揭示 Rh-CeO2 催化剂在 CO 氧化中的低温活性：探索 Rh3+ 物种的局部结构和 Red-Ox 转化,Physical Chemistry Chemical Physics

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揭示 Rh-CeO2 催化剂在 CO 氧化中的低温活性：探索 Rh3+ 物种的局部结构和 Red-Ox 转化
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-12-22 , DOI: 10.1039/d2cp04503f
Elizaveta A Fedorova ₁ , Tatyana Yu Kardash ₂ , Lidiya S Kibis ₂ , Olga A Stonkus ₂ , Elena M Slavinskaya ₂ , Valery A Svetlichnyi ₃ , Simone Pollastri ₄ , Andrei I Boronin ₂

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活性位点的局部结构是确定系统催化活性性质的关键方面之一。在这项工作中，对通过共沉淀法制备的 Rh-CeO _{2催化剂进行了详细的结构研究。}_{XRD、拉曼光谱、XPS、TEM、TPR-H 2}和XAS等多种物理化学方法的应用揭示了催化剂中存在高度分散的Rh ³⁺物种：Rh ³⁺单离子和RhO _x簇。Ce ⁴⁺离子被 Rh ³⁺物质取代，这提供了 CeO _{2的强烈畸变}格子，如图所示。XAS 数据确保了 Rh 局部结构的细化。结果表明，彼此相邻的单个 Rh ^{3+位点可以将 RhO}_x团簇的形成与 Rh 局部环境合并，接近于 Rh ₂ O ₃和 CeRh ₂ O ₅氧化物中的Rh局部环境。_{单个和簇状铑物种周围的 CeO 2}晶格变形对样品在低温 CO 氧化 (LTO-CO) 中的催化活性具有有益影响。TEM、XAS 和原位XRD 数据允许建立催化剂在 Red-Ox 处理下的结构转变。还原处理导致 Rhn 金属簇的形成局限于还原的 CeO _{2- δ}的缺陷上。还原后的样品在 0 °C 时表现出高效的 CO 转化率。然而，该系统并不稳定：它与空气的接触导致二氧化铈在室温下再氧化，Rh在室温下部分再氧化为高度分散的 Rh ^{3+物种，而在氧化气氛中加热导致金属铑物种完全再氧化。}该工作的结果揭示了基于高度分散的 Rh ^{3+的 Rh–CeO}_{2催化剂可逆性的结构方面}在反应条件下处理的物种。

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Unraveling the low-temperature activity of Rh–CeO2 catalysts in CO oxidation: probing the local structure and Red-Ox transformation of Rh3+ species

The local structure of the active sites is one of the key aspects of establishing the nature of the catalytic activity of the systems. In this work, a detailed structural investigation of the Rh–CeO₂ catalysts prepared by the co-precipitation method was carried out. The application of a variety of physicochemical methods such as XRD, Raman spectroscopy, XPS, TEM, TPR-H₂, and XAS revealed the presence of highly dispersed Rh³⁺ species in the catalysts: Rh³⁺ single ions and RhO_x clusters. The substitution of Ce⁴⁺ ions by Rh³⁺ species, which provided a strong distortion of the CeO₂ lattice, is shown. XAS data ensured the refinement of the Rh local structure. It was shown that single Rh³⁺ sites located next to each other can merge the formation of RhO_x clusters with Rh local environment close to the one in Rh₂O₃ and CeRh₂O₅ oxides. The distortion of the CeO₂ lattice around single and cluster rhodium species had a beneficial effect on the catalytic activity of the samples in low-temperature CO oxidation (LTO-CO). TEM, XAS, and in situ XRD data allowed establishing the structural transformations of the catalysts under Red-Ox treatments. The reduction treatment led to Rhn metallic cluster formation localized on defects of the reduced CeO_2−δ. The reduced sample demonstrated efficient CO conversion at 0 °C. However, this system was not stable: its contact with air led to ceria reoxidation and partial reoxidation of Rh to highly dispersed Rh³⁺ species at room temperature, while heating in an oxidizing atmosphere resulted in the complete reoxidation of metallic rhodium species. The results of the work shed light on the structural aspects of the reversibility of the Rh–CeO₂ catalysts based on the highly dispersed Rh³⁺ species under treatment in the reaction conditions.

更新日期：2022-12-22

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