甲醇电氧化催化剂Pt/CeO2-CNTs与PtRu/C的比较研究

为认识合成催化剂Pt/CeO2-CNTs与商用催化剂PtRu/C(E-TEK)的催化性能和结构特点, 用CO溶出法和恒电位氧化法比较了这两种催化剂对CO的电氧化活性, 运用循环伏安法和恒电位氧化法比较了这两种催化剂对甲醇的电氧化活性. CO电氧化实验结果表明, PtRu/C上CO的电氧化活性明显优于Pt/CeO2-CNTs; 甲醇电氧化实验结果却表明, Pt/CeO2-CNTs与PtRu/C上甲醇电氧化表观活性相当. 为从结构特点上解释PtRu/C上CO电氧化和甲醇电氧化活性的不一致, 对PtRu/C进行了循环伏安扫描和CO溶出实验. 结果表明, PtRu/C的甲醇电氧化电流之所以没有预期高, 一是由于Pt比表面积不够大, 同时Pt-Ru之间协同作用有待提高. 本研究结果表明, 尽管Ru对Pt上CO电氧化有显著助催化作用, 但要充分发挥其对Pt上甲醇电氧化的助催化作用, 需同时提高Pt表面积和Pt-Ru接触界面. 该结论对设计甲醇电氧化催化剂具有普适意义.     

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.     

利用原位红外光谱与微分电化学质谱联用技术研究在Pt以及PtRu电极上发生的甲醇氧化反应

利用电化学衰减全反射原位傅里叶变换红外光谱与微分电化学质谱联用技术,在流动电解池环境以及恒电位条件下研究了Pt电极和Pt电极通过表面电沉积Ru形成的PtRu电极（PtxRuy）上发生的甲醇氧化反应（反应电解质溶液为0.1 mol/L HClO4＋0.5 mol/L MeOH）. 在0.3-0.6 V（参比电极为可逆氢参比）实验用到的所有电极上,CO是唯一能从红外光谱观察到的与甲醇相关的表面吸附物;在Pt0.56Ru0.44电极上可以观察到CO吸附在Ru原子形成的岛上和CO线式吸附在Pt电极表面红外波段,而其他电极上只能观察到Pt表面上线式吸附的CO;甲醇氧化活性按Pt0.73Ru0.27〉Pt0.56Ru0.44〉Pt0.83Ru0.17〉Pt的顺序递减;在0.5V时,甲醇在Pt0.73Ru0.27电极上的氧化反应的CO2电流效率达到了50%.     

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.     

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.     

阵列纳米管中铂:钌原子比对甲醇电催化氧化活性的影响（英文）

采用电化学沉积技术在3-氨丙基三甲基硅氧烷修饰的多孔氧化铝膜板中制备了具有不同Pt/Ru原子比的双元Pt/Ru阵列纳米管电极（NTAEs）。分别用X-射线衍射和扫描电镜表征了催化剂结构和形态。电化学结果表明：通过控制前驱沉积液的浓度可得到不同PtRu原子比的NTAEs。所制备的Pt 或 Pt/Ru合金阵列纳米电极的真实表面积大,催化活性强,有利于物质传输,对甲醇电氧化显示出显著的催化性能。实验中还系统研究了催化剂组成与CO和CH3OH电催化氧化性能的关系,发现Pt/Ru=50:50的阵列纳米管电极对CO电氧化显示出最好的催化活性;对甲醇电氧化,则Ru原子比为40%的催化剂显示最佳催化性能。     

直接甲醇燃料电池三元催化剂PtRuCo/C的制备及其电化学性质

使用柠檬酸三钠作为稳定剂,硼氢化钠作为还原剂,用浸渍还原法制备了20%(w)Pt60Ru30Co10/C催化剂.利用透射电子显微镜(TEM)和X射线衍射(XRD)对催化剂进行了表征.考察了不同pH值对制备催化剂的催化甲醇氧化能力及稳定性的影响,并使用预吸附单层CO溶出方法研究了其抗中毒能力.结果表明,当pH=8时,制备的PtRuCo/C对甲醇氧化具有最高的催化活性,其催化活性远高于商业化的Pt50Ru50/C,同时催化剂的稳定性最好,高于商业化的Pt50Ru50/C的稳定性,而且预吸附单层CO的起始氧化电位比Pt50Ru50/C的明显负移.     

热处理对甲醇电氧化催化剂PtRu/C性能的影响

采用非离子表面活性剂Triton X-100作为稳定剂制备了催化甲醇电氧化反应的PtRu/C催化剂, 研究了热处理温度对催化剂的组成、结构、形貌和活性的影响. 利用循环伏安法研究了PtRu/C催化剂催化甲醇电氧化的活性, 用热重和差热分析(TG-DTA)、X射线能量色散谱(EDX)、X射线衍射(XRD)、X射线光电子能谱(XPS)和透射电子显微镜(TEM)对PtRu/C催化剂进行了表征. 研究结果表明, 热处理对PtRu/C催化剂粒子的大小、分布和Pt的氧化态有重要的作用. 在350 ℃下热处理的催化剂显示了最好的催化甲醇电氧化的性能, 由Triton X-100作为稳定剂制备的PtRu/C催化剂最适宜的热处理温度是350 ℃.     

