Pt/TiO_2催化剂的载体结构对甲醇催化氧化性能的影响（英文）

二氧化钛载体包括二氧化钛纳米管阵列(TNTAs)和二氧化钛纳米线阵列(TNWAs)两种,载体的结构不同对催化性能有一定的影响.然而,Pt负载在TNTAs和TNWAs催化性能的比较鲜有报道.本文通过微波法制备了Pt/TNTAs和Pt/TNWAs两种催化剂,结果表明,Pt/TNTAs催化甲醇氧化效果要优于Pt/TNWAs.相较于Pt/TNWAs,Pt/TNTAs的优越催化性能可能与纳米管的限域效应有关.可见,载体的结构对催化剂的性能有很大的影响.     

镶嵌Pt的二氧化钛纳米管的合成及其光催化性能研究

以金红石相二氧化钛(TiO₂)粉体为原料,采用水热法合成了二氧化钛纳米管(Titania nanotubes,简写为TNTs),然后把H₂PtCl₆的无水乙醇溶液引入到TNTs中,得到镶嵌Pt的二氧化钛纳米管(Pt/TNTs)。利用透射电镜(TEM)、X射线衍射(XRD)和紫外-可见光谱(UV-Vis)对产物进行了表征,并重点研究了Pt/TNTs的光催化性能。结果表明,有直径约为3 nm的 Pt纳米粒子插入到了TNTs中,且Pt粒子以Pt单质的形式存在。Pt/TNTs在可见光区域表现出较强的吸收,并且其起始吸收带边发生明显红移。紫外光催化降解甲基橙实验结果表明,金红石相TiO₂,TNTs和Pt/TNTs对甲基橙溶液的降解率分别达到46.8%, 57.2%和84.6%,Pt/TNTs的光催化活性较金红石相二氧化钛粉体和纯TNTs有显著的提高。     

基于一维TiO_2纳米管阵列薄膜的β伏特效应研究

介绍了一种采用宽禁带半导体二氧化钛纳米管阵列薄膜材料制备β伏特效应同位素电池的方法.通过对金属钛片的电化学阳极氧化制备了垂直定向、有序排列的二氧化钛纳米管阵列薄膜,研究了退火条件对二氧化钛纳米管阵列薄膜半导体光电性能的影响.通过与镍-63辐射源的集成封装,形成三明治结构镍-63/二氧化钛纳米管阵列薄膜/钛片的β伏特同位素电池.实验结果表明,基于氩气氛围下450?C退火的黑色二氧化钛纳米管阵列薄膜具有高的氧空位缺陷浓度和宽的可见-紫外吸收光谱.在使用β辐射总能量为10 m Ci的镍-63辐射源时,同位素电池的开路电压为1.02 V,短路电流75.52 n A,最大有效转换效率为22.48%.     

含贵金属的BaZrO3 储存NOx 催化剂结构及性能研究

用溶胶 凝胶法制备了钙钛矿型BaZrO3催化剂 ,再用等量浸渍法制备了Rh/BaZrO3样品 ,并制备了Rh/BaZrO3/γ Al2 O3和Pt/BaZrO3/γ Al2 O3催化剂 .对它们的NOx 储存量 (NSC)及其抗硫性能进行了测试 ,并用X射线衍射 (XRD)、X光电子能谱 (XPS)和傅里叶变换红外光谱 (FT IR)等方法研究了它们的结构及其对性能的影响 .结果表明 ,BaZrO3催化剂具有良好的储氮及抗硫性能 ,直接添加贵金属到BaZrO3中会使NSC降低 ,而混合γ Al2 O3后添加Pt或Rh可以大大提高NSC ,上述两种方式引入贵金属都能改善催化剂的抗硫性能 .     

铂修饰花状石墨烯催化还原CO_2反应

为了利用太阳能将CO_2选择性转化为高价值化工品,首次制备了担载于泡沫铜的载铂花状石墨烯电阴极与镀铂TiO_2纳米管光阳极协同光电还原CO_2。阴极催化剂的SEM图显示,载铂石墨烯呈现明显的花状结构,而阳极载铂二氧化钛纳米管的XRD图显示,经过反应的二氧化钛纳米管结构稳定,表明在反应过程中二氧化钛纳米管能够稳定的提供协同催化作用。与纯光照或纯电催化还原CO_2相比,光电协同催化有效提高了CO_2还原效率,使得产物C原子转化率达到998.6 nmol/(h·cm~2)。     

