Metal porphyrin intercalated reduced graphene oxide nanocomposite utilized for electrocatalytic oxygen reduction

In this paper, we report a simple and facile self-assembly method to successfully fabricate cationic metal porphyrin-MtTMPyP(Mt= Cobalt(Ⅱ), Manganese(Ⅲ), or Iron(Ⅲ); TMPyP = 5, 10, 15, 20-tetrakis(N-methylpyridinium-4-yl) porphyrin) intercalated into the layer of graphene oxide(GO) by the cooperative effects of electrostatic and π-π stacking interaction between positively charged metal porphyrin and negatively charged GO sheets. Followed by reduction with hydrazine vapor, a series of novel 2 D MtTMPyP/rGO_n were fabricated. The as-prepared 2 D hybrids were fully characterized and tested as non-noble metal catalysts for oxygen reduction reaction(ORR) in an alkaline medium. The MtTMPyP/rGO_n hybrids, especially CoTMPyP/rGO_5, demonstrated an improved electrocatalytic activity for ORR and a number of exchanged electrons close to 4-electron reaction, increased stability and excellent tolerance to methanol, showing a potential alternative catalyst for ORR in fuel cells and air batteries.

Nanoscale graphene oxide sheets as highly efficient carbocatalysts in green oxidation of benzylic alcohols and aromatic aldehydes

Nanoscale graphene oxide(NGO)sheets were synthesized and used as carbocatalysts for effectiveoxidation of benzylic alcohols and aromatic aldehydes.For oxidation of alcohols in the presence ofH2O2at80°C,the NGOs(20%mass fraction)as carbocatalysts showed selectivity toward aldehyde.The rate and yield of this reaction strongly depended on the nature of substituents on the alcohol.For4‐nitrobenzyl alcohol,<10%of it was converted into the corresponding carboxylic acid after24h.By contrast,4‐methoxybenzyl alcohol and diphenylmethanol were completely converted into thecorresponding carboxylic acid and ketone after only9and3h,respectively.The conversion ratesfor oxidation of aromatic aldehydes by NGO carbocatalysts were higher than those for alcohol oxidation.For all the aldehydes,complete conversion to the corresponding carboxylic acids wasachieved using7%(mass fraction)of NGO at70°C within2–3h.Possible mechanisms for NGOcarbocatalyst structure‐dependent oxidation of benzyl alcohols and structure‐independent oxidationof aromatic aldehydes are discussed.

Synthesis and characterization of a novel binuclear iron phthalocyanine/reduced graphene oxide nanocomposite for non-precious electrocatalyst for oxygen reduction

Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.

Hybrid CuO-Co_(3)O_(4)nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries

Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully applied as enhanced anodes for lithium-ion batteries(LIBs).The CuO-Co_(3)O_(4)-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^(-1)after 200 cycles’cycling at 100 mA·g^(-1)with a capacity retention of 79%.The CuO-Co_(3)O_(4)-RGO compounds show superior electrochemical properties than the comparative CuO-Co_(3)O_(4),Co_(3)O_(4)and CuO anodes,which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages;the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co_(3)O_(4) nanospheres;the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.

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.

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.

A study of highly activated hydrogen evolution reaction performance in acidic media by 2D heterostructure of N and S doped graphene on MoO_(x)

Herein,a layer of molybdenum oxide(MoO_(x)),a transition metal oxide(TMO),which has outstanding catalytic properties in combination with a carbonbased thin film,is modified to improve the hydrogen production performance and protect the MoO_(x)in acidic media.A thin film of graphene is transferred onto the MoO_(x)layer,after which the graphene structure is doped with N and S atoms at room temperature using a plasma doping method to modify the electronic structure and intrinsic properties of the material.The oxygen functional groups in graphene increase the interfacial interactions and electrical contacts between graphene and MoO_(x).The appearance of surface defects such as oxygen vacancies can result in vacancies in MoO_(x).This improves the electrical conductivity and electrochemically accessible surface area.Increasing the number of defects in graphene by adding dopants can significantly affect the chemical reaction at the interfaces and improve the electrochemical performance.These defects in graphene play a crucial role in the adsorption of H^(+)ions on the graphene surface and their transport to the MoO_(x)layer underneath.This enables MoO_(x)to participate in the reaction with the doped graphene.N^(‐)and S^(‐)doped graphene(NSGr)on MoO_(x)is active in acidic media and performs well in terms of hydrogen production.The initial overpotential value of 359 mV for the current density of−10 mA/cm^(2)is lowered to 228 mV after activation.

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.

