Nd_x作为助催化剂对PtRu/C电催化氧化甲醇活性的影响

采用沉积-还原法制备了PtRu-NdOx/C催化剂,借助TEM、EDS和XRD等测试手段对其进行了微结构和组成的表征.结果表明,催化剂中Pt与Ru以合金形式存在,而Nd的氧化物则以无定形形态存在.催化剂粒子的平均粒径在2nm左右,晶胞参数为0.3896nm,Nd氧化物的加入对PtRu合金的晶体结构影响不明显.采用循环伏安法和计时电流法,比较了PtRu-NdOx/C催化剂和PtRu/C催化剂对甲醇氧化的电催化活性,结果表明,加入Nd的氧化物作为助催化剂能明显提高PtRu/C催化剂对甲醇氧化的电催化性能.     

NdOx作为助催化剂对PtRu/C电催化氧化甲醇活性的影响

采用沉积-还原法制备了PtRu-NdOx/C催化剂, 借助TEM、EDS和XRD等测试手段对其进行了微结构和组成的表征. 结果表明, 催化剂中Pt与Ru以合金形式存在, 而Nd的氧化物则以无定形形态存在. 催化剂粒子的平均粒径在2 nm左右, 晶胞参数为0.3896 nm, Nd氧化物的加入对PtRu合金的晶体结构影响不明显. 采用循环伏安法和计时电流法, 比较了PtRu-NdOx/C催化剂和PtRu /C催化剂对甲醇氧化的电催化活性, 结果表明, 加入Nd的氧化物作为助催化剂能明显提高PtRu /C催化剂对甲醇氧化的电催化性能.     

高分散PtRu/C催化剂的制备及对甲醇及吸附态CO的电催化氧化

采用化学还原浸渍法在两种不同条件下制备炭载PtRu催化剂,通过XRD和TEM技术对催化剂的晶体结构及微观形貌进行了分析,运用循环伏安法、线性扫描法来检测不同条件下制备的催化剂对甲醇及吸附态CO(COad)电催化氧化活性的影响.结果表明,不同条件下制备的催化剂Pt和Ru形成合金的程度不同,Pt-Ru合金原子的颗粒在载体炭上的粒径大小和分布不同,导致催化剂对甲醇及COad的电氧化催化活性不同.其中以甲醛为还原剂在乙二醇体系中制备的催化剂PtRu/C-2能形成较好的合金状态,粒径小,分布均匀,对甲醇及COad的氧化具有较高的电催化活性.     

碳载Pt和PtRu催化剂的甲醇电氧化比较

利用电化学方法对商用Pt/C和PtRu/C催化剂在酸性介质中的甲醇电氧化进行了比较研究.动电位和恒电位氧化实验结果皆表明PtRu/C比Pt/C对甲醇电催化活性高.PtRu合金的形成不仅改变了催化剂表面对氢的吸附性质,而且使氧化物还原峰电位向阴极方向移动.Ru与甲醇的相互作用为温度活化过程,需要较高的温度.     

二维多层PtRu/PtNd纳米薄膜的结构效应及电催化氧化活性

采用离子束多靶溅射技术控制膜层结构制备出二维多层PtRu/PtNd纳米合金薄膜作为微型直接甲醇燃料电池(DMFCs)阳极催化电极材料. 应用X射线光电子能谱(XPS)、原子力显微镜(AFM)、X射线衍射(XRD)、掠入射X射线衍射(GIXD)研究了薄膜表面的化学状态、形貌以及薄膜表层、次表层和体相的结构,并用CO-stripping伏安法、循环伏安法(CV)、线性扫描伏安法(LSV)、计时电流法(CA)等电化学方法测试薄膜催化剂的电化学活性比表面积及其对甲醇的电催化氧化. 结果表明, 多次交替沉积制备的PtRu/PtNd薄膜, 由于溅射产生的Pt+、Ru+和Pt+、Nd+之间的相互作用, 使薄膜表面的化学状态和膜层结构发生变化, 其衍射谱峰呈现异常宽化, Pt与Nd之间产生电子转移, 证实了PtRu/PtNd纳米合金薄膜是一种具有特殊膜层结构和电子结构的二维多层PtRu/PtNd纳米合金薄膜, 电化学活性比表面积高达115.00m2 ·g-1, 在酸性溶液中电催化氧化甲醇的活性显著提高.     

