Computational Screening of Asymmetric Dual Sites by Bader Charge Variation Facilitates C–C Coupling for CO₂ Photoreduction to C₂H₄

Constructing asymmetric dual active sites is an effective strategy to promote formation of the C2 product in photocatalytic CO2 reactions, attributed to the suppressed dipole–dipole repulsion facilitating C–C coupling. However, information about the extent of asymmetry is still absent, making the precise design of asymmetric sites a challenge. Herein, Bader charge variation (Δq) in intermetallics was chosen as the descriptor to select asymmetric sites, where a linear relation between Δq and the adsorption energy of the C2 intermediate is found. From 66 intermetallic candidates, FePt stood out, with Δq = 0.503 e–, and is predicted to be a promising asymmetric candidate. Experimentally, FePt intermetallic nanoparticles were synthesized and loaded onto the photocatalytic substrate TiO2 (denoted as FePt/TiO2), and CoPt and NiPt were also synthesized as reference samples. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results reveal the electron enrichment on Pt and depletion on Fe, and DFT calculations uncover that the asymmetric electron distribution on the FePt intermetallic strengthened the CO2 intermediate’s adsorption and C–C coupling, reducing the free energy barrier to 0.68 eV. As a result, FePt/TiO2 showed efficient production of C2H4 (4.8 μmol g–1 h–1) in the absence of photosensitizers and scavengers, higher than the amounts obtained with CoPt/TiO2, NiPt/TiO2, and TiO2 (2.1, 1.5, and 0 μmol g–1 h–1, respectively). This study offers insights into the design criteria of asymmetric sites to motivate CO2 photoreduction.