Dual defect regulation of BiOCl halogen layer enables photocatalytic O2 activation into singlet oxygen for refractory aromatic pollutant removal

The generation of singlet oxygen (¹O₂) based on photocatalytic activation O₂ is considered to have important application prospects in purifying refractory organic pollutants in water. However, the uncertain dual pathway transformation of activated O₂ severely limits the generation of ¹O₂. In this work, we show a robust BiOCl with dual defects (adjacent I-substitution defect and Cl vacancy) in halogen layer for the selective activation of O₂ to generate ¹O₂. Combining experiments and theoretical calculations, we confirm that dual defects are beneficial in optimizing band structures, improving carrier separation efficiency, and promoting O₂ adsorption and activation. More importantly, it is confirmed that dual defects can directionally convert O₂ into ¹O₂ by increasing the thermodynamic conversion energy barrier of non-¹O₂ conversion pathways and serving as a necessary site for ¹O₂ generation with dual functions of oxidation and reduction. Applying dual defect modified BiOCl to the removal of refractory aromatic pollutants in water, it is found that it has efficient and stable photocatalytic degradation efficiency and broad environmental adaptability. This work not only provides in-depth insights into the mechanism of photocatalytic activation of O₂ to selective produce ¹O₂, but also lays the foundation for further development of highly active photocatalysts for environmental remediation and energy conversion.