Carbon subsurface traffic jam as driver for methane oxidation activity and selectivity on palladium surfaces

Area of Science:

• Heterogeneous catalysis
• Surface science
• Materials science

Background:

• Distinguishing surface and subsurface species effects in catalysis is difficult.
• Deposition and segregation of species at reaction conditions complicate analysis.
• Understanding these effects is crucial for designing efficient catalysts.

Purpose of the Study:

• To develop an operando approach for correlating surface/subsurface species with catalytic function.
• To investigate the distinct roles of surface and subsurface carbon in methane oxidation over a palladium (Pd) catalyst.
• To elucidate the impact of carbon subsurface dynamics on catalytic selectivity.

Main Methods:

• Utilized temperature modulations to oscillate carbon deposition and segregation on a Pd catalyst.
• Employed an operando approach to monitor catalytic composition and function simultaneously.
• Analyzed methane oxidation reactions under controlled conditions.

Main Results:

• Surface carbon coverage was found to drive partial oxidation to carbon monoxide (CO).
• Subsurface carbon was identified as the primary control for overall methane turnover.
• A 'carbon traffic jam' in the subsurface shifted selectivity from H2 to H2O formation.

Conclusions:

• The study highlights the critical and distinct roles of both surface and subsurface species in heterogeneous catalysis.
• Catalyst subsurface plays a significant role in reaction pathways and product selectivity.
• The developed operando method provides a powerful tool for in-situ catalyst characterization and mechanistic studies.