Tandem Synergistic Effect of Cu‐In Dual Sites Confined on the Edge of Monolayer CuInP 2 S 6 toward Selective Photoreduction of CO 2 into Multi‐Carbon Solar Fuels

Abstract One‐unit‐cell, single‐crystal, hexagonal CuInP 2 S 6 atomically thin sheets of≈0.81 nm in thickness was successfully synthesized for photocatalytic reduction of CO 2 . Exciting ethene (C 2 H 4 ) as the main product was dominantly generated with the yield‐based selectivity reaching ≈56.4 %, and the electron‐based selectivity as high as ≈74.6 %. The tandem synergistic effect of charge‐enriched Cu−In dual sites confined on the lateral edge of the CuInP 2 S 6 monolayer (ML) is mainly responsible for efficient conversion and high selectivity of the C 2 H 4 product as the basal surface site of the ML, exposing S atoms, can not derive the CO 2 photoreduction due to the high energy barrier for the proton‐coupled electron transfer of CO 2 into *COOH. The marginal In site of the ML preeminently targets CO 2 conversion to *CO under light illumination, and the *CO then migrates to the neighbor Cu sites for the subsequent C−C coupling reaction into C 2 H 4 with thermodynamic and kinetic feasibility. Moreover, ultrathin structure of the ML also allows to shorten the transfer distance of charge carriers from the interior onto the surface, thus inhibiting electron‐hole recombination and enabling more electrons to survive and accumulate on the exposed active sites for CO 2 reduction.