Selective Photocatalytic Reduction of CO₂ to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride

Abstract

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO₂ ) and water (H₂ O) into fuels and value-added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C₃ N₄ nanotubes (PCN) to form the photocatalyst Ag₁ @PCN with Ag-N₃ coordination for CO₂ photoreduction using H₂ O as the reductant. The as-synthesized Ag₁ @PCN exhibits a high CO production rate of 0.32 μmol h^-1 (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal-support interactions (Ag-N₃ ) favor *CO₂ adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C₃ N₄ and Ag single atoms, thereby accounting for the enhanced CO₂ photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal-support interactions in enhancing the photoactivity and CO selectivity of CO₂ photoreduction.