共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Hydrodesulfurization cobalt-based catalysts modified by gold 总被引:1,自引:0,他引:1
Cobalt catalysts supported on amorphous SiO2 and ordered mesoporous silica (MCM-41) were prepared by incipient wetness impregnation.
Gold was added by consecutive impregnation or by co-impregnation. The materials were characterised by XPS, XRD and TPR techniques
and evaluated in the hydrodesulfurization (HDS) of thiophene in order to investigate the effect of the noble metal on the
structure and on the catalytic behaviour of the supported cobalt. Co/MCM-41 exhibited higher HDS activity and higher stability
than the Co/SiO2. Moreover, in contrast to silica case, the gold impregnated MCM-41, produced an enhancement of the cobalt
catalytic activity, and this is likely to be related to an increased cobalt reducibility. Both the support and the addition
of gold improve the cobalt dispersion. 相似文献
4.
5.
碳材料的掺杂改性及其用于燃料电池催化剂的研究 总被引:1,自引:1,他引:0
开发掺杂改性的碳材料用作燃料电池的非贵金属氧还原催化剂已成为燃料电池领域的重要研究课题,相关研究对于降低燃料电池成本、促进燃料电池的商业化具有十分重要的意义。大量研究工作表明,对碳材料进行掺杂改性可以实现其形貌、微观结构、组成及其他表面物理化学性质的优化,从而得到具有较高催化活性、选择性和稳定性的氧还原催化剂。人们在这类催化剂的制备方法、性能优化和催化机理等方面进行了大量研究工作。综述了对碳纳米管、石墨烯、介孔碳、大孔碳、碳微球等碳材料进行掺杂改性的最新进展。并基于目前的研究结果,展望了掺杂碳材料作为燃料电池非贵金属氧还原催化剂的应用前景和未来的发展趋势。 相似文献
6.
7.
本文采用溶胶凝胶法以柠檬酸铁为铁源合成含Fe纳米介孔材料。室温下凝胶样品60 ℃真空干燥后得到的干凝胶采用热重分析(TG)。最终400 ℃焙烧3 h得到介孔Fe2O3/SiO2纳米粒子。合成材料的结构和性能采用XRD、N2吸脱附、TEM、FT-IF、及H2-TPR测试方法表征,结果显示合成了尺寸约50 nm的带有30-45? 介孔孔道的球形的Fe2O3/SiO2纳米粒子,并且成功引入了高分散的Fe3+物种。催化性能是通过傅克烷基化法合成二苯甲烷的反应测试的,实验结果表明该催化剂具有优异的催化性能,高达100 % 苄基氯的转化率和相对较高的二苯甲烷的选择性,并且能够重复利用。 相似文献
8.
郭瑞华 《稀有金属材料与工程》2019,48(7):2284-2291
本文采用活性炭、介孔碳、碳纳米管和石墨烯为催化剂载体,添加CeO2作为助催化剂,用微波辅助乙二醇还原氯铂酸法制备了五组催化剂。利用X射线衍射仪(XRD)、扫描电镜(SEM)和电子能谱(EDAX)、比表面积及孔径分析仪(BET)及X射线光电子能谱(XPS)等对CeO2及催化剂进行微观结构表征;利用电化学工作站对催化剂进行电化学性能测试。结果表明,以石墨烯为载体并加入CeO2助催化剂合成的催化剂对乙醇的催化氧化具有最佳的活性,稳定性及抗中毒能力,其电化学活性表面积为86.83 m2/g,峰电流密度值为751.03 A/g,且对乙醇催化氧化的活化能最低,1100s时的稳态电流密度值为67.33 A/g。 相似文献
9.
10.
设计制备低成本、高催化活性、高稳定性的ORR电催化剂对燃料电池的实际应用至关重要,良好的催化剂载体对提高催化剂的电化学催化性能具有重要意义。炭气凝胶具有孔结构可控、高比表面积、高导电性、大孔体积等优势,是一种非常具有潜力的燃料电池ORR电催化剂载体。本文对最近炭气凝胶作为燃料电池催化剂载体的研究进展进行了综述,简单介绍了炭气凝胶的种类及其负载催化剂的方法,着重讨论了炭气凝胶负载Pt等贵金属催化剂、炭气凝胶负载非贵金属催化剂以及非金属掺杂炭气凝胶催化剂的研究进展,最后总结了其面临的挑战和未来的主要发展方向。 相似文献
11.
