Water‐Mediated Selectivity Control of CH₃OH versus CO/CH₄ in CO₂ Photoreduction on Single‐Atom Implanted Nanotube Arrays

Abstract Controllable methanol production in artificial photosynthesis is highly desirable due to its high energy density and ease of storage. Herein, single atom Fe is implanted into TiO₂/SrTiO₃ (TSr) nanotube arrays by two‐step anodization and Sr‐induced crystallization. The resulting Fe‐TSr with both single Fe reduction centers and dominant oxidation facets (001) contributes to efficient CO₂ photoreduction and water oxidation for controlled production of CH₃OH and CO/CH₄. The methanol yield can reach to 154.20 µmol g_cat⁻¹ h⁻¹ with 98.90% selectivity by immersing all the catalyst in pure water, and the yield of CO/CH₄ is 147.48 µmol g_cat⁻¹ h⁻¹ with >99.99% selectivity when the catalyst completely outside water. This CH₃OH yield is 50 and 3 times higher than that of TiO₂ and TSr and stands among all the state‐of‐the‐art catalysts. The facile gas–solid and gas–liquid–solid phase switch can selectively control CH₃OH production from ≈0% (above H₂O) to 98.90% (in H₂O) via slowly immersing the catalyst into water, where abundant •OH and H₂O around Fe sites play important role in selective CH₃OH production. This work highlights a new insight for water‐mediated CO₂ photoreduction to controllably produce CH₃OH.