Conversion of a Type-II to a Z-Scheme Heterojunction by Intercalation of a 0D Electron Mediator between the Integrative NiFe2O4/g-C3N4 Composite Nanoparticles: Boosting the Radical Production for Photo-Fenton Degradation

A carbon dot (CD)-intercalated NiFe2O4 (NFO)/graphitic carbon nitride (g-C3N4, g-CN) ternary Z-scheme heterojunction was synthesized by the facile wet chemical method and used for photo-Fenton degradation. The structural, optical, electrical, vibrational, and morphological properties of the photocatalysts were investigated through various analytical methods. The CD-intercalated heterojunction formation was analyzed by high-resolution transmission electron microscopy (HRTEM). The intercalated CD acted as an electron donor/acceptor, which converted a type-II heterojunction to a Zscheme heterojunction. The formation of Z-scheme heterojunction was confirmed by the enormous production of radicals (hydroxyl (OH center dot) and superoxide (O-2(-))) and the elemental trapping experiment. In particular, the heterojunction photocatalyst NFO/5g-CN/7.5CD showed the highest photo-Fenton degradation efficiency of 99% for rhodamine B (Rh B) and 93% for tetracycline (TCN) in the presence of H2O2. The charge separation and electron transport behaviors of the photocatalyst were examined by photoluminescence (PL) and photocurrent measurements. In the Z-scheme photo- Fenton system, hydroxyl and superoxide radicals played a vital role in the visible-light-driven degradation process. Hence, the prepared Z-scheme ternary photocatalyst is well suitable for wastewater treatment in practical use.