《稀有金属(英文版)》2018,(12)
SmCo_5 nanoparticles(NPs) have promising applications in high-density magnetic storage and magnetic nanocomposites. In this work, A novel method to yield SmCo_5 particles with small size and high coercivity was reported. Firstly, Sm_2 O_3-Co NPs with size of 6-15 nm were fabricated by a solvothermal route. Then the agglomerated SmCo_5 particles were obtained by thermal reduction of the precursor, which show high coercivity of2.0 T at room temperature. At last, the as-synthesized SmCo_5 particles were further hydrogenated under high hydrogen pressure of 4 MPa at room temperature, where hydrogen absorption process could form small-sized SmCo_5 H_x particles due to their lattice expansion and hydrogen desorption process could convert SmCo_5 H_x NPs into SmCo_5 NPs. The prepared SmCo_5 NPs after hydrogenation, showing well distribution, have a small size of5-20 nm and room temperature coercivity of 1.22 T. 相似文献
12.
以活性碳(Vulcan XC-72)为载体,用化学还原法制备了不同Pd/Co摩尔比的Pdx-Co/C催化剂。用透射电镜(TEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)对催化剂进行了表征,采用循环伏安法考察了催化剂对甲酸电氧化反应的催化性能。结果表明,Pdx-Co复合催化剂粒子均匀分散在碳载体表面;催化剂中掺入的少量Co元素部分进入Pd晶格,形成了Pd-Co合金;随着Pd/Co摩尔比的增加,Pd颗粒粒径先增大后减小,催化活性也表现出相同的变化趋势;当Pd:Co=8:1时,所得Pd8-Co/C对甲酸氧化的催化活性最高,峰电流密度可达到15.907 mA/cm2。 相似文献
13.
Electrochemical codeposition and electrocatalytic properties of platinum and molybdenum oxide nanoparticles(Pt-MoOx) on carbon-nanotubes/graphite electrode for methanol oxidation were investigated.The micrograph and elemental composition of the resulting Pt-MoOx/CNTs/graphite electrode were characterized by scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).The results show that the Pt-MoOx particles with the average size of about 50 nm are highly dispersed on the CNTs surface.The Pt-MoOx/CNTs/graphite electrode delivers excellent electrocatalytic properties for methanol oxidation.The highest mass activity(Am)reaches 264.8 A/g at the loading mass of 159.3μg/cm2.This may be attributed to the small particle size and high dispersion of Pt-MoOx catalysts deposited on the CNTs surface.The kinetic analysis from electrochemical impedance spectroscopy(EIS)reveals that the existed MoOx phase can improve the chemisorptive and catalytic properties for methanol oxidation. 相似文献
14.
直接甲醇燃料电池(DMFC)以其高效、低污染的特点而备受关注。铂基电催化剂被认为是DMFC阳极的有效催化剂。但由于在甲醇氧化过程中铂的活性中心容易被产生的中间产物如CO等吸附和堵塞,导致催化活性降低,稳定性差,严重制约了直接甲醇燃料电池推广应用。稀土元素由于其4f轨道独特的电子结构和相应的镧系收缩效应,在铂基电催化剂中可有效提高铂催化剂的活性和耐久性。本文简要总结近年来稀土氧化物作为铂基电催化剂的助催化剂、碳材料掺杂改性剂和载体在甲醇氧化反应中的催化活性和抗CO中毒能力应用研究,以及铂-稀土金属(Pt-RE)纳米合金催化剂对DMFC长期运行稳定性的影响;并对稀土元素在铂基电催化剂中的应用发展提出了展望。 相似文献
15.
概括了贵金属催化剂的种类,从制备方法、载体的选择、颗粒尺寸以及催化剂活性中心结构等几个方面分析催化反应活性的影响因素,并且介绍了各种贵金属催化剂相应的催化反应。 相似文献
16.
以介孔碳材料CMK-3为载体,采用乙二醇还原的方法进行金属铂负载,制备了不同铂含量(1.5%、2.0%和3%)的催化剂。XRD、BET、TEM的表征结果表明,催化剂保持了CMK-3高度有序的介孔结构,铂粒子的平均粒径在5 nm左右,均匀地分散在CMK-3孔道内。用萘的加氢反应对此催化剂的性能进行评价,获得的最优条件为:使用Pt(2%)/CMK催化剂,在280℃、氢气压力3 MPa、氢油比500、质量空速2 h-1的条件下,萘的转化率和生成十氢萘的选择性均大于98%。此催化剂对降低石油产品中芳烃具有潜在应用价值。 相似文献
17.
