Localized Surface Plasmon Resonance in Single‐Atom Au ₁ Cu Alloy Promotes Asymmetrical C─C Coupling for CO ₂ Photoreduction to Ethanol

Abstract The photocatalytic conversion of CO ₂ and pure H ₂ O to ethanol has been challenged by low light utilization and sluggish C─C coupling kinetics. Here, single‐atom Au ₁ Cu alloys are synthesized with enhanced localized surface plasmon resonance (LSPR) effects. A strong chemical interaction is probed as electron transfer from the atomic Au site to the adjacent Cu host, giving rise to electron rearrangement and an upshift of the d band center toward the Fermi level of Cu nanoparticles. As a result, the high electron occupancy state in Au ₁ Cu alloy is excited to abundant hot charge carriers under illumination. The catalyst with an optimal amount of gold dopants delivers an excellent ethanol yield of 940 µmol g _Au ⁻¹ h ⁻¹ and a selectivity of 92.5% with outstanding stability exceeding 100 h. The structure‐reactivity correlation and mechanism studies reveal that the LSPR effect induced by the doping of single‐atom Au not only enhances light adsorption but also improves the accumulation of ^* CO intermediates, which accounts for the reduced energy barrier for C─C coupling toward ethanol formation.