Jiang Yan-Xia, Weng Wei-Zheng, Si Di, Sun Shi-Gang
State Key Laboratory for Physical Chemistry of Solid Surfaces, Department of Chemistry, Institute of Physical Chemistry, Xiamen University, Xiamen 361005, China.
J Phys Chem B. 2005 Apr 28;109(16):7637-42. doi: 10.1021/jp0480089.
Palladium clusters have been synthesized by the "ship-in-a-bottle" approach in the supercages of NaX and NaY faujasite zeolites. In comparison with CO adsorbed on a bulk Pd electrode, the same molecule adsorbed on the Pd clusters electrodes evoked an enhanced IR absorption (EIRA). The enhancement factors have been determined to be about 38 and 51 in NaX and NaY, respectively. IR band centers of linear-bonded CO, bridge-bonded CO, and multi-bonded CO in NaX are measured, respectively, 12, 14, and 11 cm(-1) lower than those of the corresponding adsorption modes in NaY. The adsorption of CO and the oxidation of adsorbed CO in NaX matrix are faster than that in NaY matrix. These results suggest that part of the Pd2+ ions in NaX are located in sites III and III' that are near the 12-ring window of the supercage of zeolite, which lead to the formation of small Pd clusters. The present study is of significant importance in exploring the dependence of catalyst properties on structures, as well as in understanding and predicting the locations and properties of metal clusters in zeolites.
钯簇已通过“瓶中造船”法在NaX和NaY八面沸石的超笼中合成。与吸附在块状钯电极上的CO相比，吸附在钯簇电极上的同一分子会引起增强的红外吸收（EIRA）。已确定在NaX和NaY中的增强因子分别约为38和51。分别测量了NaX中线性键合CO、桥式键合CO和多键合CO的红外带中心，它们比NaY中相应吸附模式的红外带中心分别低12、14和11 cm(-1)。NaX基质中CO的吸附和吸附态CO的氧化比NaY基质中的更快。这些结果表明，NaX中的部分Pd2+离子位于沸石超笼12元环窗口附近的III位和III'位，这导致形成小的钯簇。本研究对于探索催化剂性能对结构的依赖性，以及理解和预测沸石中金属簇的位置和性能具有重要意义。
