Varga E, Pusztai P, Óvári L, Oszkó A, Erdőhelyi A, Papp C, Steinrück H-P, Kónya Z, Kiss J
Department of Physical Chemistry and Materials Science, University of Szeged, Aradi v.t. 1, H-6720 Szeged, Hungary.
Phys Chem Chem Phys. 2015 Oct 28;17(40):27154-66. doi: 10.1039/c5cp03549j. Epub 2015 Sep 29.
The interaction of CeO2-supported Rh, Co and bimetallic Rh-Co nanoparticles, which are active catalysts in hydrogen production via steam reforming of ethanol, a process related to renewable energy generation, was studied by X-ray diffraction (XRD), high resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). Furthermore, diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed CO as a probe molecule was used to characterize the morphology of metal particles. At small loadings (0.1%), Rh is in a much dispersed state on ceria, while at higher contents (1-5%), Rh forms 2-8 nm particles. Between 473-673 K pronounced oxygen transfer from ceria to Rh is observed and at 773 K significant agglomeration of Rh occurs. On reduced ceria, XPS indicates a possible electron transfer from Rh to ceria. The formation of smaller ceria crystallites upon loading with Co was concluded from XRD and HRTEM; for 10% Co, the CeO2 particle size decreased from 27.6 to 10.7 nm. A strong dissolution of Co into ceria and a certain extent of encapsulation by ceria were deduced by XRD, XPS and LEIS. In the bimetallic system, the presence of Rh enhances the reduction of cobalt and ceria. During thermal treatments, reoxidation of Co occurs, and Rh agglomeration as well as oxygen migration from ceria to Rh are hindered in the presence of cobalt.
通过X射线衍射（XRD）、高分辨率电子显微镜（HRTEM）、X射线光电子能谱（XPS）和低能离子散射（LEIS）研究了负载在CeO₂上的Rh、Co以及双金属Rh-Co纳米颗粒的相互作用，这些纳米颗粒是通过乙醇蒸汽重整制氢（这一与可再生能源生产相关的过程）中的活性催化剂。此外，使用吸附的CO作为探针分子的漫反射红外光谱（DRIFTS）来表征金属颗粒的形态。在低负载量（0.1%）时，Rh在二氧化铈上处于高度分散状态，而在较高含量（1-5%）时，Rh形成2-8nm的颗粒。在473-673K之间观察到明显的氧从二氧化铈转移到Rh，在773K时Rh发生显著团聚。在还原的二氧化铈上，XPS表明可能存在从Rh到二氧化铈的电子转移。通过XRD和HRTEM得出，负载Co后形成了更小的二氧化铈微晶；对于10%的Co，CeO₂粒径从27.6nm减小到10.7nm。通过XRD、XPS和LEIS推断出Co强烈溶解于二氧化铈中，并在一定程度上被二氧化铈包裹。在双金属体系中，Rh的存在增强了钴和二氧化铈的还原。在热处理过程中，Co发生再氧化，并且在钴存在的情况下，Rh的团聚以及氧从二氧化铈向Rh的迁移受到阻碍。
