Single-molecule and -particle probing crystal edge/corner as highly efficient photocatalytic sites on a single TiO 2 particle

Significance The exposed active sites of semiconductor catalysts are essential to the photocatalytic energy conversion efficiency. Here, we applied a quasi-total internal reflection fluorescence microscopy and laser-scanning confocal microscopy to identify the photocatalytic active sites at a single-molecule level and visualized the photogenerated hole–electron pair dynamics on single TiO 2 particle. The experimental results and density functional theory calculations reveal that holes and electrons tend to reach and react at the same surface sites, i.e., crystal edge/corner, owing to the exposed (001) and (101) facets of TiO 2 . These findings offer insights into the nature of photocatalytic active sites and imply an activity-based strategy for rationally engineering catalysts for improved photocatalysis, which could be also applied for other catalytic materials.