Insight on the enhanced piezo-photocatalytic mechanism of In2O3/BiFeO3 heterojunctions for degradation of tetracycline hydrochloride

Development of highly-efficient heterojunction piezo-photocatalysts offers a great potential in depollution of environment. Herein we have constructed novel In2O3/BiFeO3 heterojunctions by decorating In2O3 nanoparticles on the surface of BiFeO3 microdiscs, and experimentally and theoretically elucidated their enhanced piezo-photocatalytic activity and mechanism for degradation of tetracycline hydrochloride (TC). Under simulated-sunlight irradiation, the optimal composite 10.7%IO/BFO shows a photodegradation activity that is increased by 2.05 and 3.97 times with respect to that of In2O3 and BiFeO3, respectively. The piezo-photodegradation activity of the 10.7%IO/BFO composite was evaluated under irradiation of both simulated sunlight and ultrasonic. It is demonstrated that the piezo-photocatalysis is much larger than the photocatalysis as well as the piezocatalysis, generating a synergistic factor SF = 1.48, which evidences an obvious synergistic enhancement between photocatalysis and piezocatalysis. The ultrasonic-induced piezopotential in the In2O3/BiFeO3 composites was studied using density functional theory (DFT) and finite-element method (FEM). The enhanced piezo-photocatalysis can be explained due to the synergistic enhancement of photocarrier separation (particularly the bulk photocarrier separation) by interface field and polarization field. Additionally, this work also elucidated the effects of various factors on the TC degradation, its degradation mechanism and toxicity of degradation intermediates.