碳载体的预处理对Pt/C催化剂结构和性能的影响

采用一种新的调变多元醇制备方法,通过调节碳载体热处理条件,制备得到不同的Pt/C燃料电池催化剂。采用pH计及物理吸附仪表征碳黑表面的含氧官能团和比表面积,利用电感耦合等离子光谱、X射线衍射、透射电镜和循环伏安法分别表征催化剂的成分、物相组成、微观组织形貌和电化学性能,并与进口的Johnson Matthey(JM) Pt/C催化剂的性能进行对比。结果表明:采用调变多元醇法,以400 ℃热处理碳黑作载体所制备的Pt/C催化剂的电化学比表面积达到83 m²·g^-1,质量电流密度为49.03 A·g^-1。而进口催化剂JM 20% Pt/C的电化学比表面积为77 m²·g^-1,质量电流密度仅11.13 A·g^-1,自制催化剂即使Pt载量降低3wt%~4wt%,其电催化活性仍优于进口催化剂。     

负载型Pt/C催化剂的制备条件对Pt晶粒尺寸的影响

纳米级催化剂;浸渍还原法;晶粒结构;负载型Pt/C催化剂的制备条件对Pt晶粒尺寸的影响     

载体硫酸化对柴油机尾气催化剂Pt/Ce-Zr活性和稳定性的影响

近年来,随着大气环境污染问题日益严重,汽车尾气排放受到政府越来越严苛的控制.柴油车排气成分主要包括碳氢化合物(HC)、一氧化碳(CO)、氮氧化物(NOx)、微粒(PM)和二氧化硫(SO2),因此常用的尾气后处理系统有颗粒捕获器(DPF)、氧化型催化转换器(DOC)以及NOx选择还原系统(SCR),在处理尾气时三者联合使用.其中柴油机氧化型催化剂(DOC)是汽车尾气后处理装置的重要组成部分,主要用于氧化CO,HC和NO,可以将CO和HC氧化成无害的CO2和H2O,将NO氧化成NO2,为后续SCR反应提供条件.柴油机排气温度一般较低(150?400°C),特别是在冷启动阶段,排气温度可降低到100°C左右,要求催化剂具有良好的低温催化活性.此外,由于柴油中存在少量含硫有机化合物,经过燃烧分解,使得柴油机尾气中含有少量SO2,对催化剂又有钝化作用,因此催化剂的抗硫性也是需要关注的重点.本文采用浸渍法制备Pt/Ce-Zr-SO42?催化剂,考察了催化剂载体硫酸化以及Pt和H2SO4的负载顺序对催化剂催化氧化C3H6和CO的活性及抗硫性的影响,并且对Pt/Ce-Zr-SO42?催化剂进行了一系列表征,探究其物理化学性质.结果表明,SO42?的添加能有效提高催化剂活性.Pt/CZ-10S对C3H6和CO的T90(转化率为90%时的温度)相较于Pt/CZ催化剂降低了约75°C,另外,Pt/CZ-10S催化剂也表现出较好的抗硫稳定性,在含硫尾气中240°C反应20 h后,其对C3H6和CO的转化率仍保持在95%以上.CO-TPD和XPS分析结果显示,Ce-Zr-SO42?载体上Pt的分散度增加,增加的Pt颗粒可以产生更多新的活性位点(Pt&+-(SO42?)&?couples),从而表现出优异的催化活性.此外,硫酸化后催化剂表面酸性的变化也是其抗硫性能提高的原因.     

