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.