Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

Carbon nanotubes-Nafion （CNTs-Nation） composites were prepared by impregnated CNTs with Nation in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, CO stripping voltammetry, cyclic voltammetry （CV） and chronoamperometry （CA）. The results showed that the Nation incorporation in CNTs-Nation composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Naton showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

Catalytic Removal of NOx by Cerium-modified Zirconium Composite Oxide

Diesel engines have been widely used due to their high thermal efficiency, good environmental adaptability, wide power adjustment range, convenient maintenance and long service life. However, the application of diesel engines is also facing a serious problem;that is, the emission of nitrogen oxides and particulate matter is serious. For marine diesel engine emission requirements, MARPOL Convention Annex VI imposes strict restrictions on the emission of atmospheric pollutants. The limit emission of nitrogen oxides in the Tier III emission standards mandated by IMO is 3.4 g/kWh. Therefore, in order to meet the requirements of international conventions and countries and regions, it is necessary to control the emissions of diesel engines. The NOx in the exhaust gas is mostly a thermal type of nitrogen oxide which is produced under high temperature and high pressure conditions formed during compression and combustion strokes. The diesel engine relies on the compression energy of the mixture to ignite, and the good injection atomization effect is not achieved. The distribution of the detonation point is not uniform, and local high temperature points are generated in some areas, which increases the NOx formation. The main means of reducing NOx emissions are organic internal control and post-treatment. However, the use of internal control technology to reduce the internal temperature of the machine will deteriorate the fuel combustion conditions, so that the fuel cannot be completely burned, and the emissions of incomplete combustion products such as PM and CO increase. It is difficult to achieve NOx reduction by simply relying on the internal control technology, so it is necessary to use post-processing technology. The combined use of different emission reduction technologies is also a hot topic in emissions control research. The post-treatment methods for NOx emission reduction include direct catalytic decomposition, selective non-catalytic reduction, selective catalytic reduction, lean-burn adsorption catalytic reduction, and low-temperature plasma assisted technology. The current research and application schemes in the industry are SCR selectivity. Catalytic reduction and LNT lean combustion adsorption reduction. In this paper, the partial replacement of Ce by La is carried out to modify the Ce/Zr composite oxide. The mass fraction of La2O3 in the prepared La/Ce/Zr composite oxide was 5%, and the physicochemical properties of La/Ce/Zr composite oxide powder were analyzed by ICP, OSC, SEM and TPR techniques. The experiment found that: 1) La can refine the grain and inhibit the grain growth, so that the powder obtains a higher specific surface area and a smaller particle size distribution. 2) The addition of La reduces the sintering of cerium-zirconium and improves the heat aging resistance of the catalyst under the inhibition of high temperature. 3) After doping La, it enhances the migration of surface lattice oxygen and enhances the oxygen storage capacity;the addition of La enhances the NO adsorption capacity of cerium-zirconium and improves the catalytic activity of the catalyst. The light-off temperature and the highest activity temperature of PM decrease, and the reduction rate of No is 19.2%.

Plasma treated M1 MoVNbTeO_(x)-CeO_(2) composite catalyst for improved performance of oxidative dehydrogenation of ethane

High activity and productivity of MoVNbTeO_(x) catalyst are challenging tasks in oxidative dehydrogenation of ethane(ODHE)for industrial application.In this work,phase-pure M1 with 30 wt%CeO_(2) composite catalyst was treated by oxygen plasma to further enhance catalyst performance.The results show that the oxygen vacancies generated by the solid-state redox reaction between M1 and CeO_(2) capture active oxygen species in gas and transform V^(4+)to V^(5+)without damage to M1 structure.The space-time yield of ethylene of the plasma-treated catalyst was significantly increased,in which the catalyst shows an enhancement near~100% than that of phase-pure M1 at 400℃ for ODHE process.Plasma treatment for catalysts demonstrates an effective way to convert electrical energy into chemical energy in catalyst materials.Energy conversion is achieved by using the catalyst as a medium.

