Lafaye Gwendoline, Siani Attilio, Marécot Patrice, Amiridis Michael D, Williams Christopher T
Department of Chemical Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, SC 29208, USA.
J Phys Chem B. 2006 Apr 20;110(15):7725-31. doi: 10.1021/jp057025a.
A high-resolution transmission electron microscopy (HRTEM) investigation of a family of supported Ru catalysts prepared from Ru hydroxyl-terminated poly(amidoamine) dendrimer-metal nanocomposite (DMN) precursors has been conducted. Ru particle sizes observed following deposition of DMNs on a HRTEM grid can be controlled within a 0.9-1.4 nm range depending on the metal-to-dendrimer molar ratio. The average particle size in this case correlates well with the theoretically predicted particle size from the molar loading of Ru in the dendrimer. Upon impregnation of Ru-DMNs on Al(2)O(3) and subsequent thermal removal of the dendrimer via reduction at 300 degrees C, significant sintering of the Ru particles was observed. Nevertheless, the resulting supported Ru particles maintained a narrow particle size distribution and average particle size below 2.5 nm. These particle sizes no longer correlate with the metal-to-dendrimer molar ratio but do correlate with the metal-to-dendrimer weight ratio, suggesting that the dendrimer may be acting as a "sintering-control" agent on the catalyst surface. This process is not affected by the surface area of the support, since almost identical particle size distributions were obtained on three different commercial supports.
对由钌羟基封端的聚（酰胺胺）树枝状大分子 - 金属纳米复合材料（DMN）前驱体制备的负载型钌催化剂家族进行了高分辨率透射电子显微镜（HRTEM）研究。根据金属与树枝状大分子的摩尔比，在HRTEM网格上沉积DMN后观察到的钌颗粒尺寸可控制在0.9 - 1.4纳米范围内。在这种情况下，平均颗粒尺寸与根据树枝状大分子中钌的摩尔负载量理论预测的颗粒尺寸相关性良好。将Ru - DMN浸渍在Al(2)O(3)上，随后在300℃下通过还原热去除树枝状大分子，观察到钌颗粒有明显的烧结现象。然而，所得的负载型钌颗粒保持了窄的颗粒尺寸分布，且平均颗粒尺寸低于2.5纳米。这些颗粒尺寸不再与金属与树枝状大分子的摩尔比相关，但与金属与树枝状大分子的重量比相关，这表明树枝状大分子可能在催化剂表面充当“烧结控制”剂。该过程不受载体表面积的影响，因为在三种不同的商业载体上获得了几乎相同的颗粒尺寸分布。
