O₂-assisted methane oxidation on single-atom Pd@SSZ-13: a combined first-principles and microkinetic study

Area of Science:

• Catalysis
• Materials Science
• Environmental Chemistry

Background:

• Complete catalytic oxidation of methane is vital for mitigating greenhouse gas emissions and converting energy.
• Palladium (Pd)-based catalysts are promising but face challenges in achieving high activity and stability.
• Single-atom Pd supported on zeolites, like SSZ-13, offers a potential solution for enhanced catalytic performance.

Purpose of the Study:

• To theoretically investigate methane oxidation over single-atom Pd supported on SSZ-13 zeolite (Pd@SSZ-13).
• To determine activation barriers and identify optimal configurations for Pd incorporation.
• To evaluate mechanistic routes and understand factors controlling catalytic activity and stability.

Main Methods:

• Density Functional Theory (DFT) calculations to model catalytic processes.
• Climbing-image nudged elastic band (CI-NEB) calculations to determine activation barriers.
• Microkinetic analysis to assess temperature and pressure dependent reaction rates.

Main Results:

• The O2-assisted oxidative dehydrogenation pathway is energetically favorable over direct dehydrogenation.
• Oxygen-rich environments significantly improve the thermodynamic feasibility of complete methane oxidation.
• Optimal methane conversion to CO2 and H2O occurs above 800 K, influenced by oxygen availability and water removal.

Conclusions:

• O2-assisted and multi-site mechanisms offer low-energy pathways for methane oxidation.
• Catalyst design should consider oxygen availability, water removal, and carbon site blocking for optimal performance.
• This research provides key insights for developing efficient Pd-zeolite catalysts for methane conversion.