Mo和W共掺杂对Ru-Se簇合物催化氧还原性能的影响

以过渡金属羰基化合物和硒粉为原料,采用低温回流技术在1,6-己二醇中合成了W和Mo共掺杂的Ru-Mo-W-Se纳米簇合物。利用SEM、XRD和旋转圆盘电极(RDE)技术表征了合成催化剂的形貌、结构和电催化性能。催化剂以六方结构的Rux簇为主相,同时形成无定形相,聚集颗粒高度分散。在氧气饱和的0.5mol·dm-3H2SO4溶液中,Ru-W-Mo-Se催化剂对氧还原反应(ORR)表现出较高的催化活性和稳定性,开路电位为0.90 V(vs.NHE),耐甲醇能力比Ru-Se明显增强。在Tafel电位范围内,催化剂的交换电流密度为4.98×10-4mA·cm-2,具有较好的催化动力学性能。     

Ru-Fe二元金属纳米粒子对氧还原的电催化性能

在1,6-己二醇溶剂中,以Ru3(CO)12和Fe3(CO)12为原料,采用低温回流方法合成了Ru-Fe纳米粒子催化剂。利用扫描电镜(SEM)、X射线衍射仪(XRD)和电化学技术表征了催化剂的物理特征和电催化性能.催化剂粉末以六方结构的Rux簇为主相,呈现出高度均匀而聚集的纳米颗粒特征.在0.5mol/L H2SO4溶液中,Ru-Fe催化剂对氧还原反应(ORR)的电催化活性高于Rux,主要归因于d电子从Ru原子到Fe原子的转移过程.     

过渡金属掺杂Ru-Se簇合物电催化剂氧还原性能的对比研究

采用羰基金属化合物低温合成法制备了不同掺杂元素的M-Ru-Se(M=Fe，W，Mo)簇合物，并应用旋转圆盘电极电位扫描法测试簇合物的电催化活性及其抗甲醇性，采用TEM、XRD、EDS技术表征催化剂的微观形貌、结构和组成。结果显示，掺杂过渡元素对簇合物的催化活性及其抗甲醇性有明显的影响，其中Mo-Ru-Se的还原电流最高，催化活性最高，W-Ru-Se次之，Fe-Ru-Se最低；电解质中加入甲醇后，W-Ru-Se的活性最高，Mo-Ru-Se次之，Fe-Ru-Se最低；相对地，W-Ru-Se具有较高的抗甲醇性。掺杂元素主要通过影响Ru核d电子结构改变簇合物的催化性能。     

高质量和深度凹陷的PtPdNi纳米立方体作为高效氧还原反应的催化剂

聚合物电解质燃料电池阴极上的氧还原反应需要使用铂基催化剂,铂是地球上的贵金属之一.采用将不同的金属优化到核心中等多种策略可提高铂基催化剂的活性,从而降低铂的负载量.通过致力于高催化活性Pt2.7Pd0.3Ni凹面立方结构与高指数晶面的复合,表明凹面结构可以提供更多的活性位和高水平的催化活性,如果与其他金属复合,可以降低...     

表面修饰型铂基氧还原电催化剂研究进展

氧气还原反应是燃料电池中的重要电极反应,但其动力学过程非常迟缓,需高度依赖资源稀缺、价格高昂的贵金属Pt.加之Pt基催化剂还面临着实际工况下耐久性不足的问题,这些都严重阻碍了燃料电池的产业化进程.对Pt基纳米催化剂进行表面功能化修饰可有效优化和提升其氧还原活性和稳定性.本文综述了最近几年表面修饰型Pt基氧还原催化剂的最...     

一体式可再生燃料电池双功能氧催化剂的研究进展

双功能氧催化剂的催化活性及稳定性是决定一体式可再生燃料电池能否高效运作的关键因素之一。得益于分别对于氧还原及氧析出反应特定中间产物适当的结合能,铂与铱、钌及其氧化物所制成的贵金属催化剂常被应用于一体式可再生燃料电池中作为双功能氧催化剂。同时,近年来对于非铂族双功能氧催化剂的研究也取得了较大进展。本篇综述从一体式可再生燃料电池中氧还原及氧析出反应的作用机理出发,首先着重对传统铂基双功能催化剂的构效关系进行了总结,其次介绍了钙钛矿型、尖晶石型氧化物、非金属等新型双功能氧催化剂的发展趋势。此外,本文对于该研究领域所存在的限制条件和发展路线也进行了总结与展望。     

