Breaking the Activity-Selectivity Trade-off for CH₄-to-C₂H₆ Photoconversion

Area of Science:

• Heterogeneous Photocatalysis
• Methane Conversion
• Sustainable Chemistry

Background:

• Traditional methane coupling methods (OCM and NOCM) face challenges with selectivity and activity, respectively.
• Overoxidation limits selectivity in OCM, while NOCM suffers from unfavorable thermodynamics.
• A need exists for efficient and selective methane-to-ethane conversion strategies.

Purpose of the Study:

• To develop a novel photocatalytic pathway for methane to ethane conversion that overcomes the activity-selectivity trade-off.
• To investigate a H2O2-triggered mechanism utilizing ·OH radicals for efficient methane activation.
• To achieve high ethane productivity and selectivity using designed photocatalysts.

Main Methods:

• Design and synthesis of Au-WO3 nanosheets as a photocatalyst.
• Utilized in situ characterization, femtosecond transient absorption spectroscopy, and DFT calculations to elucidate the reaction mechanism.
• Performed experiments in a self-designed flow reactor under simulated and natural sunlight.

Main Results:

• Achieved unprecedented ethane productivity of 76.3 mol molAu−1 h−1 with 95.2% selectivity using Au-WO3 nanosheets.
• Demonstrated high catalytic performance with a turnover number (TON) of 1542.7 and turnover frequency (TOF) of 77.1 h−1.
• The H2O2-triggered mechanism efficiently activates methane via ·CH3 radicals, bypassing endothermic steps and radical recombination.

Conclusions:

• The H2O2-triggered methane coupling mechanism offers a superior alternative to traditional OCM and NOCM pathways.
• Au-WO3 nanosheets exhibit excellent performance and potential for practical applications, including under natural sunlight.
• The proposed strategy shows universality across various photocatalyst systems, advancing the field of methane conversion.