Nanometric‐Mapping and In Situ Quantification of Site‐specific Photoredox Activities on 2D Nanoplates

Abstract Defective layered bismuth oxychloride (BiOCl) exhibits excellent photocatalytic activities in water purification and environmental remediation. Herein, in situ single‐molecule fluorescence microscopy is used to spatially resolve the photocatalytic heterogeneity and quantify the photoredox activities on individual structural features of BiOCl. The BiOCl nanoplates with respective dominant {001} and {010} facets (BOC‐001 and BOC‐010) are fabricated through tuning the pH of the solution. The corner position of BOC‐001 exhibits the highest photo‐oxidation turnover rate of 262.7 ± 30.8 s −1 µm −2 , which is 2.1 and 65.7 times of those of edges and basal planes, respectively. A similar trend is also observed on BOC‐010, which can be explained by the heterogeneous distribution of defects at each structure. Besides, BOC‐001 shows a higher photoredox activity than BOC‐010 at corners and edges. This can be attributed to the superior charge separation ability, active high‐index facets of BOC‐001, and its co‐exposure of anisotropic facets steering the charge flow. Therefore, this work provides an effective strategy to understand the facet‐dependent properties of single‐crystalline materials at nanometer resolution. The quantification of site‐specific photoredox activities on BiOCl nanoplates sheds more light on the design and optimization of 2D materials at the single‐molecule level.