BEHAVIOR OF SUPPORTED NANO-COPPER CATALYST IN CO OXIDATION

IntroductionNanomaterialisanewkindofmaterialwithparticlesizebetWeenIurnand100urn.Becauseofthesmallparticlesizeandthelargespecificsufficearea,nanomaterialpossessesmanyparticularproperties,suchashighersufficeenergyandhighersurfaceactivity.t.[l]Thehigheracti…     

Clean Synthesis of an Economical 3D Nanochain Network of PdCu Alloy with Enhanced Electrocatalytic Performance towards Ethanol Oxidation

A one‐pot method for the fast synthesis of a 3D nanochain network (NNC) of PdCu alloy without any surfactants is described. The composition of the as‐prepared PdCu alloy catalysts can be precisely controlled by changing the precursor ratio of Pd to Cu. First, the Cu content changes the electronic structure of Pd in the 3D NNC of PdCu alloy. Second, the 3D network structure offers large open pores, high surface areas, and self‐supported properties. Third, the surfactant‐free strategy results in a relatively clean surface. These factors all contribute to better electrocatalytic activity and durability towards ethanol oxidation. Moreover, the use of copper in the alloy lowers the price of the catalyst by replacing the noble metal palladium with non‐noble metal copper. The composition‐optimized Pd₈₀Cu₂₀ alloy in the 3D NNC catalyst shows an increased electrochemically active surface area (80.95 m² g^?1) and a 3.62‐fold enhancement of mass activity (6.16 A mg^?1) over a commercial Pd/C catalyst.     

Catalytic CO Oxidation by O2 Mediated by Noble‐Metal‐Free Cluster Anions Cu2VO3–5−

Catalytic CO oxidation by molecular O₂ is an important model reaction in both the condensed phase and gas‐phase studies. Available gas‐phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O₂ under thermal collision conditions. Herein, we identified the first example of noble‐metal‐free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu₂VO_3–5^? for CO oxidation by O₂. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu?Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O₂ activation during the catalysis.     

高活性Co3O4负载单原子Au催化剂室温催化CO氧化

CO低温氧化是多相催化领域研究最多的反应之一.作为简单、典型的探针反应,其不仅具有重要的基础研究价值,而且在环境污染消除等方面也有着非常重要的实际应用价值.金属氧化物如铜锰(Hopcalite)、铜铬复合氧化物以及氧化钴等都具有优异的低温CO氧化活性.然而氧化物催化剂热稳定性低、反复启动性能差、以及对硫化物、水等物质敏感,严重制约了其实际应用.相对而言,负载型贵金属催化剂因具有较高的CO氧化活性、反应稳定性以及热稳定性而受到关注.但是贵金属价格昂贵、资源稀少,使其持续应用面临严峻挑战.为了提高贵金属利用效率、降低贵金属使用量,在负载型贵金属催化剂中,贵金属多以纳米尺度分散于高比表面载体上.由于多相催化一般在纳米粒子表面发生,只有表面金属原子能够接触到反应物,因而贵金属原子利用率仍然有待提高.最近本课题组成功开发以原子级分散的单原子催化剂并提出“单原子催化”的概念.后续研究以及其他研究人员相继证明氧化物负载贵金属单原子具有高活性和/或不同于纳米粒子的反应性能,表明开发单原子催化剂是最大化贵金属利用效率、降低贵金属用量的可行途径.对于CO氧化而言,目前普遍认为负载Au催化剂具有最高活性.然而负载Au单原子催化剂是否具有活性仍存争议：理论计算表明氧化物负载Au单原子催化剂具有很好的活性,但是缺少实验证据;目前已有一些氧化物负载Au正价离子催化剂的报道,结果也都表明Au单原子活性远低于纳米粒子或纳米团簇.最近本课题组发现氧化铁负载Au单原子不仅具有与Au纳米粒子相当的单位活性位(TOF)活性而且具有更高的单位金属重量(反应速率)活性以及非常高的反应稳定性.本文将载体拓展到氧化钴,开发了具有更高活性的氧化钴负载Au单原子催化剂, Au负载量仅为0.05 wt%即可在室温条件下实现CO完全转化. Co3O4载体用Co(NO3)3与Na2CO3通过共沉淀法制备,400 oC焙烧.然后通过简单的沉淀吸附法制备Co3O4负载Au单原子催化剂(Au1/Co3O4),确保Au单原子能够分散于载体的表面.具有原子分辨率的球差校正高分辨电镜照片显示Au原子确实以单原子形式分散于载体上.催化剂在第一个循环中活性并不非常高,但是在第二个循环中活性提高非常明显,可以在室温条件下实现CO全转化.为了弄清楚活性提高的原因,我们用惰性气体(He)、氧化性气体(5%O2/He)以及还原性气体(5%CO/He)对催化剂进行了热处理,但是活性提高并不明显.由此推断催化剂是在第一个循环反应过程中发生了某些变化,导致活性显著提高.空白载体实验表明Co3O4载体本身虽然具有反应活性,但是远不如负载少量Au原子活性高,表明Au原子或Au原子与载体一起起到高活性的作用.稳定性研究表明该催化剂在室温条件下容易失活,但经惰性气体或氧化气体处理后活性可恢复,表明不是结构性失活而是可逆失活,说明单原子非常稳定.     

