Chemistry Department, ICCOM-CNR Trieste Research Unit, Centre of Excellence for Nanostructured Materials (CENMAT) and INSTM Trieste Research Unit, University of Trieste, Via L. Giorgieri 1, 34127, Trieste, Italy.
Dalton Trans. 2010 Feb 28;39(8):2122-7. doi: 10.1039/b916035c. Epub 2009 Dec 23.
1-wt% Pd-CeO(2) catalysts were prepared by co-precipitation of Pd nanoparticles with ceria (Pd@CeO(2)-CP), by a microemulsion procedure (Pd@CeO(2)-ME), and by normal impregnation of Pd salts (Pd/CeO(2)-IMP) in order to test the concept that Pd-CeO(2) catalysts could be more stable for the water-gas-shift (WGS) reaction when the Pd is embedded in CeO(2). Initial WGS rates measured at 250 degrees C were similar for the Pd@CeO(2)-CP and Pd/CeO(2)-IMP, indicating that Pd was accessible for gas-phase reactions on both catalysts. Pd@CeO(2)-CP exhibited better stability for WGS than did Pd/CeO(2)-IMP but exposure to the WGS environment at 400 degrees C still caused a decrease in activity. Physical characterization of the Pd@CeO(2)-ME implied that the core-shell nanoparticles underwent condensation that resulted in a low surface area and poor Pd accessibility. However, the Pd@CeO(2)-ME sample exhibited good stability for WGS, suggesting that more effective encapsulation of Pd can limit the sintering of the metal phase, thus resulting in stable catalysts under high temperature reaction conditions.
1-wt% Pd-CeO(2) 催化剂通过共沉淀法（Pd@CeO(2)-CP）、微乳液法（Pd@CeO(2)-ME）和 Pd 盐的常规浸渍法（Pd/CeO(2)-IMP）制备，以测试 Pd 嵌入 CeO(2) 时 Pd-CeO(2) 催化剂对于水煤气变换（WGS）反应可能更稳定的概念。在 250°C 下测量的初始 WGS 速率对于 Pd@CeO(2)-CP 和 Pd/CeO(2)-IMP 相似，表明在这两种催化剂上 Pd 都可用于气相反应。与 Pd/CeO(2)-IMP 相比，Pd@CeO(2)-CP 对于 WGS 表现出更好的稳定性，但在 400°C 的 WGS 环境下暴露仍会导致活性下降。Pd@CeO(2)-ME 的物理特性表明，核壳纳米粒子经历了缩合，导致比表面积低且 Pd 可及性差。然而，Pd@CeO(2)-ME 样品对于 WGS 表现出良好的稳定性，这表明 Pd 的有效封装可以限制金属相的烧结，从而在高温反应条件下得到稳定的催化剂。
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