Dynamic Structure of a Working Methanol Steam Reforming Catalyst: In Situ Quick-EXAFS on Pd/ZnO Nanoparticles
Dynamic Structure of a Working Methanol Steam Reforming Catalyst: In Situ Quick-EXAFS on Pd/ZnO Nanoparticles
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DOI：
10.1021/jz101751s
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发表时间：
2011-03-03
影响因子：
5.7
通讯作者：
Rupprechter, Guenther
中科院分区：
文献类型：
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作者：
Foettinger, Karin;van Bokhoven, Jeroen A.;Rupprechter, Guenther
结合时间分辨 X 射线吸收光谱 (XAS) 和同步质谱活性测量（两者均在催化甲醇蒸汽重整过程中进行），我们研究了 ZnO 负载的 Pd 纳米颗粒的动态变化。实时明确监测催化活性相 PdZn 的形成。因此，我们首次直接证明催化反应过程中形成的 PdZn 合金对 H-2 和 CO2 具有优异的选择性。合金化从纳米颗粒表面开始，并向颗粒中心“向内”进行。基于扩展 X 射线吸收精细结构 (EXAFS) 分析，估计了 PdZn 合金形成的程度。合金化是可逆的。与氧气接触时，PdZn 偏析成钯金属和 ZnO。 XAS 数据通过傅里叶变换红外 (FTIR) 光谱得到证实。结果表明，operando fast-EXAFS 的应用是研究纳米材料及其对反应环境的动态适应的强大工具。
Combining time-resolved X-ray absorption spectroscopy (XAS) with simultaneous mass spectrometric activity measurements, both performed during catalytic methanol steam reforming, we have studied the dynamic changes of Pd nanoparticles supported on ZnO. The formation of the catalytically active phase PdZn was unambiguously monitored in real time. We thus directly prove for the first time that the PdZn alloy formed in the course of the catalytic reaction is responsible for the excellent selectivity to H-2 and CO2. Alloying started at the nanoparticle surface and proceeded "inwards" toward the particle center. On the basis of extended X-ray absorption fine structure (EXAFS) analysis, the extent of PdZn alloy formation was estimated. Alloying was reversible. In contact with oxygen, PdZn segregated into palladium metal and ZnO. The XAS data were corroborated by Fourier transform infrared (FTIR) spectroscopy. It is demonstrated that the application of operando quick-EXAFS is a powerful tool for studying nanomaterials and their dynamic adaptation to reactive environments.