Generalized approach for the synthesis of silica supported Pd-Zn, Cu-Zn and Ni-Zn gamma brass phase nanoparticles
Generalized approach for the synthesis of silica supported Pd-Zn, Cu-Zn and Ni-Zn gamma brass phase nanoparticles
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DOI：
10.1016/j.cattod.2018.10.050
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发表时间：
2019-08-15
期刊：
影响因子：
5.3
通讯作者：
Rioux, Robert M.
中科院分区：
文献类型：
--
作者：
Dasgupta, Anish;Zimmerer, Eric K.;Rioux, Robert M.
现有文献表明，通过传统的纳米颗粒（NP）合成技术获得催化相关的且相对复杂的金属间γ-黄铜晶体结构是特别困难的。我们介绍了一种简单而合理的方法来访问这个阶段在M-Zn（M=Pd，Cu，Ni）系统作为二氧化硅支撑的单相纳米晶体。这种混合方法包括通过传统方法（干浸渍和强静电吸附）初始合成负载的M/SiO2，然后在真空封闭系统中在化学计量量的金属Zn存在下加热至高温几个小时。我们证明了这种方法的通用性与三个不同的催化重要的双金属系统：Pd-Zn，Ni-Zn和Cu-Zn。在这三种中，Pd-Zn在催化应用方面是迄今为止最受欢迎的，并且产生最小的颗粒尺寸（类似于8 nm）。我们测试了各种合成参数对合成的γ-黄铜Pd-Zn/SiO2负载型催化剂的相纯度和粒度分布的影响，并提供了合成优化的一般指导方针。当Pd/SiO2转变为γ-黄铜Pd-Zn/SiO2时，观察到CO吸附的急剧下降和乙烯加氢势垒的25 kJ/mol增加，表明催化活性位点作为合金化的结果被显著地修饰。我们预计这些催化剂可以在各种Pd催化的化学中找到应用。
The existing literature suggests it is particularly difficult to access the catalytically relevant, and relatively complex, intermetallic gamma-brass crystal structure through traditional nanoparticle (NP) synthesis techniques. We introduce a simple and rational approach to access this phase in M-Zn (M=Pd, Cu, Ni) systems as silica-supported single-phase nanocrystals. This hybrid approach involves the initial synthesis of supported M/SiO2 through traditional approaches (dry impregnation and strong electrostatic adsorption) followed by heating to high temperatures in the presence of a stoichiometric amount of metallic Zn in an evacuated closed system for several hours. We demonstrate the generality of this method with three different catalytically important bimetallic systems: Pd-Zn, Ni-Zn and Cu-Zn. Of these three, Pd-Zn is by the far the most popular in terms of catalytic applications and yields the smallest particle size (similar to 8 nm). We tested the influence of various synthesis parameters on phase purity and particle size distribution in case of the synthesized gamma-brass Pd-Zn/SiO2 supported catalysts and provide general guidelines towards optimization of synthesis. Upon transformation of Pd/SiO2 to gamma-brass Pd-Zn/SiO2, a precipitous drop in CO adsorption and a 25 kJ/mol increase in the ethylene hydrogenation barrier is observed, indicating the catalytic active sites are significantly modified as a result of alloying. We anticipate these catalysts may find applications in various Pd-catalyzed chemistries.