电沉积三维多孔Pt/SnO2薄膜及其对甲醇的电催化氧化

在高电流密度下以阴极析出的氢气泡为“模板”电沉积三维多孔Sn薄膜, 经在200 ℃ 2 h和400 ℃ 2 h热处理氧化后电沉积金属Pt, 制得三维多孔的Pt/SnO₂ (3D-Pt/SnO₂)薄膜. 通过扫描电镜(SEM)和X射线衍射(XRD)分析了薄膜的形貌和结构. 结果显示Pt主要沉积在SnO₂枝晶上, 形成Pt_shell/SnO_2core结构的枝晶. 在0.5 mol•dm^－3 H₂SO₄＋1.0 mol•dm^－3 CH₃OH溶液中的循环伏安结果表明, 3D-Pt/SnO₂薄膜电极在酸性溶液中电催化氧化甲醇的性能优于电沉积的纯铂电极, 而且具有较高的稳定性.     

电沉积三维多孔Pt/SnO2薄膜及其对甲醇的电催化氧化

在高电流密度下以阴极析出的氢气泡为“模板”电沉积三维多孔Sn薄膜, 经在200 ℃ 2 h和400 ℃ 2 h热处理氧化后电沉积金属Pt, 制得三维多孔的Pt/SnO₂ (3D-Pt/SnO₂)薄膜. 通过扫描电镜(SEM)和X射线衍射(XRD)分析了薄膜的形貌和结构. 结果显示Pt主要沉积在SnO₂枝晶上, 形成Pt_shell/SnO_2core结构的枝晶. 在0.5 mol•dm^－3 H₂SO₄＋1.0 mol•dm^－3 CH₃OH溶液中的循环伏安结果表明, 3D-Pt/SnO₂薄膜电极在酸性溶液中电催化氧化甲醇的性能优于电沉积的纯铂电极, 而且具有较高的稳定性.     

高度分散的Pt/TiO2的制备及光催化活性

用柠檬酸作为空穴捕获剂和分散剂, 在温和条件下用光催化还原法将3 nm金属铂沉积在7 nm的锐钛矿相及介孔二氧化钛纳米晶表面. TEM观察显示铂的负载量为w＝1.0%时, 多数二氧化钛纳米晶表面沉积了岛状的铂团簇, XPS和电子衍射结果表明铂以游离态存在. 负载w＝1.0%～2.0%铂的TiO₂在苯酚光氧化反应中活性显著提高. Pt/TiO₂在氨气中经550 ℃氮化, 可制得氮掺杂的Pt/TiO₂可见光光催化剂, 氮化过程中铂团簇没有烧结和显著长大.     

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.     

铂铋金属间化合物催化剂的氧还原与抗甲醇氧化性能

采用氩弧熔炼后热处理方法制备了PtBi金属间化合物材料.采用循环伏安法和旋转圆盘电极进行电化学性能测试.通过在0.5 mol•L^－1 H₂SO₄＋0.25 mol•L^－1 CH₃OH溶液中对氧还原的起始电位和电流密度大小比较发现,与光滑铂电极相比,PtBi金属间化合物具有良好的氧还原催化性能和抗甲醇中毒性能.从结构方面分析了PtBi具有抗甲醇中毒性能的原因,认为是PtBi中Pt-Pt的间距大，不利于甲醇的吸附解离. X射线光电子能谱(XPS)结果表明,PtBi材料中Pt的d电子空穴增加,可能是导致PtBi电极表面氧还原电流增大的原因.     

氨·环己胺·羧酸根合铂(Ⅱ)类配合物的合成、抗肿瘤活性和与DNA的键合水平

本工作设计合成了6种新型氨·环己胺·羧酸根合铂(Ⅱ)类配合物[Pt(NH₃)((?)-NH₂)X₂](a～f){其中，X=CH₃COO^-(乙酸根)，CH₂ClCOO^-(氯乙酸根)，C₆H₅-COO^-(苯甲酸根)，p-CH₃O-C₆     

1R，3S-1，2，2-三甲基-1，3-环戊二胺为配体的铂(Ⅱ) 配合物的合成、表征和抗肿瘤活性

本文合成了9种含有由天然D(+)-樟脑衍生的1R，3S-1，2，2-三甲基-1，3-环戊二胺(A)为配体的铂(Ⅱ)配合物[Pt(Ⅱ)AX]{其中，X=(CH₂)₃C(COO^-)₂(1，1-环丁烷二羧酸根)，2CH₃OCH₂COO^-，2CH₃CH₂OCH₂COO^-，2CH₃(CH₂)₃OCH₂COO^-，[OCH(CH₃)COO]^2-(乳酸根)，(OCH₂COO)^2-(乙醇酸根)，2CH₃OCH₂CH₂OCH₂COO^-，2CH₃CH₂OCH₂CH₂OCH₂COO^-和2CH₃(CH₂)₃OCH₂CH₂OCH₂COO^-}。通过元素分析、热重分析、红外光谱、¹H核磁共振谱和电喷雾质谱等对配合物进行了表征。体外生物活性测试表明，部分配合物对A549人肺癌细胞和HCT-116人结肠癌细胞具有较强的抗肿瘤活性。     

