铂、钯基纳米材料的合成及催化性能研究

发布时间：2018-05-29 04:54

本文选题：电催化 + 加氢　；参考：《苏州大学》2015年博士论文

【摘要】：金属纳米材料由于具有催化活性高,生物相容性好,抗菌性能好等诸多优点备受研究者的强烈关注。金属纳米材料的合成方法很多,其中液相合成法依旧是主要的合成方法。一般分为油相法和水相法两类。近年来,氢气用于纳米金属的合成已经取得一些进展。从铂纳米立方体,四面体到枝状纳米晶,氢气都被证明是一种有效清洁的还原剂。基于这一点,我们尝试以氢气作为主要还原剂,在常压下,液相合成了一些新型纳米材料。主要研究工作可以分为以下几个方面:(1)在纯油胺溶液中,常压低温下,合成了铂树突状纳米立方体。对材料合成的过程跟踪分析发现,动态组成的油胺和十八胺是调节铂纳米树突成立方体的关键。氢气还原诱发铂前驱体分解成核,快速形成晶种,在油胺的保护下生长并催化油胺加氢,使得纳米铂的表面不断更新,因此,这种方法制备的纳米铂材料表面比较干净。从材料的空间构型看,此种方法制备的铂纳米材料空间孔洞非常丰富,是催化剂的首选。随后,对不饱和烃和硝基苯的加氢反应上,显示了出色的催化性能。对甲醇的电氧化反应,立方纳米铂树突的催化活性达到了铂纳米粒子的5.3倍。(2)通过两步法,在纯油胺溶液中制备了Au@Pt系列纳米材料,外层的铂先是包覆在金粒子上,然后在外层的铂表面再长上树枝状的铂条。整个过程来说,外层的铂同样参与了油胺的氢化,结果是铂条表面更新带来整个催化剂的有效活性面积的变化。与商业的JM-Pt/C相比,制备的Au@Pt纳米材料在甲醇电催化和甲酸电催化方面都表现出来更好的催化性能。对甲酸的氧化上主要是脱水历程,其催化活性是商业铂碳的2倍以上。(3)利用顺式和反式1,2-环己烷二酸作为修饰剂,在油胺体系中,制备了空心纳米钯球。无碱条件下,两种纳米催化剂对苯乙酮的加氢显示出不同的选择性。顺式二酸修饰的纳米钯球倾向于生成苯乙醇,反式二酸修饰的二酸偏重于生成乙苯,添加NH3·H2O,可以实现选择性的转变,使顺式二酸修饰的催化剂选择性转向了乙苯。(4)使用邻苯二胺进行修饰铂纳米可以得到海绵状的纳米铂,使用R(+)-α-甲基苄胺和S(-)-α-甲基苄胺修饰的纳米金银可以得到手性纳米线和纳米链。这些材料都有潜在的催化应用前景。纳米铂在氢气氛围下,生长快速,在Pt NPs上沿着八个角生长速度最快,而在Fe Pt rods和Fe Pt NWs表面生长成双向外延生长,但在Au NWs上却是单向外延生长。即使是PVP包裹的Pd NWs和Ag NWs,在油相中,氢气还原下,纳米铂依旧可以还原生长在表面,形成异质结构。UV/O3处理的Pd NWs可有效去除材料表面的PVP,但是在处理过程中会出现断裂现象。(5)邻卤苯胺是重要的化工中间体,通常由邻卤硝基苯选择性加氢制备,但由于副反应较多,脱卤严重。所以寻求合适的催化体系一直都吸引着许多研究者。Fe(CO)5诱发成核制备的Pt NPs和适当的弱碱(Na HCO3和NH3·H2O)构成的催化体系用于邻卤硝基苯制邻卤苯胺。低温常压下即可实现加氢过程,产率达到99%以上,并且催化剂重现性好。
[Abstract]:Metal nanomaterials have attracted much attention due to their high catalytic activity, good biocompatibility and good antibacterial properties. There are many synthetic methods for metal nanomaterials, in which liquid phase synthesis is still the main synthetic method. The two types are usually divided into oil phase and water phase method. In recent years, hydrogen is used in the synthesis of nanoscale metal. Some progress has been made. From platinum nanometers, tetrahedron to dendrite nanocrystals, hydrogen is proved to be an effective and clean reducing agent. Based on this, we try to use hydrogen as the main reducing agent to synthesize new nanomaterials at atmospheric pressure. The main research work can be divided into the following aspects: (1) Platinum dendritic nanocubes were synthesized at low temperature in pure oil amine solution. The process tracking analysis of the synthesis of materials found that the dynamic composition of oleamine and eighteen amines was the key to regulate the platinum nanoscale dendrites. The hydrogen reduction induced platinum precursors to decompose into nucleation, quickly form a crystal, grow and catalyze oleamine under the protection of oleamine. As a result, the surface of the nano platinum is constantly updated. Therefore, the nano platinum materials prepared by this method are relatively clean. From the spatial configuration of the materials, the space pore of the platinum nanomaterials prepared by this method is very rich and the first choice of the catalyst. Subsequently, the hydrogenation of unsaturated hydrocarbons and nitrobenzene shows excellent catalytic properties. As