Removal of ammonia from aqueous solutions by catalytic oxidation with copper-based rare earth composite metal materials: catalytic performance, characterization, and cytotoxicity evaluation

Ammonia （NH3） has an important use in the chemical industry and is widely found in industrial wastewater. For this investigation of copper-based rare earth composite metal materials, aqueous solutions containing 400 mg/L of ammonia were oxidized in a batch-bed reac-tor with a catalyst prepared by the co-precipitation of copper nitrate, lanthanum nitrate and cerium nitrate. Barely any of the dissolved ammo-nia was removed by wet oxidation without a catalyst, but about 88% of the ammonia was reduced during wet oxidation over the catalysts at 423 K with an oxygen partial pressure of 4.0 MPa. The catalytic redox behavior was determined by cyclic voltammetry （CV）. Furthermore, the catalysts were characterized using thermogravimetric analyzer （TGA） and scanning electron microscope-energy dispersive X-ray spectroscopy （SEM-EDX）, which showed that the catalytic behavior was related to the metal oxide properties of the catalyst. In addition, the copper-lanthanum-cerium composite-induced cytotoxicity in the human lung MRC-5 cell line was tested, and the percentage cell survival was determined by 3-（4,5-dimethylthiazol-2-yl）-5-（3-carboxymethoxyphenyl）-2-（4-sulfophenyl）-2H-tetra-zolium （MTS） analysis in vitro. No ap-parent cytotoxicity was observed when the human lung cells were exposed to the copper-lanthanum-cerium composite.

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。

Ni、Mg掺杂钴尖晶石催化分解N_(2)O的实验

为了解决氨燃料发动机的氧化亚氮(N_(2)O)排放问题,研究一种Ni、Mg掺杂的钴尖晶石催化剂用于N_(2)O高效分解。采用共沉淀法合成一系列过渡金属M(Cu、Ni、Mg)掺杂钴尖晶石(Co3O_(4))形成M_(x)Co_(3-x)O_(4)复合金属氧化物,并探究其在不同气氛下的催化活性。Ni_(0.4)Mg_(0.2)Co_(2.4)O_(4)催化剂可在350℃时达到90%的N_(2)O分解效率,在通有10%水蒸气反应的情况下480℃完全转化。通过一系列表征手段发现:Ni、Mg同时掺杂进入晶格结构较好,形成较为完整的整体尖晶石结构;Ni、Mg协同Co作为活性位点,使钴尖晶石分散度更好,并未像Cu等掺杂时形成对应金属氧化物的杂相而减少活性中心是其改性效果进一步提升的重要原因;同时因Ni、Mg同时掺杂进入晶格,使掺杂后钴尖晶石晶格膨胀,晶格尺寸变大,比表面积有明显提升,高于Ni、Mg单独掺杂,增加了接触活性位点,使其拥有更低的反应温度;通过XPS发现Ni_(0.4)Mg_(0.2)Co_(2.4)O_(4)中Co^(2+)、Ni^(2+)的结合能均最高,电子云密度相对最低,有助于N、O中的电子向其转移,且作为主要分解活性中心的Co^(2+)占比最高,从能量和价态角度解释了其同温度下分解效率最高的现象;此外,在H_(2)-TPR下,随着Ni、Mg掺杂量的增加,H_(2)的还原温度更高,说明其在高低温下的还原性更强,有助于对N_(2)O中的高价N进行吸附还原,而Ni_(0.4)Mg_(0.2)Co_(2.4)O_(4)在60 h时的60000 h-1空速气流下也显示出较好的稳定性(350℃下转化率维持在90%左右)。

Advances in selective catalytic oxidation of ammonia (NH_(3)-SCO): A review of catalyst structure-activity relationship and design principles

NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Controlling NH_(3) emissions caused by ammonia escaping from mobile and industrial sources can effectively reduce the NH_(3) content in ambient air. Among the various NH_(3) removal methods, the selective catalytic oxygen method (NH_(3)-SCO) is committed to oxidizing NH_(3) to environmentally harmless H_(2)O and N_(2);therefore, it is the most valuable and ideal ammonia removal method. In this review, the characteristics of loaded and core-shell catalysts in NH_(3)-SCO have been reviewed in the context of catalyst structure-activity relationships, and the H_(2)O resistance and SO2 resistance of the catalysts are discussed in the context of practical application conditions. Then the effects of the valence state of the active center, oxygen species on the catalyst surface, dispersion of the active center and acidic sites on the catalyst performance are discussed comprehensively. Finally, the shortcomings of the existing catalysts are summarized and the catalyst development is discussed based on the existing studies.

Synthesis of La_2MoO_6@MWCNTs composite catalysts as Pt-free counter electrodes for dye-sensitized solar cell

Pt-free counter electrode(CE) composed of La2 MoO(LaO-MoO) was successfully synthesized by simple pyrolysis of lanthanum acetate(CHOLa·xHO) and hexaammonium heptamolybdate tetrahydrate((NH4)6 MoO·4 HO). Furthermore,three proportions composites catalysts of La2 MoO@MWCNTs based on La2 MoOand multiwall carbon nanotubes(MWCNTs) were prepared and characterized as Ptfree catalyst for CE in dye-sensitized solar cells(DSSCs). The morphology and structure of La2 MoO@MWCNTs composites were determined by scanning electron microscopy, transmission electron microscope and X-ray diffraction. The electrochemical performance of La2 MoO@MWCNTs composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry,electrochemical impedance spectroscopy, and Tafel polarization. The power conversion efficiencies of4.68%, 4.87% and 5.06% are obtained for La2 MoO:MWCNTs with the mass ratios of 5:1, 3:1 and 1:1 towards the reduction of I~-to I~-under the same conditions,respectively,which are superior to those of MWCNTs(3,94%) and La2 MoO(1.71%) electrodes. The experimental results reveal that the presence of MWCNTs results in an augmented active catalytic surface area and enhanced charge transfer from CE to the electrolyte.

