High {001} facets dominated BiOBr lamellas: facile hydrolysis preparation and selective visible-light photocatalytic activity

Efficient photocatalytic nanocrystals with high-ratio exposure of active facets have aroused a great number of research interests in recent years. However, most preparations of such materials need the addition of special capping agents (like surfactants) or harsh reaction conditions (such as hydrothermal reactions). In this work, a controllable synthesis of BiOBr nanosheets with a thickness from 9 nm to 32 nm was easily achieved in a hydrolysis system through adjusting temperature and solvent, without adding any surfactant or capping agents. As the thickness of the nanosheets decreases from 32 nm to 9 nm, the ratio of exposed {001} facets, the active photocatalysis facets in BiOBr crystals, increases from 83% to 94%, along with an increased photocatalytic efficiency over rhodamine B (RhB) under visible-light. Various methods such as SEM, TEM, AFM, DRS and Raman spectroscopy were used to fully characterize the as-obtained BiOBr nanosheets. More importantly, the obtained BiOBr nanosheets exhibit a selective visible-light photocatalytic behavior as the activity over RhB is much higher than that over Methyl Orange (MO) or Methylene Blue (MB). This phenomenon was studied with in situ electron paramagnetic resonance (EPR) measurements and the potential mechanism was explored.