稀土Eu掺杂PtRu/C催化剂及其对甲醇电氧化的性能

采用化学还原和热处理方法对商业PtRu/C催化剂进行稀土Eu掺杂,制备了不同Eu含量的PtRuEux/C催化剂.透射电子显微镜(TEM)、X射线能量色散光谱(EDX)、X射线衍射(XRD)和X射线光电子能谱(XPS)等方法表征催化剂的结果表明,Eu的掺杂未改变PtRu/C催化剂的平均粒径(约为3nm),并且Eu以金属和氧化物两种形态修饰PtRu表面.循环伏安和计时电流法测试显示,PtRuEux/C催化剂较商业PtRu/C对甲醇氧化具有更高的活性,其中PtRuEu0.3/C的活性最高.运用原位傅里叶变换红外(FTIR)光谱从分子水平研究了该催化剂对甲醇电催化氧化的反应过程,检测到甲醇在催化剂上解离吸附的吸附态产物是线型吸附态CO(COL),Eu的掺杂使COL的氧化电位降低,明显提高了催化剂的活性和抗CO毒化的能力.     

高负载率纳米Pt-Ru/C催化剂的制备和表征

以Vulcan XC-72R碳黑为载体, 通过在含十二烷基硫酸钠(SDS)的乙二醇溶液中直接还原氯铂酸和三氯化钌, 制备了负载率为60%的纳米PtRu/C催化剂. 透射电镜(TEM)和X射线衍射(XRD)分析结果表明, SDS的加入可显著改善PtRu纳米颗粒在载体表面分散性, 平均粒径达到2.7 nm. 电化学循环伏安法(CV)测试的结果显示, 利用这种方法制备的纳米PtRu/C催化剂对于甲醇氧化具有较强的抗中毒能力和较高的电催化活性.     

纳米多孔Pt,PtRu及PtRuIr催化剂的电化学FTIR光谱之比较(英文)

近年来,致力于Pt基电催化剂在燃料电池中的应用已取得显著成果.但随贵金属(如Pt)成本的增加,提高催化剂的活性以及降低负载量的需求也日益迫切.为此,作者合成并比较了纳米多孔Pt,PtRu及PtRuIr3种电催化剂.以扫描电镜(SEM)、能量色散谱(EDS)、X射线衍射(XRD)和X射线光电子能谱(XPS)表征水热法制得的纳米多孔电极.CO汽提实验和甲醇氧化反应测试上述纳米多孔材料的电催化活性.结果表明,添加Ir极大改善纳米多孔PtRu的活性.采用现场电化学FTIR光谱技术研究纳米多孔Pt,PtRu及PtRuIr电极上的甲醇氧化反应,以进一步揭示这种显著增强效应的成因.     

XC-72碳和碳纳米管负载PtRu纳米粒子的微波快速合成及其对甲醇的电化学氧化

利用微波辐射加热技术快速合成了XC-72碳和碳纳米管(CNTs)负载的PtRu合金纳米粒子,合金负载的质量分数为20%,Pt和Ru的原子比接近于1:1.透射电镜观察表明微波合成的PtRu合金纳米粒子具有细小的粒径和狭窄的尺寸分布,所合成的PtRu合金纳米粒子高度分散在XC-72碳和CNTs的表面,其平均粒径分别为3.3 nm和2.8 nm.电化学实验表明微波合成的PtRu/XC-72和PtRu/CNTs纳米催化剂比用湿化学方法以KBH₄还原制备的催化剂对甲醇的电化学氧化具有更高的催化活性.     

直接甲醇燃料电池催化剂性能的影响因素

考察了温度、电位及中间产物等因素对直接甲醇燃料电池催化剂性能的影响.结果表明,温度的升高会显著促进Pt催化剂粒子的聚结.对于PtRu催化剂,Ru氧化物/水合氧化物对Pt微晶的聚结具有抑制作用.高温放电实验后,PtRu催化剂的合金化程度有所提高.高电位会加速电催化剂的降解.电极反应中间产物甲酸和甲醛对甲醇电催化氧化反应具有一定的抑制作用,其中甲醛的影响更大.     

不同结构颗粒对PMMA基复合材料性能影响

采用原位本体聚合法制备PMMA/MCM-41(with template),PMMA/SBA-15(with template),PMMA/SiO2三种复合材料.研究了介孔分子筛MCM-41,SBA-15和SiO2对PMMA复合材料拉伸强度,冲击强度,热稳定性的影响.由于合成介孔分子筛MCM-41,SBA-15时所用的模板剂CTAB和P123分布于孔口处和颗粒表面上,分别与PMMA基体产生物理缠结作用,增加了两者的相容性;且P123(EO20PO70EO20)表面有较大的PO/EO比率,与小分子量的CTAB相比有较强的疏水性,使得PMMA/SBA-15(with template)复合材料的性能要优于PMMA/MCM-41(with template).     

