Periodic density functional theory (DFT) calculations using the hybrid PBE0 functional and atom-centered Gaussian functions as basis sets were carried out to investigate the absorption and the first steps involved in the decomposition of hydrogen peroxide (H2O2) on three different models of the ceria (111) surface. One of the models is a clean surface, and the others are defective and partially hydroxylated ceria surfaces. On the clean surface, we found that the minimum energy path of hydrogen peroxide decomposition involves a three-step process, i.e., adsorption, deprotonation, and formation of the peroxide anion, stabilized through its interaction with the surface at a Ce (IV) site, with activation barriers of less than about 0.5 eV. The subsequent formation of superoxide anions and molecular oxygen species is attributed to electron transfer from the reactants to the Ce (IV) ions underneath. On the defective surface, H2O2dissociation is an energetically downhill reaction thermodynamically driven by the healing of the O vacancies, after the reduction and decomposition of H2O2into oxygen and water. On the hydroxylated surface, H2O2is first adsorbed by forming a favorable H-bond and then undergoes heterolytic dissociation, forming two hydroxyl groups at two vicinal Ce sites.
Keywords: ceria; density functional theory; hydrogen peroxide; reactivity.
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