Sol–gel-derived ErFeO3/Fe3O4/graphene oxide hybrid nanocomposites: green auto-combustion synthesis, structural evolution, and visible-light functional performance

The development of multifunctional materials through sol-gel processing offers a powerful route for controlling composition, interfacial chemistry, and charge transport at the nanoscale. In this study, ErFeO3/Fe3O4/graphene oxide (GO) hybrid nanocomposites were synthesized via a green sol-gel auto-combustion method, employing kiwifruit extract as a natural chelating and reducing agent to promote homogeneous phase formation and reduced thermal budget. X-ray diffraction and spectroscopic analyses confirmed the successful crystallization of orthorhombic ErFeO3 and spinel Fe3O4 phases uniformly anchored on graphene oxide sheets, while electron microscopy and Brunauer-Emmett-Teller (BET) measurements revealed a hierarchically porous nanostructure with enhanced interfacial contact. Optical investigations using ultraviolet–visible (UV–Vis) spectroscopy demonstrated extended visible-light absorption and reduced bandgap energy, attributed to the synergistic coupling between ferrite components and GO. Magnetic measurements confirmed superparamagnetic behavior, enabling facile catalyst recovery. Under visible-light irradiation, the optimized hybrid nanocomposite achieved 86.6% degradation of Eriochrome Black T and 31.3% degradation of methylene blue, significantly outperforming the individual constituents. The enhanced photocatalytic activity is attributed to sol-gel-driven interfacial engineering, which promotes efficient charge separation and suppresses electron–hole recombination. These results underscore the potential of green sol-gel-derived rare-earth ferrite/graphene oxide hybrids as multifunctional materials for photocatalytic and optoelectronic applications.