Formation and oxidation mechanisms of Pd-Zn nanoparticles on a ZnO supported Pd catalyst studied by in situ time-resolved QXAFS and DXAFS.
Formation and oxidation mechanisms of Pd-Zn nanoparticles on a ZnO supported Pd catalyst studied by in situ time-resolved QXAFS and DXAFS.
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DOI：
10.1039/c1cp22466b
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
Y. Uemura;Y. Inada;Y. Niwa;M. Kimura;K. Bando;A. Yagishita;Y. Iwasawa;M. Nomura
中科院分区：
文献类型：
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作者：
Y. Uemura;Y. Inada;Y. Niwa;M. Kimura;K. Bando;A. Yagishita;Y. Iwasawa;M. Nomura
利用X射线吸收精细结构谱（XAFS）技术，成功地观察了ZnO上PdZn纳米粒子的形成和氧化过程，并对近边（XANES）和扩展（EXAFS）结构数据进行了分析，揭示了Pd在这两个过程中的详细变化.在氢气气氛下，通过两步方案在ZnO上形成PdZn纳米颗粒。第一个过程是金属Pd纳米颗粒的形成，该过程在1 s内快速完成。第二个过程是形成PdZn纳米颗粒，这需要几十分钟。PdZn纳米颗粒的氧化也由两个过程组成。Zn原子先于Pd原子被氧化，随后形成ZnO包裹的金属Pd纳米粒子。金属Pd纳米颗粒的氧化很少并且非常缓慢。动力学分析结果表明，在氧化气氛下，被ZnO包裹的金属Pd是一种稳定的物种。
Formation and oxidation processes of PdZn nanoparticles on ZnO were successfully observed by means of in situ time-resolved X-ray absorption fine structure spectroscopy (XAFS), and the analysis of data on near-edge (XANES) and extended (EXAFS) structures revealed detailed changes in Pd during both processes. PdZn nanoparticles were formed on ZnO through a two-step scheme under a hydrogen atmosphere. The first process was the formation of metallic Pd nanoparticles, which was quickly finished within 1 s. The second process was the formation of PdZn nanoparticles, which took several tens of minutes. Oxidation of the PdZn nanoparticles also consisted of two processes. Zn atoms were oxidized prior to Pd atoms and the metallic Pd nanoparticles surrounded by ZnO were formed afterwards. Oxidation of the metallic Pd nanoparticles was scarce and very slow. According to the results of kinetic analyses, the metallic Pd surrounded by ZnO was a stable species under the oxidative atmosphere.