Effects of preparation conditions of Au/FeO_x /Al_2O_3 catalysts prepared by a modified two-step method on the stability for CO oxidation

Composite oxide FeO x /Al 2 O 3 -supported gold catalysts were prepared by a modified two-step method. The effects of preparation conditions on the initial catalytic activity and long-time stability were studied for CO oxidation. XRD, XPS and in situ FTIR were employed to investigate the state of FeO x and the species on the catalyst surface. The results showed that Au/FeO x /Al 2 O 3 catalysts prepared by this method exhibited high activity and high stability in a wide pH value range. Calcination pretreatment was proved to be beneficial to improving the activity and stability. The beneficial effects of FeO x acting as a structural promoter could be ascribed to the ability to supply active oxygen species. As the precursor of FeO x , Fe（NO 3 ） 3 is superior to FeCl 3 for obtaining higher stability.

Synthesis,Characterization and Catalytic Properties of Mesoporous HPMo/SiO_2 Composite

A novel mesoporous HPMo/SiO2 composite was synthesized by the sol-gel method with triblock copolymer EO20PO70EO20 as template.The properties of the product were characterized by X-ray diffraction,transmission electron microscopy,N2 adsorption-desorption isotherms,Fourier transform infrared spectrometer and inductively-coupled plasma analysis.The experimental results show that the product has a very ordered hexagonal mesostructure,and the HPMo is immobilized into the framework of silica.The final mesoporous composite shows excellent stability in polar solvents.Results of catalytic tests indicate that the composite is an effective catalyst for oxidation of dibenzothiophen,and there are few activity losses even after the third cycle of uses.The high catalytic activity and good insolubility make it a promising catalyst in oxidative desulfurization process.

Synthesis and study of λ-MnO_2 supported Pt nanocatalyst for methanol electro-oxidation

A λ-MnO2 supported Pt nanocatalyst（5 wt.% Pt/λ-MnO2） was synthesized using a facile approach.X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, scanning electronic microscope（SEM）, transmission electron microscopy（TEM）, and energy disperse spectroscopy（EDS） were used for catalyst structure and morphology characterization, which showed that the metallic Pt particles were attached on a λ-MnO2 surface through the interaction between Pt and λ-MnO2.Cyclic voltammetry（CV） was used to test the catalytic activity of Pt/λ-MnO2 toward methanol oxidation, which showed that Pt/λ-MnO2 catalyst has much higher catalytic activity than baseline Pt/C catalyst.

Preparation and reaction mechanism of novel Ce_(x)Co_(y)Cuz oxide composite catalysts towards oxidation of o-xylene

Ce_(x)Co_(y)Cuzoxide composite catalysts were prepared by using polyethylene glycol, citrate sol-gel method combined with PMMA template for the oxidation of o-xylene. The catalysts were characterized by the Xray diffraction(XRD), H2-temperature programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FT-IR), etc. The catalytic activity for o-xylene was investigated. The catalytic degradation pathway and mechanism of o-xylene were inferred. The results show that Ce O_(2)is mainly present on the surface of all catalysts. The surface area of Ce_(2)Co1Cu1is up to 77.2 m^(2)/g, and the average pore size is 10.62 nm. It exhibits redox and sufficient Ce^(4+)and Ce^(^(3+)), and reactive oxygen species, and has maximum O-H and C=O in the five catalyst samples. The catalytic activity of Ce2Co1Cu1is the best at low temperature, with the T50and T90values of 235 and 258°C at a space velocity of 32000 h-1, respectively. The o-xylene is oxidized to o-methyl benzaldehyde, and then further oxidized to o-methylbenzoic acid, and finally CO_(2)and H2O are formed.

A review on transition metal oxides based photocatalysts for degradation of synthetic organic pollutants

This review provides insight into the current research trend in transition metal oxides(TMOs)-based photocatalysis in removing the organic colouring matters from water.For easy understanding,the research progress has been presented in four generations according to the catalyst composition and mode of application,viz:single component TMOs(the firstgeneration),doped TMOs/binary TMOs/doped binary TMOs(the second-generation),inactive/active support-immobilized TMOs(the third-generation),and ternary/quaternary compositions(the fourth-generation).The first two generations represent suspended catalysts,the third generation is supported catalysts,and the fourth generation can be suspended or supported.The review provides an elaborated comparison between suspended and supported catalysts,their general/specific requirements,key factors controlling degradation,and the methodologies for performance evaluation.All the plausible fundamental and advanced dye degradation mechanisms involved in each generation of catalysts were demonstrated.The existing challenges in TMOs-based photocatalysis and how the researchers approach the hitch to resolve it effectively are discussed.Future research trends are also presented.

