Mechanistic insights into the enhanced photocatalytic efficiency of MoS2-tuned DyFeO3 heterojunction nanocomposites for pollutant degradation

Abstract

In this study, DyFeO₃–MoS₂ heterojunction nanocomposites were synthesized by integrating porous DyFeO₃ nanoparticles (an n-type semiconductor) with MoS₂ nanosheets (a p-type semiconductor). The resulting p–n heterojunction substantially improved the photocatalytic efficiency for degrading methylene blue (MB) and levofloxacin (LFX). This design introduces a built-in electric field at the interface, promoting efficient charge separation and suppressing electron–hole recombination, thereby significantly enhancing photocatalytic performance under solar irradiation compared to DyFeO₃ alone. Characterization studies, including XRD, FESEM, TEM, XPS, UV-visible absorbance, photoluminescence, and Mott–Schottky analysis, confirmed the nanocomposites’ crystalline structure, well-dispersed MoS₂ nanosheets, oxygen vacancies, enhanced visible light absorption, and favorable band positions. The incorporation of MoS₂ increased light absorption, enhanced charge separation, and improved surface area by mitigating DyFeO₃ aggregation, leading to significantly higher photocatalytic degradation rates. Among the tested compositions, the DyFeO₃–MoS₂ (80 : 20) nanocomposite, containing 20 wt% MoS₂, exhibited the highest efficiencies, with 96.5% degradation for MB and 88.7% for LFX. Further analyses, including activation energy determination, quantum yield measurement, scavenger tests, and reusability assessments, confirmed the optimized nanocomposite's performance and durability. The reduced activation energies and high quantum yields (35.5% for MB, 25.8% for LFX) indicate efficient photon conversion and radical generation, with superoxide radicals (˙O₂⁻) identified as the primary reactive species. Stability tests revealed over 85% retention of activity after four cycles, underscoring the composite's robustness. Moreover, the photocatalytic mechanism revealed key insights into the degradation pathways of pollutants. This investigation demonstrates a viable solar-driven solution for efficient pollutant degradation in wastewater treatment by incorporating MoS₂ into porous DyFeO₃ nanostructures.