无机胶体法制备Pt/C催化剂及其性能表征

采用无机胶体法制备用于质子交换膜燃料电池(PEMFC)的Pt/C催化剂。研究了影响PtO₂胶体生成和稳定性的因素(溶液的pH值、浓度和温度条件等)以及不同还原剂浓度对Pt/C催化剂性能的影响。透射电子显微镜测试结果表明，采用经优化的工艺条件所制备的Pt/C催化剂平均粒径为3 nm，且分散性好、粒度均匀。X-射线衍射分析表明，催化剂中Pt(111)晶面的相对含量较高，有利于加速氧还原反应。单体PEMFC的电压/电流密度曲线测试表明，所制备的Pt/C催化剂具有良好的电化学性能。     

PEMFC催化剂的研究：自制Pt/C电催化剂的性质

研究了一种用于质子交换膜燃料电池(PEMFC)的自制Pt/C电催化剂(标记为THYT-1)的物理化学和电化学性质.将THYT-1电催化剂与E-TEK公司的同类电催化剂的组成、形态及电催化性能进行了比较.单电池测试结果显示, THYT-1的电催化性能优于E-TEK电催化剂. CV测试结果表明CO在这两种电催化剂上的电氧化性能相近；TEM分析表明两种催化剂上Pt晶粒在炭载体上呈均匀分布，平均粒径均为2～3 nm； XPS和XRD测试结果表明两种催化剂中Pt主要以金属态存在.这些数据表明THYT-1催化剂的物理化学性质与E-TEK公司的相类似.     

氢水液相交换反应用高分散度Pt/C/FN疏水催化剂制备及Pt粒径效应研究

以乙二醇代替常规的异丙醇为分散溶剂, H₂PtCl₆为前驱体溶剂, 甲醛为还原剂, 采用改进浸渍还原法制备Pt/C催化剂, 用XRD, TEM和XPS对其进行表征. 改进浸渍还原法容易制备高分散度Pt/C催化剂, 催化剂Pt粒径大小可通过改变溶液pH值控制, pH值从1.6增加至11.3, 铂纳米粒子的平均粒径由3.3 nm减小到1.8 nm. pH值11.3时催化剂中Pt(0), Pt(II)和Pt(IV)的含量分别为43.3%, 30.8%和25.9%. 选择不同Pt粒径大小的Pt/C催化剂与聚四氟乙烯(PTFE)一起负载于泡沫镍(FN), 得到Pt/C/FN疏水催化剂, 考查其对氢水液相交换反应的催化活性, Pt粒径越小, 催化剂活性越高.     

固相反应制备的Pt/C催化剂对乙醇氧化的电催化活性

用固相反应法制备了Pt/C催化剂(Pt/C(s))，并研究了该催化剂对乙醇氧化的电催化活性. XRD和TEM测量表明， Pt/C(s)中Pt的平均粒径为3.8 nm，结晶度为2.38，远小于用传统的液相还原方法制得的Pt/C催化剂(Pt/C(l))的平均粒径(8.5 nm)和结晶度(5.56).因此, Pt/C(s)对乙醇的电催化氧化性能远好于液相还原法制得的Pt/C(l).     

直接甲醇燃料电池高稳定性Pt/RuO_2/C阴极催化剂研究

应用湿化学法制备RuO2/C纳米复合物,并以其为载体借助微波法制备成Pt/RuO2/C催化剂.使用透射电镜和X射线衍射分析RuO2/C载体、Pt/RuO2/C催化剂的形貌及晶体结构;循环伏安、稳态阳极腐蚀和旋转圆盘电极等测试电化学性能.结果表明,Pt/RuO2/C催化剂具有良好的耐甲醇渗透性和稳定性,可有效延长催化剂的使用寿命.本文为探索新型高性能DMFC阴极催化剂之制备提供了一条较好的途径.     

Pt/MnO2纳米结构催化剂的制备与结构表征

采用一种简单的方法合成了Pt/MnO2纳米结构催化剂.通过改变还原时间、反应温度、聚乙烯吡咯烷酮（PVP）的用量、Pt负载量等,研究了反应条件对Pt/MnO2纳米结构催化剂的Pt纳米粒子的粒径大小、粒径分布和分散性影响.并在最佳条件下合成一系列不同载体和Pt负载量的Pt/MnO2纳米结构催化剂.通过X射线衍射（XRD）...     

