Enhanced visible-light photocatalytic activity of hydrogenated Fe 3 O 4 nanooctahedrons with {111} polar facets in degradation of Basic Fuchsin and the photocatalytic mechanism

Fe 3 O 4 nanooctahedrons with exposed 111 crystallographic planes have been synthesized by employing Cl − ion as a control agent of crystal facet. The Fe 3 O 4 nanooctahedron exhibits higher photocatalytic activity in degradation of basic fuchsin (BF), compared with Fe 3 O 4 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 Fe 3 O 4 111 crystallographic planes, we found the exposed 111 crystallographic planes are polar Fe-Fe 3 O 4 (111) and O-Fe 3 O 4 (111) surfaces. And thus, we present a photocatalytic mechanism of the spontaneous electric field between polar Fe-Fe 3 O 4 (111) and O-Fe 3 O 4 (111) planes driving photogenerated charge separation. The photoinduced redox reactions occur at the Fe-Fe 3 O 4 (111) and O-Fe 3 O 4 (111) 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.