for the electrooxidation of methanol, the catalytic activity of the cubic nanometer platinum dendrite reached 5.3 times that of the platinum nanoparticles. (2) the Au@Pt series nanomaterials were prepared in the pure oleamine solution by the two step method. The platinum in the outer layer was first coated on the gold particles and then on the platinum surface in the outer layer, and the whole process, the outer layer. Platinum also participates in the hydrogenation of oleamine, which results in a change in the active active area of the whole catalyst with the surface renewal of the platinum strip. Compared with the commercial JM-Pt/C, the prepared Au@Pt nanomaterials exhibit better catalytic performance in both methanol electrocatalysis and formic acid electrocatalysis. The oxidation of methacol is mainly the dehydration process and its catalytic activity. 2 times more than 2 times of commercial platinum carbon. (3) using CIS and trans 1,2- cyclohexane acid as a modifier, hollow nano palladium spheres were prepared in the oil amine system. Under alkali free conditions, the hydrogenation of acetophenone showed different selectivity. The CIS diacid modified nano palladium ball was inclined to produce phenylene alcohol and trans diacid repair. The ornament diacid is partial to the formation of ethylbenzene and the addition of NH3. H2O, the selective transition can be achieved, and the CIS diacid modified catalyst is selectively turned to ethylbenzene. (4) the modified platinum nanoparticles can be obtained by using phthalic two amine to obtain the sponge like nano platinum. The nano gold and Silver Modified by R (+) - alpha methylbenzamine and S (-) - alpha methylbenzamine can be obtained. Nanowires and nanoscale chains. These materials have potential catalytic applications. Nano platinum grows fast in a hydrogen atmosphere, grows fastest at eight angles on Pt NPs, and grows on the surface of Fe Pt rods and Fe Pt NWs, but is unidirectional epitaxial growth on Au NWs. In the oil phase, in the hydrogen reduction, the nano platinum can still be reduced to the surface, and the Pd NWs treated by the heterostructure.UV/O3 can effectively remove the PVP on the surface of the material, but there will be a fracture phenomenon during the process. (5) the o-halide is an important chemical intermediate, usually prepared by the selective hydrogenation of the adjacent halogen nitrobenzene, but the side reaction is due to the side reaction. More dehalogenation is serious, so the search for a suitable catalytic system has been attracting many researchers.Fe (CO) 5 to induce the nucleated Pt NPs and the proper weak base (Na HCO3 and NH3. H2O) as a catalytic system for the adjacent halide aniline. The hydrogenation process can be achieved at low temperature at low temperature, and the catalyst weight is more than 99%. It's good at present.
【学位授予单位】：苏州大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

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