The Active Phase of Palladium during Methane Oxidation

Area of Science:

• Catalysis
• Surface Science
• Materials Chemistry

Background:

• The precise role of palladium (Pd) in methane oxidation catalysis remains incompletely understood, hindering the development of more efficient catalytic converters.
• Identifying the active phase and specific atomic configurations responsible for high methane conversion is critical for catalyst design.

Purpose of the Study:

• To elucidate the active phase of palladium during methane oxidation.
• To identify and characterize specific atomic sites and surface structures that promote high methane conversion.
• To establish a structure-activity relationship for designing improved palladium-based catalysts.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model methane dissociation on various palladium and palladium oxide (PdOx) surfaces.
• In situ surface X-ray diffraction (SXRD) experiments were conducted to experimentally probe the surface structures under reaction conditions.
• Computational and experimental results were correlated to validate findings on active sites and surface requirements.

Main Results:

• Density Functional Theory calculations revealed facile methane dissociation on under-coordinated palladium sites within PdO(101) and on metallic palladium surfaces.
• In situ surface X-ray diffraction experiments confirmed that high methane conversion necessitates sufficiently thick PdO(101) films or metallic palladium.
• A clear correlation was established between specific atomic structures (under-coordinated Pd sites, thick PdO(101) films, metallic Pd) and high catalytic activity.

Conclusions:

• The active phase of palladium in methane oxidation involves specific under-coordinated sites on PdO(101) and metallic palladium surfaces.
• The study provides unambiguous experimental and computational evidence linking high methane conversion to the presence of these specific structures.
• This work lays the foundation for the rational design of next-generation palladium catalysts with enhanced methane oxidation performance.