Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA.
ACS Appl Mater Interfaces. 2009 Nov;1(11):2624-35. doi: 10.1021/am900533p.
A flame synthesis method has been used to prepare nanosized, high-surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction and then gas to particle conversion. The specific surface areas of the synthesized powders ranged from 127 to 163 m(2)/g. High-resolution transmission electron microscope imaging showed that the particle diameters for the ceria materials are in the range of 3-10 nm, and a thin layer of amorphous material was observed on the surface of the particles. The presence and surface enrichment of the transition-metal oxides (CuO, NiO, and Fe(2)O(3)) on the ceria particles were detected using X-ray photoelectron spectroscopy. Electron energy-loss spectroscopic studies suggest the formation of a core-shell structure in the as-prepared particles. Extended X-ray absorption fine structure studies suggest that the dopants in all M-Ce-O systems are almost isostructural with their oxide counterparts, indicating the doping materials form separate oxide phases (CuO, Fe(2)O(3), NiO) within the host matrix (CeO(2)). Etching results confirm that most of the transition-metal oxides are present on the surface of CeO(2), easily dissolved by nitric acid. The performance of the flame-synthesized catalysts was examined toward water-gas shift (WGS) activity for fuel processing applications. The WGS activity of metal ceria catalysts decreases in the order Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO(2) with a feed mixture having a hydrogen to carbon monoxide (H(2)/CO) ratio of 1. There was no methane formation for these catalysts under the tested conditions.
一种火焰合成方法已被用于从金属醋酸盐前体的水溶液中制备纳米级、高表面积的 Cu-Ce-O、Ni-Ce-O 和 Fe-Ce-O 催化剂。颗粒通过前体的蒸发形成，然后进行反应和气体到颗粒的转化。合成粉末的比表面积范围为 127 至 163 m²/g。高分辨率透射电子显微镜成像表明，CeO2 材料的粒径在 3-10nm 范围内，并且在颗粒表面观察到一层非晶态物质。X 射线光电子能谱检测到过渡金属氧化物（CuO、NiO 和 Fe2O3）在 CeO2 颗粒上的存在和表面富集。电子能量损失谱研究表明，在制备的颗粒中形成了核壳结构。扩展 X 射线吸收精细结构研究表明，所有 M-Ce-O 体系中的掺杂剂几乎与它们的氧化物对应物具有同构性，表明掺杂材料在宿主基质（CeO2）中形成独立的氧化物相（CuO、Fe2O3、NiO）。蚀刻结果证实，大多数过渡金属氧化物存在于 CeO2 的表面上，容易被硝酸溶解。火焰合成催化剂的性能在燃料处理应用的水汽变换（WGS）活性方面进行了考察。对于具有氢气与一氧化碳（H2/CO）摩尔比为 1 的进料混合物，金属 CeO2 催化剂的 WGS 活性按 Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO2 的顺序降低。在测试条件下，这些催化剂没有甲烷形成。
