Hierarchically structured NiFe2O4/CeO2 nanocomposites for visible light photocatalytic degradation of oxytetracycline

Abstract

Nickel ferrite (NiFe₂O₄, NFO)/cerium dioxide (CeO₂) nanocomposites (NFCs) with varying ratios were synthesized by a hydrothermal route and tested as photocatalysts for oxytetracycline (OTC) degradation under visible light. Unlike conventional ferrite-ceria composites, this work introduces hierarchical flower-like architectures with reduced crystallite sizes ($\approx$8.2 nm–10 nm) and an S-scheme (broken-gap) heterojunction that promotes efficient charge separation. Structural and spectroscopic analyses, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), infrared spectroscopy (IR), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) confirmed strong interfacial coupling and defect-rich surfaces, enhancing redox activity. Among the samples, NFC4 achieved the highest degradation efficiency (84.72%), while NFC1 exhibited the fastest kinetics ($k=0.0122$ min⁻¹). Scavenger tests identified hydroxyl radicals (

) as the main active species, synergistically assisted by

and

redox cycling through a photo-Fenton-like pathway. The composites showed high stability, with NFC4 retaining $>$96% activity after four reuse cycles. These findings highlight the novelty of designing hierarchical NFO/CeO₂ nanocomposites as efficient, durable, and magnetically recoverable photocatalysts for the visible-light remediation of emerging pharmaceutical contaminants.