Single-Atom-Layer Metallization of Plasmonic Semiconductor Surface for Selectively Enhancing IR-Driven Photocatalytic Reduction of CO2 into CH4

Efficient harvesting and utilization of abundant infrared (IR) photons from sunlight is crucial for the industrial application of photocatalytic CO₂ reduction. Plasmonic semiconductors have significant potential in absorbing low-energy IR photons to generate energetic hot electrons. However, modulating these hot electrons to selectively enhance the activity of CO₂ reduction into CH₄ remains a challenge. Herein, the study proposes a single-atom-layer (SAL) metallization strategy to enhance the generation of IR-driven hot electrons and facilitate their transfer from plasmonic semiconductors to CO₂ for producing CH₄. This strategy is demonstrated using a paradigmatic W₁₈O₄₉@W-Sn nanowire array (NWA), where Sn²⁺ ions are grafted onto exposed O atoms on the surface of plasmonic W₁₈O₄₉ to form a surface W-Sn SAL. The incorporation of Sn single atoms enhances plasmonic absorption in IR light for W₁₈O₄₉ NWA. The W-Sn SAL not only promotes CO₂ adsorption and reduces its reaction activation energy barrier but also shifts the endoergic CO-protonation process toward an exoergic reaction pathway. Thus, the W₁₈O₄₉@W-Sn NWA exhibits >98% selectivity for IR-driven CO₂ reduction to CH₄ with an activity over 9.0 times higher than that of bare W₁₈O₄₉ NWA. This SAL metallization strategy can also be applied to other plasmonic semiconductors for selectively enhancing CO₂-to-CH₄ reduction reactions.