Modelling hydrogen peroxide adsorption on cerium dioxide: the effect of surface strain†

Ceria nanoparticles are nanozymes that can serve as important biomedical tools mimicking enzymes. The main issue with using metal oxide nanoparticles is the control of their surface speciation, which ultimately affects catalytic activity. Herein, we employ density functional theory calculations to unravel the adsorption of hydrogen peroxide and its dissociation products (hydroxyl, peroxide, superoxide and hydroperoxide) and the effect of strain on the absorption. Indeed, all nanoparticles are affected by intrinsic strain. We found that molecular H₂O₂ is unstable on the {100} surface at all strains, whereas hydroxyl radicals can be stabilized on reduced surfaces because of the electron transfer from surface Ce³⁺. Upon dissociation, the peroxide ion is not always the most stable adsorbed species on all surfaces, whether strained, unstrained, stoichiometric or reduced, and superoxide species may also occur under tensile strains. Our thermodynamic methodology connects atomic-level findings to particle morphology in relation to environmental factors such as temperature and vapor pressure. Regardless of the strain applied, the adsorption of hydrogen peroxide and its dissociation products fails to access nanoparticle shapes other than octahedral, which is not ideal for peroxidase activity considering the characteristics of the {111} surface which is less effective in anchoring the adsorbed species.