Tuning Ag Loading and Particle Size in Ag@g-C₃N₄ Photocatalysts for Selective CO₂ Conversion to CO and CH₄.

Area of Science:

• Materials Science
• Catalysis
• Environmental Chemistry

Background:

• Carbon neutrality goals necessitate efficient carbon dioxide (CO₂) conversion technologies.
• Photocatalytic CO₂ reduction offers a promising route for sustainable chemical production.
• Understanding reaction mechanisms is vital for optimizing photocatalyst performance.

Purpose of the Study:

• To investigate the impact of silver nanoparticle (Ag NP) size on Ag@g-C₃N₄ photocatalyst selectivity for CO₂ reduction.
• To elucidate the mechanistic role of Ag NP size in regulating product distribution.
• To provide guidance for designing highly selective CO₂ photocatalytic systems.

Main Methods:

• Synthesis of Ag@g-C₃N₄ photocatalysts with controlled Ag NP sizes.
• Systematic characterization using techniques like visible light absorption, charge separation analysis, and energy band analysis.
• Photocatalytic activity testing for CO₂ reduction.
• Density-functional theory (DFT) calculations to study intermediate adsorption and reaction pathways.

Main Results:

• Increasing Ag NP size enhanced visible light absorption and charge separation.
• Larger Ag NPs promoted selectivity towards methane (CH₄) production.
• Ag_3.0%@CN demonstrated optimal activity and electron utilization.
• DFT calculations revealed Ag NP size influences intermediate stability and conversion barriers, favoring CO or CH₄ pathways.

Conclusions:

• Ag NP size is a critical factor in controlling the selectivity of CO₂ photoreduction.
• Larger Ag NPs stabilize key intermediates, directing the reaction towards CH₄ formation.
• This study offers mechanistic insights for developing efficient and selective CO₂ photocatalytic systems.