Composition-dependent morphologies of CeO nanoparticles in the presence of Co-adsorbed HO and CO: a density functional theory study.

Catalytic activity is affected by surface morphology, and specific surfaces display greater activity than others. A key challenge is to define synthetic strategies to enhance the expression of more active surfaces and to maintain their stability during the lifespan of the catalyst. In this work, we outline an approach, based on density functional theory, to predict surface composition and particle morphology as a function of environmental conditions, and we apply this to CeO nanoparticles in the presence of co-adsorbed HO and CO as an industrially relevant test case. We find that dissociative adsorption of both molecules is generally the most favourable, and that the presence of HO can stabilise co-adsorbed CO. We show that changes in adsorption strength with temperature and adsorbate partial pressure lead to significant changes in surface stability, and in particular that co-adsorption of HO and CO stabilizes the {100} and {110} surfaces over the {111} surface. Based on the changes in surface free energy induced by the adsorbed species, we predict that cuboidal nanoparticles are favoured in the presence of co-adsorbed HO and CO, suggesting that cuboidal particles should experience a lower thermodynamic driving force to reconstruct and thus be more stable as catalysts for processes involving these species.