基于超重力技术开展Co-N-CNTs催化剂制备及其氧还原性能的研究

开发高效的非贵金属氧还原(ORR)催化剂是促进燃料电池商业化进程的关键。本研究利用超重力技术制备了一种优良的非贵金属ORR催化剂Co-N-CNTs。物理表征表明,通过超重力技术可以使作为活性位点的金属Co纳米颗粒均匀分布在Co-N-CNTs催化剂表面,X射线光电子能谱(XPS)揭示Co-N-CNTs催化剂中的N元素不仅可以和碳纳米管(CNTs)中的C元素形成吡咯氮和石墨氮,还可以形成具有更高氧还原活性的吡啶氮结构。电化学测试结果表明,通过超重力技术制备的Co-N-CNTs催化剂的起始电位和半波电位与商业Pt/C催化剂相当;而且,Co-N-CNTs催化剂展现出优良的抗甲醇性能。     

非Pt基催化剂在质子交换膜燃料电池阴极氧还原反应中的研究进展

对绿色、高效能源储存装置日趋强烈的需求,使得用于清洁能源转换的先进技术获得了研究者的密切关注。具有环境友好、高能量转换效率等优势的燃料电池是传统能源转换装置极具希望的替代品。然而,工业催化界中商业化程度高的Pt体系催化剂存在成本高、稳定性差和抗毒化能力弱等问题,限制了燃料电池的进一步发展。开发储量丰富、成本低廉且性能优异的非Pt体系氧还原（ORR）催化剂是降低燃料电池成本,促进其大规模应用的有效途径。对此,结合近10年来国内外研究成果,系统介绍了当前各类非Pt体系ORR催化剂的研究进展,包括非贵金属基以及非金属基催化剂。同时,针对各类催化剂的优点、不足及改性策略进行了归纳与总结,并对未来ORR电催化剂的发展提出挑战、做出展望。     

碳载Pt-P催化剂对氧还原的电催化性能

用NaH2PO2液相还原方法制得碳载Pt-P(Pt-P/C)催化剂(m(Pt)∶m(P)=5∶1)。 X射线衍射谱测量表明,Pt-P/C催化剂的Pt衍射峰的2θ值稍大于Pt/C催化剂的相应值,表明P进入了Pt晶格,形成了Pt-P合金。 电化学测试表明,Pt-P/C催化剂对氧还原的电催化性能要比商品化的E-TEK Pt/C催化剂好,其还原电位正移了40 mV。 由于Pt-P/C催化剂中Pt-P粒子的平均粒径和相对结晶度与Pt/C催化剂相似,推测Pt-P/C催化剂对氧还原的电催化性能好于Pt/C催化剂的原因可能为P的作用。     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

SO2-tolerant Pt-MoO3/C catalyst for oxygen reduction reaction

A Pt-MoO3/C catalyst,aimed to eliminate the harmful effect of sulfur dioxide（SCb） on the performance of Pt nanoparticles（NPs） for catalysis of oxygen reduction reaction（ORR） in proton exchange membrane fuel cells（PEMFC）,is developed and characterized by TEM,XRD and XPS.The results reveal that Pt-MoO3/C catalyst exhibits not only a higher catalytic activity,but also a better SO2 poisoning resistance and a better recovery performance than the commercial Pt/C catalyst does.     

不同pH下多晶Au电极上的氧还原反应

利用旋转圆盘电极体系系统研究了不同pH下氧气在多晶Au电极上的还原反应,并计算了不同pH条件及不同超电势范围内的Tafel斜率.研究发现,同在酸性（但是pH不同）或同在碱性（但是pH不同）的介质中氧还原起始电位以及纯粹动力学控制区（电流较小的区域）的氧还原电流几乎不随溶液的pH值而变化.酸性条件下以及碱性条件的高超电势范围内,Tafel斜率接近120mV/dec;而碱性条件的低超电势范围内,Tafel斜率接近60mV/dec.金电极上ORR的活化超电势随着pH值的增加而降低约79mV/pH.初步讨论了pH对氧还原机理和动力学的影响及其内在原因.     

