一步法制备还原态氧化石墨烯载铂纳米粒子及其对甲醇氧化的电催化性能

以天然石墨为原料,采用改进的Hummers法制备氧化石墨.然后采用简单的一步化学还原法在乙二醇(EG)中同时还原氧化石墨烯(GO)和H₂PtCl₆制备高分散的铂/还原态氧化石墨烯(Pt/RGO)催化剂.采用傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)和透射电子显微镜(TEM)对催化剂的微结构、组成和形貌进行表征.结果表明, GO已被还原成RGO, Pt纳米粒子均匀分散在RGO表面,粒径约为2.3 nm.采用循环伏安法和计时电流法评价催化剂对甲醇氧化的电催化性能,测试结果表明, Pt/RGO催化剂对甲醇氧化的电催化活性和稳定性与Pt/C和Pt/CNT相比有了很大提高.另外其对甲醇电催化氧化的循环伏安图中正扫峰电流密度(I_f)和反扫峰电流密度(I_b)的比值高达1.3,分别是Pt/C和Pt/CNT催化剂的2.2和1.9倍,表明Pt/RGO催化剂具有高的抗甲醇氧化中间体CO_ad的中毒能力.     

以切短多壁碳纳米管为载体制备高活性Pt/SCNT及PtRu/SCNT燃料电池催化剂

采用乙醇为助磨剂,利用球磨的方法将5-15μm长的多壁碳纳米管切短成长度约为200nm,并且分布较为均匀的短碳纳米管(SCNT).以SCNT为载体,采用有机溶胶法制得了含铂20%(w)的Pt/SCNT及PtRu/SCNT催化剂.实验发现:对于甲醇的阳极电氧化过程,以切短碳纳米管为载体的Pt/SCNT催化剂具有比相同条件制得的Pt/CNT催化剂高得多的催化活性,前者甲醇氧化峰电流密度是后者的1.4倍,并且远远高于商品的Pt/C催化剂.同时我们发现添加了钌的PtRu/SCNT具有比不含钌的催化剂更好的活性.采用X射线衍射(XRD)、透射电镜(TEM)、比表面积分析(BET)等方法对催化剂进行表征,结果表明,切短碳纳米管的晶相结构并未改变,但Pt/SCNT和PtRu/SCNT催化剂的比表面积和电化学活性得到了显著的提高.     

纳米三氧化钨修饰碳纳米管载铂催化剂对甲醇氧化的电催化性能

采用表面修饰技术将碳纳米管(CNT)表面羧基化, 通过羧基将钨离子基团修饰到碳纳米管的外表面, 再通过高温焙烧处理将钨离子基团氧化成WO₃, 成功合成了纳米WO₃/CNT复合物, 进一步还原Pt 的前驱体而得到Pt-WO₃/CNT复合催化剂. 采用X射线粉末衍射(XRD)和透射电镜(TEM)对样品的形貌和晶型结构进行了表征, 结果表明, Pt纳米粒子为面心立方晶体结构, 均匀地分布在WO₃修饰的碳纳米管表面. 采用循环伏安(CV)和计时电流法研究了在酸性溶液中Pt-WO₃/CNT催化剂对甲醇的电催化氧化活性, 结果表明WO₃修饰的碳纳米管载铂催化剂比用混酸处理的碳纳米管载铂催化剂对甲醇呈现出更高的电催化氧化活性和更好的稳定性.     

低铂催化剂Pd@Pt/C及PdPt@Pt/C在燃料电池中的应用

采用分步高压有机溶剂法制备了金属含量为20%(w)的低铂核壳结构催化剂Pd12%Pt3%@Pt5%/C(记为:PdPt@Pt/C)和Pd12%@Pt8%/C(记为:Pd@Pt/C),其中金属钯、铂的含量分别为12%和8%(w)。研究表明:对于甲醇的阳极氧化过程,催化剂PdPt@Pt/C甲醇氧化峰电流密度是Pd@Pt/C的1. 87倍;且催化剂PdPt@Pt/C氧还原催化具有较大的扩散电流密度,比Pd@Pt/C具有较好的氧还原催化能力。采用X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)等方法对催化剂进行表征的结果表明:催化剂采用PdPt为核,Pt为壳的催化剂PdPt@Pt/C,其分散性及电化学活性均比Pd为核,Pt为壳制得的催化剂Pd@Pt/C好。     

具有高活性和突出的抗中毒性能的Pt修饰Ru/C催化剂的制备和表征(英文)

