应温度为80℃、反应时间为8h、四丁基溴化铵(TBABr)作为溶剂和三丁胺作为碱的条件下,钯碳催化剂对不同取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应具有良好的催化性能,产物收率在80%以上.     

多壁碳纳米管负载钯(II)催化剂催化Suzuki-Miyaura反应的研究

多壁碳纳米管(MWNTs)负载钯(II)催化剂以乙醇/水(V/V=1∶1)混合溶液为溶剂,室温条件下,高效催化卤代芳烃与苯硼酸的Suzuki-Miyaura偶联反应。该催化剂绿色环保,能够在循环使用5次后仍有较好的稳定性。     

Preparation and application of SBA-15-supported palladium catalyst for Heck reaction in supercritical carbon dioxide

A new method for the preparation of SBA-15-supported palladium catalyst for Heck reaction in supercritical carbon dioxide was presented.The newly formed SBA-15-supported palladium catalyst（Ph-SBA-15-PPh₃-Pd） exhibited high catalytic activity for the Heck reaction of 4-nitrobromobenzene with methyl acrylate.The catalyst can be reused several times without a loss of activity.     

简便方法制备氮掺杂的碳球用作高效非金属氧还原催化剂（英文）

随着人们环保意识的不断增强,社会对清洁能源的需求也日益增加.燃料电池具有效率高,燃料来源丰富,可直接将化学能转化成电能且污染小等优点,因而受到了广泛关注.然而,燃料电池的阴极氧还原反应(ORR)速率较慢,成为提高燃料电池整体效率的制约因素.因此,开发高性能的ORR催化剂,加快ORR反应速率具有非常重要的意义.目前,Pt基催化剂被认为是活性最好的商用ORR电催化剂.尽管此类催化剂具有较高的催化活性和良好的稳定性,但Pt的储量有限,价格高昂,抗燃料毒化性能差,限制了其大规模应用.近年来,为了减小Pt的用量,降低催化剂成本,人们除了致力于研究贵金属合金催化剂及非贵金属催化剂外,还把目光聚焦在了非金属催化剂,特别是碳及其复合材料的研究上.在众多碳材料中,碳球因具有良好的表面渗透性和较高的机械稳定性而被广泛应用于催化、吸附、药物输送和能量存储及转化等领域中.然而,碳球的表面化学惰性较强,比表面积较低,使其部分应用受到了限制.因此,人们采用了多种方法来调控碳球的物理化学性质.其中,向碳材料中掺入杂原子,尤其是氮原子的方法广受青睐.因为杂原子的掺入会显著增强作为主体的碳原子给电子的能力和表面吸附性质,从而对ORR表现出优异的催化活性和稳定性.本文以蔗糖作为碳源,三聚氰胺作为氮源,采用水热法及高温热解法制备了一系列氮掺杂的生物质碳球.并对氮掺杂量及热解温度进行了优化.结果表明,石墨化程度及石墨氮含量的提高,能有效地提高催化剂的活性.在优化了的条件下得到的催化剂N0.1C1.9S-900,表现出了比商业Pt/C催化剂更好的ORR催化性能.在0.1 mol/L KOH中,该催化剂催化ORR的起始电位和半波电位分别为–22.6和–133.6 mV(vs.Ag/AgCl),极限电流密度为4.6 mA/cm~2,分别比商业Pt/C高出7.2 mV,5.9 mV和0.2 mA/cm~2.同时,在经过30000 s的稳定性测试中,N0.1C1.9S-900催化剂的电流损失也远低于Pt/C,表明该催化剂具有良好的稳定性.此外,在抗甲醇毒化实验中,相比于商业Pt/C,N0.1C1.9S-900催化剂对甲醇有更好的耐受性.另外,该催化剂催化的ORR属于高效的4e~–途径.可见,该催化剂作为燃料电池的阴极氧还原反应催化剂具有广阔的前景.     

One step NaBH4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

The ternary catalyst Pt₇₅Ru₅Ni₂₀ was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt₇₅Ru₅Ni₂₀/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.     

