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

Abstract

· Carbon doped Bi 12 O 17 C l2 nanosheets was synthesized by a facile hydrothermal reaction using sodium oleate as surfactant and carbon source. · Oxygen vacancies was in-situ introduced on the Bi 12 O 17 C l2 nanosheets by the reductive H 2 generated from the water gas reaction between water vapor and the doped carbon. · The introduction of OVs significantly improved the photocatalytic activity of Bi 12 O 17 C l2 nanosheets for NO removal. · The OVs on Bi 12 O 17 C l2 not only enhanced the photogenerated e − /h + separation efficiency but also facilitated the O 2 activation to produce more reactive oxygen species. 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 H 2 atmosphere is usually indispensable for OVs formation. In this work, C-doped Bi 12 O 17 C l2 nanosheets were facially heat-treated in H 2 O vapor (∼2.3 vol%) mixed with Ar at 300 °C to in-situ introduce OVs by the proposed reactions of C(s) + H 2 O(g) → CO(g) + H 2 (g) and H 2 (g) + O Lattice → H 2 O(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 Bi 12 O 17 C l2 . Moreover, OVs-rich Bi 12 O 17 C l2 nanosheets can facilitate molecular O 2 activation and produce more reactive oxygen species (ROS), especially 1 O 2 , which greatly improve the NO to NO 3 − conversion efficiency with NO removal rate of ∼63% and NO 3 − production selectivity of ∼92.6 %. The present work will bring new insights into the construction and roles of OVs in semiconductor-based photocatalysis.