Ionic‐Liquid‐Grafted Rigid Poly(p‐Phenylene) Microspheres: Efficient Heterogeneous Media for Metal Scavenging and Catalysis

Novel guanidinium ionic liquid‐grafted rigid poly(p‐phenylene) (PPPIL) microspheres have been developed for metal scavenging and catalysis. The noble‐metal nanoparticles supported on the microspheres surface can be used as efficient heterogeneous catalysts. The combination of nanoparticles and ionic liquid fragments on the microsphere surfaces enhance the activity and durability of the catalyst. The PPPIL ? Pd⁰ catalyst has been tested in the Suzuki cross‐coupling reaction, and exhibits much higher catalytic activity than Pd catalysts supported on porous polymer matrices. The PPPIL ? Pd⁰ catalyst can be recycled at least for nine runs without any significant loss of activity. The present approach may, therefore, have potential applications in transition‐metal‐nanocatalyzed reactions.     

Phase‐Contact Engineering in Mono‐ and Bimetallic Cu‐Ni Co‐catalysts for Hydrogen Photocatalytic Materials

Understanding how a photocatalyst modulates its oxidation state, size, and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physicochemical techniques and probes employed to study them. A synchrotron micro‐beam X‐ray absorption spectroscopy study together with the computational simulation and analysis (at the X‐ray cell) of the light‐matter interaction occurring in powdered TiO₂‐based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non‐noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu‐Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials.     

Controlling carbon monoxide emissions from automobile vehicle exhaust using copper oxide catalysts in a catalytic converter

Carbon monoxide (CO) is a very poisonous gas present in the atmosphere. It has significant effects on human beings, animals, plants and the climate. Automobile vehicle exhaust contributes 64% of the CO pollution in urban areas. To control this exhaust pollution, various types of catalysts in catalytic converters have been investigated. Increasing costs of noble metals as a catalyst in automobile vehicles motivates the investigation of material that can be substituted for noble metals. Among the non-noble metals, copper (Cu) is found to be the most capable and highly active catalyst for CO oxidation, compared to precious metal catalysts. Lower cost, easy availability and advance preparation conditions with stabilizers, promoters and so on, make Cu a good choice as an auto exhaust purification catalyst. The oxidation of CO proceeds very quickly over Cu°, followed by Cu⁺ and Cu²⁺. The Cu₂O catalyst is more active in an O₂-rich atmosphere than in O₂-lean conditions. The reduced species of copper (Cu⁰, Cu⁺) are essential for better CO oxidation but smaller Cu particles could be less active than the higher ones. There is a great deal of research available on the Cu catalyst for CO oxidation, but there is a gap in the literature for a review article individually applied to the Cu catalyst for CO oxidation. To fill this gap, the present review updates information on Cu catalysts in the purification of exhaust gases.     

