Pd─N₄ Sites in MOFs Modulate Oxygen Reduction Pathways for 100% Selective Photocatalytic CO₂-to-CH₄ Conversion from...

Area of Science:

• Materials Science
• Catalysis
• Environmental Chemistry

Background:

• Direct photocatalytic CO2 reduction is hindered by the competing oxygen reduction reaction (ORR).
• Existing catalysts struggle to suppress ORR due to the high affinity of metals for oxygen, limiting CO2 conversion to methane.
• Developing selective catalysts for CO2 reduction in the presence of oxygen is crucial for industrial applications.

Purpose of the Study:

• To develop a photocatalyst that selectively converts CO2 to CH4 in flue gas under aerobic conditions.
• To investigate a CO-mediated oxygen scavenging mechanism to suppress the ORR.
• To engineer catalytic sites for pathway-selective oxygen reduction.

Main Methods:

• Fabrication of a Pd/Cu3(HITP)2/TiO2 composite with engineered Pd-N4 sites.
• Utilizing control experiments to validate catalyst performance.
• Employing density functional theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• The engineered Pd-N4 sites effectively suppressed the ORR by steering oxygen reduction through a CO-mediated pathway.
• The composite achieved selective CO2-to-CH4 conversion with complete CH4 selectivity.
• A high conversion rate of 6.7 µmol g-1 h-1 was observed under simulated flue gas conditions (15% CO2, 3% O2).

Conclusions:

• Catalytic site modulation is key to advancing photocatalytic CO2 reduction in oxygenated environments.
• The developed strategy offers a new pathway for selective CO2 reduction in industrial flue gas.
• The CO-mediated oxygen scavenging mechanism effectively mitigates competitive oxygen effects, enhancing CO2 utilization.