Cobalt Incorporated Graphitic Carbon Nitride as a Bifunctional Catalyst for Electrochemical Water-Splitting Reactions in Acidic Media

Non-noble metal-based bifunctional electrocatalysts may be a promising new resource for electrocatalytic water-splitting devices. In this work, transition metal (cobalt)-incorporated graphitic carbon nitride was synthesized and fabricated in electrodes for use as bifunctional catalysts. The optimum catalytic activity of this bifunctional material for the hydrogen evolution reaction (HER), which benefitted at a cobalt content of 10.6 wt%, was promoted by the highest surface area and conductivity. The activity achieved a minimum overpotential of ~85 mV at 10 mA/cm² and a Tafel slope of 44.2 mV/dec in an acidic electrolyte. These values of the HER were close to those of a benchmark catalyst (platinum on carbon paper electrode). Moreover, the kinetics evaluation at the optimum catalyst ensured the catalyst flows (Volmer–Heyrovsky mechanism), indicating that the adsorption step is rate-determining for the HER. The activity for the oxygen evolution reaction (OER) indicated an overpotential of ~530 mV at 10 mAcm⁻² and a Tafel slope of 193.3 mV/dec, which were slightly less or nearly the same as those of the benchmark catalyst. Stability tests using long-term potential cycles confirmed the high durability of the catalyst for both HER and OER. Moreover, the optimal bifunctional catalyst achieved a current density of 10 mAcm⁻² at a cell voltage of 1.84 V, which was slightly less than that of the benchmark catalyst (1.98 V). Thus, this research reveals that the present bifunctional, non-noble metallic electrocatalyst is adequate for use as a water-splitting technology in acidic media.     

Synthesis of Biphenyl-Based Ligand: Application in Copper-Mediated Chemoselective Michael Reaction

A biphenyl-based ligand attached was synthesized and screened in copper-mediated Michael reaction. The catalyst system works well with carbon or sulfur nucleophiles as Michael donors and cyclohexenone or chalcones as the acceptors under mild and neutral reaction conditions in a chemoselective manner.     

聚偏二氯乙烯负载金鸡纳碱催化剂的合成及其对不对称Michael反应的催化性能

将天然的金鸡纳碱——辛可宁与聚偏二氯乙烯进行接枝反应,制备了聚偏二氯乙烯负载辛可宁的催化剂.将制备的催化剂用于催化不对称Michael反应,并探索了溶剂、催化剂用量、温度、底物等不同条件对其催化性能的影响.结果表明,该催化剂在甲苯中有很高的催化活性和较好的立体选择性,Michael反应中部分产率达到80%以上,e.e值达到72%,且该催化剂具有一定的重复使用性能.     

高效的尖晶石铁钴氧/氮掺杂有序介孔碳催化剂应用于可充电锌-空气电池

以电催化为核心的新能源储存和转换技术为缓解能源与环境问题提供了有效手段.可充电锌空气电池因其理论能量密度(1086 Wh·kg–1)高、成本效益显著、安全系数高、环境友好及放电平稳等优点被认为是一种具有前景的能源存储/转换装置,有望在新能源汽车、便携式电源等领域广泛应用.氧还原反应(ORR)和氧析出反应(OER)是锌-空气电池中的核心反应,目前,虽然贵金属催化剂对上述反应表现出一定的电催化活性,但由于其稀缺性、高昂价格和低稳定性因素严重阻碍了它们在锌-空气电池中的广泛应用.而非贵金属催化剂所面临的瓶颈在于ORR/OER反应动力学缓慢,导致其在实际应用过程中存在电压效率低和催化剂腐蚀等问题.因此,为了推进锌-空气电池商业化进程,研制低成本、高效、稳定的非贵金属催化剂迫在眉睫.本文通过一步法将双金属前驱体嵌入氮掺杂有序介孔碳(NOMC)中,合成了具有尖晶石型铁钴氧化物的高性能非贵金属电催化剂(FexCo/NOMC,x代表铁钴的摩尔比).实验结果表明,在x=0.5时,所制备的催化剂具有最佳的催化活性,与商业贵金属催化剂相比,该催化剂展现更优的电催化活性和稳定性.电化学测试结果表明,其ORR的半波电位为0.89 V(vs.RHE),当OER电流密度为10 mA·cm–1时,过电势仅为0.31 V,且电流-时间曲线测试结果表明催化剂表现出较好的稳定性.通过X射线光电子能谱(XPS)、穆斯堡尔谱(M?ssbauer)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉曼光谱(Raman)等表征手段对电催化剂的物化性质进行表征,结果表明该材料优异的氧电催化性能归因于双金属氧化物的电子调控作用、NOMC的介孔结构、高导电性和高比表面积,其ORR与OER的催化活性位点分别是氮活化的碳(N-C)和双金属氧化物.以优化的Fe0.5Co/NOMC为正极组装可充电锌-空气电池,该电池在空气环境下展现出优良的充放电性能,其在电流密度为100 mA·cm–2条件下操作时能量密度达到820 Wh·kg–1,在1.0 V时功率密度达到153 mW·cm–2,它还表现出较好的稳定性,经过144 h的循环实验,活性没有明显下降.本文不仅制备了一种有前景的尖晶石型氧化物碳基氧电催化材料,还为高效氧电催化剂的合理开发与构筑提供了一条新的思路.     