Titanium Dioxide‐Grafted Copper Complexes: High‐Performance Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathodes of fuel cells significantly hampers fuel cell performance. Therefore, the development of high‐performance, non‐precious‐metal catalysts as alternatives to noble metal Pt‐based ORR electrocatalysts is highly desirable for the large‐scale commercialization of fuel cells. TiO₂‐grafted copper complexes deposited on multiwalled carbon nanotubes (CNTs) form stable and efficient electrocatalysts for the ORR. The optimized catalyst composite CNTs@TiO₂–ZA–[Cu(phen)(BTC)] shows surprisingly high selectivity for the 4 e^? reduction of O₂ to water (approximately 97 %) in alkaline solution with an onset potential of 0.988 V vs. RHE, and demonstrates superior stability and excellent tolerance for the methanol crossover effect in comparison to a commercial Pt/C catalyst. The copper complexes were grafted onto the surface of TiO₂ through coordination of an imidazole‐containing ligand, zoledronic acid (ZA), which binds to TiO₂ through its bis‐phosphoric acid anchoring group. Rational optimization of the copper catalyst’s ORR performance was achieved by using an electron‐deficient ligand, 5‐nitro‐1,10‐phenanthroline (phen), and bridging benzene‐1,3,5‐tricarboxylate (BTC). This facile approach to the assembly of copper catalysts on TiO₂ with rationally tuned ORR activity will have significant implications for the development of high‐performance, non‐precious‐metal ORR catalysts.     

Copper‐Mediated C6‐Selective Dehydrogenative Heteroarylation of 2‐Pyridones with 1,3‐Azoles

A copper‐mediated C6‐selective dehydrogenative heteroarylation of 2‐pyridones with 1,3‐azoles has been developed. The reaction proceeded smoothly by twofold C? H cleavage even in the absence of noble‐metal catalysts. The observed site selectivity was directed by a pyridyl substituent on the nitrogen atom of the pyridone ring. This directing group was readily removed after the coupling event, thus leading to 2‐pyridone derivatives with a free N? H group. Moreover, in some cases, catalytic turnover of the Cu salt was also possible with the ideal terminal oxidant: molecular oxygen in air.     

Noble‐Metal‐Free Single‐Atom Catalysts CuAl4O7–9− for CO Oxidation by O2

The single copper atom doped clusters CuAl₄O_7–9^? can catalyze CO oxidation by O₂. The CuAl₄O_7–9^? clusters are the first group of experimentally identified noble‐metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl₄O₉CO^? is much more reactive than CuAl₄O₉^? in the reaction with CO to generate CO₂. One adsorbed CO is crucial to stabilize Cu of CuAl₄O₉^? around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble‐metal catalysis was discussed.     

Iron‐Based Molecular Water Oxidation Catalysts: Abundant,Cheap, and Promising

An efficient and robust water oxidation catalyst based on abundant and cheap materials is the key to converting solar energy into fuels through artificial photosynthesis for the future of humans. The development of molecular water oxidation catalysts (MWOCs) is a smart way to achieve promising catalytic activity, thanks to the clear structures and catalytic mechanisms of molecular catalysts. Efficient MWOCs based on noble‐metal complexes, for example, ruthenium and iridium, have been well developed over the last 30 years; however, the development of earth‐abundant metal‐based MWOCs is very limited and still challenging. Herein, the promising prospect of iron‐based MWOCs is highlighted, with a comprehensive summary of previously reported studies and future research focus in this area.     

