Photocatalytic Evaluation of Fe2O3–TiO2 Nanocomposites: Influence of TiO2 Content on Their Structure and Activity

Abstract

In this study, Fe2O3–TiO2 nanocomposites with different TiO2 contents (1–50%) were synthesized via a solvothermal method using pre-formed α-Fe2O3 nanoparticles as cores. We systematically evaluated the influence of TiO2 loading on the nanocomposites’ structural, morphological, optical, and photocatalytic properties. X-ray diffraction revealed the coexistence of hematite and anatase phases, with an increase in TiO2 content inducing reduced crystallite size, enhanced dislocation density, and microstrain, indicating interfacial lattice distortion. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) showed a uniform elemental distribution at low TiO2 contents, evolving into irregular agglomerates at higher loadings. Fourier-transform infrared (FTIR) spectra indicated the suppression of Fe–O vibrations and the appearance of hydroxyl-related bands with TiO2 enrichment. Diffuse reflectance spectroscopy (DRS) analysis confirmed the simultaneous presence of hematite (~2.0 eV) and anatase (3.2–3.35 eV) absorption edges, with a slight blue shift in the TiO2 band gap at higher concentrations. Photocatalytic activity, assessed using methylene blue degradation under xenon lamp irradiation, demonstrated a strong dependence on the TiO2 fraction. The composite containing 33% TiO2 achieved the best performance, with 98% dye removal and a pseudo-first-order rate constant of 0.045 min−1, outperforming both pure hematite and commercial P25 TiO2. These results highlight that intermediate TiO2 content (~33%) provides an optimal balance between structural integrity and photocatalytic efficiency, making Fe2O3–TiO2 heterostructures promising candidates for water purification under simulated solar irradiation.