Enhanced piezocatalytic activity of BiFeO3 hollow spheres with surface iodine-grafting

[Display omitted] •BiFeO3-Ix hollow spheres with surface iodine-grafting were fabricated.•The existence of abundant active site was derived from the hollow structure.•A surface local electric field and regulated band structure were induced by iodine-grafting.•BiFeO3-I2 exhibited the highest efficiency on removal of bisphenol A.•The possible piezocatalytic mechanism was carefully proposed. The insufficient active sites, low separation efficiency of free carriers and poor capacity to generate active free radicals are limitations of asymmetrical BiFeO3 in piezocatalysis. To address these issues, BiFeO3 hollow nanospheres with exposed abundant catalytic active sites were fabricated via a solvothermal method for the first time. In addition, surface iodine-grafting was introduced, resulting in a local electric field and the conduction band potential of BiFeO3 closer to the O2/·O2– redox potential (-0.33 eV). It facilitated charge transmission and active species generation to remove bisphenol A under ultrasonic vibration. Thus, the iodine-grafted BiFeO3 hollow nanospheres could completely degrade 20 mL bisphenol A (10 ppm) within 60 min with a relatively fast rate constant of 0.153 min−1, which was 4.5 times higher than that of un-grafted BiFeO3. This work provides a feasible approach to construct efficient piezocatalysts for industrial wastewater purification.