Barroso-Bogeat Adrián, Daza Raposo Iván, Blanco Ginesa, Pintado José María
Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, Universidad de Cádiz, Campus Río San Pedro s/n, 11510 Puerto Real (Cádiz), Spain.
Instituto Universitario de Investigación en Microscopía Electrónica y Materiales (IMEYMAT), Facultad de Ciencias, Universidad de Cádiz, Campus Río San Pedro s/n, 11510 Puerto Real (Cádiz), Spain.
Materials (Basel). 2020 Jun 23;13(12):2818. doi: 10.3390/ma13122818.
Three nanostructured catalysts with low total rare earth elements (REEs) content (i.e., 15 mol.%) were prepared by depositing CeO or Ln-doped CeO (Ln = Y or La; Ln/Ce = 0.15) on the surface of ZrO nanoparticles, as nanometre-thick, fluorite-type clusters. These samples were subjected to successive reduction treatments at increasing temperatures, from 500 to 900 °C. A characterisation study by XPS was performed to clarify the diffusion process of cerium into the bulk of ZrO crystallites upon reduction to yield CeZrO surface phases, and the influence of the incorporation of non-reducible trivalent REE cations, with sizes smaller (Y) and larger (La) than Ce and Ce. For all nanocatalysts, a reduction treatment at a minimum temperature of 900 °C was required to accomplish a significant cerium diffusion. Notwithstanding, the size of the dopant noticeably affected the extent of this diffusion process. As compared to the undoped ZrO-CeO sample, Y incorporation slightly hindered the cerium diffusion, while the opposite effect was found for the La-doped nanocatalyst. Furthermore, such differences in cerium diffusion led to changes in the surface and nanostructural features of the oxides, which were tentatively correlated with the redox response of the thermally aged samples.
通过将CeO或Ln掺杂的CeO（Ln = Y或La；Ln/Ce = 0.15）以纳米厚的萤石型簇的形式沉积在ZrO纳米颗粒表面，制备了三种总稀土元素（REEs）含量低（即15摩尔%）的纳米结构催化剂。这些样品在500至900°C的温度下进行了连续的还原处理。通过XPS进行了表征研究，以阐明还原时铈扩散到ZrO微晶本体中以生成CeZrO表面相的过程，以及掺入尺寸比Ce和Ce小（Y）和大（La）的不可还原三价REE阳离子的影响。对于所有纳米催化剂，需要在最低900°C的温度下进行还原处理才能实现显著的铈扩散。尽管如此，掺杂剂的尺寸明显影响了这种扩散过程的程度。与未掺杂的ZrO-CeO样品相比，掺入Y略微阻碍了铈的扩散，而对于La掺杂的纳米催化剂则发现了相反的效果。此外，铈扩散的这种差异导致了氧化物表面和纳米结构特征的变化，这与热老化样品的氧化还原响应初步相关。