Influence of the pore structure of MCM-41 and SBA-15 silica fibers on atomic layer chemical vapor deposition of cobalt carbonyl

Mesoporous high surface area MCM-41 and SBA-15 type silica materials with fibrous morphology were synthesized and used as support materials for the ALCVD (atomic layer chemical vapor deposition) preparation of Co/MCM-41 and Co/SBA-15 catalysts. Co/MCM-41 and Co/SBA-15 catalysts were prepared by deposition of Co2(CO)8 from the gas phase onto the surfaces of preheated support materials in a fluidized bed reactor. For both silica materials, two different kinds of preparation methods, direct deposition and a pulse deposition method, were used. Pure silica supports as well as supported cobalt catalysts were characterized by various spectroscopic (IR) and analytical (X-ray diffraction, Brunauer-Emmett-Teller, elemental analysis) methods. MCM-41 and SBA-15 fibers showed considerable ability to adsorb Co2(CO)8 from the gas phase. For MCM-41 and SBA-15 silicas, cobalt loadings of 13.7 and 12.1 wt % were obtained using the direct deposition method. The cobalt loadings increased to 23.0 and 20.7 wt % for MCM-41 and SBA-15 silicas, respectively, when the pulse deposition method was used. The reduction behavior of silica-supported cobalt catalysts was found to depend on the catalyst preparation method and on the mesoporous structure of the support material. Almost identical reduction properties of SBA-15-supported catalysts prepared by different deposition methods are explained by the structural properties of the mesoporous support and, in particular, by the chemical structure of the inner surfaces and walls of the mesopores. Pulse O2/H2 chemisorption experiments showed catalytically promising redox properties and surface stability of the prepared MCM-41- and SBA-15-supported cobalt catalysts.     

Structures and catalytic properties of PtRu electrocatalysts prepared via the reduced RuO2 nanorods array

Structures and properties of PtRu electrocatalyts, derived from the aligned RuO2 nanorods (RuO2NR), are investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and cyclic voltammetry toward COads and methanol oxidation. The catalytic activity of methanol oxidation and the CO tolerance are promoted significantly by reducing RuO2 into Ru metal before decorating with Pt. Reduction of RuO2NR was carried out by either thermal decomposition at 650 degrees C in vacuum or H2-reduction at 130 degrees C in low-pressure hydrogen. Reduction assisted by hydrogen allows infiltrating decomposition at low temperature and produces an array of nanorods with rugged walls featuring small Ru nuclei and larger surface area. Pt-RuNR, whose surface Pt:Ru ratio=0.58:0.42 was prepared by decorating with 0.1 mg cm(-2) Pt on the H2-reduced array containing 0.39 mg cm(-2) Ru, demonstrates a favorable combination of CO tolerance and high methanol oxidation activity superior to other RuO2NR-derived catalysts. When compared with a commercial electrocatalyst of PtRu (1:1) alloy (<4 nm), the activity of Pt-RuNR in methanol oxidation is shown to be somewhat lower at potential<0.48 V and higher at potential>or=0.48 V.     

Ag/SBA-15表面催化过程的现场SERS研究

以三嵌段共聚物P₁₂₃为模板剂, 正硅酸乙酯为硅源, 水热合成了介孔分子筛SBA-15, 通过对SBA-15内外表面修饰, 使用银氨溶液和硝酸银溶液作为金属源合成Ag/SBA-15, 透射电镜(TEM)研究表明在SBA-15孔道内较好地分散了颗粒状和棒状的Ag纳米粒子. 以苯硫酚作为探针分子, 研究了负载Ag纳米粒子的SBA-15的SERS效应, 结果表明Ag/SBA-15具有良好的SERS活性. 另外, 该材料对催化硼氢化钠还原对硝基苯酚具有良好的催化效果, 通过结合现场SERS技术, 研究了该催化过程的机理.     

MCM-41 and SBA-15 supported Cp2ZrCl2 catalysts for the preparation of nano-polyethylene fibres via in situ ethylene extrusion polymerization

Under atmospheric pressure, nano-polyethylene fibres were prepared via in situ ethylene extrusion polymerization, with MCM-41 and SBA-15 supported zirconocene dichloride (Cp₂ZrCl₂) catalytic systems, respectively. The effects of the geometrical structures and surface properties of MCM-41 and SBA-15 on the morphology of the resultant polyethylene, catalytic activity and polymerization rate were investigated and compared in various polymerization conditions. The possible formation mechanism of nano-polyethylene fibres with MCM-41 and SBA-15 supported Cp₂ZrCl₂ as catalyst was discussed.     

