Ag–Au Antenna-Reactor System with Enhanced Superimposed LSPR-Induced Electric Fields for Plasmon-Mediated CO2 Photoreduction

Plasmon-mediated CO₂ photoreduction (PMCPR) to value-added fuels provides a fascinating approach for conversion of CO₂ and renewable energy supply, yet its practical implementation remains hindered by the low efficiency in the generation, separation, and transportation of hot carriers. Herein, a unique antenna-reactor system of Ag–Au core–shell nanocubes (Ag–Au AR) is constructed. Atomic-resolution HAADF-STEM images and XPS spectra evidence that the discrete shell consisting of three or four layers of Au atoms (a thickness of ∼1 nm) is wrapped on the surface of Ag nanocubes (Ag NCs) with an average size of 30 nm. Through FDTD simulations, a significantly enhanced superimposed LSPR-induced electric field emerges due to the Ag–Au plasmonic antenna, and its field intensity enhancement is 7.7-fold compared with that of Ag NCs. Femtosecond-resolved ultrafast TAS and quasi-in situ KPFM results reveal that the generation, separation, and transfer processes of hot carriers are significantly accelerated owing to the introduction of the discrete Au shell as the nanoreactor in Ag–Au AR. In situ DRIFTS and DFT calculations further suggest the positive role of the Ag–Au interfaces on the formation and stabilization of the key intermediate of *CHO. As a result, Ag–Au AR exhibits a high plasmonic photocatalytic CH₄ production rate of 865.8 μmol·g^–1·h^–1 with a superior selectivity of 94%, surpassing the majority of state-of-the-art catalysts.