反应pH值对微波法合成的Mo修饰的Pt/C催化剂结构和乙醇电氧化催化性能的影响

通过调节微波反应溶液的pH值合成了一系列Mo修饰的Pt/C催化剂并用于乙醇的电氧化催化反应.利用X射线衍射(XRD)、透射电子显微镜(TEM)及X射线光电子能谱(XPS)对催化剂的晶型结构、微观形貌、粒径尺寸和表面电子结构进行了表征,并采用循环伏安法(CV)、计时电流法(CA)和电化学阻抗谱(EIS)对催化剂的乙醇电氧化催化性能进行了测试.结果表明,碱性环境有利于催化剂组分在碳载体上的均匀分布,pH值为14时制得的催化剂组分颗粒尺寸最小,且分布最均匀.该催化剂不仅表现出了最大的有效电化学比表面积和最高的乙醇电氧化催化活性,而且具有最稳定的乙醇氧化催化性能.     

Effect of metal loading and carbon support microstructure on the dispersion of Pt/C catalysts prepared viaadsorption of chloroplatinic acid

Summary Adsorption of<span lang=EN-US style='mso-ansi-language:EN-US'>H₂PtCl₆onto a carbon support followed by reduction of the adsorbed platinum species with H₂at 250°C leads to<span lang=EN-GB style='mso-ansi-language:EN-GB'>Pt/C catalysts, which show universal volcano-like dependence of platinum dispersion on the metal loading in the range from 0.01 to 0.55mmol (Pt)/m²(S_BET)<span lang=EN-GB style='mso-ansi-language:EN-GB'>when highly disordered carbons, namely, active carbons and carbon blacks, are used as supports. The maximal dispersion D(CO/Pt) = 0.8 is attained at<span lang=EN-US style='mso-ansi-language:EN-US'>0.18mmol (Pt)/m² (S_BET). With<span lang=EN-GB style='mso-ansi-language:EN-GB'>other factors being equal, the dispersion of platinum supported on carbons with a more regular crystal structure, especially Sibunit-type supports, proves to be the highest and independent of the metal loading.The differences between the two groups of carbon supports are explained by the differences in the state of the adsorbed platinum precursors.     

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.     

碳载体预处理对CoTMPP/BP电催化剂氧还原性能的影响

采用微波加热合成法制备了CoTMPP/BP电化学氧还原催化剂。采用旋转圆盘电极(RDE)研究了BP2000碳载体经30% H₂O₂或6 mol·L^-1 HNO₃化学预处理后对催化剂氧还原催化活性的影响，并且在PEM燃料电池工作站上测试了不同CoTMPP/BP催化剂的燃料电池单电池性能。结果表明，碳载体经过化学预处理后催化剂性能有显著的提高，并且30% H₂O₂处理效果更好。采用IR、XRD和XPS进一步分析了载体化学预处理对催化剂活性影响的机理：IR结果表明预处理后载体表面羟基(-OH)等含氧基团增多；XRD分析表明900℃热处理后催化剂中有Co₃C(101)和金属态Co(111)结构出现；XPS分析表明碳载体预处理后N原子表面浓度以及组分N1和Co^Ⅲ相对比例升高，有利于Co-N4-C活性位的形成，然而组分N1，O1s Co^Ⅲ和Co^Ⅱ的结合能(BE)有所下降。     

高压微波制备Pt／C催化剂的工艺研究

利用高压微波消解仪密闭带压、升温速率可控的特点,选择XC-72碳黑为载体,乙二醇为碳黑分散溶剂和还原剂,研究反应温度、升温速率、水含量、Pt含量及表面活性剂等工艺条件对Pt粒子尺寸及其分散度的影响．研究结果表明,快速升温到190℃、控制反应体系中水含量和Pt含量等工艺条件,可以得到Pt粒子平均粒径小于3．1nm的Pt／C催化剂,且Pt粒子分布均匀,无团聚．     

Synthesis of Pt/C Electrocatalysts Under Protection of Glucose and Their Improved Methanol Electrooxidation Activity

Carbon supported Pt(Pt/C) electrocatalysts were prepared with glucose as protection agent and NaBH₄ as reductant. The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attributed to the protection effect of glucose. Glucose absorbed on the particle surface was readily removed by water washing without leading to agglomeration of the Pt nanoparticles. The as-prepared Pt/C electrocatalysts showed improved mass activity for methanol electrooxidation compared to the catalyst prepared without glucose protection. The improved performance is attributed to the larger electrochemical active surface area thus increased active sites on the Pt/C elctrocatalysts prepared under the protection of glucose.     

