Enhanced visible-light photocatalytic activity of hydrogenated Fe3O4 nanooctahedrons with {111} polar facets in degradation of Basic Fuchsin and the photocatalytic mechanism

Fe3O4 nanooctahedrons with exposed {111} crystallographic planes have been synthesized by employing Cl- ion as a control agent of crystal facet. The Fe3O4 nanooctahedron exhibits higher photocatalytic activity in degradation of basic fuchsin (BF), compared with Fe3O4 commercial powder. And the photocatalytic activity is significantly improved by removing Cl- ions and -OH groups at the (111) surface via hydrogenation. The exposed clean {111} crystal planes are evidenced to be the photocatalytic reactive crystal facets. Based on the atomic arrangement of Fe3O4 {111} crystallographic planes, we found the exposed {111} crystallographic planes are polar Fe-Fe3O4 (111) and O-Fe3O4 ((111) over bar) surfaces. And thus, we present a photocatalytic mechanism of the spontaneous electric field between polar Fe-Fe3O4 (111) and O-Fe3O4 ((111) over bar) planes driving photogenerated charge separation. The photoinduced redox reactions occur at the Fe-Fe3O4 (111) and O-Fe3O4 ((111) over bar) crystal planes, respectively. The good separation of photogenerated charges results in the excellent photocatalytic performance. The findings suggest that this charge separation model is a universal photocatalytic mechanism. This mechanism can deepen the comprehension of the crystal plane-dependent photocatalytic performances and contributes to the rational design and preparation of high-performance photocatalysts.

Automated summary

Fe3O4 nanooctahedrons with exposed {111} crystallographic planes were synthesized using Cl- ions as a control agent. The photocatalytic activity of Fe3O4 nanooctahedron in the degradation of basic fuchsin was higher compared to Fe3O4 commercial powder. The removal of Cl- ions and -OH groups at the (111) surface via hydrogenation significantly improved the photocatalytic activity. The clean {111} crystal planes were found to be the reactive crystal facets for photocatalysis. The separation of photogenerated charges between the polar Fe-Fe3O4 (111) and O-Fe3O4 ((111) over bar) surfaces drove the photogenerated charge separation and contributed to the excellent photocatalytic performance.