Reaction pathway of nitric oxide oxidation on nano-sized Pt/SiO2 catalysts for diesel exhaust purification

Abstract

Catalytic NO oxidation on the diesel oxidation catalyst is of great significance for the low-temperature abatement of diesel soot and NOx pollutants. Here, a series of Pt/SiO2 catalysts with different particle sizes (2.78–13.94 nm) were prepared and their effects on NO oxidation activity and reaction pathway were investigated. The results show that the size of platinum nanoparticles is a relevant factor for NO oxidation activity by influencing platinum chemical states during the reaction. Furthermore, NO catalytic oxidation on Pt/SiO2 catalysts are primarily through the bidentate nitrite and bridged nitrate intermediates pathways. Relatively larger platinum nanoparticles (∼13.94 nm) will lead to the generation of nitrates between layers that are difficult to decompose and desorb from catalyst surface, and thereby adverse to NO oxidation activity. Thus, this work suggests that the size of Pt nanoparticles do not only influence the catalytic NO oxidation activity, but also the reaction pathway on the catalyst.