Mechanisms for O2 dissociation over the BaO (100) surface

Area of Science:

• Surface Science
• Materials Chemistry
• Catalysis

Background:

• Barium oxide (BaO) is a key material in various catalytic applications.
• Understanding oxygen adsorption is vital for optimizing BaO-based catalysts.
• Previous studies have not fully elucidated the mechanisms of oxygen adsorption and dissociation on BaO surfaces.

Purpose of the Study:

• To investigate atomic and molecular oxygen adsorption on BaO (100) surfaces.
• To determine the preferred adsorption sites and binding energies.
• To elucidate the mechanism of molecular oxygen dissociation on BaO.

Main Methods:

• Utilized both cluster models and periodic slab models for theoretical calculations.
• Analyzed adsorption energies and reaction pathways.
• Investigated the electronic structure of adsorbed oxygen species.

Main Results:

• Atomic oxygen preferentially adsorbs to form stable surface peroxides (O2(2-)) with high binding energies (83-88 kcal/mol).
• Molecular oxygen adsorption involves initial electrostatic binding followed by quenching to a singlet state, forming an O3(2-) intermediate.
• The O3(2-) species is proposed as a key precursor for the dissociation of molecular oxygen into surface peroxides.

Conclusions:

• The high exothermicity of atomic oxygen adsorption drives molecular oxygen dissociation on BaO surfaces.
• A plausible mechanism involving an O3(2-) intermediate explains the formation of surface peroxides.
• This understanding is crucial for advancing catalytic processes like oxidative coupling of methane and NOx storage reduction.