New strategy for reversal tolerant anode for automotive polymer electrolyte fuel cell

New approach for the reversal tolerant anode for polymer electrolyte membrane fuel cell is suggested by using the multifunctional IrRu alloy catalyst having concurrent superior activities towards hydrogen oxidation reaction and oxygen evolution reaction to mitigate the degradation of anode under the fuel starvation condition.     

N,P-co-Doped Graphdiyne as Efficient Metal-free Catalysts for Oxygen Reduction Reaction

The carbon-based metal-free catalyst is one of the ideal alternatives to Pt as electrocatalysts for oxygen reduction reaction,which can reduce the cost of fuel cells and zinc-air batteries.Here,graphdiyne(GDY),a carbon material with uneven charge distribution,was used as substrate.By doping nitrogen and phosphorus,a N-P-GDY catalyst was prepared,which further regulated the electron structure of GDY.The sheet-like morphology of GDY was preserved in N-P-GDY.The N and P were distributed uniformly in the catalyst,whereas defects and active sites were created by doping N and P,as demonstrated by the element mapping images and Raman spectra.X-Ray photoelectron spectroscopy results indicated N and P existed in many forms in N-P-GDY.The N-P-GDY exhibited higher activity for ORR than only N or P doped GDY,due to the synergistic effect of N and P in N-P-GDY.Moreover,the activity of N-P-GDY changed little after a long time cyclic voltammetry test or injecting methanol in the electrolyte.Besides,the four electrons transfer reaction to produce water was the main process for ORR on N-P-GDY catalysts.     

铜系催化剂上甲醇蒸气转化制氢过程的原位红外研究

 用原位红外光谱法跟踪研究了不同条件下铜系催化剂上甲醇蒸气转化制氢反应的初始开车过程．结果表明，反应过程中二氧化碳不是在一氧化碳之后产生的．可以推断，铜系催化剂上的甲醇蒸气转化制氢过程不是先进行甲醇分解为一氧化碳和氢气，然后一氧化碳和水蒸气发生变换反应生成二氧化碳和氢气．甲醇蒸气转化反应的主要过程是甲醇和水直接生成二氧化碳和氢气．     