原位红外光谱研究Pt/FeO_x催化剂的CO氧化反应机理

低浓度CO氧化是催化领域的重要研究方向之一,在大气污染治理、CO气体防护面具、燃料电池气体净化、CO气体传感器、封闭式CO2激光器等方面具有重要应用前景。近年来,我们课题组采用胶体沉积法制备出Pt/FeOx催化剂,该催化剂具有良好的CO低温催化氧化性能[1,2]。利用原位红外光谱监测Pt/FeOx催化剂上的低温CO氧化反应过程,研究结果发现氧气活化能力对Pt/FeOx催化剂的低温CO催化性能影响较大。     

氮掺杂碳纳米管负载铂催化剂的简易制备及催化性能

以氮掺杂碳纳米管为载体,在温和条件下采用简单的浸渍法制备得到铂催化剂,铂的粒径分布在4～7 nm,且氮掺杂碳纳米管无需进行预处理. 采用X射线衍射仪、扫描电子显微镜、透射电镜和能量色散X射线仪等对Pt/CN_x催化剂进行了详细的表征. 结果表明,氮掺杂碳纳米管中高含量的氮原子能够有效俘获Pt(IV) 离子,且表面的含氮官能团及亲水性能的提高都有利于铂纳米粒子的分散. Pt/CN_x催化剂在烯丙醇加氢反应中表现出高的催化性能及循环使用性能,这是由于铂纳米粒子的高分散性及铂与载体间强的连接性阻止了Pt的流失及聚积,从而避免生成Pt黑导致失活等.     

纳米碳管作为氧扩散电极催化层第二相碳载体的电极特性

以纳米碳管和活性碳二元碳材料为催化层碳载体制备了氧扩散电极,采用稳态极化和电化学阻抗技术对其在碱性介质中氧还原反应的电催化活性进行了研究.结果表明,双载体电极比单载体纳米碳管、活性炭电极具有更高的电催化活性,纳米碳管和活性炭质量比为50∶50时双载体电极的催化活性最好;电极动力学参数测试表明,催化层中引入第二相纳米碳管载体提高了电极比表面积、电子导电性和氧还原反应速度;采用浸渍还原法在第二相纳米碳管载体中负载纳米级Pt催化剂,即使在低Pt负载量下(45.7μg/cm2)也明显改善了双载体电极的催化活性.阻抗测试表明,载Pt与未载Pt催化剂的双载体电极均受氧在薄液膜中的扩散控制.     

聚乙二醇-b-聚(4-乙烯基吡啶)/氢氧化钇杂化纳米管在金纳米粒子负载方面的应用

利用聚乙二醇-b-聚(4-乙烯基吡啶)(PEO-b-P4VP)胶束在氢氧化钇纳米管(YNTs)表面上的吸附,制备出被致密的P4VP内层和伸展的PEO外层包裹的杂化纳米管. 通过小分子交联剂1,4-二溴丁烷交联P4VP层可进一步稳定其结构. 然后将交联的杂化纳米管(CHNTs)作为金纳米粒子(GNPs)催化剂的新型纳米载体. 金纳米粒子被负载在交联杂化纳米管的P4VP层中(GNPs/CHNTs),并应用于催化对硝基苯酚的还原反应. 结果表明,这种新型的纳米载体在水溶液中具有良好的分散性, 对金纳米粒子有很高的负载效率(0.87 mmol/g),负载的金纳米粒子保持了很高的催化活性(12.9 μmol^-1min^-1),且GNPs/CHNTs有较好的可重复使用性.     

有序TiO2纳米管阵列结构的可控生长及其物相研究

分别在HF水溶液、含NH₄F和H₂O的乙二醇有机溶液中对Ti箔进行阳极氧化,得到TiO₂纳米管阵列结构.该结构高度有序、分布均匀、垂直取向,且通过阳极氧化工艺条件(如阳极氧化电压、电解液的选择与配比以及氧化时间等)可实现对其结构参数(如管径、管壁厚度、管密度、管长等)的有效控制.利用XRD研究了TiO₂纳米管阵列的物相结构.结果表明：退火前的TiO₂纳米管阵列为无定形结构;分别在真空和氧气氛中50 关键词： 2纳米管阵列')" href="#">TiO₂纳米管阵列 阳极氧化 可控生长     

