Oxygen-vacancy-induced charge localization and atomic site activation in ultrathin Bi₄O₅Br₂ nanotubes for boosted CO₂ photoreduction

Solar CO₂ reduction into value-added carbon fuels emerges as a sustainable and significant approach for CO₂ conversion. However, poor photoabsorption, sluggish dynamics of multi-electrons transfer and high CO₂ activation barrier substantially hamper CO₂ photoreduction efficiency. Herein, freestanding ultrathin Bi₄O₅Br₂ nanotubes with abundant oxygen vacancies were initially fabricated for optimizing these crucial processes. The ultrathin-shelled topologies of open tubular scaffolds and abundant surface oxygen vacancies endow the Bi₄O₅Br₂ nanotubes with extended photo-response region and boosted charge separation. Furthermore, the presence of oxygen vacancies alters charge density distribution and affords abundant localized electrons on the catalysts’ surface. These not only reinforce covalent interactions, electron exchange and transfer between CO₂ and oxygen vacancies, but also lower the CO₂ reaction energy barriers and stabilize the rate-limiting COOH* intermediate. As a result, the OV-rich Bi₄O₅Br₂ ultrathin nanotubes exhibit an outstanding CO production rate of 19.56 µmol g⁻¹h⁻¹ without using any cocatalyst or sacrificial agent, approximately 11.2 times higher than the Bi₄O₅Br₂ nanoplates counterpart. This work provides insights into the future design of ultrathin hollow scaffolds for solar fuel photosynthesis and other applications.