介孔结构Fe/N/C作为质子交换膜燃料电池氧还原催化剂

燃料电池具有高效、低排放等优势,非常有希望作为未来电动汽车的能源转化装置.目前,燃料电池的商业化受制于昂贵的铂基催化剂,特别是动力学迟缓的阴极氧还原反应(ORR)铂催化剂. Fe/N/C被认为是最有潜力的ORR非贵金属催化剂,但其活性仍远低于Pt催化剂,必须依靠增加载量来弥补其与Pt催化剂的活性差距.然而,较厚的催化层(~100mm)会降低阴极传质速率.因此,改善Fe/N/C阴极的传质是提高电池性能的重要途径.
　　本文选择高N含量的2-氨基苯并咪唑(ABI)为氮源,通过水热聚合包覆在碳黑表面,然后掺入FeCl3,经高温热解/酸洗制备了Fe/N/C-ABI催化剂,并与基于间苯二胺的微孔型Fe/N/C催化剂(Fe/N/C-PmPDA)进行比较. Ar等温吸附-脱附结果表明, Fe/N/C-ABI催化剂具有较高的比表面积(662 m2/g)和丰富的双级孔结构(微孔和介孔);透射电镜表征显示Fe/N/C-ABI催化剂具有中空结构,介孔孔径大约为10–25 nm.而Fe/N/C-PmPDA催化剂具有相当的比表面积(656 m2/g),但以微孔为主,基本不含介孔.旋转环圆盘电极(RRDE)测试表明,在0.1 mol/L H2SO4溶液中, Fe/N/C-ABI催化剂的起始还原电位为0.92 V,在0.8 V电位下质量电流密度可达9.21 A/g;而Fe/N/C-PmPDA催化剂具有相近的起始电位,但具有更高的催化活性,质量电流密度为13.4 A/g.氢氧燃料电池(PEMFC)系统测试结果表明, Fe/N/C-ABI催化剂在1个背压和80oC测试条件下的最大功率密度达710 mW/cm2,高于Fe/N/C-PmPDA催化剂(616 mW/cm2).燃料电池与RRDE测试活性顺序的差异归结于Fe/N/C-ABI的中空球状结构. PEMFC工作时阴极会产生大量的水,很容易堵塞氧气传输通道. Fe/N/C-ABI的介孔结构可以作为水的产生和排除的缓存空间,也有利于提高O2传质,从而提高燃料电池性能.本文为具有高传质速率的Fe/N/C催化剂研制提供了一种新思路.     

Methane Decomposition into Carbon Fibers over Coprecipitated Nickel-Based Catalysts

Decomposition of methane in the presence of coprecipitated nickel-based catalysts to produce carbon fibers was investigated. The reaction was studied in the temperature range of 773 K to 1073 K. At 1023 K, the catalytic activities of three catalysts kept high at the initial period and then decreased with the reaction time. The lifetimes of Ni-Cu-Al and Ni-La-Al catalysts are longer than that of Ni-Al catalyst. With three catalysts, the yield of carbon fibers was very low at 773 K. The yield of carbon fibers for Ni-La-Al catalyst was more than those for Ni-Al and Ni-Cu-Al catalysts. For Ni-La-Al catalyst, the elevation of temperature from 873 K up to 1073 K led gradually to an increase in the yield of carbon fibers. XRD studies on the Ni-La-Al catalyst indicate that La2NiO4 was formed. The formation of La2NiO4 is responsible for the increase in the catalytic lifetime and the yield of carbon fibers synthesized on Ni-La-Al at 773 1073 K. Carbon fibers synthesized on Ni-Al catalyst are thin, long carbon nanotubes. There are bamboo-shaped carbon fibers synthesized on Ni-Cu-Al catalyst. Carbon fibers synthesized on Ni-La-Al catalyst have large hollow core, thin wall and good graphitization.     

N-Doped porous carbon supported palladium nanoparticles as a highly efficient and recyclable catalyst for the Suzuki coupling reaction

A new catalyst, Pd particles supported on the N-doped porous carbon(PC) derived from Zn-based metal–organic frameworks(zeolitic imidazolate framework: ZIF-8), was successfully prepared for the first time.The as-prepared catalyst was designated as N-doped PC-Pd, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, N_2 adsorption and inductively coupled plasma atomic emission spectroscopy. The N-doped PC-Pd composite exhibited high catalytic activity toward the Suzuki–Miyaura cross-coupling reactions. The yields of the products were in the range of 90%–99%. The catalyst could be readily recycled and reused at least 6 consecutive cycles without a significant loss of its catalytic activity.     

