Methane oxidation mechanism on Pt(111): a cluster model DFT study

Area of Science:

• Surface science
• Electrochemistry
• Computational chemistry

Background:

• Methane electrooxidation on platinum (Pt) is crucial for fuel cells.
• Understanding the reaction mechanism is key to catalyst development.
• Previous studies suggest complex surface reactions on Pt.

Purpose of the Study:

• To elucidate the electronic energy barriers of surface reactions in methane electrooxidation on Pt (111).
• To identify the rate-limiting step in the conversion of methane to adsorbed carbon monoxide (CO).
• To computationally model the reaction pathway using density functional theory.

Main Methods:

• Density functional theory (DFT) calculations on a 10-atom Pt cluster.
• Optimization of initial and transition states for elementary steps.
• Frequency analysis and transition-state theory to determine rate-limiting steps.

Main Results:

• The main reaction pathway was identified as CH(4) -> *CH(3) -> *CH(2) -> *CH -> *CHOH -> *CHO -> *CO.
• Methane dissociative chemisorption was found to be the rate-limiting elementary step.
• Electrolyte effects were not included in this initial approximation.

Conclusions:

• The dissociative chemisorption of methane is the rate-determining step for its electrooxidation on Pt (111).
• The proposed mechanism aligns with experimental observations of CO oxidation occurring at higher potentials.
• This study provides a detailed computational insight into the methane electrooxidation mechanism on platinum catalysts.