ZnO quantum dots decorated TiO2 nanorod p-n heterojunction for efficient photoelectrocatalysis

The construction of semiconductor heterojunction (especially p-n junction) is an effective approach to promote the stability and separation of photoexcited charge carriers in photoelectrochemical and photocatalytic processes. Herein, we fabricated p-n heterojunction by in-situ metal-defective p-ZnO quantum dots (QDs) decorated on oxygen-defective TiO2 nanorod (p-ZnO QDs/n-TiO2) through a facile solvothermal method. P-ZnO QDs/n-TiO2 exhibited typical characteristics of p-n heterojunction such as V-shaped Mott-Schottky plots. Compared with type-II heterojunction, the difference between Fermi level in p-ZnO QDs and n-TiO2 is large and the internal electric field is strong, and thus p-ZnO QDs/n-TiO2 exhibited promoted charge separation and PEC performance. The optimal TZ-10 exhibited the highest photocurrent of 1.70 mA/cm2 at 1.23 V (vs. RHE) and good stability. Compared with the pure TiO2 device, the p-ZnO QDs/n-TiO2 catalyst has significantly improved photoelectrochemical performance. Moreover, NiOOH was further deposited on the surface of p-n heterojunction by electro-deposition to promote the kinetics of surface reaction, and the photocurrent was as high as 2.28 mA/cm2 at 1.23 V (vs. RHE).