Visible-light driven CO2 reduction coupled with water oxidation on Cl-doped Cu2O nanorods

Highlights: • Cl-doped Cu₂O nanorods are synthesized via a facile electrodeposition method. • Cl-doping optimizes the band structure of Cu₂O, resulting in a more positive valence-band position for H₂O oxidation. • The Cl-doped Cu₂O acts as an efficient catalyst for CO₂ reduction and H₂O oxidation under visible-light irradiation. • The best sample achieves an apparent quantum efficiency of 2.2% with 1.13% for CO and 1.07% for CH₄ at 400 nm. -- Abstract: Visible-light driven overall conversion of CO₂ and H₂O into chemical fuels and O₂ is a challenging but promising reaction for artificial photosynthesis. Here we demonstrate Cl-doped Cu₂O nanorods for photocatalytic CO₂ reduction conjugated with H₂O oxidation under visible-light irradiation. Cl-doping optimizes the band structure of Cu₂O, resulting in a more positive valence-band position for H₂O oxidation, and promotes CO₂ adsorption capacity as well as separation and transfer efficiency of photogenerated charge carriers. Consequently, the Cl-doped Cu₂O shows excellent photocatalytic CO₂ reduction performance accompanied by favorable H₂O oxidation ability under visible-light irradiation. The best sample achieves an apparent quantum efficiency of 2.2% with 1.13% for CO and 1.07% for CH₄ at 400 nm and demonstrates superior stability. Density functional theory calculations further reveal that Cl-doped Cu₂O is beneficial for the transformation of CO₂ into the intermediates of *COOH, *CO, and *CH₃O, which contributes to the enhanced activity of CO and CH₄ production. Additionally, Cl-doped Cu₂O shows stronger affinity toward the *CO intermediate, which tends to be protonated and ultimately transforms into CH₄, leading to higher selectivity of CH₄ than that of pure Cu₂O. This work validates an effective strategy to engineer Cu₂O for visible-light driven overall conversion of CO₂ reduction and H₂O oxidation.