Phase‐Selective Syntheses of Cobalt Telluride Nanofleeces for Efficient Oxygen Evolution Catalysts

Cobalt‐based nanomaterials have been intensively explored as promising noble‐metal‐free oxygen evolution reaction (OER) electrocatalysts. Herein, we report phase‐selective syntheses of novel hierarchical CoTe₂ and CoTe nanofleeces for efficient OER catalysts. The CoTe₂ nanofleeces exhibited excellent electrocatalytic activity and stablity for OER in alkaline media. The CoTe₂ catalyst exhibited superior OER activity compared to the CoTe catalyst, which is comparable to the state‐of‐the‐art RuO₂ catalyst. Density functional theory calculations showed that the binding strength and lateral interaction of the reaction intermediates on CoTe₂ and CoTe are essential for determining the overpotential required under different conditions. This study provides valuable insights for the rational design of noble‐metal‐free OER catalysts with high performance and low cost by use of Co‐based chalcogenides.     

Bottom‐Up Design of a Copper–Ruthenium Nanoparticulate Catalyst for Low‐Temperature Ammonia Oxidation

A novel nanoparticulate catalyst of copper (Cu) and ruthenium (Ru) was designed for low‐temperature ammonia oxidation at near‐stoichiometric mixtures using a bottom‐up approach. A synergistic effect of the two metals was found. An optimum CuRu catalyst presents a reaction rate threefold higher than that for Ru and forty‐fold higher than that for Cu. X‐ray absorption spectroscopy suggests that in the most active catalyst Cu forms one or two monolayer thick patches on Ru and the catalysts are less active once 3D Cu islands form. The good performance of the tuned Cu/Ru catalyst is attributed to changes in the electronic structure, and thus the altered adsorption properties of the surface Cu sites.     

Investigation of Platinum Dispersed on Reduced Graphene Oxide‐supported Tungsten Carbide via Sacrificial Cu Adlayers for Methanol Oxidation

Reduced graphene oxide‐supported tungsten carbide composite (WC/RGO) was prepared by program‐controlled reduction‐carburization technique. Scanning electron microscope (SEM) and transmission electron microscope (TEM) show that WC nanoparticles with a narrow distribution (10–20 nm) are highly dispersed both on the edge and between the layers of RGO. And then it was used as a support to load different low contents (no more than 0.4 wt%) of Pt via sacrificial Cu adlayers. The morphology and the electrocatalytic activity of the prepared catalysts were characterized by TEM and cyclic voltammograms (CV), respectively. The results indicate that a small amount of isolated Pt atoms show low or even no activity for methanol oxidation. With the increasing deposition cycles, the content of Pt and the ensembles of neighboring Pt atoms are increased, which makes the onset potential shift negatively and mass current density increase. The results demonstrate that controllable amount of Pt can be deposited on WC/RGO by galvanic displacement with Cu, and the extent and domain of Pt loading affect the electrochemical performance. Meanwhile, this research also provides another route to prepare a catalyst with ultra low noble metal on WC/RGO for solving the problem of high cost of the catalyst.     

High‐Performance Bismuth‐Doped Nickel Aerogel Electrocatalyst for the Methanol Oxidation Reaction

Low‐cost, non‐noble‐metal electrocatalysts are required for direct methanol fuel cells, but their development has been hindered by limited activity, high onset potential, low conductivity, and poor durability. A surface electronic structure tuning strategy is presented, which involves doping of a foreign oxophilic post‐transition metal onto transition metal aerogels to achieve a non‐noble‐metal aerogel Ni₉₇Bi₃ with unprecedented electrocatalytic activity and durability in methanol oxidation. Trace amounts of Bi are atomically dispersed on the surface of the Ni₉₇Bi₃ aerogel, which leads to an optimum shift of the d‐band center of Ni, large compressive strain of Bi, and greatly increased conductivity of the aerogel. The electrocatalyst is endowed with abundant active sites, efficient electron and mass transfer, resistance to CO poisoning, and outstanding performance in methanol oxidation. This work sheds light on the design of high‐performance non‐noble‐metal electrocatalysts.     

