Dilute Limit Alloy Pd–Cu Bimetallic Catalysts Prepared by Simultaneous Strong Electrostatic Adsorption: A Combined Infrared Spectroscopic and Density Functional Theory Investigation
Dilute Limit Alloy Pd–Cu Bimetallic Catalysts Prepared by Simultaneous Strong Electrostatic Adsorption: A Combined Infrared Spectroscopic and Density Functional Theory Investigation
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DOI：
10.1021/acs.jpcc.2c00234
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
Leandro T. De Castro;Dia Sahsah;Andreas Heyden;J. Regalbuto;C. Williams
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文献类型：
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作者：
Leandro T. De Castro;Dia Sahsah;Andreas Heyden;J. Regalbuto;C. Williams
具有独特几何和电子特性的明确定义的单原子催化（SAC）位点处于催化剂研究的前沿。 SAC 的一种类型是所谓的稀极限合金 (DLA)，其中单金属原子位点支撑在第二种金属的表面（或内部）。这项贡献探索了简单且可扩展的强静电吸附 (SEA) 方法来合成二氧化硅负载的铜上钯 DLA。使用 X 射线衍射、程序升温还原和透射电子显微镜图像对催化剂进行表征，以确认紧密分布的金属纳米颗粒的存在。利用透射傅里叶变换红外（FTIR）光谱对CO吸附过程中Cu上孤立的Pd位点进行探测。通过光谱曲线拟合提取高斯峰参数，结合密度泛函理论（DFT）计算，确定了Pd位点的性质和结构。除了观察到铜上 CO 的典型振动特征外，还观察到 DLA Pd-Cu 体系在 2046、2021 和 1908 cm-1 处出现了三个附加峰。同一体系的 DFT 分析表明，这些峰与线性吸附在 Cu(100) 表面嵌入钯原子上的 CO、Cu(111) 表面上 Pd 以及 Pd 嵌入 Cu(211) 表面上 Pd 和 Cu 之间桥联 CO 一致。使用杜瓦-查特-邓肯森 (DCD) 模型可以很好地解释 CO 振动波数的实验和计算趋势。将根据这些发现讨论 SEA 方法生产 DLA 的前景以及这种组合 FTIR/DFT 方法对其表征的实用性。
Well-defined single-atom catalytic (SAC) sites with unique geometric and electronic properties are at the forefront of catalyst research. One type of SAC is a so-called dilute limit alloy (DLA), where single-metal atom sites are supported on (or in) the surface of a second metal. This contribution explores the simple and scalable approach of strong electrostatic adsorption (SEA) to synthesize silica-supported DLA of palladium on copper. The catalysts were characterized using X-ray diffraction, temperature-programmed reduction, and transmission electron microscopy images to confirm the presence of tightly distributed metal nanoparticles. The isolated Pd sites on Cu were probed using transmission Fourier-transform infrared (FTIR) spectroscopy during adsorption of CO. Through spectral curve fitting to extract Gaussian peak parameters, coupled with density functional theory (DFT) calculations, the nature and structure of the Pd sites were determined. In addition to typical vibrational features observed for CO on copper, three additional peaks at 2046, 2021, and 1908 cm–1were observed for the DLA Pd–Cu system. The DFT analysis of the same system showed that these peaks are consistent with CO linearly adsorbed on an embedded palladium atom on a Cu(100) surface, a Pd on a Cu(111) surface, and a bridge CO between Pd and Cu with the Pd embedded on a Cu(211) surface. Experimental and computation trends in CO vibration wavenumbers could be well interpreted using the Dewar–Chatt–Duncanson (DCD) model. The promise of the SEA approach for producing DLAs and the utility of this combined FTIR/DFT approach for their characterization will be discussed in light of these findings.