BiFeO3/BiVO4 p−n heterojunction for efficient and stable photocatalytic and photoelectrochemical water splitting under visible-light irradiation

The fabrication of p–n junctions with built-in electric field effect between n-type BiVO4 (BVO) and p- type BiFeO3 (BFO) can be efficient strategy to separate photogenerated carriers and enhances photocurrent density and photostability in BVO. We developed a facile ultrasonic/hydrothermal route to successfully synthesize BFO/BVO p–n junction that greatly improved the performance of n-type BVO and p-type BFO for photocatalytic degradation of tetracycline (TC) and photoelectrochemical (PEC) water splitting. The photodegradation of TC by BVO and BFO was highly dependent on solution pH, but that by BFO/BVO was not. The BFO/BFO p–n junction nanostructures improved the photocatalytic degradation of TC from 31% and 22% with BFO to 84% and 95% with BFO/BVO p–n junction at pH 6.7 and 9.5, respectively, and also from 37% with BVO to 84% with BFO/BVO p–n junction at pH = 2.5. The BFO/BVO nanostructures showed good photocurrent density of 0.36 mA cm −2 under UV–vis light and 0.23 mA cm-2 under visible light at 1.0 V vs. Ag/AgCl, which are 3.0- and 3.28-fold greater than those of BVO. The structures also showed great stability (more than 88% of the initial photocurrent density) over 1 h, whereas BVO had poor stability (63%). The difference between photocurrent densities from front- and back-side illumination in the BFO/BVO p–n junction was substantially reduced to 0.04 mA cm-2 as compared to 0.11 mA cm-2 in BVO due to the formation of a p–n heterojunction between p-type BFO and n-type BVO. The stable BFO/BVO p–n junction also showed the highest charge carrier density as compared to BVO.