Ultrathin WO₃·0.33H₂O Nanotubes for CO₂ Photoreduction to Acetate with High Selectivity

Artificial photosynthesis from CO₂ reduction is severely hampered by the kinetically challenging multi-electron reaction process. Oxygen vacancies (Vo) with abundant localized electrons have great potential to overcome this limitation. However, surface Vo usually have low concentrations and are easily oxidized, causing them to lose their activities. For practical application of CO₂ photoreduction, fabricating and enhancing the stability of Vo on semiconductors is indispensable. Here we report the first synthesis of ultrathin WO₃·0.33H₂O nanotubes with a large amount of exposed surface Vo sites, which can realize excellent and stable CO₂ photoreduction to CH₃COOH in pure water under solar light. The selectivity for acetum generation is up to 85%, with an average productivity of about 9.4 μmol g⁻¹ h⁻¹. More importantly, Vo in the catalyst are sustainable, and their concentration was not decreased even after 60 h of reaction. Quantum chemical calculations and in situ DRIFT studies revealed that the main reaction pathway might be CO₂ → •COOH → (COOH)₂ → CH₃COOH.