Zinc Promotion of Platinum for Catalytic Light Alkane Dehydrogenation: Insights into Geometric and Electronic Effects
Zinc Promotion of Platinum for Catalytic Light Alkane Dehydrogenation: Insights into Geometric and Electronic Effects
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DOI：
10.1021/acscatal.6b03603
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发表时间：
2017-06-01
期刊：
影响因子：
12.9
通讯作者：
Miller, Jeffrey T.
中科院分区：
文献类型：
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作者：
Cybulskis, Viktor J.;Bukowski, Brandon C.;Miller, Jeffrey T.
负载型金属纳米颗粒作为非均相催化剂在烃类资源的化学转化中具有重要作用。这些材料的催化性能由表面电子结构和活性金属位点的价轨道决定，并且可以选择性地用促进剂或合金化来调节。通过使用密度功能理论（DFT）、动力学和原位x射线光谱的综合方法，我们展示了Zn添加到Pt/SiO2中如何形成具有分离Pt表面位置的高对称性Pt1Zn1纳米颗粒合金，在乙烷脱氢（EDH）过程中具有接近100%的C2H4选择性，与单金属Pt/SiO2相比，在600℃下每摩尔表面Pt的周转率（TOR）高6倍。此外，我们展示了DFT计算如何准确地再现Pt/SiO2和PtZn/SiO2催化剂中与EDH过程中动力学性能相关的Pt 5d价态轨道的共振非弹性x射线光谱（RIXS）特征。该技术表明，Zn改变了PtZn中Pt 5d电子的能量，这与TOR的促进直接相关，而Zn在催化剂表面的结合产生的系综效应导致了产物选择性的增强。
Supported metal nanoparticles are vital as heterogeneous catalysts in the chemical transformation of hydrocarbon resources. The catalytic properties of these materials are governed by the surface electronic structure and valence orbitals at the active metal site and can be selectively tuned with promoters or by alloying. Through an integrated approach using density functional theory (DFT), kinetics, and in situ X-ray spectroscopies, we demonstrate how Zn addition to Pt/SiO2 forms high symmetry Pt1Zn1 nanoparticle alloys with isolated Pt surface sites that enable near 100% C2H4 selectivity during ethane dehydrogenation (EDH) with a 6-fold higher turnover rate (TOR) per mole of surface Pt at 600 degrees C compared to monometallic Pt/SiO2. Furthermore, we show how DFT calculations accurately reproduce the resonant inelastic X-ray spectroscopic (RIXS) signatures of Pt 5d valence orbitals in the Pt/SiO2 and PtZn/SiO2 catalysts that correlate with their kinetic performance during EDH. This technique reveals that Zn modifies the energy of the Pt 5d electrons in PtZn, which directly relates to TOR promotion, while ensemble effects from the incorporation of Zn into the catalyst surface lead to enhanced product selectivity.