A novel S-scheme heterojunction NH2-MIL-101(Fe)/In2S3 with significantly enhanced photocatalytic activity for the degradation of tetracycline: Insight into interfacial charge transfer mechanism

The Photocatalytic elimination of emerging contaminants and the development of efficient heterojunction photocatalysts are the research focus in the environmental domain. In this work, a novel 0D/3D S-scheme heterojunction photocatalyst NH2-MIL-101(Fe)/In2S3 (NMI-X, X = wt% of NM101-Fe to In2S3) was synthesized by in-situ growth of NH2-MIL-101(Fe) nanoparticles onto the surface of In2S3 flower-like microspheres. The prepared photocatalysts were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic activity of NH2-MIL-101(Fe)/In2S3 was investigated via the photodegradation of tetracycline (TC) under visible light. NH2-MIL-101(Fe)/In2S3 presents excellent activity toward TC. The optimum composites NMI-10 % exhibits a TC degradation rate of 86 %. The photo- catalytic reaction rate constant (0.01307 min-1) of TC by NMI-10 % is 4.77 and 7.18 times that of In2S3 and NH2- MIL101(Fe), respectively. ESR result demonstrates that center dot O2- , center dot OH, and h+ all are active species in TC photo- degradation. The analysis of in situ irradiated XPS, Fermi energy levels, band arrangement, and ESR spectra confirms the S-scheme charge transfer mechanism at the interface of NMI-10 %. The enhanced photocatalytic activity of NMI-10 % is attributed to the outstanding visible light absorption ability, accelerated migration and separation of the photocarriers, and preservation of the photoelectrons and holes with the best redox ability due to the formation of 0D/3D hierarchical S-scheme heterostructure between NH2-MIL-101(Fe) and In2S3. In addition, NMI-10 % has excellent stability and reusability. It is a potential photocatalyst for environment restoration. This work supplies an idea for designing efficient S-scheme heterostructure photocatalysts.