载体对Pt催化剂制备邻苯基苯酚催化性能的影响

分别以活性炭(AC)、γ-Al2O3、MgO、TiO2为载体,氯铂酸为活性金属前驱体,采用等体积浸渍法制得不同载体负载的Pt催化剂,考察了它们对环己烯基环己酮(dimer)脱氢制备邻苯基苯酚(OPP)的催化活性和选择性。并用X射线衍射(XRD)、X射线光电子能谱(XPS)、H2程序升温脱附(H2-TPD)、CO2程序升温脱附(CO2-TPD)等对催化剂进行表征。结果表明,载体对所制备的催化剂表面Pt含量、酸碱性和对氢吸附能力等微观性能有影响,以γ-Al2O3为载体制备的Pt-K/γ-Al2O3催化剂,由于催化剂表面Pt质量分数高达0.41%,碱性强和碱中心多,利于氢和中间产物在催化剂表面的吸附,从而提高环己烯基环己酮的转化率和OPP选择性。Pt/γ-Al2O3催化剂在LHSV 0.12 h-1、H2空速33 mL/(g.h)、反应温度380℃的条件下,在200 t/a的工业化装置运转8 000h后,环己酮二聚物转化率仍能达99%以上,OPP选择性达90%以上。     

碳化钨/碳气凝胶纳米复合材料增强Pt电催化甲醇性能的研究

以间苯二酚和甲醛为原料,采用溶胶-凝胶法原位合成WC纳米颗粒制备了碳化钨/碳气凝胶(WC/CAs);以WC/CAs为载体,利用微波加热乙二醇还原法制备了Pt/WC/CAs催化剂。运用循环伏安法(CV)、线性扫描(LSV)、计时电流法(CA)、能谱(EDS)、透射电子显微镜(TEM)和X射线衍射(XRD)等技术分析Pt/WC/CAs催化剂的组成、结构及其对甲醇的电催化氧化活性的影响。实验结果表明,载体中WC纳米颗粒的加入促进Pt贵金属颗粒对甲醇的电催化氧化活性,正扫电流峰ip与扫描速率的平方根v1/2线性相关,Pt/WC/C催化氧化甲醇的过程受扩散控制;且电催化活性比Pt/C要好。     

络合还原法制备Pd/C催化剂及甲酸电催化氧化性能

分别以硼氢化钠和乙二醇为还原剂,经络合还原法制备了炭载钯(Pd/C)催化剂。透射电镜(TEM)和X射线粉末衍射谱(XRD)结果表明,以乙二醇为还原剂制备的Pd/C催化剂中Pd粒子具有较小的粒径、均匀的粒径分布和较大的相对结晶度,Pd粒子的平均粒径和相对结晶度分别为(4.2±2)nm和1.88。电化学测试结果显示,Pd/C催化剂具有较大的电化学活性面积,对甲酸氧化表现出较高的电催化活性和稳定性。     

室温原位合成Pt纳米粒子/氧化石墨烯复合物及其对甲醇的高活性电催化氧化性能

利用甲酸作为还原剂,在室温条件下原位制备了不同配比的Pt/GO复合物,用电化学方法研究了催化剂对甲醇的电催化氧化性能。与相对商业提供的E-TEK(20%)催化剂相比,Pt/GO具有更高的活性和稳定性。     

载体的碱处理对Pd/C催化剂电催化性能的影响

将活性炭放入质量分数为10%的NaOH溶液中进行预处理,然后将其与未处理的活性炭分别作为载体制备Pd/C催化剂。对比两种催化剂的电化学性能发现,预处理的活性炭所制备的Pd/C催化剂,在甲酸电催化氧化活性和稳定性方面好于未处理的活性炭所制备的Pd/C催化剂。     

纳米铂修饰玻碳电极对乙二醇的电催化氧化研究

采用化学原位一步还原法制得纳米铂修饰玻碳电极,并测试比较了其在酸性介质和碱性介质中对乙二醇氧化的电催化作用.结果表明,相比铂片电极,纳米铂修饰玻碳电极对乙二醇表现出更好的电催化性能,且该修饰电极在碱性介质中对乙二醇的催化作用更明显.     