三组Pt- Ru/C催化剂前驱体对其性能的影响

分别以三组不同的Pt和Ru化合物为前驱体, 采用热还原法制备了Pt-Ru/C催化剂, 比较不同前驱体对催化剂性能的影响；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. 结果表明以H₂PtCl₆+RuCl₃和自制(NH₄)₂PtCl₆+Ru(OH)₃为前驱体的催化剂Pt和Ru没有完全形成合金状态, 在Pt(111)和Pt(200)之间有Ru(101)存在；以Pt(NH₃)₂(NO₂)₂和自制含钌化合物为前驱体制备的催化剂未检测出Ru金属或其氧化物的衍射峰, Pt-Ru颗粒在载体上分散均匀, 粒径最小, 为3.7 nm. 利用玻碳电极测试了循环伏安、记时电流和阶跃电位曲线, 考核了上述催化剂对甲醇阳极催化氧化活性的影响；结果表明：以Pt(NH₃)₂(NO₂)₂和自制含钌化合物为前驱体制备的催化剂对甲醇的电催化氧化活性最高, 循环伏安曲线峰电流密度达11.5 mA•cm^-2.     

碳黑预处理对Pt/C催化剂对甲醇氧化电催化活性的影响

直接甲醇燃料电池(DMFC)由于具有较多的优点而受到广泛的关注. 但是碳载Pt (Pt/C)阳极催化剂电催化活性低是限制其应用的一个主要问题. 为了提高Pt/C催化剂对甲醇氧化的电催化性能, 分别用CO₂, 空气, H₂O₂或HNO₃对常用作为载体的Vulcan XC-72碳黑进行预处理. 结果表明, 在用CO₂, 空气, HNO₃, H₂O₂处理的及未处理的碳黑作载体制得的Pt/C催化剂电极上, 甲醇氧化峰的峰电流密度顺序为39, 33, 32, 20和18 mA•cm^－2, 表明用CO₂处理的碳载体制备的Pt/C催化剂对甲醇氧化有最好的电催化活性和稳定性. 其主要原因是用CO₂处理能减少碳黑表面的含氧基团和增加石墨化程度, 而使碳黑的电阻降低及Pt粒子在碳黑上的分散性变好.     

纳米三氧化钨复合催化剂的制备及对甲醇电催化性能

采用浸渍沉淀法制备出WO₃-碳纳米管(WO₃-CNTs)纳米复合材料, 微波辅助乙二醇法在其表面负载活性成分Pt, 得到纳米Pt/WO₃-CNTs 催化剂. 采用X射线衍射(XRD), 透射电子显微镜(TEM)和X射线光电子能谱(XPS)等测试手段对催化剂的结构和形貌进行表征, 结果表明Pt 纳米粒子为面心立方晶体结构, 粒径大小在3-5 nm之间, 均匀地分布在WO₃-CNTs 纳米复合材料表面, 同时发现催化剂中的Pt 主要以金属态的形式存在. 采用循环伏安和计时电流法研究了在酸性溶液中Pt/WO₃-CNTs 催化剂对甲醇的电催化氧化性能, 结果表明Pt/WO₃-CNTs 催化剂比用硝酸处理的碳纳米管载铂催化剂(Pt/CNTs)对甲醇呈现出更高的电催化氧化活性和抗CO中毒性能.     

CO and methanol adsorption on (2 × 1)Pt(110) and ion‐eroded Pt(111) model catalysts

Methanol adsorption on ion‐sputtered Pt(111) surface exhibiting high concentration of vacancy islands and on (2 × 1)Pt(110) single crystal were investigated by means of photoelectron spectroscopy (PES) and thermal desorption spectroscopy. The measurements showed that methanol adsorbed at low temperature on sputtered Pt(111) and on (2 × 1)Pt(110) surfaces decomposed upon heating. The PES data of methanol adsorption were compared to the data of CO adsorbed on the same Pt single crystal surfaces. In the case of the sputtered Pt(111) surface, the dehydrogenation of H_xCO intermediates is followed by the CO bond breakage. On the (2 × 1)Pt(110) surface, carbon monoxide, as product of methanol decomposition, desorbed molecularly without appearance of any traces of atomic carbon. By comparing both platinum surfaces we conclude that methanol decomposition occurs at higher temperature on sputtered Pt(111) than on (2 × 1)Pt(110). Copyright © 2010 John Wiley & Sons, Ltd.     

