Interaction of hydrogen with cerium oxide surfaces: a quantum mechanical computational study

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Ceria (CeO2) is a crucial material in catalysis and oxidation due to its redox properties.
• Understanding the interaction of ceria surfaces with hydrogen is vital for optimizing catalytic processes.
• Previous studies have explored ceria's reactivity, but detailed atomic-level interactions with hydrogen require further investigation.

Purpose of the Study:

• To investigate the interaction of atomic hydrogen with the (110) and (111) surfaces of ceria using ab initio calculations.
• To determine the preferred adsorption configurations and energetics of hydrogen on these ceria surfaces.
• To elucidate the electronic and structural changes in ceria upon hydrogen adsorption.

Main Methods:

• Ab initio calculations based on density functional theory (DFT).
• Inclusion of a Hubbard U term to accurately describe ceria's electronic structure.
• Determination of minimum energy configurations and adsorption energies.

Main Results:

• Atomic hydrogen forms an O-H-O bridge on the (110) surface and an axial tricoordinated OH group on the (111) surface.
• Hydrogen adsorption leads to the reduction of a neighboring Ce ion and outward protrusion of bound oxygen atoms on both surfaces.
• Energetically favorable adsorption: -150.8 kJ/mol for (110) and -128.3 kJ/mol for (111) relative to H2.

Conclusions:

• The (110) and (111) ceria surfaces exhibit distinct and energetically favorable interactions with atomic hydrogen.
• The observed structural and electronic changes, including Ce reduction, are key features of hydrogen interaction with ceria.
• Calculated OH stretching frequencies show good agreement with experimental data, validating the computational approach.