Pt-Pd/MnCo_(2)O_(4)复合型催化剂的制备及其对低碳烃等有机物的催化燃烧性能

在涂覆氧化铝的陶瓷蜂窝载体上,通过化学还原法原位构建MnCo_(2)O_(4)纳米小球颗粒使其生长于氧化铝涂层,制备出两种Pt-Pd/MnCo_(2)O_(4)复合型催化燃烧催化剂MnCo-2、MnCo-3。MnCo-2的贵金属含量比国外参比剂少约44%、比国产参比剂少约16%,乙烷等低碳烃氧化活性与国外参比剂相当,其乙烷转化率为99%时的氧化转化温度(T_(99))、丙烷T_(99)、甲烷转化率为90%时的氧化转化温度(T_(90))分别为440,380,460℃,比国产参比剂低60℃,且在累积800 h的测试中性能稳定。MnCo-3的贵金属含量比国外参比剂少约61%、比国产参比剂少约41%,其试剂总成本约比国产参比剂低38%,其乙烷T 99为475℃,比国产参比剂低25℃。

金属复合氧化物基燃烧催化剂在固体推进剂中的研究进展

为了阐明不同结构类型的金属复合氧化物及其复合材料作为燃烧催化剂时对固体推进剂含能组分的热分解催化性能,分别对尖晶石型、钙钛矿型、类钙钛矿型、碳材料基金属复合氧化物及金属元素掺杂的金属复合氧化物的催化活性进行总结。根据其结构及负载材料的不同,分析其对固体推进剂燃烧速率、压力指数及含能组分热分解峰温、放热量及表观活化能的影响,发现金属复合氧化物及其复合材料表现出比单一金属氧化物更为优异的催化活性。最后,指出了今后金属复合氧化物基燃烧催化剂在固体推进剂中的研究方向。

二氧化钛/氧化石墨烯复合光催化剂的合成

采用水热法,以钛酸四正丁酯及氧化石墨烯(GO)为原料,在水性体系中合成了一系列具有不同GO质量分数的TiO2/GO复合光催化剂。FE-SEM分析结果表明,分散的钛酸四正丁酯以多分子层的形式吸附到氧化石墨烯的表面,最后在水热过程中转化为锐钛型TiO2粒子。当氧化石墨烯的质量分数低于3%时,产物中含有纯TiO2微球及TiO2/GO复合物;当氧化石墨烯质量分数大于5%时,产物为单纯的TiO2/GO复合物。电化学性能测试结果表明,GO复合后,TiO2电极中载流子的传输效率提高。氧化石墨烯复合量为10%时,复合光催化剂显示了对亚甲基蓝最佳的光催化活性。当复合氧化石墨烯转化为石墨烯后,其光催化活性可得到进一步大幅度的提高。

非贵金属催化剂上CO氧化的研究与进展

非贵金属催化剂催化CO氧化反应研究,不仅拓展了非贵金属的应用,而且为探求可替代贵金属催化CO氧化反应的催化剂提供了新机遇,成为当前催化研究中的热点课题之一。本文综述了近年来铜、钴等非贵金属催化剂体系催化CO氧化反应的研究进展。

纳米PbZrO_3/GO复合材料的制备及其对RDX的催化分解

采用自组装法将纳米PbZrO_3和氧化石墨烯(GO)复合,制备了PbZrO_3/GO纳米复合材料;通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、拉曼光谱(Raman)等对其结构进行表征分析;采用差示扫描量热法(DSC)比较并分析了PbZrO_3/GO、PbZrO_3和GO对RDX的催化分解性能。结果表明,通过调整前驱体溶液的pH值,改变纳米颗粒的表面电荷,成功将纳米PbZrO_3(40nm)颗粒紧密负载于GO薄片上;GO的引入有效抑制了PbZrO_3纳米颗粒团聚,比表面积增加了13.73m^2/g;与RDX相比,PbZrO_3/GO、PbZrO_3和GO分别使RDX的热分解峰温降低24.35、14.43和16.57℃;PbZrO_3/GO使RDX热分解过程的表观活化能降低24.4kJ/mol;PbZrO_3/GO复合材料对RDX的催化性能显著优于单一组分的PbZrO_3和GO。

石墨烯金属氧化物复合电极超级电容器

石墨烯/金属氧化物复合材料是一种非常优异的超级电容器电极材料。石墨烯/金属氧化物复合材料结合了石墨烯和金属氧化物两种材料的优点,既可以提高材料的比能量和比功率,又可以提高材料的循环稳定性。综述了石墨烯/金属氧化物复合材料在超级电容器领域的应用现状,并简述了其在超级电容器领域的应用前景和挑战。

锂离子电池用石墨烯基负极材料的研究进展

综述了石墨烯和石墨烯基复合材料作为锂离子电池负极材料的研究进展,重点论述了金属氧化物/石墨烯复合材料,对石墨烯基复合材料的发展趋势进行了展望。