Shape-dependent catalytic activity of palladium nanocrystals for the oxidation of carbon monoxide

It is of great interest to study the shape effect on the catalytic activity of metal nanocrystals, which exposed different crystallographic facets upon adopting various shapes. The investigations on shape-dependent catalysis of supported metal nanocrystals need to be conducted over nanocrystals with well-defined shapes and cleaned surface. The palladium nanocrystals with cubic, octahedral, and spherical morphologies were synthesized and well dispersed onto the inert silica support after removing the capping agents, which were used as the heterogeneous catalysts for carbon monoxide (CO) oxidation. It was found that the crystal facets of Pd nanoparticles played an essential role in determining the catalytic oxidation properties. As a result, the octahedral and spherical nanoparticles that predominantly exposed the Pd {111} crystal facets exhibited significantly better catalytic activity than the palladium nanocubes that possessed the Pd {100} crystal facets as the basal plane for the CO catalytic oxidation. It was inferred that the appropriate adsorption strength of CO molecules on Pd {111} planes was beneficial to the enhancement of the catalytic activity.