Recyclable Porous Polymer‐Supported Copper Catalysts for Glaser and Huisgen 1,3‐Diolar Cycloaddition Reactions

A family of polymer‐attached phenanthrolines was prepared from solvothermal copolymerization of divinylbenzene with N‐(1,10‐phenanthroline‐5‐yl)acrylamide in different ratios. The polymer‐supported copper catalysts were obtained through typical impregnation with copper(II) salts. The polymers and supported copper catalysts have been characterized by N₂ adsortion, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TG); they exhibit a high surface area, hierarchical porosity, large pore volume, and high thermal and chemical stabilities. The copper catalyst has proved to be highly active for Glaser homocoupling of alkynes and Huisgen 1,3‐diolar cycloaddition of alkynes with benzyl azide under mild conditions at low catalyst loading. The heterogeneous copper catalyst is more active than commonly used homogeneous and nonporous polystyrene‐supported copper catalysts. In particular, the catalyst is easily recovered and can be recycled at least ten times without any obvious loss in catalytic activity. Metal leaching was prevented due to the strong binding ability of phenanthroline and products were not contaminated with copper, as determined by ICP analysis.     

Host (Nano Cage NaY)/Guest Mn(II), Co(II), Ni(II) and Cu(II) Complexes of N,N‐Bis(3,5‐Di‐Tert‐Butylsalicyidene)‐2,2‐Dimethyle‐1,3‐Diaminopropane: Synthesis and Catalyst Activity

Mn(II), Co(II), Ni(II) and Cu(II) and N,N‐bis(3,5‐di‐tert‐butylsalicyidene)‐2,2‐dimethyle‐1,3‐diaminopropane complexes have been synthesized in Y zeolite cavity by the reaction of ion‐exchanged metal ions with the flexible ligand molecules. The host‐guest materials obtained have been characterized by elemental analysis, XRD, surface area, pore volume, TGA, FT‐IR and UV‐Vis techniques. Analysis of data indicates that formation of complexes in the pores Y zeolite without affecting the zeolite framework structure. Also, we report the oxidation of cyclohexanol catalyzed by host‐guest catalyst with tert‐buthyl hydrogen peroxide as oxygen donor. The activity of benzyl alcohol oxidation decreases in the series‐[Co(L)]/NaY > [Cu(L)]/NaY > [Mn(L)]/NaY > [Ni(L)]/NaY and the percent of product completely depend to catalyst. Zeolite complexes are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts.     

Delivery of Highly Active Noble‐Metal Nanoparticles into Microspherical Supports by an Aerosol‐Spray Method

Noble metal nanoparticles (NPs) with 1–5 nm diameter obtained from NaHB₄ reduction possess high catalytic activity. However, they are rarely used directly. This work presents a facile, versatile, and efficient aerosol‐spray approach to deliver noble‐metal NPs into metal oxide supports, while maintaining the size of the NPs and the ability to easily adjust the loading amount. In comparison with the conventional spray approach, the size of the loaded noble‐metal nanoparticles can be significantly decreased. An investigation of the 4‐nitrophenol hydrogenation reaction catalyzed by these materials suggests that the NPs/oxides catalysts have high activity and good endurance. For 1 % Au/CeO₂ and Pd/Al₂O₃ catalysts, the rate constants reach 2.03 and 1.46 min^?1, which is much higher than many other reports with the same noble‐metal loading scale. Besides, the thermal stability of catalysts can be significantly enhanced by modifying the supports. Therefore, this work contributes an efficient method as well as some guidance on how to produce highly active and stable supported noble‐metal catalysts.     

Molybdenum Phosphosulfide: An Active,Acid‐Stable,Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.     

Molybdenum Phosphosulfide: An Active,Acid‐Stable,Earth‐Abundant Catalyst for the Hydrogen Evolution Reaction

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non‐noble‐metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed‐metal alloy catalysts are well‐known, MoP|S represents a more uncommon mixed‐anion catalyst where synergistic effects between sulfur and phosphorus produce a high‐surface‐area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water‐splitting cells.