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 po-tential 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 hetero-structure has been successfully developed as a promising piezo-photocatalyst for organic pollutant degradation and photoelectrochemical water splitting.