Dynamic Dual-Site Relay Catalysis Enables Selective Solar-Driven CO2 Reduction Toward Ethanol.

Photocatalytic CO2 reduction to ethanol (C2H5OH) offers a sustainable carbon recycling route but is limited by inefficient C-C coupling under visible light irradiation. Here, we report a defect-engineered WO3-x/InSAs (SAs, single atoms) photocatalyst with a dynamic dual-site relay mechanism, where electron-rich W-VO (VO, oxygen-vacancy) and electron-deficient In single atom sites cooperatively drive selective ethanol synthesis. The W-VO site acts as a persistent *CO supply hub for CO2-to-*CO conversion, while In site functions as an ethanol-selective coupling center for targeted *CO-*CO coupling. This relay enables exceptional ethanol production and high selectivity (97.43% electrons selectivity and 86.35% yield-based selectivity). Notably, the photocatalyst maintains efficient CO2-to-ethanol conversion efficiency under natural sunlight illumination in scaled-up experiments using a reactor equipped with a 20 × 20 cm2 plate coated with WO3-x/InSAs. Combined in situ spectroscopy and DFT calculations reveal that W-VO orchestrates CO2-to-*CO feeding and relays electrons to InSAs, reducing the C-C coupling barrier via asymmetric electron distribution. Electron-trapping at oxyphilic In stabilizes *CO via O-lone-pair donation; subsequent W d-orbital hybridization anchors *OCCO, dictating ethanol selectivity. Our work provides a design strategy for efficient photogenerated carrier utilization in CO2-to-ethanol conversion, with implications for scalable solar fuel synthesis.