Tandem Synergistic Effect of Cu‐In Dual Sites Confined on the Edge of Monolayer CuInP₂S₆ toward Selective Photoreduction of CO₂ into Multi‐Carbon Solar Fuels

Abstract

One-unit-cell, single-crystal, hexagonal CuInP₂ S₆ atomically thin sheets of≈0.81 nm in thickness was successfully synthesized for photocatalytic reduction of CO₂ . Exciting ethene (C₂ H₄ ) 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 CuInP₂ S₆ monolayer (ML) is mainly responsible for efficient conversion and high selectivity of the C₂ H₄ product as the basal surface site of the ML, exposing S atoms, can not derive the CO₂ photoreduction due to the high energy barrier for the proton-coupled electron transfer of CO₂ into *COOH. The marginal In site of the ML preeminently targets CO₂ conversion to *CO under light illumination, and the *CO then migrates to the neighbor Cu sites for the subsequent C-C coupling reaction into C₂ H₄ 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 CO₂ reduction.