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.     

团聚铂纳米粒子电极在甲醇氧化中的电催化特性

用H2还原法并以Nafion作为稳定剂合成团聚的Pt纳米粒子，附载于玻碳表面制备电催化剂.透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征结果指出,团聚Pt纳米粒子的平均尺寸约为400 nm.运用电化学循环伏安法(CV)和原位傅立叶变换红外反射光谱（in situ FTIRS）研究甲醇的氧化过程，发现团聚Pt纳米粒子电极具有较高的电催化活性.原位FTIRS研究结果检测到甲醇在所制备的电催化剂上氧化的中间体为线型吸附态CO物种，其红外吸收给出异常红外效应的光谱特征.     

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.     

Nanostructure PtRu/MWNTs as anode catalysts prepared in a vacuum for direct methanol oxidation

Platinum and ruthenium nanoparticles that are uniformly dispersed on multiwalled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using Pt(acac)2 and Ru(acac)3 as the metal precursors. The resulting nanocomposites were characterized by transmission electron microscopy and X-ray diffraction. The Pt, Pt45Ru55, and Ru nanoparticles had mean diameters of 3.0 +/- 0.6, 2.7 +/- 0.6, and 2.5 +/- 0.4 nm and the same mole number as their metal precursors at 500 degrees C. The electrocatalytic activity of the Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs exhibited a high level of catalytic activity for methanol oxidation as a result of the large surface area of the supporting carbon nanotubes and the wide dispersion of the Pt and Ru nanoparticles. Compared with the Pt/MWNTs, the onset potential for methanol oxidation of the PtRu/MWNTs was significantly lower, and the ratio of the forward anodic peak current to the reverse anodic peak current during methanol oxidation was somewhat higher. The Pt45Ru55/MWNTs displayed the best electrocatalytic activity of all of the carbon-nanotube-supported Pt and PtRu catalysts.     

In-situ X-ray absorption spectroscopy study of Pt and Ru chemistry during methanol electrooxidation

Methanol electrooxidation in a 0.5 M sulfuric acid electrolyte containing 1.0 M CH3OH was studied on 30% Pt/carbon and 30% PtRu/carbon (Pt/Ru = 1:1) catalysts using X-ray absorption spectroscopy (XAS). Absorption by Pt and Ru was measured at constant photon energy in the near edge region during linear potential sweeps of 10-50 mV/s between 0.01 and 1.36 V vs rhe. The absorption results were used to follow Pt and Ru oxidation and reduction under transient conditions as well as to monitor Ru dissolution. Both catalysts exhibited higher activity for methanol oxidation at high potential following multiple potential cycles. Correlation of XAS data with the potential sweeps indicates that Pt catalysts lose activity at high potentials due to Pt oxidation. The addition of Ru to Pt accelerates the rate of methanol oxidation at all potentials. Ru is more readily oxidized than Pt, but unlike Pt, its oxidation does not result in a decrease in catalytic activity. PtRu/carbon catalysts underwent significant changes during potential cycling due to Ru loss. Similar current density vs potential results were obtained using the same PtRu/carbon catalyst at the same loading in a membrane electrode assembly half cell with only a Nafion (DuPont) solid electrolyte. The results are interpreted in terms of a bifunctional catalyst mechanism in which Pt surface sites serve to chemisorb and dissociate methanol to protons and carbon monoxide, while Ru surface sites activate water and accelerate the oxidation of the chemisorbed CO intermediate. PtRu/carbon catalysts maintain their activity at very high potentials, which is attributed to the ability of the added Ru to keep Pt present in a reduced state, a necessary requirement for methanol chemisorption and dissociation.     

Physical and electrochemical characterizations of microwave-assisted polyol preparation of carbon-supported PtRu nanoparticles

PtRu nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The PtRu nanoparticles, which were uniformly dispersed on carbon, were 2-6 nm in diameter. All PtRu/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt face-centered cubic structure, excepting that the 2theta values were shifted to slightly higher values. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The electro-oxidation of methanol was studied by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. It was found that both PtRu/C catalysts had high and more durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell single stack test cell using the Vulcan-carbon-supported PtRu alloy as the anode catalyst showed high power density.     

