Solar-driven CO₂-to-ethanol conversion enabled by continuous CO₂ transport via a superhydrophobic Cu₂O nano fence

The overall photocatalytic CO₂ reduction reaction presents an eco-friendly approach for generating high-value products, specifically ethanol. However, ethanol production still faces efficiency issues (typically formation rates <605 μmol g^-1 h^-1). One significant challenge arises from the difficulty of continuously transporting CO₂ to the catalyst surface, leading to inadequate gas reactant concentration at reactive sites. Here, we develop a mesoporous superhydrophobic Cu₂O hollow structure (O-CHS) for efficient gas transport. O-CHS is designed to float on an aqueous solution and act as a nano fence, effectively impeding water infiltration into its inner space and enabling CO₂ accumulation within. As CO₂ is consumed at reactive sites, O-CHS serves as a gas transport channel and diffuser, continuously and promptly conveying CO₂ from the gas phase to the reactive sites. This ensures a stable high CO₂ concentration at reactive sites. Consequently, O-CHS achieves the highest recorded ethanol formation rate (996.18 μmol g^-1 h^-1) to the best of our knowledge. This strategy combines surface engineering with geometric modulation, providing a promising pathway for multi-carbon production.