O vacancies on steps on the CeO2(111) surface

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Cerium dioxide (ceria) is vital for heterogeneous catalysis, energy technologies, and biomedical uses.
• A key property of ceria is its low oxygen vacancy (Ovac) formation energy (Ef), which is further reduced by nanostructuring.
• Nanostructured ceria exhibits increased activity in oxidative reactions due to reduced Ef.

Purpose of the Study:

• To computationally investigate oxygen vacancy formation on nanostructured CeO2(111) surfaces featuring steps.
• To quantify the impact of surface roughness on ceria's reducibility.

Main Methods:

• Employed an efficient computational scheme combining density functional theory (DFT) with a DFT+U approach.
• Utilized a pre-screening procedure based on plain DFT calculations to identify low Ef configurations.
• Calculated Ef for oxygen vacancies on stepped CeO2(111) surfaces with experimentally observed structures.

Main Results:

• Oxygen vacancy formation energies on stepped surfaces were up to 0.7 eV lower than on regular CeO2(111) surfaces.
• Identified energetically stable configurations for oxygen vacancies and Ce(3+) ions, some involving subsurface Ce(3+) ions.
• Demonstrated that surface roughness significantly affects the reducibility of ceria.

Conclusions:

• Nanostructuring ceria surfaces, specifically by introducing steps, effectively reduces oxygen vacancy formation energy.
• The findings provide quantitative insights into how surface topography influences ceria's reducibility.
• This study highlights the importance of surface structure in optimizing ceria-based materials for catalytic applications.