Preparation of hierarchical layer-stacking Mn-Ce composite oxide for catalytic total oxidation of VOCs

Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs（benzene, toluene and ethyl acetate） were examined. The Mn-Ce oxalate precursor was obtained from metal salt and oxalic acid without any additives. The resulting materials were characterized by X-ray diffraction（XRD）, Brunauer-Emmett-Teller（BET）, scanning electron microscopy（SEM）, energy dispersive X-ray spectroscopy（EDX）, hydrogen temperature programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS）. Compared with Mn-Ce composite oxide synthesized through a traditional method（Na2CO3 route）, the hierarchical layer-stacking Mn-Ce composite oxide exhibited higher catalytic activity in the complete oxidation of volatile organic compounds（VOCs）. By means of testing, the data revealed that the hierarchical layer-stacking Mn-Ce composite oxide possessed superior physiochemical properties such as good low-temperature reducibility, high manganese oxidation state and rich adsorbed surface oxygen species which resulted in the enhancement of catalytic abilities.

Preparation and characteristics of nano-crystalline Cu-Ce-Zr-O composite oxides via a green route: supercritical anti-solvent process

The nano-crystalline Cu-Ce-Zr-O composite oxides were successfully prepared by the supercritical anti-solvent （SAS） process. The physicochemical properties and catalytic performances were investigated by X-ray diffraction （XRD）, Raman spectroscopy, H2 temperature-programmed reduction （H2 -TPR）, oxygen storage capacity （OSC） measurement and catalytic activity evaluation. It was found that Cu2＋ ions incorporated into CeO2 -ZrO2 lattice to form Cu-Ce-Zr-O solid solution associated with the formation of oxygen vacancies. The Cu-Ce-Zr-O catalysts prepared via the SAS process with the Cu content 2.63 mol.% showed the highest OSC index of 636.9 μmol/g. Compared with the samples prepared by impregnation method, Cu doping using SAS process could improve the dispersion of Cu2＋ in the composite oxide, enhance the interaction between Cu2＋ and CeO2-ZrO2 , improve the reducibility of catalyst, and thus improve the OSC performance and increase the catalytic activity for CO oxidation at low temperature.

Fe- and Co-doped lanthanum oxides catalysts for ammonia decomposition:Structure and catalytic performances

In this paper, a series of Fe- and Co-doped lanthanum（hydr）oxides catalysts were prepared by a simple coprecipitationhydrothermal method. The as-prepared catalysts were characterized with various techniques including powder X-ray diffraction（XRD）, N2 adsorption/desorption, inductively coupled plasma（ICP） and transmission electron microscopy（TEM）. The Fe-based catalysts exhibited consecutive phase changes of amorphous Fe Ox→FeLaO3→Fe2N under different stages（as-prepared→calcination→ammonia decomposition reaction）; as for Co-based catalysts, the phase transformation followed a sequence of Co（OH）2→Co3O4→metallic Co. It was revealed that Fe2N and metallic Co were most probably the active crystalline phase respectively for Feand Co-based catalysts in the decomposition of ammonia.

Reduction of CeO2 in composites with transition metal complex oxides under hydrogen containing atmosphere and its correlation with catalytic activity

Reduction behavior of pure and doped CeO2, the multi-phase La0.6Sr0.4CoO3.xCeO2, La0.sSr0.2MnO3 . xCeO2, and La0.95Ni0.6Fe0.4O3.xCeO2 composites, was studied under hydrogen containing atmosphere to address issues related to the improvement of electrochemical and catalytic performance of electrodes in fuel cells. The enhanced reduction of cerium oxide was observed initially at 800~C in all composites in spite of the presence of highly reducible transition metal cations that could lead to the increase in surface concentration of oxygen vacancies and generation of the electron enriched surface. Due to continuous reduction of cerium oxide in La0.6Sr0.4CoO3 ＂x- CeO2 and La0.sSr0.zMnO3 ＂xCeO2 （up to 10 h） composites the redox activity of the Ce4＋/Ce3＋ pair could be suppressed and additional measures are required for reversible spontaneous regeneration of Ce4＋. After 3 h exposure to H2-Ar at 800~C the reduction of cerium oxides and perovskite phases in La0.95Ni0.6Fe0.403 ＂xCeO2 com- posites was diminished. The extent of cerium oxide involvement in the reduction process varies with time, and depends on its initial deviation from oxygen stoichiometry （that results in the larger lattice parameter and the longer pathway for O2 transport through the fluorite lattice）, chemical origin of transition metal cations in the perovskite, and phase diversity in multi-phase composites.

