Enhancement of CeO₂ Silanization by Spontaneous Breakage of Si–O Bonds through Facet Engineering

Facet engineering is a new method of materials design with considerable potential for many technological applications. The present work uses DFT calculations to understand how this strategy can be used to accelerate the silanization of tetraethyl orthosilicate (TEOS) on the surface of ceria (CeO₂), which is a key technology in biomedical and other fields. Cubic CeO₂ nanoparticles with exposed {100} facets are shown to represent the most favorable morphology for silanization owing to (1) the facilitated adsorption of TEOS on these facets compared to the {110} and {111} facets and (2) spontaneous breakage of the Si–O bonds of TEOS, which is found to be the rate-determining step for silanization of CeO₂. The favorable adsorption on the {100} facets arises from its superior structural and electronic properties as well as higher reactivity, which are attributed to its more open arrangement of the surface atoms and consequently reduced steric hindrance, higher density of dangling bonds and surface active sites, and the larger difference in Mulliken charges between the surface and bulk atoms.