采用两步浸渍-还原法制备了一种具有高Pt利用效率,高性能的Pt修饰的Ru/C催化剂(Ru@Pt/C).对于甲醇的阳极氧化反应,该催化剂的单位质量铂的催化活性分别为Pt/C、自制PtRu/C和商业JMPtRu/C催化剂的1.9、1.5和1.4倍;其电化学活性比表面积分别为Pt/C和自制PtRu/C的1.6和1.3倍.尤为重要的是该催化剂对甲醇氧化中间体具有很好的去除能力,其正向扫描的氧化峰的峰电流密度(If)与反向扫描氧化峰的峰电流密度(Ib)之比可高达2.4,为Pt/C催化剂的If/Ib的2.7倍,表明催化剂具有很好的抗甲醇氧化中间体毒化的能力.另外,Ru@Pt/C催化剂的稳定性也高于Pt/C、自制PtRu/C和商业JMPtRu/C催化剂的稳定性.采用X射线衍射(XRD)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂进行了表征,Pt在Ru表面的包覆结构得到了印证.Ru@Pt/C的高铂利用效率、高性能和高抗毒能力使其有望成为一种理想的直接甲醇燃料电池电催化剂.     

Pt/CNT纳米催化剂的微波快速合成及其对甲醇电化学氧化的电催化性能

碳纳米管 (CNT)作为制备新型催化剂载体已有广泛的研究 [1～ 8] ,例如 ,在其表面负载 Pt,Ru和Pt Ru后则具有良好的催化性能[1,2 ,6～ 8] .但在 CNT表面负载金属微粒的方法难以获得尺寸和形状均匀的纳米粒子 .因此 ,如何制备超细和均匀的纳米粒子是一项具有重要的学术意义和技术价值的工作 .我们利用微波加热的多元醇工艺合成了 XC-72碳负载铂纳米粒子的催化剂 ,并发现它对甲醇的氧化具有较高的电催化活性 [9] .本文进一步以 CNT作为载体 ,利用微波加热法快速合成了 Pt/ CNT纳米催化剂 ,并对其对甲醇电化学氧化的性能进行了初步研究 …     

新型核壳结构催化剂的制备及其对甲酸氧化的催化作用

本文通过采用脉冲电沉积技术在氮化物纳米粒子表面沉积原子层厚度的铂,成功地制得了以碳纳米管负载氮化物纳米粒子为核的新型核壳结构催化剂TiN@Pt/NCNTs,并考察了催化剂对于甲酸氧化的催化活性和稳定性.在相同铂负载量情况下,TiN@Pt/NCNTs催化剂的甲酸氧化质量活性可达商业Pt/C催化剂的3.3倍,并表现出良好的抗CO中毒能力和电化学稳定性.研究发现,在TiN中添加少量Cu制得的TiCuN@Pt/NCNTs比TiN@Pt/NCNTs表现出更高的催化活性,其Pt的质量活性可达商品Pt/C催化剂的4.5倍.扫描透射电镜(STEM)及能谱图谱(EDS mapping)清楚地揭示了催化剂的核壳结构.独特的核壳结构使得Pt原子得到了良好的分散是催化剂表现出良好活性的重要原因,同时Cu元素在氮化钛中的掺杂可使得Pt的d电子能级进一步降低,使得催化剂的活性得到了进一步的提升.     

不同方法制备Pt/C催化剂对燃料电池催化活性的影响

分别采用高压有机溶剂法和回流法不同的制备方法,制备了含铂20%(w)的催化剂Pt/C-HP(高压有机溶剂法)和Pt/C-Reflux(回流法)。实验发现:对于甲醇的阳极氧化过程,高压有机溶胶法制得的催化剂活性较高,催化剂Pt/C-HP甲醇氧化峰电流密度是Pt/C-Reflux的1.5倍,且远远高于商业催化剂JM3000含铂20%(w)Pt/C催化剂,催化剂Pt/C-Reflux甲醇氧化峰电流密度与商业催化剂JM3000催化剂相当。采用X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)等方法对催化剂进行表征的结果表明:高压有机溶胶法制得的催化剂分散性比回流法制得的催化剂好,使得前者催化剂的电化学活性比表面积得到了显著的提高。     