埃洛石负载的纳米金可控制备及对环己烷选择性氧化的催化性能

埃洛石纳米管（HNTs）是一类具有独特物理结构和化学性质的天然黏土化合物,本文以经过提纯和聚二烯丙基二甲基氯化铵溶液（PDDA）改性的埃洛石为载体,将预先制备的粒径可控的金溶胶负载到改性埃洛石（PHNTs）表面得到负载型的纳米金颗粒,通过调节氯金酸前体的浓度和用量,实现了对负载型纳米金尺寸的有效调控,透射电镜表征结果显示,埃洛石负载的纳米金分散性良好,平均粒径分别处于2nm以下、2～5nm和5nm以上。以环己烷的液相选择性氧化为模型反应,评价了所制备的不同尺度负载型纳米金粒子的活性和对环己醇和环己酮的选择性。结果表明：纳米金颗粒的平均粒径处于2～5nm时,表现出最好的催化活性和选择性,在170℃和2.0MPa下反应2h,环己烷的转化率可达10.29%,环己醇和环己酮的选择性达85.75%,优于该反应体系使用的工业催化剂对活性和选择性的指标要求。此外,X射线光电子能谱仪表征结果显示,当埃洛石负载的纳米金平均粒径处于2～5nm时,金元素主要以Au⁰ 的形式存在。     

Nd修饰的PtSn/C催化剂对乙醇的电催化氧化性能

利用浸渍还原法,以甲酸为还原剂制备了PtSnNd/C和PtSn/C纳米催化剂。XRD测量了催化剂的粒径和晶格参数,循环伏安法和计时电流法测试了催化剂对乙醇的催化氧化性能。结果表明,添加Nd可以明显提高PtSn/C催化剂对乙醇的电催化氧化活性,峰电流密度增大了86%。     

Pt/CeO_2/RGO复合材料的制备以及对乙醇的电催化性能研究

利用改进的Hummers法合成氧化石墨烯并还原,再利用水热合成法制得Ce O2/RGO复合材料,将其修饰玻碳电极后镀铂后获得Pt/Ce O2/RGO修饰电极。通过SEM和EDS对其形貌进行了表征,同时利用紫外—可见吸收光谱和循环伏安法等方法研究了其在酸性条件下对乙醇的电催化性能。结果表明:酸性条件下RGO在0.05 V处将乙醇氧化成乙醛,在0.5 V处氧化成乙酸;复合材料RGO/Ce O2(1∶1)/Pt在0.04V处将乙醇氧化成乙醛,在0.45 V处氧化成乙酸;复合材料RGO/Ce O2(1∶2)/Pt在0.03 V处将乙醇氧化生成乙酸。     

Pt/CNTs金属纳米催化剂的制备及对甲醇的电催化氧化

采用混酸(HNO3-H2SO4)浸泡法对碳纳米管(CNTs)进行表面功能化,以氯铂酸(H2PtCl6·6H2O)为前躯体,通过液相化学还原法快速合成了Pt/CNTs纳米催化剂(负载Pt的质量分数为20%)。透射电镜(TEM)观察表明,该法合成的Pt纳米粒子粒径小且尺寸分布窄,Pt纳米粒子高度分散在CNTs的表面,其平均粒径为4.5 nm,与XRD表征所计算的平均粒径相符合(4.46 nm)。电化学实验表明,该法合成的Pt/CNTs催化剂比商业Pt/CNTs催化剂对甲醇的电化学催化活性要高。     

Relationship among the physicochemical properties, electrocatalytic performance and kinetics of carbon supported Pt catalyst for ethanol oxidation

A new carbon supported Pt (Pt/C(b)) catalyst was prepared by reducing H₂PtCl₆ in glycol solution using formic acid as a reducing agent, and has been found in this work to be highly active and stable for the electrochemical oxidation of ethanol. The preparation produces highly dispersed Pt particles, of 2.6 nm average size, and with high electrochemical surface area, 98 m²/g. The apparent activation energy of ethanol oxidation over the Pt/C(b) catalyst electrode is low, 10–14 kJ/mol, over the range of potentials from 0.3 to 0.6 V.     

