A novel NiO/BaTiO heterojunction for piezocatalytic water purification under ultrasonic vibration.

This work designed and prepared a novel heterojunction composite NiO/BaTiO through a method of photodeposition and used it in piezocatalytic dye removal for the first time. Results of the piezocatalytic test indicated that the NiO/BaTiO composite presented superior efficiency and stability in the RhB degradation under the vibration of ultrasonic waves. The best NiO/BaTiO sample synthesized under light irradiation for 2 h displayed an RhB degradation rate of 2.41 h, which was 6.3 times faster than that of pure BaTiO. By optimizing the piezocatalytic reaction conditions, the degradation rate constant of NiO/BaTiO can further reach 4.14 h A variety of systematic characterizations were executed to determine the reason for the excellent piezocatalytic performance of NiO/BaTiO. The band potentials of NiO and BaTiO are found to coincide, and at their contact interface, they may create a type-II p-n heterojunction structure. Driven by the potential difference and the built-in electric field, piezoelectrically enriched charge carriers can migrate between NiO and BaTiO, resulting in improved efficiency in charge separation and an increase in the piezoelectric catalytic performance. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient catalysts in the field of piezoelectric catalysis.