Enhancing the charge transfer driving force in ZnO/g-C₃N₄ S-scheme heterojunction via piezoelectric field for photocatalytic H₂ evolution

AbstractA ZnO/g-C₃N₄ S-scheme heterojunction was successfully fabricated via a facile calcination method. Under the synergistic effect of visible light and ultrasonic oscillation, the piezoelectric polarization of ZnO offered an extra driving force for charge separation. The induced piezoelectric field (PEF) accelerated the charge transfer and improved the visible-light response and photocatalytic H₂ production efficiency. Under such coupled excitation, the extra driving force enlarged the energy band bending and strengthened the inherent internal electric field (IEF) of the heterojunction. Benefiting from the cooperation between the PEF and IEF, the heterojunction exhibited an excellent H₂ evolution rate (HER) of 6739.25 μmolg−1h−1 over 4 h under simultaneous visible-light irradiation and ultrasonic treatment, which was 15.51 times higher than that of pure g-C₃N₄. This work provides a new and universal strategy: promoting carrier migration in photocatalysts by piezoelectric polarization to enhance their energy conversion efficiency.