COMPARATIVE-STUDY OF SUPPORTED CATALYST PARTICLES BY ELECTRON-MICROSCOPY METHODS

High-resolution transmission electron microscopy, high-resolution scan ning electron microscopy and high-angle annular dark-field imaging wer e used to study the size distribution and surface structures of Pt mod el catalysts on various oxide supports. The relative merits of differe nt electron microscopy methods for catalyst research were evaluated by comparing images recorded with microscopes of different type. It was concluded that HRTEM profile imaging was the most effective technique for direct observation of microstructure, especially the surface struc ture of supported particles, while HRSEM and HAADF, respectively, were preferred for characterizing the surface topology of catalyst support s and the size distribution of supported particles. Using profile imag ing, crystalline monolayers caused by high-temperature reduction on {1 11} surfaces of Pt/TiO2 could be recorded with atomic resolution. Thes e overlayers help explain the drop in chemisorption ability due to hig h-temperature reduction, a phenomenon usually referred to as strong me tal-support interaction. HRSEM showed the presence of surface steps on model TiO2 and a concentration of larger Pt particles on these steps.