Construction of oxygen vacancy on Bi12O17Cl2 nanosheets by heat-treatment in H2O vapor for photocatalytic NO oxidation

Oxygen-vacancies (OVs) play significant roles in semiconductor-based photocatalysis, such as elevating light absorption property, photogenerated carries separation efficiency, molecular activation, and photocatalytic activity. However, heat-treatment of semiconductors in dangerous H2 atmosphere is usually indispensable for OVs formation. In this work, C-doped Bi12O17Cl2 nanosheets were facially heat-treated in H2O vapor (∼2.3 vol%) mixed with Ar at 300 °C to in-situ introduce OVs by the proposed reactions of C(s) + H2O(g) → CO(g) + H2(g) and H2(g) + OLattice → H2O(g) + OV. The formation of OVs, which was confirmed by electron paramagnetic resonance (EPR), can narrow the band gap, and enhance the photogenerated e−/h+ separation efficiency on Bi12O17Cl2. Moreover, OVs-rich Bi12O17Cl2 nanosheets can facilitate molecular O2 activation and produce more reactive oxygen species (ROS), especially 1O2, which greatly improve the NO to NO3− conversion efficiency with NO removal rate of ∼63% and NO3− production selectivity of ∼92.6 %. The present work will bring new insights into the construction and roles of OVs in semiconductor-based photocatalysis.