Fe vacancies in FeOCl enhanced reactive oxygen species generation for photocatalytic elimination of emerging pollutants

Reactive oxygen species (ROS) play an important role when using semiconductor photocatalysts in water remediation. Nonetheless, the insufficient conduction band potentials, as well as the limited mobility and quick recombination of charge carriers, often inhibit the ROS generation by many pristine photocatalysts. Here, we prepared FeOCl with tunable Fe-vacancy concentrations by using a NaCl-assisted thermal decomposition method. The defective FeOCl exhibited significantly higher rates of degradation and mineralization for organic pollutants compared to the non-defective FeOCl. This superior performance is attributed to the much faster superoxide (O₂ ^•−) and singlet oxygen (¹O₂) generation. Based on the experimental data and DFT simulations, Fe vacancies serve as electron trapping sites, leading to enhanced carrier lifetime and mobility, and can also reduce the conduction band potential of FeOCl, hence facilitating the formation of ROS. This study provides useful insights for developing cation-defected inorganic semiconductors and for improving the efficiency of O₂ activation in photocatalysis.