时间分辨红外光谱研究Pt/TiO2上甲醇光催化反应中光生电子衰减动力学

采用时间分辨红外光谱直接观测了甲醇在Pt/TiO2上光催化反应制氢过程中光生电子还原氢离子生成氢气的反应过程．结果表明Pt的担载量存在一最佳值，使得该催化剂中光生电子的反应速度最快．当Pt担载量相同时，Pt/TiO2催化剂中光生电子参与产氢反应的速度随样品还原温度的不同而明显变化．可能的原因是较高温度下氢气还原的Pt/TiO2催化剂中Pt粒子占据了TiO2表面的一些能够解离吸附甲醇的活性位置，而对于较低温度下氢气还原的Pt/TiO2催化剂，这种占据作用很不明显．实验中还发现瞬态动力学研究中光生电子衰减较快     

A comparative study for the electrocatalytic oxidation of alcohol on Pt-Au nanoparticle-supported copolymer-grafted graphene oxide composite for fuel cell application

The platinum-gold bimetallic nanoparticles supported poly(cyclotriphosphazene-co-benzidine)-grafted graphene oxide (poly(CP-co-BZ)-g-GO) composite has been prepared for electrochemical performance studies. Cyclic voltammetry and chronoamperometric studies were carried out to check the electrochemical properties of Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO catalysts for methanol, ethylene glycol and glycerol in alkaline medium. The morphology and crystalline structure of the prepared Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO and catalysts have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). From the electrochemical results, it was concluded that Pt-Au/poly(CP-co-BZ)-g-GO catalyst shows higher catalytic activity and stability compared to Pt/poly(CP-co-BZ)-g-GO catalyst. The catalytic activity of Pt/poly(CP-co-BZ)-g-GO catalyst has been compared with Pt/poly(CP-co-BZ), Pt/GO and Pt/C catalysts. In addition, oxidation current of ethylene glycol is higher than the methanol and glycerol in alkaline medium on the prepared catalyst.     

Platinum catalyst on ordered mesoporous carbon with controlled morphology for methanol electrochemical oxidation

Ordered mesoporous carbons CMK-3 with various morphologies are synthesized by using various mesoporous silica SBA-15 as template and then support to prepare Pt/CMK-3 catalyst. The obtained catalysts are compared in terms of the electrocatalytic activity for methanol oxidation in sulfuric acidic solutions. The structure characterizations and electrochemical analysis reveal that Pt catalysts with the CMK-3 support of large particle size and long channel lengths possess larger electrochemical active surface area (ECSA) and higher activity toward methanol oxidation than those with the other two supports. The better performance of Pt/CMK-3 catalyst may be due to the larger area of electrode/electrolyte interface and larger ECSA value of Pt catalyst, which will provide better structure in favor of the mass transport and the electron transport.     

Electrocatalytic performance of bimetallic platinum–ruthenium nanoclusters supported on graphite nanofibers

In this work, graphite nanofibers (GNFs) as a catalysts supports were impregnated with Pt and Ru precursor compounds to investigate the effect of various Pt–Ru compositions on the catalytic activity of direct methanol fuel cells (DMFCs). The particle sizes and morphological structures of the catalysts were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical oxidation of the prepared catalysts was investigated by cyclic voltammetry (CV) measurement. Inductive coupled plasma-mass spectrometer (ICP-MS) analysis showed that the metallic ratio in the catalysts was very near to expectations. Cyclic voltammetry showed that the catalysts were electro catalytically active in the methanol oxidation. Among the prepared catalysts, the Pt₅₀Ru₅₀ catalysts exhibited the best electrocatalytic performance. It was concluded that catalytic activity is dependent on the alloy compositions of the catalysts, and that Ru metal has a positive effect on CO poisoning of Pt metal for methanol oxidation.     

Preparation of carbon supported Pt-P catalysts and its electrocatalytic performance for oxygen reduction

The carbon supported PtP (PtP/C) catalysts were synthesized from Pt(NO₃)₂ and phosphorus yellow at the room temperature. The content of P in the PtP/C catalysts prepared with this method is high and the average size of the PtP particles is decreased with increasing the content of P. The electrocatalytic performances of the PtP/C catalysts prepared with this method for the oxygen reduction reaction (ORR) are better than that of the commercial Pt/C catalyst. The promotion action of P for enhancing the electrocatalytic performance of the PtP/C catalyst for ORR is mainly due to that Pt and P form the alloy and then the electron density of Pt is decreased.     

