Water-induced stacking of α-Fe2O3 hexagonal nanoplates along the [001] direction and their facet-dependent catalytic performances

Abstract

Controlling the growth of nanocrystals to expose a specific facet is of great significance for the rational design of effective crystal catalysts. Herein, a water-induced stacking process was developed to obtain stacked α-Fe₂O₃ hexagonal nanoplates (HNP) along the [001] direction, and the ratio of the side exposed {012} + {104} facet over the exposed {001} facet was flexibly controlled by oriented attachment, which was determined by the added H₂O dosage. The number of stacked HNP can increase from 6 to 18 when the H₂O usage varied from 56 mmol to 444 mmol, and the ratio of {012} + {104}/{001} increased from 0.296 to 39.756. The control experiments suggest that the increase in hydrogen bonds and Ac⁻ anion desorption from the polar {001} facet were considered to be the possible reasons for the formation of stacked α-Fe₂O₃ HNP. Finally, their facet-dependent catalytic performances were determined in visible photocatalytic degradation of MB dye and CO oxidation, and an exactly opposite catalytic activity was suggested. This work provides a facile and feasible method for the controlled synthesis of α-Fe₂O₃ crystal facets.