聚乙酰苯胺修饰碳纳米管载铂催化剂对甲醇电催化氧化

以原位化学聚合的聚乙酰苯胺/多壁碳纳米管(PAANI-MWCNTs)复合纳米材料作为载体,采用硼氢化钠还原法将Pt纳米粒子担载到PAANI-MWCNTs复合纳米材料表面,制备了Pt/PAANI-MWCNTs复合纳米催化剂.样品的结构和形貌用紫外-可见(UV-Vis)光谱、拉曼光谱、扫描电镜(SEM)、透射电镜(TEM)和X射线衍射(XRD)进行了表征.结果表明,聚乙酰苯胺与碳纳米管之间存在较强的π-π相互作用,使其能牢固地吸附于多壁碳纳米管表面,对碳纳米管的结构完整性和导电性有一定的改善作用.同时,金属Pt纳米颗粒较为均匀地分散在PAANI-MWCNTs表面,粒径分布范围较窄.采用循环伏安法和计时电流法在酸性溶液中研究了Pt/PAANI-MWCNTs催化剂对甲醇的电催化氧化活性,结果表明Pt/PAANI-MWCNTs复合纳米催化剂比用混酸处理的碳纳米管载铂催化剂对甲醇呈现出更高的电催化氧化活性和更好的抗中毒能力及稳定性.     

用于直接甲醇燃料电池的高活性PtCo-CNT@TiO_2复合纳米阳极催化剂

采用溶胶凝胶法制备CNT@TiO_2载体,利用电沉积法制备用于直接甲醇燃料电池的PtCo-CNT@TiO_2阳极催化剂。采用透射电子显微镜(TEM)、X射线衍射(XRD)和电化学工作站对其进行表征。结果表明,PtCo-CNT@TiO_2复合纳米材料有明显的结晶,且金属粒子围绕在TiO_2包覆的碳纳米管的周围,用于直接甲醇燃料电池阳极催化剂具有较高的活性与稳定性。该PtCo-CNT@TiO_2催化剂的电化学比表面积为164 m~2/g,65℃时甲醇的氧化峰电流达到45 mA/cm~2,计时电流曲线表明300 s后PtCo-CNT@TiO_2的氧化电流趋于24 mA/cm~2,在碱性条件下甲醇的氧化峰电流为39.7 mA/cm~2。     

Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active,Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom‐doped carbon (CNT/HDC) core–sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom‐containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom‐containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom‐doped nanocarbon catalysts in terms of half‐wave potential and kinetic current density. The four‐electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long‐term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.     

Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active,Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom‐doped carbon (CNT/HDC) core–sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom‐containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom‐containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom‐doped nanocarbon catalysts in terms of half‐wave potential and kinetic current density. The four‐electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long‐term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.     

Pt-MoOx/CNT电极的制备及其对乙醇氧化电催化性能研究

MoOx,a non-noble secondary catalyst instead of noble metal Ru,was dispersed on carbon nanotubes(CNT)andthen the primary catalyst Pt was electrodeposited on MoO_x/CNT/graphite electrode by potential-step method.CNTused was grown directly on graphite disk by chemical vapor deposition.The Pt-MoO_x/CNT/graphite electrode wascharacterized by scanning electron microscopy and energy dispersive X-ray spectroscopy.The electrocatalyticproperty and the long-term cyclic stability of Pt-MoO_x/CNT/graphite electrode for ethanol oxidation have been in-vestigated in 1.0 mol/L CH_3CH_2OH 0.1 mol/L H_2SO_4 by cyclic voltammetry.On the other hand,the effect of theloading mass of MoO_x on specific activity of Pt-MoO_x/CNT/graphite electrode and the activation energy of ethanoloxidation were investigated.The Pt-MoO_x/CNT/graphite electrode shows good long-term cyclic stability.82%value of peak current density at the oxidation peak around 0.69 V(vs.SCE)remains after 500 cycles,which ishigher than those of Pt/CNT/graphite and Pt-Ru/CNT/graphite electrodes with the corresponding values of 55% and72%,respectively.     

Carbon nanotubes as a secondary support of a catalyst layer in a gas diffusion electrode for metal air batteries

In this paper, we report the use of binary carbon supports (carbon nanotubes (CNTs) and active carbon) as a catalyst layer for fabricating gas diffusion electrodes. The electrocatalytic properties for the oxygen reduction reaction (ORR) were evaluated by polarization curves and electrochemical impedance spectroscopy (EIS) in an alkaline electrolyte. The binary-support electrode exhibits better performance than the single-support electrode, and the best performance is obtained when the mass ratio of carbon nanotubes and active carbon is 50:50. The results from the electrode kinetic parameters indicate that the introduction of carbon nanotubes as a secondary support provides high accessible surface area, good electronic conductivity, and fast ORR kinetics. Furthermore, the effect of CNT support on the electrocatalytic properties of Pt nanoparticles for binary-support electrodes was also investigated by different loading-reduction methods. The electrocatalytic activity of the binary-support electrodes is improved dramatically by Pt loading on CNT carbon support, even at very low Pt loading. Additionally, the EIS analysis results indicate that the process of ORR may be controlled by diffusion of oxygen in the electrode thin film for binary-support electrodes with or without Pt catalyst.     

