Enhancing the Multifunctional Photocatalytic Activity of Sustainable Magnetic Nanoparticles

Abstract

The development of efficient photocatalytic materials has intensified in response to increasing emphasis on sustainable energy conversion and environmental restoration. However, the excessive use and indiscriminate release of heavy metals from photocatalytic nanoparticles pose potential environmental risks. This study provides insights into optimizing visible-light-active photocatalysts to enhance their photocatalytic properties and stability. Specifically, cobalt doping and controlled pH modulation are employed on the modified Fe3O4, forming two distinct samples: Co@Fe3O4-B (base-treated) and Co@Fe3O4-A (acid-treated) nanoparticles. Microscopic characterization reveals that Co@Fe3O4-A undergoes a phase transition to hematite, whereas Co@Fe3O4-B retains its mixed-phase configuration. Spectroscopic analyses confirm that the cobalt dopants decorate the outskirts of each nanoparticle, forming a core–shell structure. However, Co@Fe3O4-B exhibit Co2+ states with a high oxygen vacancy content, whereas Co@Fe3O4-A contain mixed Co2+/3+ states. The high density of defect states in the Co@Fe3O4-B results in superior photocatalytic efficiency, achieving near-complete oxidation of furfuraldehyde (97% conversion) and 5-hydroxymethylfurfural (94% conversion), as well as effective degradation of toluene (78% conversion). This