目的通过Pb元素的添加来提高Pt/C催化剂电催化氧化甲酸的性能。方法通过乙二醇协助硼氢化钠还原法,以氯铂酸为Pt源和硝酸铅为Pb源制备不同原子比的PtxPb/C催化剂。采用X射线衍射光谱法(XRD)和透射电子显微镜技术(TEM)表征样品的晶体结构和颗粒形貌;采用循环伏安法表征样品催化氧化甲酸的性能。结果利用乙二醇协助硼氢化钠还原法成功制得了Pt和Pb原子比不同的PtxPb/C催化剂,XRD和TEM测试结果表明这些样品均为Pt的面心立方结构,且颗粒大小均一、分散均匀,其平均粒径为4 nm左右。循环伏安测试结果表明PtxPb/C催化剂催化氧化甲酸的性能优于商业Pt/C催化剂的催化性能,且受Pt和Pb原子比的影响,当原子比为5∶1时,其对氧化甲酸的催化性能最好,峰电位对应的Pt的比质量活性达到2000 m A/(mg Pt),远远高于商业Pt/C,同时计时电流曲线表明其具备良好的稳定性。结论 Pb原子的加入影响了Pt原子的电子结构,与Pb对Pt的协同作用共同促进了CO等中间产物在Pt表面的快速氧化,降低了催化氧化甲酸的初始电位,促使甲酸在低电位直接氧化为CO2和H2O,提高了其催化氧化甲酸的峰电流,有效减轻了Pt中毒,提高了其催化活性。 相似文献
18.
Gold nanoparticles used in most experiments (1–10 nm) in gold catalysis show varying degrees of reactivity, with particles
below 5 nm generally being more reactive. The origin of this activity is a subject of a number of model experiments and theoretical
studies on either clusters of a few atoms in size or extended surfaces (smooth or stepped). In the work described here, a
classical theory for the variation of the metal workfunction with cluster size, Extended Hückel Theory (EHT) calculations
combined with DFT calculations, as well as a carbon monoxide (CO) chemisorption model are combined to develop a relationship
between metal particle size and the particle's reactivity towards CO. For gold, it is shown that while the contribution of
the d-band hybridization energy to the total CO chemisorption energy is unfavourable for bulk gold, this is not true for gold
particles below 5–6 nm. That is, the d-band hybridization energy is negative for small gold particles. This is believed to
be explanation of the onset of high reactivity for small gold particles. 相似文献
19.
采用化学共还原法制备了聚乙烯吡咯烷酮(PVP)稳定的Pd/Ni双金属纳米溶胶,采用TEM、HR-TEM等对所合成的Pd/Ni双金属纳米溶胶进行了表征,并系统研究了PVP用量、还原剂用量、金属盐离子浓度及金属比例等对该溶胶型双金属纳米催化剂的影响。结果表明:所制备的Pd/Ni双金属纳米溶胶的平均粒径在2 nm左右,双金属纳米溶胶催化剂催化NaBH_4制氢活性优于单金属Pd和Ni纳米溶胶的活性。其中Pd_(10)Ni_(90)双金属纳米溶胶的催化活性最高,其催化NaBH_4制取氢气的活性可以达到8250 mol_(H2)·mol_(Pd)~(-1)·h~(-1),Pd_(20)Ni_(80)双金属纳米溶胶催化剂催化NaBH_4水解反应的活化能为35.7 kJ/mol,反应焓为33.3 kJ/mol,反应熵为-150 J/mol。研究结果还表明,所制备的Pd/Ni双金属纳米溶胶催化剂具有很好的催化稳定性,即使4次催化试验后该催化剂仍然保持着较高的催化活性。密度泛函理论计算结果表明,Ni原子与Pd原子之间发生的电子转移使得Pd原子带负电而Ni原子带正电,荷电的Pd和Ni原子成为催化反应的活性中心。 相似文献
20.
The electrochemical ammonia synthesis has attracted increasing attention due to its energy saving characteristics.However,developing novel electrocatalysts and their mechanism remain great challenges.Here,several transition metal(TM) atoms doped on phosphorene were studied as N2 fixation electrocatalysts by using density functional theory(DFT) calculations.The results demonstrate that single Ru atom doped phosphorene shows an excellent catalytic activity for ammonia synthesis via the ... 相似文献