Abstract
The sintering mechanism of Pd particles on the three way catalyst (TWC) was investigated by aberration-corrected environmental transmission electron microscopy (ETEM) which enabled us to measure under high temperature and simulated gas condition including H2, CO (as a reductant agent) and O2 (as an oxidant agent). In reducing condition over 900 degC, migration and aggregation of the Pd particles on Al2O3 were observed using ETEM. On the other hand, in oxidizing condition over 800 degC, we observed not only growing of the Pd particles but also becoming far smaller size particles and dispersion. In addition, it was found out that PdO existed in oxidizing condition. Hence we presumed that the growing of the Pd particles under oxidizing condition was due to re-aggregation of dispersed PdO nanoparticles. We studied the effect of the sintering of the Pd particles on a Pd-loaded support. The Pd particles on Matrix-B which suppressed oxidization of Pd kept smaller size than them on Matrix-A which advanced oxidized Pd.
