100% Selective Photoreduction of CO ₂ to CO on a Macroscopic CuO/Au/g‐C ₃ N ₄ Film Enabled by Syn

ABSTRACT

Steering product selectivity is a paramount challenge in CO ₂ photoreduction. Herein, a series of macroscopic p‐n heterojunction photocatalysts, composed of the g‐C ₃ N ₄ shell coated on Au nanoparticle‐decorated CuO (CuO/Au/g‐C ₃ N ₄ and CAC‐X), were constructed in situ on a Cu‐mesh for highly selective CO ₂ photoreduction to CO. Under the irradiation of UV–Vis light in a gas–solid system for 4 h, the optimized CAC‐2 achieved an excellent CO evolution rate of about 760.0 μmol·m ⁻² with ≈ 100% selectivity, representing a 4‐fold enhancement over pure CuO. ¹³ C isotope labeling experiments confirmed the produced CO originated exclusively from CO ₂ . The underlying mechanisms were elucidated through a combination of experimental and theoretical analyses. Photoelectrochemical tests revealed that the localized surface plasmon resonance (LSPR) effect of Au NPs significantly accelerated the charge separation at the CuO/g‐C ₃ N ₄ p‐n interface. Besides, density functional theory (DFT) calculations revealed that the introduction of Au NPs lowered the crucial formation energy barrier for *COOH intermediate by about 18.6%, thereby accelerating CO ₂ activation and reduction. Furthermore, the in situ infrared thermal imaging and finite‐difference time‐domain (FDTD) simulations confirmed that the LSPR‐induced photothermal effect elevated the local catalyst temperature to ∼500 K. DFT calculations further verified that this localized heating effect diminished the desorption energy barrier of CO by approximately 34.4%, promoting the rapid release process of CO from active sites and thereby suppressing the deep reduction.