Stabilization of nanoscale noble metal islands on oxide supports by manipulation of the surface texture

金属纳米颗粒的催化活性通过比表面积与其尺寸相关，但在结构敏感反应的情况下，也与其内在相关。为了保持催化活性相在反应器中的高度分散，金属因此通常以负载形式使用，其中纳米颗粒沉积在氧化物载体材料的表面上。然而，在升高的工艺温度下，通常观察到烧结和颗粒生长。拟议项目的目标是固定氧化物上的金属岛，以防止通过纹理支撑表面烧结。载体材料将通过化学气相合成和火焰喷雾热解以SiO2、TiO2和Al2O3颗粒的形式合成，其将以各种方式纹理化。在项目的第一阶段建立了表面纹理库之后，将测试这些材料稳定金属颗粒的能力。为此，Pt岛将通过化学气相沉积沉积在选定的氧化物结构上。在随后的回火实验中，岛的流动性和它们的尺寸的演变将被监测，并提取烧结过程的动力学参数。在项目期间，小角X射线散射（SAXS）将作为一种分析方法发挥重要作用，通过确定表面分形维数来量化表面纹理。此外，将使用X射线光电子能谱（XPS）详细检查载体颗粒的表面化学，以使得能够从所确定的烧结动力学中提取纯物理结构效应。

Catalytic activity of metal nanoparticles is tied to their size via the specific surface area but also intrinsically, in the case of structure sensitive reactions. To maintain a high dispersion of the catalytically active phase in a reactor metals are therefore commonly used in supported form, where nanoparticles are deposited onto the surfaces of oxide carrier materials. However, under elevated process temperatures sintering and particle growth are commonly observed. The goal of the proposed project is the immobilization of metal islands on oxides to prevent sintering by texturing the support surface. Support material will be synthesized in the form of particles of SiO2, TiO2 and Al2O3 via Chemical Vapor Synthesis and flame spray pyrolysis which will be textured in various ways. After establishing a library of surface textures in the first phase of the project, the materials will be tested for their ability to stabilize metallic particles. For this Pt-islands will be deposited on selected oxide structures by chemical vapor deposition. In subsequent tempering experiments the mobility of the islands and the evolution of their size will be monitored and kinetic parameters of the sintering process will be extracted. Over the duration of the project small angle x-ray scattering (SAXS) will play an important role as an analytic method allowing the quantification of surface texture by determining the surface fractal dimension. In addition, the surface chemistry of the support particles will be examined in detail using x-ray photoelectron spectroscopy (XPS) to enable the extraction of the purely physical structural effects from the sintering kinetics determined.