Rare-Earth Single-Atom La–N Charge-Transfer Bridge on Carbon Nitride for Highly Efficient and Selective Photocatalytic CO₂ Reduction

Abstract

Photocatalytic CO₂ conversion into valuable solar fuels is highly appealing, but lack of directional charge-transfer channel and insufficient active sites resulted in limited CO₂ reduction efficiency and selectivity for most photocatalytic systems. Herein, we designed and fabricated rare-earth La single-atoms on carbon nitride with La-N charge-transfer bridge as the active center for photocatalytic CO₂ reaction. The formation of La single-atoms was certified by spherical aberration-corrected HAADF-STEM, STEM-EELS, EXAFS, and theoretical calculations. The electronic structure of the La-N bridge enables a high CO-yielding rate of 92 μmol·g^-1·h^-1 and CO selectivity of 80.3%, which is superior to most g-C₃N₄-based photocatalytic CO₂ reductions. The CO production rate remained nearly constant under light irradiation for five cycles of 20 h, indicating its stability. The closely combined experimental and DFT calculations clearly elucidated that the variety of electronic states induced by 4f and 5d orbitals of the La single atom and the p-d orbital hybridization of La-N atoms enabled the formation of charge-transfer channel. The La-N charge bridges are found to function as the key active center for CO₂ activation, rapid COOH* formation, and CO desorption. The present work would provide a mechanistic understanding into the utilization of rare-earth single-atoms in photocatalysis for solar energy conversion.