Photocatalytic hydrogen evolution and tetracycline degradation over a novel Z-scheme Ni-MOF/g-C3N4 heterojunction

The fabrication of non-metallic semiconductor heterojunction with superior redox capability for hydrogen (H2) evolution from water and environmental remediation has been emerging as a prospective strategy. Herein, a novel two-dimensional (2D) g-C3N4/Ni-MOF Z-scheme heterojunction was prepared by a facile sonication-gel self-assembly method with g-C3N4 and nickel metal-organic framework (Ni-MOF) nanosheets. The ultra-thin nanosheet structure of Ni-MOF was conducive to the formation of stable 2D heterojunctions. The opposite surface charge and matched band difference caused the charge flow from g-C3N4 to Ni-MOF, resulting in an interfacial built-in electric field. The optimized NMF/CN-9 attained the optimal 3aphotocatalytic activity towards the degradation of tetracycline (TC) and H2 evolution from water. Under visible light irradiation, the reaction rate for TC degradation (0.00497 min−1) and H2 evolution (15.6 μmol·h−1) over NMF/CN-9 was nearly 2.4 and 2.1 folds higher than that of g-C3N4, respectively. Besides, the photocatalytic performance of NMF/CN-9 was also nearly 2 times higher than that of g-C3N4 under simulated solar illumination. Such improvements were originated from higher photo-excited charge separation and superior redox ability derived from Z-scheme interfacial charge transfer. A possible photocatalytic mechanism was also proposed and the results indicated that efficient photo-induced electrons and reactive hole (h+), superoxide radical (·O2-) and hydroxyl radical (·OH) played a major role during the photocatalytic route. This work offers an intense insight into the construction of non-metallic semiconductor 2D heterojunctions for H2 evolution and environmental wastewater treatment.