Origin of the Photocatalytic Activity of Crystalline Phase Structures

Understanding photocatalysts with different crystal structures significantly improves the activity of photocatalysts and solar-conversion materials. However, the difference in the performance of various phase structures remains obscure. Despite a significant amount of gathered evidence, prior literature mainly focuses on the band and electronic structure from a thermodynamic aspect. Moreover, quantitative analyses of the differences in electron–hole dynamics between different crystalline structures are scarce but essentially desired. Herein, we constructed a research model using a simple instrument to determine the electron–hole diffusion length (LD). Furthermore, we selected five classical different crystal phase photocatalytic materials such as ZnIn2S4, TiO2, KNbO3, BiVO4, and BiPO4 as prototypes to demonstrate that LD might play a dominant role in determining their photocatalytic activities. We also observed a positive correlation between LD and catalytic activity. These results help in elucidating the origin of the photoelectric properties of the different crystal phases.