Fabrication and catalytic properties of Pt and Ru decorated TiO2⧹CNTs catalyst for methanol electrooxidation

Highly ordered anodic titania nanotube arrays provide a large surface area for electrodepositing nickel nanoparticles which are used as the catalyst for carbon nanotube growth. Pt and Ru nanoparticles, approximately 3 nm in diameter, are uniformly electrodeposited on the as synthesized titania-supported carbon nanotubes (CNTs), constructing a novel catalyst for electrocatalytic oxidation of methanol. An enhanced and stable catalytic activity is obtained due to the uniformly dispersed Pt and Ru nanoparticles, and the large CNT network facilitating the electron transfer between the adsorbed methanol molecules and the catalyst substrate. An oxidation peak current density of 55 mA/cm² is achieved at a low Pt load of 0.126 mg/cm² with a Pt/Ru mole ratio of 1:1.     

Electrocatalytic oxidation of ethylene glycol on Pt and Pt-Ru nanoparticles modified multi-walled carbon nanotubes

The synthesis and characterization of catalysts based on nanomaterials, supported on multi-walled carbon nanotubes (CNT) for ethylene glycol (EG) oxidation is investigated. Platinum (Pt) and platinum-ruthenium (Pt-Ru) nanoparticles are deposited on surface-oxidized multi-walled carbon nanotubes [Pt/CNT; Pt-Ru/CNT] by the aqueous solution reduction of the corresponding metal salts with glycerol. The electrocatalytic properties of the modified electrodes for oxidation of ethylene glycol in acidic solution have been studied by cyclic voltammetry (CV), and excellent activity is observed. This may be attributed to the small particle size of the metal nanoparticles, the efficacy of carbon nanotubes acting as good catalyst support and uniform dispersion of nanoparticles on CNT surfaces. The nature of the resulting nanoparticles decorated multiwalled carbon nanotubes are characterized by scanning electron microscopy (SEM) and transmission electron microscopic (TEM) analysis. The cyclic voltammetry response indicates that Pt-Ru/CNT catalyst displays a higher performance than Pt/CNT, which may be due to the efficiency of the nature of Ru species in Pt-Ru systems. The fabricated Pt and Pt-Ru nanoparticles decorated CNT electrodes shows better catalytic performance towards ethylene glycol oxidation than the corresponding nanoparticles decorated carbon electrodes, demonstrating that it is more promising for use in fuel cells.     

A novel CNT@SnO2 core–sheath nanocomposite as a stabilizing support for catalysts of proton exchange membrane fuel cells

Mesoporous SnO₂ coated carbon nanotube (CNT) core–sheath nanocomposite, CNT@SnO₂, was prepared by a hydrothermal method and proposed as a catalyst support for proton exchange membrane fuel cells (PEMFCs). The CNT@SnO₂ and its supported Pt catalyst, Pt/(CNT@SnO₂), were characterized by TEM, XRD, cyclic voltammetry, and polarization curves. The CNT@SnO₂ composite showed a much lower anodic current than the CNT, especially at high potentials, indicating the CNT@SnO₂ was more corrosion resistant. The Pt/(CNT@SnO₂) catalyst was electrochemically active and exhibited comparable activity for the oxygen reduction reaction to the CNT supported catalyst (Pt/CNT). More importantly, the long-term stability of the Pt/(CNT@SnO₂) catalyst was significantly higher than that of the Pt/CNT catalyst, which might be mainly due to the fact that the CNT@SnO₂ was more corrosion resistant and mesoporous SnO₂ was beneficial to restrict the Pt migration and aggregation. Consequently, the CNT@SnO₂ would be a promising durable catalyst support for PEMFCs.     

A facile approach for constructing nitrogen-doped carbon layers over carbon nanotube surface for oxygen reduction reaction

Fabricating nitrogen-doped carbon layers over the conductive substrate is a cost-effective and efficient approach to develop practical oxygen reduction reaction (ORR) catalyst. In the current work, relying on the commercially available carbon nanotube (CNT), nitrogen-doped carbon layers over CNT is constructed by annealing the in situ formed complex over the CNT surface derived from iron ion inducing diaminonaphthalene (DAN) polymerization and DAN self-polymerization. Physical and electrochemical characterizations are carefully conducted to comparatively analyze the structure and activity relationship. The significance of iron in constructing nitrogen-doped carbon layers and tuning active sites of N types over multiwall carbon nanotube for ORR is demonstrated by X-ray photoelectron spectroscopy and Raman scattering spectrum. The excellent performance of nitrogen-doped carbon layers over CNT (catalyzed by iron) towards ORR is displayed by rotating ring-disk electrode. Specifically, the onset potential, half-wave potential, and limiting current density are 0.961 V, 0.831 V, and 5.20 mA cm^?2 respectively, very close to the state-of-the-art commercial Pt/C catalyst. Both high surface area and efficient N active sites should be considered in the nitrogen-doped carbon materials design and fabrication for ORR. Considering the large-scale availability, it has significant value in fuel cells commercial applications.     

