The synthesis of novel heterojunction h-YbFeO3/o-YbFeO3 photocatalyst with enhanced Fenton-like activity under visible-light

Abstract

In this work, a simple solution combustion synthesis followed by heat treatment was proposed to produce nanocrystalline h-YbFeO₃/o-YbFeO₃ heterojunction and phase-pure o-YbFeO₃. A detailed investigation on the formation process of h-YbFeO₃ and o-YbFeO₃ nanocrystals was carried out using a wide variety of methods, including EDS, SEM, PXRD, ⁵⁷Fe Mössbauer spectroscopy, DRS. The most prospective samples of the h-YbFeO₃/o-YbFeO₃ nanocomposite and o-YbFeO₃ nanopowder were examined towards the photo-Fenton decolorization of methyl violet (MV) under visible light. It was shown that the proposed approach allows for obtaining h-YbFeO₃ and o-YbFeO₃ nanocrystals with an average size of 15.7–21.1 nm and 41.1–65.5 nm, respectively, and with a specific surface area of up to 16 m² g⁻¹. It was found that the h-YbFeO₃/o-YbFeO₃ nanocomposite has a mesoporous structure and foam-like morphology, while the o-YbFeO₃ nanopowder is non-porous and represented by agglomerates of individual nanoparticles with isometric morphology. Based on the DRS results, it was found that the band gap value was 2.05 eV and 2.16 eV for the h-YbFeO₃/o-YbFeO₃ and o-YbFeO₃ samples, respectively, providing strong visible-light absorption of the samples. It was shown that the electron structure of the h-YbFeO₃/o-YbFeO₃ nanocomposite refers to I type heterojunction, leading to effective electron and hole transfer from o-YbFeO₃ to h-YbFeO₃ bands. This feature determines the higher photocatalytic activity of the h-YbFeO₃/o-YbFeO₃ nanocomposite as compared to pure o-YbFeO₃ in the process of the Fenton-like decolorization of methyl violet under visible light with the pseudo-first-order reaction rate of 0.004848 min⁻¹ and 0.003123 min⁻¹, respectively. In conclusion, the mechanism of the photocatalytic decolorization of MV over the heterojunction nanocomposite was proposed to explain its high activity in the Fenton-like process.