Ferromagnetic photocatalysts of FeTiO3–Fe2O3 nanocomposites

Abstract

Besides harvesting sunlight over a broad wavelength range as much as possible, the efficient separation of photo-generated electron–hole pairs is vital for the development of high-quality photocatalysts. In this work, we design FeTiO₃ (FTO) and Fe₂O₃ (FO) nanocomposites (xFTO–(1 − x)FO), which are simply prepared using a hydrothermal method. The FTO is epitaxially grown on FO nanoparticles, and with the increasing concentration of FTO, the band gaps decrease from 2.43 eV (x = 1.00) to 1.56 eV (x = 0.60). The photocatalytic capability is significantly improved such that xFTO–(1 − x)FO (x = 0.60) shows the highest value, which is about 8 times that of FO and 4 times that of FTO. Furthermore, strong ferromagnetism with saturated magnetization larger than 6 emu g⁻¹ is observed in xFTO–(1 − x)FO with x ≥ 0.60. xFTO–(1 − x)FO (x = 0.60) is further annealed at various temperatures. After annealing at 300 °C, the photocatalytic capability and ferromagnetism are both improved, by 38% and 31%, respectively, but drastically decrease with further increase of the annealing temperature to higher than 400 °C. The mechanism of the enhanced photocatalytic capability has been ascribed to the interdiffusion between FTO and FO at interfaces inside the nanocomposite particles, resulting in the formation of p–n junctions, which may facilitate the separation of photo-generated electron–hole pairs by the built-in-electric field. A significant enhancement of ferromagnetism occurs at the interdiffusion region with higher concentrations of FTO.