Hollow nitrogen-containing core/shell fibrous carbon nanomaterials as support to platinum nanocatalysts and their TEM tomography study

Core/shell nanostructured carbon materials with carbon nanofiber (CNF) as the core and a nitrogen (N)-doped graphitic layer as the shell were synthesized by pyrolysis of CNF/polyaniline (CNF/PANI) composites prepared by in situ polymerization of aniline on CNFs. High-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared and Raman analyses indicated that the PANI shell was carbonized at 900°C. Platinum (Pt) nanoparticles were reduced by formic acid with catalyst supports. Compared to the untreated CNF/PANI composites, the carbonized composites were proven to be better supporting materials for the Pt nanocatalysts and showed superior performance as catalyst supports for methanol electrochemical oxidation. The current density of methanol oxidation on the catalyst with the core/shell nanostructured carbon materials is approximately seven times of that on the catalyst with CNF/PANI support. TEM tomography revealed that some Pt nanoparticles were embedded in the PANI shells of the CNF/PANI composites, which might decrease the electrocatalyst activity. TEM-energy dispersive spectroscopy mapping confirmed that the Pt nanoparticles in the inner tube of N-doped hollow CNFs could be accessed by the Nafion ionomer electrolyte, contributing to the catalytic oxidation of methanol.     

High efficient electrocatalytic oxidation of formic acid on Pt/polyindoles composite catalysts

Four novel composite catalysts have been developed by the electrodeposition of Pt onto glassy carbon electrode (GCE) modified with polyindoles: polyindole, poly(5-methoxyindole), poly(5-nitroindole) and poly(5-cyanoindole). As-formed composite catalysts are characterized by SEM, XRD and electrochemical analysis. Compared with Pt nanoparticles, respectively, deposited on the bare GCE and on the GCE modified with polypyrrole, the four newly developed composite catalysts exhibit higher catalytic activity towards formic acid electrooxidation by improving selectivity of the reaction via dehydrogenation pathway and thus mostly suppressing the generation of poisonous CO_ads species. The enhanced performance is proposed to come from the synergetic effect between Pt and polyindoles and the increase of electrochemical active surface area (EASA) of Pt on polyindoles.     

Platinum supported on resorcinol–formaldehyde based carbon aerogels for PEMFC electrodes: Influence of the carbon support on electrocatalytic properties

Two carbon aerogels with different nanopore size distributions but both with high surface area, high nanoporous volume and low bulk density have been compared as platinum support. The influence of the nanostructure of the carbon aerogel on the platinum nanoparticle deposit was investigated. The platinum was deposited on the carbon by means of two different techniques, one employing an anionic platinum precursor, the other using a cationic one. The porosity of the carbon aerogels was characterized by combining N₂-sorption and mercury porosimetry. The platinum deposit was characterized by transmission electron microscopy and rotating disk electrode experimentation to measure the platinum active surface area and its activity towards oxygen reduction reaction (ORR). The structural differences between the carbon aerogels did not yield any difference in platinum deposits in terms of Pt-surface area and ORR activity. Interestingly, the ORR mass activity of the high Pt-surface area samples, obtained by the cationic insertion technique, was several times lower than that of the samples obtained by the anionic technique. This observation was attributed to the particle size effect, detrimental in the case of platinum particle size around 1 nm.     