3D hierarchically macro-/mesoporous graphene frameworks enriched with pyridinic-nitrogen-cobalt active sites as efficient reversible oxygen electrocatalysts for rechargeable zinc-air batteries

Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions(ORR and OER,respectively)are highly sought-after for use in rechargeable metal-air batteries.However,the construction of high-performance electrocatalysts that possess both largely accessible active sites and superior ORR/OER intrinsic activities is challenging.Herein,we report the design and successful preparation of a 3D hierarchically porous graphene framework with interconnected interlayer macropores and in-plane mesopores,enriched with pyridinic-nitrogen-cobalt(pyri-N-Co)active sites,namely,CoFe/3D-NLG.The pyri-N-Co bonding significantly accelerates sluggish oxygen electrocatalysis kinetics,in turn substantially improving the intrinsic ORR/OER activities per active site,while copious interlayer macropores and in-plane mesopores enable ultra-efficient mass transfer throughout the graphene architecture,thus ensuring sufficient exposure of accessible pyri-N-Co active sites to the reagents.Such a robust catalyst structure endows CoFe/3D-NLG with a remarkably enhanced reversible oxygen electrocatalysis performance,with the ORR half-wave potential identical to that of the benchmark Pt/C catalyst,and OER activity far surpassing that of the noble-metal-based RuO2 catalyst.Moreover,when employed as an air electrode for a rechargeable Zn-air battery,CoFe/3D-NLG manifests an exceedingly high open-circuit voltage(1.56 V),high peak power density(213 mW cm^(–2)),ultra-low charge/discharge voltage(0.63 V),and excellent charge/discharge cycling stability,outperforming state-of-the-art noble-metal electrocatalysts.

Increased utilization and mass activity of PtRu on reduced graphene oxide by heat treatment of its aerogel followed by composite with nanomaterials

The method to increase PtRu utilization and its catalytic activity of PtRu nanoparticles supported on reduced graphene oxide(RGO)by avoiding its restacking was proposed with the aim of developing an active catalyst for a direct methanol fuel cell.The heat treatment at 200◦C of the GO aerogel(GOA)prepared by freeze drying of GO ice was introduced to weaken the attractive force of the hydrogen bonding between the GO sheets followed by the composite with the nanoparticles,i.e.,ketjenblack(KB),TiO_(2)and Ti_(4)O_(7),at different weight ratios.The catalyst supported on the heat-treated GOA(RGOA),PtRu/RGOA,improved the PtRu utilization to some extent and also increased the ECSA and mass activity compared to that of PtRu/RGO.RGOA had fewer oxygen functional groups,especially the epoxy groups.Due to the treatment and composite,the PtRu utilization was increased from 66.5%for PtRu/RGO to 128.6%for PtRu/RGOA+Ti_(4)O_(7)(4:1)and the mass activity was improved from 50.7 A/g-PtRu for PtRu/RGO to 130.5 A/g-PtRu for PtRu/RGOA+Ti_(4)O_(7)(1:1).The Ti_(4)O_(7)nanoparticles showed the best catalytic performance for the composite suggesting that the strong interaction between Ti_(4)O_(7)and the Pt nanoparticles was effective due to its high electronic conductivity.

CeMO_(δ)/3DOM ZrTiO_(4)(M=Mn,Fe,Co)催化剂的制备及其对炭烟颗粒的催化消除性能

消除柴油机尾气中的炭烟颗粒对人体健康和社会发展都具有重要的现实意义。采用胶体晶体模板法和等体积浸渍法制备了CeMO_(δ)/3DOM ZrTiO_(4)(M=Mn,Fe,Co)系列复合金属氧化物催化剂,利用X射线衍射仪、全自动比表面和孔隙分析仪、扫描电镜等表征了催化剂的物化性能,并测试了Ce M O_(δ)/3DOM ZrTiO_(4)(M=Mn,Fe,Co)系列催化剂对炭烟颗粒的催化消除性能。研究结果表明,所制备的催化剂均具有独特的三维有序大孔结构,其中CeMnO_(δ)/3DOM ZrTiO_(4)催化剂对炭烟的催化活性最高,是一种具有应用前景的复合金属氧化物催化剂。

