Size effect in CO oxidation on CeO2 − x nanoparticles

Abstract

The change in physicochemical properties of sub� stances in transition to the nanocrystalline state has attracted considerable attention of researchers and engineers in the last decade. However, known exam� ples of change in catalytic properties in such a transi� tion are relatively few, and most of them involve an increase in the specific surface area and a correspond� ing increase in the number of active sites, whereas the issue of a possible change in the crystal structure of a catalyst with a decrease in the particle size remains vir� tually unstudied. Indeed, minor changes in the crystal lattice parameters of the active component of a cata� lyst are usually caused by introducing various modify� ing additives, which increase the number of defects [1]; meanwhile, a comparable result can also be achieved by transition to the nanocrystalline state, in which the crystal lattice parameters change because of a sharp increase in the contribution of the surface forces and the necessity of balancing them. Note that a decrease in the particle size of the active component may lead both to a desirable increase in the activity and to an abrupt decrease in it, which is also caused by structural changes [2].