负载银纳米催化剂的聚多巴胺基微球的高效催化性能

利用聚多巴胺（PDA）的还原性和黏附性,成功制备了分别负载银（Ag）纳米催化剂的聚N-异丙基丙烯酰胺-聚多巴胺（PN@PDA/Ag）核壳型微球、聚苯乙烯-聚多巴胺（PS@PDA/Ag）核壳型微球和聚多巴胺（PDA/Ag）均质型微球。系统研究了PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球的微观结构、化学组成及Ag纳米颗粒的分布情况,并考察了在模型催化反应中,还原剂硼氢化钠（NaBH₄）和反应物对硝基苯酚（4-NP）摩尔比对微球催化性能的影响。结果表明,3种微球均成功负载了Ag纳米催化剂,相比于两种核壳型微球,PDA/Ag微球负载Ag纳米催化剂的含量最多。随着NaBH₄和4-NP摩尔比的增加,PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球对4-NP的转化率逐渐增大。在考察的摩尔比下,PDA/Ag微球均表现出比PN@PDA/Ag和PS@PDA/Ag微球更优异的催化性能。当摩尔比为500∶1时,PN@PDA/Ag、PS@PDA/Ag和PDA/Ag微球的表观反应速率常数（k_app）值分别为0.21min^-1、0.35min^-1和1.78min^-1。PDA/Ag微球的k_app值远高于文献报道的PDA/Ag微球k_app的最大值0.35min^-1。研究结果将为高效催化微球的设计和制备提供理论指导和实验基础。     

Pt/C催化剂制备方法的选择

研究了以HCl酸洗、H_2O_2、浓H_2SO_4、HNO_3氧化处理后的活性炭为载体,用不同方法制备了Pt担载量为3%的担载型Pt/C催化剂。TEM统计结果表明,HCl酸洗、HNO_3氧化活性炭为载体,甲醛还原法制备的催化剂分散度最高,平均粒径最小为2．2nm。FT-IR结果表明,HNO_3氧化处理活性炭,活性炭表面含氧基团明显增加。     

Facile Preparation of 2‐Substituted Benzoxazoles and Benzothiazoles via Aerobic Oxidation of Phenolic and Thiophenolic Imines Catalyzed by Polymer‐Incarcerated Platinum Nanoclusters

Platinum nanoclusters supported on a polymer/carbon black composite material was found to be an excellent catalyst for the oxidative cyclization of phenolic and thiophenolic Schiff bases to 2‐substituted benzoxazoles and benzothiazoles under ambient conditions.     

负载途径对炭气凝胶载Pt催化剂性能的影响

选择孔隙率高、孔隙尺寸小、比表面积大、电导率高、孔径大小及分布可控的新型炭材料炭气凝胶(CAs)为载体,通过在成品CAs表面负载和在CAs制备过程中同步负载两种途径制备了CAs负载的Pt催化剂,利用XRD、TEM、ICP及电化学循环伏安测试等手段对比讨论了负载途径对CAs载Pt催化剂物化性能及甲醇氧化催化活性的影响。结果表明,同步负载虽然可以简化制备工艺,但所制得的催化剂样品中催化活性组分Pt颗粒大、团聚严重、分散性差、负载量低,而且有许多Pt颗粒被包裹在CAs内部,因而导致了催化剂的有效利用率和催化性能降低。相反,通过在成品CAs表面负载的方法可以制得Pt颗粒小、分散均匀、实际负载量接近理论设计的高性能催化剂。     

Electrocatalytic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carbon substrates

To achieve methanol fuel cell electrodes allowing a high catalyst use, thin layers of various carbon powders and recast Nafion® were electrochemically plated with platinum. The resulting Pt deposits were characterized by hydrogen and carbon monoxide electrosorption, as well as by transmission electron microscopy. Methanol oxidation was then carried out using cyclic voltammetry. The influence of the amount of carbon surface oxides and the effect of Pt specific surface area on the Pt catalytic activity were thus investigated.