铈改性CuMn/Al_(2)O_(3)/堇青石整体催化剂的甲苯催化燃烧性能研究

本研究以堇青石为载体,采用超声浸渍法制备了一系列CuMnCe_(x)/Al_(2)O_(3)/堇青石整体式催化剂,同时,通过N_(2)吸附-脱附、XRD、SEM、EDX、H_(2)-TPR、O_(2)-TPD、XPS和EPR等方法对样品的物理、化学性质进行了系统的表征分析。实验结果表明,CuMnCe_(x)/Al_(2)O_(3)/堇青石整体式催化剂中的Ce含量明显影响甲苯催化燃烧性能。其中,CuMnCe_(2)/Al_(2)O_(3)/堇青石整体式催化剂对甲苯氧化具有最高活性,当甲苯浓度为1 g/L、空速为78000 mL/(g·h)、温度为263℃时甲苯转化率达到90%,究其原因为CeO_(2)在CuMnO_(x)上分散均匀,不仅提高了氧空位的浓度和氧物种的迁移率,还增强了催化剂的低温还原性。同时,CuMnCe_(2)/Al_(2)O_(3)/堇青石整体式催化剂在长期评价和循环测试中呈现良好的稳定性。

UiO-66-NH_(2)负载铜催化剂的制备及其对醇的催化氧化

通过溶剂热法成功制备了一种基于金属有机骨架(MOF)的复合材料Cu-Cu_(2)O/UiO-66-NH_(2),采用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)对材料进行全面表征。在空气作氧化剂条件下,以苯甲醇氧化为苯甲醛作为模型反应,系统地考察了溶剂、温度、催化剂各组分用量等因素对催化效果的影响。研究结果表明,该复合催化剂在醇选择性氧化反应中表现出优异的催化性能,60℃下反应5 h便可将苯甲醇定量转化为苯甲醛,并对其他苄基醇、烯丙基醇和杂芳基醇等底物也展现出良好活性。此外,循环利用3次后,该催化剂活性几乎不变,表明其具有良好的稳定性和重复使用性。

二元复合氧化物载体在加氢脱硫催化剂中的应用进展

加氢脱硫技术对实现劣质油品清洁化、低碳化与多元化高效利用至关重要,其关键是高性能催化剂的开发,核心之一是适宜催化剂载体材料的创新。本工作分别总结了向Al_(2)O_(3)及TiO_(2)中引入第二组元后作为加氢脱硫催化剂载体的研究进展。第二组元氧化物的引入克服了Al_(2)O_(3)载体酸类型单一及商用催化剂金属与载体间相互作用过强等缺点,同时保持了较大的比表面积;第二组元氧化物能够有效提升TiO_(2)载体材料的热稳定性及比表面积的同时调节了载体材料表面酸性等。究其原因在于第二组元的引入可显著改变Al_(2)O_(3)或TiO_(2)表面羟基环境,进而促进了活性金属前驱体在载体表面的锚定和分散,有利于更多NiMo(W)S活性相的形成,提升了催化剂的加氢脱硫性能。

Cu对Fe基催化剂NH_(3)-SCR性能助力作用研究

Fe基催化剂在中温范围有着良好的催化活性,而Cu基催化剂有着低温优势,因此将两者相结合,采用表面活性剂辅助法制备了Fe-Cu复合氧化物.引入Cu后,Fe-Cu催化剂的NO x转化率达90%,起燃温度下降至150℃.Fe_(2)O_(3)和CuO之间的相互作用使得催化剂的比表面积增大约1/4,且增强了Fe^(3+)的亲电性,促进NO_(2)等电负性物质的吸附.同时提高了催化剂的氧化还原能力与表面吸附氧Oα比例,NO更易向NO_(2)转变,快速SCR(选择性催化还原)进程更易发生.此外,Fe_(2)O_(3)和CuO的相互作用让催化剂拥有较多的酸性位点,有利于催化活性的提升.最终使得Fe-Cu催化剂不仅继承了Cu基催化剂的低温优势,还保持了优良的N_(2)选择性.