Carbon-Based Material-Supported Palladium Nanocatalysts in Coupling Reactions: Discussion on their Stability and Heterogeneity

Scientific interest in carbon-based materials (CBMs) has grown dramatically over the past few decades. Due to a variety of atomic orbital hybrid forms (sp, sp² and sp³ hybridization), carbon can form a variety of materials with diverse structures and characteristics. CBMs used as efficient catalyst supports show extensive promise in organic reactions, which is attributed to their structural similarity with organics, large specific surface area, chemical stability, and photocatalytic properties. This review presents the synthesis of CBM-supported palladium nanocatalysts based on impregnation, template methods, etc. The CBMs include activated carbon (AC), graphene, carbon nanotubes (CNTs), and their functionalized products, as supports for improving the activity and recyclability of simple Pd nanocatalysts. After surveying the literature where these catalysts have been utilized for carbon–carbon coupling reactions, there is a particular emphasis on Suzuki, Heck, and Sonogashira reactions. The catalytic mechanism of these Pd nanocatalysts (surface heterogeneous catalysis or homogeneous catalysis caused by Pd leaching) is discussed in detail, especially the effect of Pd leaching on the stability of the catalyst.     

Simultaneous soot combustion and NOx reduction over a vanadia-based selective catalytic reduction catalyst

Simultaneous NO_x reduction and soot combustion over a commercial vanadia-based selective catalytic reduction (SCR) catalyst were investigated. Carbon black was used as model soot. The impact of the contact intensity between carbon and catalyst was studied. The experiments appeared as promising results for the utilization of vanadia-based SCR catalysts in SCR on filter system as, in the SCR operating temperature range (250–400 °C), no significant impact of the presence of carbon black on NO_x reduction was observed. However, a decrease in the specific carbon oxidation rate was highlighted. This latter increases with the contact between carbon and catalyst and is attributed to a lack of NO₂, consumed by the fast SCR reaction. At temperatures greater than 400 °C, the contact between carbon particles and the SCR catalyst partially inhibits the NO_x reduction, whereas it exhibits a catalytic effect on the carbon oxidation rate. The tighter the contact between the two materials, the more significant is this behavior. A redox mechanism, which competes with the redox cycle of the SCR mechanism, was proposed. The impregnation of a V-based SCR catalyst with 2 wt % of calcium was also performed. A drastic loss of DeNO_x activity was observed, whereas the effect of the contact between carbon and catalyst was reduced.     

固载超强酸催化剂制备及催化合成乙酸正丁酯的研究

研究了把稀土硫酸盐,分别固载于人工沸石、活性炭和强酸型阳离子树脂作为酯化催化剂,从中选出了较好的酯化催化剂－强酸型阳离子树脂固载稀土催化剂,此催化剂用于合成乙酸正丁酯,产率达到97.24%,并对催化剂的催化性能进行了讨论。     

Bottom‐Up Fabrication of a Sandwich‐Like Carbon/Graphene Heterostructure with Built‐In FeNC Dopants as Non‐Noble Electrocatalyst for Oxygen Reduction Reaction

High‐performance non‐noble electrocatalysts for oxygen reduction reaction (ORR) are the prerequisite for large‐scale utilization of fuel cells. Herein, a type of sandwiched‐like non‐noble electrocatalyst with highly dispersed FeN_x active sites embedded in a hierarchically porous carbon/graphene heterostructure was fabricated using a bottom‐up strategy. The in situ ion substitution of Fe³⁺ in a nitrogen‐containing MOF (ZIF‐8) allows the Fe‐heteroatoms to be uniformly distributed in the MOF precursor, and the assembly of Fe‐doped ZIF‐8 nano‐crystals with graphene‐oxide and in situ reduction of graphene‐oxide afford a sandwiched‐like Fe‐doped ZIF‐8/graphene heterostructure. This type of heterostructure enables simultaneous optimization of FeN_x active sites, architecture and interface properties for obtaining an electron‐catalyst after a one‐step carbonization. The synergistic effect of these factors render the resulting catalysts with excellent ORR activities. The half‐wave potential of 0.88 V vs. RHE outperforms most of the none‐noble metal catalyst and is comparable with the commercial Pt/C (20 wt %) catalyst. Apart from the high activity, this catalyst exhibits excellent durability and good methanol‐tolerance. Detailed investigations demonstrate that a moderate content of Fe dopants can effectively increase the intrinsic activities, and the hybridization of graphene can enhance the reaction kinetics of ORR. The strategy proposed in this work gives an inspiration towards developing efficient noble‐metal‐free electrocatalysts for ORR.