NiFe2O4/La-ZnO Heterojunction Photocatalyst with Engineered Band Alignment for Enhanced Visible-Light-Driven Dye Degradation

The development of sustainable and efficient photocatalysts for solar-driven wastewater treatment remains a critical challenge. In this work, a green-synthesized magnetically retrievable NiFe 2 O 4 /La-ZnO heterojunction nanocomposite was fabricated using Syzygium aromaticum (clove) extract as a biogenic fuel and complexing agent. Structural and surface analyses confirmed the formation of a well-coupled spinel-wurtzite heterointerface with La-induced lattice modulation. UV-visible diffuse reflectance spectroscopy revealed a narrowed band gap of 1.64 eV, while electrochemical impedance analysis indicated reduced charge-transfer resistance and suppressed carrier recombination. Under natural sunlight irradiation, the optimized NFO/La–ZnO (1:1) composite achieved 97 % degradation of Eosin Yellow (20 ppm) within 100 min, outperforming pristine counterparts. Scavenger and kinetic studies identified superoxide ( • O 2 ⁻ ) and hydroxyl radicals ( • OH) as the dominant reactive species governing the degradation process. The photocatalyst exhibited excellent magnetic recoverability and stable performance over repeated cycles. This study demonstrates a sustainable heterostructure design strategy integrating green synthesis, band-gap engineering, and magnetic recyclability for efficient solar photocatalytic water remediation.