Nanostructured PtRu/C as anode catalysts prepared in a pseudomicroemulsion with ionic surfactant for direct methanol fuel cell

Nanostructured PtRu/C catalysts have been prepared from a water-in-oil pseudomicroemulsion with the aqueous phase of a mixed concentrated solution of H(2)PtCl(6), RuCl(3), and carbon powder, oil phase of cyclohexane, ionic surfactant of sodium dodecylbenzene sulfonate (C(18)H(29)NaO(3)S), and cosurfactant n-butanol (C(4)H(10)O). Two different composing PtRu/C nanocatalysts (catalyst 1, Pt 20 wt %, Ru 15 wt %; catalyst 2, Pt 20 wt %, Ru 10 wt %) were synthesized. The catalysts were characterized by transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis, and the particles were found to be nanosized (2-4 nm) and inherit the Pt face-centered cubic structure with Pt and Ru mainly in the zero valance oxidation state. The ruthenium oxide and hydrous ruthenium oxide (RuO(x)()H(y)()) were also found in these catalysts. The cyclic voltammograms (CVs) and chronoamperometries for methanol oxidation on these catalysts showed that catalyst 1 with a higher Ru content (15 wt %) has a higher and more durable electrocatalytic activity to methanol oxidation than catalyst 2 with low Ru content (10 wt %). The CV results for catalysts 1 and 2 strongly support the bifunctional mechanism of PtRu/C catalysts for methanol oxidation. The data from direct methanol single cells using these two PtRu/C as anode catalysts show the cell with catalyst 1 has higher open circuit voltage (OCV = 0.75 V) and maximal power density (78 mW/cm(2)) than that with catalyst 2 (OCV = 0.70 V, P(max) = 56 mW/cm(2)) at 80 degrees C.     

Pt／C－SPE和PtRu／C－SPE膜电极上甲醇的催化氧化

采用化学还原法制得直接甲醇燃料电池中甲醇阳极氧化的Ｐｔ／Ｃ和ＰｔＲｕ／Ｃ催化剂．结果表明后者比前者具有更高的催化活性．通过ＸＲＤ和ＸＰＳ的分析,阐明了Ｒｕ对提高甲醇电催化氧化活性的作用．     

Heat-induced alterations in the surface population of metal sites in bimetallic nanoparticles

The ability to alter the surface population of metal sites in bimetallic nanoparticles (NPs) is of great interest in the context of heterogeneous catalysis. Here, we report findings of surface alterations of Pt and Ru metallic sites in bimetallic carbon-supported (PtRu/C) NPs that were induced by employing a controlled thermal-treatment strategy. The thermal-treatment procedure was designed in such a way that the particle size of the initial NPs was not altered and only the surface population of Pt and Ru was changed, thus allowing us to deduce structural information independent of particle-size effects. X-ray absorption spectroscopy (XAS) was utilized to deduce the structural parameters that can provide information on atomic distribution and/or extent of alloying as well as the surface population of Pt and Ru in PtRu/C NPs. The PtRu/C catalyst sample was obtained from Johnson Matthey, and first the as-received catalyst was reduced in 2 % H2 and 98 % Ar gas mixture at 300 degrees C for 4 h (PtRu/C as-reduced). Later this sample was subjected to thermal treatment in either oxygen (PtRu/C-O2-300) or hydrogen (PtRu/C-H2-350). The XAS results reveal that when the as-reduced PtRu/C catalyst was exposed to the O2 thermal-treatment strategy, a considerable amount of Ru was moved to the catalyst surface. In contrast, the H2 thermal-treatment strategy led to a higher population of Pt on the PtRu/C surface. Characterization of the heat-treated PtRu/C samples by X-ray diffraction and transmission electron microscopy reveals that there is no significant change in the particle size of thermally treated samples when compared to the as-received PtRu/C sample. The electrochemical properties of the as-reduced and heat-treated PtRu/C catalyst samples were confirmed by cyclic voltammetry, CO-adsorption stripping voltammetry, and linear sweep voltammetry. Both XAS and electrochemical investigations concluded that the PtRu/C-H2-350 sample exhibits significant enhancement in reactivity toward methanol oxidation as a result of the increased surface population of the Pt when compared to the PtRu/C-O2-300 and PtRu/C as-reduced samples.     

PtRu/Ti anodes with varying Pt ratio: Ru ratio prepared by electrodeposition for the direct methanol fuel cell

PtRu/Ti anodes with varying Pt ratio Ru ratio were prepared by electrodeposition of a thin PtRu catalyst layer onto Ti mesh for a direct methanol fuel cell (DMFC). The morphology and structure of the catalyst layers were analyzed by SEM, EDX and XRD. The catalyst coating layer shows an alloy character. The relative activities of the PtRu/Ti electrodes were assessed and compared in half cell and single DMFC experiments. The results show that these electrodes are very active for the methanol oxidation and that the optimum Ru surface coverage was ca. 9 at.% for DMFC operating at 20 degrees C and 11 at.% at 60 degrees C. The PtRu/Ti anode shows a performance comparable to that of the conventional carbon-based anode in a DMFC operating with 0.25 M or 0.5 M methanol solution and atmosphere oxygen gas at 90 degrees C.