Computational\nScreening of Asymmetric Dual Sites by\nBader Charge Variation Facilitates C–C Coupling for CO<sub>2</sub> Photoreduction to C<sub>2</sub>H<sub>4</sub>

Constructing asymmetric dual active sites is an effective\nstrategy\nto promote formation of the C<sub>2</sub> product in photocatalytic\nCO<sub>2</sub> reactions, attributed to the suppressed dipole–dipole\nrepulsion facilitating C–C coupling. However, information about\nthe extent of asymmetry is still absent, making the precise design\nof asymmetric sites a challenge. Herein, Bader charge variation (Δ<i>q</i>) in intermetallics was chosen as the descriptor to select\nasymmetric sites, where a linear relation between Δ<i>q</i> and the adsorption energy of the C<sub>2</sub> intermediate is found.\nFrom 66 intermetallic candidates, FePt stood out, with Δ<i>q</i> = 0.503 e<sup>–</sup>, and is predicted to be a\npromising asymmetric candidate. Experimentally, FePt intermetallic\nnanoparticles were synthesized and loaded onto the photocatalytic\nsubstrate TiO<sub>2</sub> (denoted as FePt/TiO<sub>2</sub>), and CoPt\nand NiPt were also synthesized as reference samples. X-ray photoelectron\nspectroscopy and X-ray absorption spectroscopy results reveal the\nelectron enrichment on Pt and depletion on Fe, and DFT calculations\nuncover that the asymmetric electron distribution on the FePt intermetallic\nstrengthened the CO<sub>2</sub> intermediate’s adsorption and\nC–C coupling, reducing the free energy barrier to 0.68 eV.\nAs a result, FePt/TiO<sub>2</sub> showed efficient production of C<sub>2</sub>H<sub>4</sub> (4.8 μmol g<sup>–1</sup> h<sup>–1</sup>) in the absence of photosensitizers and scavengers,\nhigher than the amounts obtained with CoPt/TiO<sub>2</sub>, NiPt/TiO<sub>2</sub>, and TiO<sub>2</sub> (2.1, 1.5, and 0 μmol g<sup>–1</sup> h<sup>–1</sup>, respectively). This study offers insights\ninto the design criteria of asymmetric sites to motivate CO<sub>2</sub> photoreduction.