100% Selective Photoreduction of CO 2 to CO on a Macroscopic CuO/Au/g‐C 3 N 4 Film Enabled by Synergistic Photothermal and p‐n Heterojunction Effects

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.