Mechanisms of methanol decomposition on platinum: A combined experimental and ab initio approach

The dual path mechanism for methanol decomposition on well-defined low Miller index platinum single crystal planes, Pt(111), Pt(110), and Pt(100), was studied using a combination of chronoamperometry, fast scan cyclic voltammetry, and theoretical methods. The main focus was on the electrode potential range when the adsorbed intermediate, CO(ad), is stable. At such "CO stability" potentials, the decomposition proceeds through a pure dehydrogenation reaction, and the dual path mechanism is then independent of the electrode-substrate surface structure. However, the threshold potential where the decomposition of methanol proceeds via parallel pathways, forming other than CO(ad) products, depends on the surface structure. This is rationalized theoretically. To gain insights into the controlling surface chemistry, density functional theory calculations for the energy of dehydrogenation were used to approximate the potential-dependent methanol dehydrogenation pathways over aqueous-solvated platinum interfaces.     

Methanol dehydrogenation and oxidation on Pt(111) in alkaline solutions

Adsorption, dehydrogenation, and oxidation of methanol on Pt(111) in alkaline solutions has been examined from a fundamental mechanistic perspective, focusing on the role of adsorbate-adsorbate interactions and the effect of defects on reactivity. CO has been confirmed as the main poisoning species, affecting the rate of methanol dehydrogenation primarily through repulsive interactions with methanol dehydrogenation intermediates. At direct methanol fuel cell (DMFC)-relevant potentials, methanol oxidation occurs almost entirely through a CO intermediate, and the rate of CO oxidation is the main limiting factor in methanol oxidation. Small Pt island defects greatly enhance CO oxidation, though they are effective only when the CO coverage is 0.20 ML or higher. Large Pt islands enhance CO oxidation as well, but unlike small Pt islands, they also promote methanol dehydrogenation. Perturbations in electronic structure are responsible for the CO oxidation effect of defects, but the role of large Pt islands in promoting methanol dehydrogenation is primarily explained by surface geometric structure.     

甲醇在欠电位沉积Sn/Pt电极上催化氧化

在欠电位沉积（upd）锡修饰的铂电极（upd-Sn/Pt）上,对甲醇电化学催化氧化过程进行了研究.发现当Pt表面upd-Sn的覆盖率在20％附近时,对甲醇的催化氧化的增强作用最为明显；在电位低于0.35 V （vs RHE）时,甲醇在Pt与upd-Sn/Pt电极上氧化只进行到脱氢生成CO的步骤;在0.35 V以后,表面Sn－OH形成,反应Sn－OH＋COads=Sn＋CO2＋H＋＋e有利于表面CO的去除;而Pt电极上,只有0.6 V以后,才有反应Pt－OH＋COads=Pt＋CO2＋H＋＋e发生.因此,Sn的存在有利于甲醇在较低的电位下氧化; Pt电极上CH3OH脱氢并释放出电子的过程是一个快速的过程,表面CO的去除是甲醇氧化过程的控制步骤;甲醇氧化产生的表面吸附态CO 以线式吸附为主,少量的桥式吸附态CO在反应初期即达到吸附饱和; Pt表面上upd-Sn表现的催化增强作用,在光亮铂电极和在高分散铂黑电极上是一致的.     

Binding maps for the study and prediction of bimetallic catalyst surface reactions: The case of methanol oxidation

Focusing on the competing pathways of methanol oxidation on platinum and platinum/gold bimetallic catalysts, we explore a novel density functional theory (DFT)‐based approach to the study of reactions on catalyst surfaces. Traditionally, DFT has been used to compute binding energies of products and intermediates as proxies for catalytic activity, and to compute full reaction pathways and their activation energy barriers. Merging the computational simplicity and intuitive clarity of binding energy calculations with the site sensitivity of transition state calculations, we construct maps of the binding energies of relevant atoms and molecules at all sites on a surface. We show that knowledge of the arrangement of strong and weak binding sites on a surface is powerful in rationalizing the ease with which a reaction step proceeds on a given local motif of surface atoms. We highlight the prospects and challenges of this approach toward catalyst screening and prediction.     

