Operando Infrared Spectroscopy Insights into Methane C-H Bond Activation and Conversion on Platinum.

Area of Science:

• Electrochemistry
• Catalysis
• Surface Science

Background:

• Sustainable C1 chemical synthesis relies on efficient methane electrooxidation.
• Elucidating reaction mechanisms is crucial for designing effective catalysts.
• Platinum-based catalysts are promising for methane conversion.

Purpose of the Study:

• To comprehensively investigate the mechanistic pathways of methane electrooxidation on Pt/C membrane electrode assemblies (MEAs).
• To identify key intermediates and understand their formation and transformation during the reaction.
• To provide a mechanistic foundation for designing selective methane electrooxidation catalysts.

Main Methods:

• Utilized highly sensitive *operando* infrared spectroscopy to monitor reaction intermediates.
• Employed density functional theory (DFT) calculations to validate experimental findings and explore energetics.
• Investigated methane electrooxidation across a wide potential window (-0.4 to 0.3 V vs RHE).

Main Results:

• Detected a characteristic band at ~2916 cm^-1, assigned to *CH intermediates formed via methane dehydrogenation.
• Found methane activation to be thermodynamically favorable and nearly potential-independent.
• Demonstrated that subsequent oxidation steps (*CH to *CO, *COOH, CO₂) are potential-dependent and influenced by *OH adsorption and surface coverage.

Conclusions:

• Provided direct spectroscopic evidence for methane activation on Pt surfaces.
• Highlighted the critical role of *CH intermediate stabilization and selective oxidation for catalyst design.
• Established a mechanistic understanding to guide the rational design of catalysts for selective methane electrooxidation.