Synthesis and characterization of iron‐ and nitrogen‐functionalized graphene catalysts for oxygen reduction reaction

Iron‐ and nitrogen‐functionalized graphene (Fe‐N‐G), as well as iron‐ and nitrogen‐functionalized oxidized graphene (Fe‐N‐Gox) catalysts were synthesized as non‐noble metal electrocatalysts for oxygen reduction reaction (ORR). The physical properties of the resultant catalysts were characterized using nitrogen adsorption measurements, X‐ray diffraction, Raman and X‐ray photoelectron spectroscopies and transmission electron microscopy. Subsequently, ORR activities of the catalysts were determined electrochemically using a conventional three‐electrode cell via cyclic voltammetry with a rotating disc electrode, the results of which indicated that the synthesized catalysts had a marked electrocatalytic activity towards ORR in acid media. Among the synthesized catalysts, that functionalized using 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine as nitrogen source had the highest electrocatalytic activity with the highest onset potential (0.98 V/SHE) and limiting current density (5.12 mA cm⁻²). The findings are particularly important to determine a non‐precious metal catalyst for ORR activity in fuel cells.     

Rational design of platinum-group-metal-free electrocatalysts for oxygen reduction reaction

Platinum-group-metal (PGM)-free materials have been promised as potential replacement for Pt as the cathodic catalyst in proton exchange membrane fuel cells. Critical design criteria of the PGM-free catalyst reside on the high active site density to compensate its generally lower turn-over frequency and improved mass-charge transfers during the electrocatalysis. This short review summarizes the research activities in recent years from our team at Argonne National Laboratory in preparing highly active oxygen reduction reaction (ORR) catalysts using rationally designed porous organic precursors, as reported in the First Telluride Science Research Center (TSRC) Workshop on PGM-free Electrocatalysis in 2019. More recent studies by others are also discussed.     

聚苯胺衍生Fe-N-C催化剂在碱性电解质中对氧还原反应的催化性能

经过热解聚苯胺、碳和FeCl₃的混合物制备的Fe-N-C材料在酸性电解质中对氧还原反应表现出高的催化活性;由于材料中不存在任何贵金属, 因而被认为是一类新型非贵金属氧还原催化剂. 然而这类催化剂在碱性电解质中催化氧还原反应的性能如何尚不清楚. 本文使用旋转圆盘电极技术考察了制备的两个Fe-N-C催化剂在KOH水溶液中催化氧还原反应性能, 发现这两个催化剂表现出比无金属的N掺杂碳材料更高的活性. 与商业Pt/C催化剂相比, 它们催化氧还原反应的起始电势和半波电势分别仅低60和40 mV左右, 计时电流测试表明, 它们比Pt/C催化剂显示出更好的稳定性. 此外, 在这两个Fe-N-C催化剂上的氧还原反应主要遵循四电子途径. 本工作显示, Fe-N-C材料有望用于碱性燃料电池氧还原反应催化剂.     

Oxygen-deficient titania as alternative support for Pt catalysts for the oxygen reduction reaction

Insufficient electrochemical stability is a major challenge for carbon materials in oxygen reduction reaction （ORR） due to carbon corrosion and insufficient metal-support interactions. In this work, titania is explored as an alternative support for Pt catalysts. Oxygen deficient titania samples including TiO2-x and TiO2_xNy were obtained by thermal treatment of anatase TiO2 under flowing H2 and NH3, respectively. Pt nanoparticles were deposited on the titania by a modified ethylene glycol method. The samples were characterized by N2-physisorption, X-ray diffraction and X-ray photoelectron spectroscopy. The ORR activity and long-term stability of supported Pt catalysts were evaluated using linear sweep voltammetry and chronoamperometry in 0.1 mol/L HC104. Pt/TiO2_x and Pt/TiO2_xNy showed higher ORR activities than Pt/TiO2 as indicated by higher onset potentials. Oxygen deficiency in TiO2-x and TiO2-xNy contributed to the high ORR activity due to enhanced charge transfer, as disclosed by electrochemical impedance spectroscopy studies. Electrochemical stability studies revealed that Pt/TiOE_x exhibited a higher stability with a lower current decay rate than commercial Pt/C, which can be attributed to the stable oxide support and strong interaction between Pt nanoparticles and the oxygen-deficient TiO2-x support.