Origin of the Photocatalytic Activity of Crystalline Phase Structures

Abstract

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 (L D). Furthermore, we selected five classical different crystal phase photocatalytic materials such as ZnIn2S4, TiO2, KNbO3, BiVO4, and BiPO4 as prototypes to demonstrate that L D might play a dominant role in determining their photocatalytic activities. We also observed a positive correlation between L D and catalytic activity. These results help in elucidating the origin of the photoelectric properties of the different crystal phases.

Zn 2 SnO 4 ternary metal oxide for ultraviolet radiation filter application: a comparative study with TiO 2 and ZnO

“…36–1451). The crystalline structure types of ZNO CANP and ZTO NP are different than those of TiO 2 NP and ZnO NP which can significantly affect their photoelectronic properties and thus their photocatalytic activities [ 22 , 27 ]. (This will be discussed in detail in the 3.3 section.)…”

“…This indicates that all the materials can absorb UV radiation and serve as UV filters. As known, the crystal structure phase influences the band gap, the separation, and transport efficiencies of photogenerated carriers in photocatalysts [ 27 , 29 ]. It can be noted that all materials have a close value of band gap which indicates similar absorption over the UV region.…”

“…From Figure 2 , ZTO NP, TiO 2 NP, and ZnO NP have nanoparticulate structures with particle sizes (8, 16, and 22 nm respectively). While, ZTO CANP has facets cubic aggregated nanoparticles with a size of 75 nm for the cubic structure and 5 nm for the individual aggregated nanoparticles, which may affect the surface active sites and thus cause the lowest photocatalytic activity [ 27 ]. Thus, the morphology in terms of the particle size and surface area has a minor effect and is likely not the predominant factor affecting their photocatalytic activity as there is no significant difference between their particle sizes.…”

“…Recently, It has been reported that the electron-hole diffusion length length plays a significant role in determining the photocatalytic activity [ 27 ]. The highest photocatalytic activity of TiO 2 NP mainly rises from high diffusion length correlated with low electron-hole recombination due to the indirect band gap of TiO 2 NP ( Figure 4(c) ) which allows less recombination [ 22 , 32 ].…”

Crystal structure engineering of metal halide perovskites for photocatalytic organic synthesis

“…1 The basic principle of photocatalysis starts at the electronic band structure of the semiconductors, which dominates the optoelectronic properties and drives the charge carrier that underpin their photocatalytic properties. 2 Consequently, the semiconductor crystal structure, which determines the electronic band structures, as well as the photogenerated charge carrier dynamics, is a key factor affecting their photocatalytic performance. 3 For example, anatase TiO 2 has often been reported to exhibit better photoactivity than the rutile crystal phase, originating from the difference in photogenerated charge generation and transfer.…”