In summary, this work establishes a correlation between OVs and bound exciton luminescence by single-particle spectroscopy. It confirms that the PL emission of m-BiVO₄ originates from the defect state. Additionally, the study achieves visual imaging of the spatial distribution of oxygen defects by PL lifetime imaging maps. Furthermore, single-particle spectroscopy can be used to monitor charge transfer during photocatalysis in situ, indicating that the generation of OVs at specific crystal facets facilitates efficient charge transfer between electrons and reactants. This work provides an imaging technique to accurately monitor the spatial distribution of defects in single-crystal materials, and a method for spatial high-resolution real-time monitoring of multiphase catalytic reactions, aiming to provide an in-depth understanding of the relationship between the structure-activity of materials.