Preparation and characteristic of platinum catalyst deposited on boron-doped carbon nanotubes

In this work, boron doped multi-walled carbon nanotubes (BMWNTs) were introduced as a Pt catalyst support due to their unique physicochemical properties. The effect of BMWNTs on methanol oxidation was investigated with different Pt loading contents. The surface and structural properties of the modified MWNT supports were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The Pt loading contents in the catalysts were confirmed by inductive coupled plasma-mass spectrometer (ICP-MS) and the morphological structures of the catalysts were analyzed by transmission electron microscopy (TEM). The electrocatalytic activity of Pt/MWNTs was investigated by cyclic voltammetry measurement. As a result, the boron oxide vapor reacted with MWNTS to form BMWNTs, which led to enhancing the properties, such as graphitization and electrochemical behaviors. Moreover, Pt deposited on BMWNTs exhibited better electrocatalytic activity than on MWNTs for methanol oxidation. Consequently, it was found that partial boron doped MWNTs could influence on the properties of the MWNTs, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.     

Promotion of partial oxidation of methanol over thin Pt and Pd film catalysts by resonance oscillation of acoustic waves

The thickness extension mode resonance oscillation (TERO) of bulk acoustic waves generated on z-cut LiNbO₃ by rf electric power was employed to the catalytic oxidation of methanol over thin Pt and Pd film catalysts deposited. Both the catalysts produced formaldehyde, methyl formate, and carbon dioxide as carbon-containing products in the gas phase. The TERO considerably increased the selectivity for formaldehyde production on Pt at a moderate rf power, indicating the ability of promoting the partial oxidation of methanol, whereas a small and monotonous decrease in the selectivity of the reaction on Pd occurred with power. The different TERO effects on the selectivity are discussed.     

Successive electrodeposition of polydopamine and PtPd metal on a graphene oxide support for use as anode fuel cell catalysts

Successive electropolymerization of dopamine and electrodeposition of Pd and/or Pt on a graphene oxide (GO) support were used to prepare anode catalysts for low-temperature fuel cells. Transmission electron microscopy images were used to investigate the morphologies and distribution of the prepared catalysts, which showed the metal formed as nanoparticles on the catalysts. The GO surface was favorable for the modification with electropolymerized polydopamine (PDA) and the electrodeposition of metal catalyst nanoparticles using a simple preparation process. The PDA-loaded GO composite was used as a matrix for the dispersion of Pt and Pd nanoparticles. GO could be simultaneously modified by PDA and reduced without using reducing agents. The electrocatalytic performance of the catalysts for the oxidation of selected small molecule fuels (e.g., methanol, ethanol and formic acid) was examined. An outstanding catalytic activity and stability was found for the prepared Pt/Pd/PDA/GO composite, which was attributed to the high active surface area.     

Selective oxidation of CO in the presence of air over gold-based catalysts Au/TiO2/C (sonochemistry) and Au/TiO2/C (microwave)

Two model catalysts, Au/TiO2/C (S) (sonochemically derived) and Au/TiO2/C (M) (microwave derived), were produced by employing ultrasound irradiation and microwave irradiation, respectively. The deposition of gold colloids onto the support powders, TiO2/C, was accomplished by using a solvated metal atom impregnation (SMAI) method. The SMAI technique provides highly-dispersed gold particles on the TiO2/C support. The catalytic performance of Au based catalysts 1 wt% Au-TiO2/C (S) and 1 wt%Au-TiO2(M)/C (M) have been tested for the oxidation of CO in the temperature range of 0-300 degrees C and compared to that of 1 wt% Au-TiO2 (Degussa-P25). A boost in the conversion of CO was observed for the sonochemically-derived catalyst, Au/TiO2/C (S), at low temperature. Hence, the reactivity order found for CO oxidation is (Au/TiO2/C (S)>Au/TiO2 (P25)>Au/TiO2/C (M)).     

ESCA Studies of Supported Catalysts

Abstract

Since ESCA measurement reveals the chemical composition and oxidation states of atoms on the surface of solids [1], it provides a new probe for investigation in the field of catalysis. It has been widely used to investigate directly the surface structure and composition, mechanisms of reaction, poisoning and reactivation; composition activity performance correlationship, etc. ESCA on catalysts has been reviewed by several workers [2–71, but its use in supported catalysts has not received the attention of workers. In this review the potential applications of XPS on several supported catalysts are discussed.