Competitive paths for methanol decomposition on Pt(111)

Periodic, self-consistent, Density Functional Theory (PW91-GGA) calculations are used to study competitive paths for the decomposition of methanol on Pt(111). Pathways proceeding through initial C-H and C-O bond scission events in methanol are considered, and the results are compared to data for a pathway proceeding through an initial O-H scission event [Greeley et al. J. Am. Chem. Soc. 2002, 124, 7193]. The DFT results suggest that methanol decomposition via CH(2)OH and either formaldehyde or HCOH intermediates is an energetically feasible pathway; O-H scission to CH(3)O, followed by sequential dehydrogenation, may be another realistic route. Microkinetic modeling based on the first-principles results shows that, under realistic reaction conditions, C-H scission in methanol is the initial decomposition step with the highest net rate. The elementary steps of all reaction pathways (with the exception of C-O scission) follow a linear correlation between the transition state and final state energies. Simulated HREELS spectra of the intermediates show good agreement with available experimental data, and HREELS spectra of experimentally elusive reaction intermediates are predicted.     

甲醇在Pt-Fe(111)/C表面吸附的理论研究

采用密度泛函理论和周期平板模型相结合的方法, 对CH3OH分子在Pt-Fe(111)/C表面top, fcc, hcp和bridge位的吸附模型进行了构型优化、能量计算, 结果表明bridge位是较有利的吸附位. 掺杂后费米能级的位置发生了右移, 价带和导带均增宽, 极利于电子-空穴的迁移, 这对提高催化活性是非常有利的. 考察抗中毒性发现: CO在Pt(111)/C面上的吸附能比甲醇吸附能要高, CO在Pt-Fe(111)/C的吸附能比甲醇吸附能要低, 可说明CO在Pt(111)/C面上有中毒效应, 而Pt-Fe(111)/C的抗CO中毒能力增强, 是催化氧化甲醇良好的催化剂.     

Direct‐methanol Fuel Cell Based on Functionalized Graphene Oxide with Mono‐metallic and Bi‐metallic Nanoparticles: Electrochemical Performances of Nanomaterials for Methanol Oxidation

The catalysts based on 2‐aminoethanethiol functionalized graphene oxide (AETGO) with several mono‐metallic and bi‐metallic nanoparticles such as rod gold (rAuNPs), rod silver (rAgNPs), rod gold‐platinum (rAu‐Pt NPs) and rod silver‐platinum (rAg‐Pt NPs) were synthesized. The successful synthesis of nanomaterials was confirmed by various methods. The effective surface area (ESA) of the rAu‐Pt NPs/AETGO is 1.44, 1.64 and 2.40 times higher than those of rAg‐Pt NPs/AETGO, rAuNPs/AETGO and rAgNPs/AETGO, respectively, under the same amount of Pt. The rAu‐Pt NPs/AETGO exhibited a higher peak current for methanol oxidation than those of comparable rAg‐Pt NPs/AETGO under the same amount of Pt loading.     

Theoretical Study on the Adsorption and Decomposition of Methanol over the Pt-Mo（111）/C Surface

The density functional theory(DFT) and self-consistent periodic calculation were used to investigate the methanol adsorption on the Pt-Mo(111)/C surface.The adsorption energies,equilibrium geometries and vibration frequencies of CH3OH on nine types of sites on the Pt-Mo(111)/C surface were predicted and the favorite adsorption site for methanol is the top-Pt site.Both sites of valence and conduction bands of doped system have been broadened,which are favorable for electrons to transfer to the cavity.The possible decomposition pathway was investigated with transition state searching and the calculation results indicate that the O-H bond is first broken,and then the methanol decomposes into methoxy.The activation barrier of O-H bond breaking with Pt-Mo catalyst is only 104.8 kJ mol-1,showing that carbon supported Pt-Mo alloys have promoted the decomposition of methanol.Comparing with the adsorption energies of CH3OH on the Pt(111)/C surface and that of CO,the adsorption energies of CO are higher,and Pt(111)/C is liable to be oxidized and loses the activity,which suggests that the catalyst Pt-Mo(111)/C is in favor of decomposing methanol and has better anti-poisoning ability than Pt(111)/C.     

Ab initio calculations of the reaction pathways for methane decomposition over the Cu (111) surface

Growth of large-area, few-layer graphene has been reported recently through the catalytic decomposition of methane (CH(4)) over a Cu surface at high temperature. In this study, we used ab initio calculations to investigate the minimum energy pathways of successive dehydrogenation reactions of CH(4) over the Cu (111) surface. The geometries and energies of all the reaction intermediates and transition states were identified using the climbing image nudged elastic band method. The activation barriers for CH(4) decomposition over this Cu surface are much lower than those in the gas phase; furthermore, analysis of electron density differences revealed significant degrees of charge transfer between the adsorbates and the Cu atoms along the reaction path; these features reveal the role of Cu as the catalytic material for graphene growth. All the dehydrogenation reactions are endothermic, except for carbon dimer (C(2)) formation, which is, therefore, the most critical step for subsequent graphene growth, in particular, on Cu (111) surface.