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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Geometric Arrangement of Components in Bimetallic PdZn/Pd(111) Surfaces Modified by CO Adsorption: A Combined Study by Density Functional Calculations, Polarization-Modulated Infrared Reflection Absorption Spectroscopy, and Temperature-Programmed Desorption
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Geometric Arrangement of Components in Bimetallic PdZn/Pd(111) Surfaces Modified by CO Adsorption: A Combined Study by Density Functional Calculations, Polarization-Modulated Infrared Reflection Absorption Spectroscopy, and Temperature-Programmed Desorption

机译：CO吸附改性的双金属PdZn / Pd（111）表面中组分的几何排列：密度泛函计算，偏振调制红外反射吸收光谱和程序升温脱附的组合研究

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Combining density functional theory (DFT) calculations with experimental data from temperature-programmed desorption (TPD) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRAS), we have provided evidence for the rearrangement of Pd and Zn atoms in PdZn surface alloys on Pd(111) in the presence of CO. Such systems represent valuable models for novel methanol steam reforming catalysts, with CO being an undesired byproduct of this reaction. The reconstructed surface was calculated to be more stable in the presence of CO and capable of adsorbing CO on top of Pd atoms up to a saturation coverage of 1/2 monolayer (ML). To the contrary, on a surface with conventional, bulklike geometric arrangement of Pd and Zn atoms in rows, CO adsorption on bridge sites with a saturation coverage of ?1/3 ML was predicted. Adsorption of CO on top sites was confirmed with PM-IRAS and the saturation coverage of V2 ML was derived from TPD experiments, supporting the suggested reconstruction of PdZn/Pd(111). The rearrangement of the atomic components on the surface was calculated to affect structural and adsorptive properties but kept essentially unchanged the electronic structure, reflecting the intermetallic character of PdZn on Pd(111). This study sheds light on a new degree of complexity of bimetallic systems, that is, changes of component arrangement on the surface in the presence of certain adsorbates, which is not accompanied by surface segregation. Such rearrangement is expected to notably affect the properties of a bimetallic catalyst.
机译：将密度泛函理论（DFT）计算与温度程序解吸（TPD）和偏振调制红外反射吸收光谱（PM-IRAS）的实验数据相结合，我们为PdZn表面合金中Pd和Zn原子的重排提供了证据。 Pd（111）在CO的存在下。此类系统代表了新型甲醇蒸汽重整催化剂的有价值的模型，其中CO是该反应的不良副产物。经计算，重建表面在存在CO的情况下更稳定，并且能够将CO吸附在Pd原子的顶部，直至饱和覆盖率达到1/2单层（ML）。相反，在具有Pd和Zn原子按排的常规的，大块状几何排列的表面上，预计CO吸附在饱和覆盖度为1/3 ML的桥位上。 PM-IRAS证实了顶部位置上CO的吸附，并且TPD实验得出了V2 ML的饱和覆盖率，支持了PdZn / Pd（111）的建议重建。计算表面上原子成分的重排会影响结构和吸附性能，但电子结构基本保持不变，反映了Pd（111）上PdZn的金属间特征。这项研究揭示了双金属系统新的复杂程度，即在存在某些被吸附物的情况下，表面上组分排列的变化，而这并没有伴随表面偏析。预期这种重排将显着影响双金属催化剂的性能。

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