Ionic liquid-assisted hydrothermal synthesis of square BiOBr nanoplates with highly efficient photocatalytic activity

•For the first time, square BiOBr nanoplates were successfully synthesized under hydrothermal conditions with the assistance of ionic liquids.•The BiOBr square nanoplates are revealed as tetragonal structure with exposed {001} facets.•The possible formation mechanism is discussed.•The square BiOBr nanoplates with exposed {001} facets exhibit excellent photocatalytic activity under visible-light.

The square BiOBr nanoplates were successfully synthesized under hydrothermal conditions with the ionic liquids used as solvent, reactant and the directing agent. The prepared BiOBr nanoplates were characterized by XRD, TEM, HRTEM, SAED, EDX, and DRS, which showed that the square BiOBr nanoplates possessed pure tetragonal BiOBr phase with high-ratio exposure of {001} facets. It was found that the ionic liquid played a key role in the formation of square BiOBr nanoplates and the possible growth mechanism was also discussed. According to the results in the photodegradation of Rhodamine B under visible-light irradiation, the square BiOBr nanoplates exhibited excellent photocatalytic activity.