Efficient photocatalytic dye degradation over Er-doped BiOBr hollow microspheres wrapped with graphene nanosheets: enhanced solar energy harvesting and charge separation

In this work, Er-doped BiOBr hollow microspheres wrapped with graphene nanosheets, which acted as a photocatalyst with excellent photocatalytic activity and stability, have been successfully synthesized through a simple two-step hydrothermal method. The related properties of the as-prepared photocatalyst were analyzed and a possible reaction mechanism was proposed. Incorporating the rareearth element Er into the BiOBr crystal lattice can greatly expand the optical window, maybe owing to the reduced energy band gap by the impurity energy level introduced below the conduction band and indirect utilization of long-wavelength visible light caused by the up-conversion performance. The wrapping with surface graphene nanosheets can efficiently promote charge separation and transmission over the hybrid photocatalyst. The synergistic effect between efficient solar energy harvesting and charge separation gives rise to a remarkable improvement of photocatalytic activity for RhB degradation under simulated sunlight irradiation. In addition, the as-prepared photocatalyst possesses excellent photocatalytic stability, mainly due to the robust coordination interaction between the graphene and the (001) facets of the BiOBr subunits. The rational design of this highly active and stable photocatalyst provides a promising approach for future applications.