Size-dependent CO and propylene oxidation activities of platinum nanoparticles on the monolithic Pt/TiO2–YOx diesel oxidation catalyst under simulative diesel exhaust conditions

In this work, we determined the CO and C3H6 oxidation rates of size-selected Pt nanoparticles (1 nm ultrafine size and 8.8 nm nanoscale size average diameters) deposited on TiO2–YOx supports. Both Pt/TiO2–YOx catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and H2 temperature-programmed reduction (H2-TPR). The results show that platinum particles on the fresh as-synthesized catalysts are fully oxidized to PtO2 during calcination in air; PtO2 can be partly regenerated to the Pt0 active phase under oxygen rich diesel exhaust conditions (containing about 1000 ppm CO), in which the ultrafine Pt particles supplying a larger surface to volume ratio are more beneficial for Pt0 regeneration than the nanoscale ones. Such regeneration of Pt0 occurred even under oxygen rich diesel exhaust conditions, leading to a significantly better global catalytic performance for the DOC reaction. Thus, this work suggests that Pt0 occupation ratio under DOC reaction conditions may become a criteria for identifying the quality of DOC catalysts.