Ag₂O@BiFeO₃ heterostructure composite coupling built-in electric field with piezopotential for enhanced photocatalytic pollutant degradation and photoelectrochemical water splitting

Formation of p–n heterojunction is an effective strategy in developing the high performance photocatalysts with wide-spectrum response and efficient separation of photogenerated carriers. Coupling with piezoelectric potential can further drive the separation of photogenerated charges to improve the photocatalytic activity. So, a heterostructure of p-Ag₂O nanoparticles and n-BiFeO₃ nanowires was fabricated as a novel piezo-photocatalyst. The formation of p–n heterojunction was demonstrated and the associated energy band diagram was constructed. As compared to the individual BiFeO₃ and Ag₂O, the heterostructure exhibited significantly higher rate constants for photocatalytic degradation of Rhodamine B (5.70 and 2.05 times) and tetracycline (2.4 and 1.4 times), and photocurrent density for photoelectrochemical water splitting (3.75 and 2.50 times) under visible-near-infrared irradiation because the formed p–n heterojunction promoted the efficient utilization of light and the built-in electric field in the depletion region helped the separation of photoexcited electron−hole pairs. Furthermore, the rate constants for Rhodamine B/tetracycline and photocurrent density could be further enhanced (2.18/1.99 and 1.38 times) by simultaneous ultrasonication owing to the piezoelectric polarization in BiFeO₃ nanowires which also boosted the separation of photoinduced charges. Accordingly, the novel Ag₂O@BiFeO₃ heterostructure has been successfully developed as a promising piezo-photocatalyst for organic pollutant degradation and photoelectrochemical water splitting.