Electron microscopy study of novel Pt nanowires synthesized in the spaces of silica mesoporous materials.

Structures of Pt-nanowires, synthesized in channels of silica mesoporous materials MCM-41, SBA-15 and MCM-48, were investigated by transmission electron microscopy. One dimensional (1D) Pt-nanowires were formed inside the channels of the MCM-41, and were single crystals with a length of several tens to several hundreds nanometers and a diameter of ca. 3 nm pt-nanowires synthesized in SBA-15 formed a new 3D-network following 3D-pore geometry of SBA-15; that is, the main 1D-channels are interconnected to each other through randomly distributed tunnels. These Pt-nanowires showed a well single crystalline. MCM-48 has two non-intersecting chiral channels, and Pt-networks were mostly formed in one of the two channels. Therefore the networks were also chiral; however, the chirality of Pt-networks remained to be determined. It was shown that all Pt-nanowires were formed following the channel geometries of silica mesoporous materials used.     

Synthesis of highly active nanostructured PtRu electrocatalyst with three-dimensional mesoporous silica template

Nanostructured PtRu material has been successively synthesized via chemical co-reduction of hexachloroplatinic acid and ruthenium trichloride using three-dimensional (3D) hexagonal mesoporous SBA-12 silica as a solid template, and has been studied as an electrocatalyst toward methanol electro-oxidation. The ordered nanostructure of the PtRu particles has been disclosed by transmission electron micrographs and is characterized by regular pores of ca. 3.0 ± 0.3 nm in diameter separated by walls of ca. 3.0 ± 0.3 nm thick. X-ray diffraction and energy dispersive X-ray spectroscope studies indicate that the PtRu material comprises of complicated phases rather than a single alloy phase of Pt and Ru. The specific electrochemical surface area of the nanostructured powder measured using both CO and underpotential deposited Cu stripping techniques is 74–78 m² g^–1, higher than that of unsupported precious metal catalysts prepared using standard techniques. The combination of high surface area and periodic nanostructure of the templated PtRu makes it an interesting promising fuel cell electrocatalyst. This has been demonstrated by the high activity of the templated PtRu towards the methanol electrooxidation. Therefore the solid template route based on 3D mesoporous silica with controlled pore size and high pore interconnectivity provides an interesting alternative to produce promising high-surface-area electrode materials.     

有序介孔二氧化硅对正丁醛的吸附性能

合成了一系列具有不同孔结构与性质的有序介孔二氧化硅材料SBA-15、MCM-41、SBA-16、KIT-6, 同时通过改变水热温度制备了不同孔径大小的SBA-15, 并利用小角X射线散射、透射电镜、扫描电镜和氮气吸附-脱附等手段, 对其介孔结构进行了表征. 以正丁醛为探针分子, 考察了其对有机醛的吸附, 并与Y-沸石的吸附性能做了对比. 结果表明, 材料的介孔比表面积与其对正丁醛的吸附量成正比, 吸附等温线符合Langmuir 模型, 属于单层吸附, 具有最大介孔比表面积的MCM-41对正丁醛的吸附量最大(484 mg·g^-1). 最后将SBA-15添加到卷烟滤嘴中, 实验结果表明, SBA-15能显著降低卷烟烟气中巴豆醛的释放量.     

有序介孔二氧化硅对正丁醛的吸附性能

合成了一系列具有不同孔结构与性质的有序介孔二氧化硅材料SBA-15、MCM-41、SBA-16、KIT-6,同时通过改变水热温度制备了不同孔径大小的SBA-15,并利用小角X射线散射、透射电镜、扫描电镜和氮气吸附-脱附等手段,对其介孔结构进行了表征.以正丁醛为探针分子,考察了其对有机醛的吸附,并与Y-沸石的吸附性能做了对比.结果表明,材料的介孔比表面积与其对正丁醛的吸附量成正比,吸附等温线符合Langmuir模型,属于单层吸附,具有最大介孔比表面积的MCM-41对正丁醛的吸附量最大(484 mg·g-1).最后将SBA-15添加到卷烟滤嘴中,实验结果表明,SBA-15能显著降低卷烟烟气中巴豆醛的释放量.     

Influence of the Morphology of Mesoporous Carbon on the Electrocatalytic Activity of Pt in Oxygen Reduction

Russian Journal of Applied Chemistry - Mesostructured silicates MCM-48, SBA-15, and MCM-41 were synthesized, and the corresponding ordered mesoporous carbons CMK-1, CMK-3, and CS41 were prepared on...