分级结构氮掺杂碳纳米笼担载的铂基高效甲醇氧化电催化剂

高性能低成本的担载型铂基催化剂是直接甲醇燃料电池(DMFC)实用化过程中的一大挑战.利用高比表面积、高稳定性、容易负载金属的载体实现 Pt颗粒的高度分散,既可提高催化剂的催化性能,又可提高 Pt的利用率以降低成本,是担载型 Pt基催化剂实用化的有效途径.碳材料是一种常用的催化剂载体,近年来我们课题组发展了一种高性能的碳纳米笼材料,并可通过异原子掺杂调变其表面性能,提高其活性和负载能力.我们采用原位氧化镁模板法制备氮掺杂碳纳米笼：以具有多级结构的碱式碳酸镁作为氧化镁模板的前体,吡啶为碳源和氮源,经高温热解沉积,在原位形成的氧化镁模板表面形成氮掺杂的石墨化碳纳米薄层;经稀盐酸浸泡并洗涤,获得高纯度的氮掺杂碳纳米笼.氮掺杂碳纳米笼具有分等级的微纳米结构、高导电性、高比表面积和可调变的孔结构,结合表面氮原子的锚钉作用,氮掺杂碳纳米笼有望成为电化学催化剂 Pt的优良载体.
　　在前期研究基础上,本文探索多级结构氮掺杂碳纳米笼(hNCNC)作为新型载体负载 Pt的能力,并评价所构建的负载型催化剂 Pt/hNCNC的电催化性能.通过简便的微波辅助多元醇还原法,将氯铂酸还原成 Pt纳米粒子负载于 hNCNC的表面.为了揭示氮掺杂的效应,我们对比研究了具有相似分级结构但无掺杂的碳纳米笼(hCNC)以及商业化活性炭(Val-can XC-72)作为载体的情况.经热重(TG)和 X射线光电子能谱(XPS)分析,三种催化剂 Pt/hNCNC、Pt/hCNC和 Pt/XC-72的负载量均接近理论负载量(23.1 wt%),都主要以金属态存在.然而,扫描电子显微镜(SEM)和透射电子显微镜(TEM)结果表明, Pt/hNCNC的 Pt分散状态优于 Pt/hCNC,更远优于 Pt/XC-72. Pt/hNCNC的平均 Pt粒径最小,仅约3.3 nm.这种良好的分散状态主要得益于氮原子掺杂,高负电性的氮原子改变了局域的表面极性,有利于 Pt颗粒的成核,也有利于固定 Pt颗粒.
　　由于 hNCNC对 Pt的优异分散能力, Pt/hNCNC表现出高的电化学活性面积.氢吸附和一氧化碳溶出伏安曲线表明, Pt/hNCNC的电化学活性面积高于 Pt/hCNC和 Pt/XC-72,这与显微观察和 X射线衍射(XRD)结果相吻合. Pt/hNCNC展现出优异的甲醇电催化氧化活性和高稳定性,其催化电流明显高于 Pt/hCNC和 Pt/XC-72,电流衰减亦慢于 Pt/hCNC和 Pt/XC-72. hNCNC的分级微纳米结构有利于孔内传质和电子输运,从而提高反应速度. hNCNC的氮掺杂有利于 Pt在载体表面的分散,增强了载体-金属相互作用,提高了电化学活性面积和催化活性.为了进一步考察 hNCNC对 Pt的负载能力,本文还考察了高负载量 Pt/hNCNC的性能.在负载量高达60 wt%时, Pt/hNCNC中的 Pt颗粒仍无明显聚集,其甲醇氧化电流增加了30%,可以有效提高 DMFC的输出电流密度.
　　综上可见, hNCNC可以有效分散并稳定 Pt颗粒,从而提高电化学活性面积和甲醇电催化氧化活性,优于未掺杂的碳纳米笼和传统碳材料,展示了 hNCNC高分散 Pt颗粒用作 DMFC的高效阳极催化剂的重要前景,也表明 hNCNC有望成为应用广泛的新型载体.