Effect of TiO2 Calcination Pretreatment on the Performance of Pt/TiO2 Catalyst for CO Oxidation

In order to improve the CO catalytic oxidation performance of a Pt/TiO₂ catalyst, a series of Pt/TiO₂ catalysts were prepared via an impregnation method in this study, and various characterization methods were used to explore the effect of TiO₂ calcination pretreatment on the CO catalytic oxidation performance of the catalysts. The results revealed that Pt/TiO₂ (700 °C) prepared by TiO₂ after calcination pretreatment at 700 °C exhibits a superior CO oxidation activity at low temperatures. After calcination pretreatment, the catalyst exhibited a suitable specific surface area and pore structure, which is beneficial to the diffusion of reactants and reaction products. At the same time, the proportion of adsorbed oxygen on the catalyst surface was increased, which promoted the oxidation of CO. After calcination pretreatment, the adsorption capacity of the catalyst for CO and CO₂ decreased, which was beneficial for the simultaneous inhibition of the CO self-poisoning of Pt sites. In addition, the Pt species exhibited a higher degree of dispersion and a smaller particle size, thereby increasing the CO oxidation activity of the Pt/TiO₂ (700 °C) catalyst.     

The influence of hydrogen peroxide on carbon monoxide electrooxidation at Pt/C and Pt:Ru/C electrodes

Polymer electrolyte fuel cells constitute one of the most important efficiency energy converters for non-centralised uses. However, the use of fuels arising from reformate processes significantly lowers the current efficiency because of anodic catalytic poison coming from adsorbed carbon monoxide (CO_ad). In this work, the influence of the addition of hydrogen peroxide in the flow current is studied, considering the adsorption and electrochemical oxidation of carbon monoxide on carbon-supported Pt (20% Pt/Vulcan) and Pt:Ru (1:1, 20% Pt:Ru/Vulcan) catalysts in 2 M sulphuric acid. The investigation was conducted applying cyclic voltammetry and on-line differential electrochemical mass spectrometry. A series of experiments has been performed to investigate the influence of the temperature as well as the time of contact and the concentration of hydrogen peroxide. Oxidation of CO_ad to carbon dioxide occurs at lower potentials in the presence of hydrogen peroxide. Moreover, it is possible to remove ca. 70% of CO_ad on Pt/C electrodes. On the other hand, for PtRu/C electrodes, similar charge values to those of Pt/C electrodes were obtained for the CO stripping, but the process occurs at more negative potentials. In this case, the effect of partial desorption for CO_ad by interaction with hydrogen peroxide is added to the bifunctional mechanism usually considered for this alloy. This paper is dedicated to Prof. Francisco Nart, in memoriam.     

石墨化的有序介孔碳的制备及其作为载体的Pt催化剂对甲醇的电催化氧化

以低分子量的酚醛树脂为碳源, F127为模板剂, NiCl₂为石墨化促进剂, 通过一步模板法辅助合成有序介孔碳. X射线衍射(XRD)、激光拉曼和透射电子显微镜(TEM)等测试结果表明, Ni以金属颗粒的方式进入碳材料的骨架中, 明显提高了有序介孔碳的石墨化程度, 而碳的有序介孔结构几乎没有变化. 在700 ℃热解温度下, Ni含量为5%时, 可以清晰地观察到Ni周围呈现碳的石墨结构. 在硫酸和甲醇溶液中进行循环伏安测试, 结果显示, 碳材料的石墨化有利于提高其电催化活性, 含Ni 5%的碳载Pt催化剂电化学活性面积可达24.84 m²•g^－1, 甲醇氧化峰电流为3.92 mA.