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

In this work, a simple solution combustion synthesis followed by the heat treatment was proposed to produce nanocrystalline h-YbFeO3/o-YbFeO3 heterojunction and phase-pure o-YbFeO3. Detailed investigation on the formation process of h-YbFeO3 and o-YbFeO3 nanocrystals from amorphous combustion products was carried out using a wide complex of methods – EDS, SEM, PXRD, 57Fe Mossbauer spectroscopy, DRS, etc. The most perspective samples of h-YbFeO3/o-YbFeO3 nanocomposite and o-YbFeO3 nanopowder were examined then towards photo-Fenton decolorization of methyl violet (MV) under visible light. It was shown that the proposed approach allows obtaining h-YbFeO3 and o-YbFeO3 nanocrystals with an average size of 15.7-21.1 nm and 41.1-65.5 nm, correspondently, and with a specific surface area up to 16 m2/g. It was found that the h-YbFeO3/o-YbFeO3 nanocomposite has a mesoporous structure and foam-like morphology while o-YbFeO3 nanopowder is non-porous and represented by the agglomerates of individual nanoparticles with isometric morphology. Based on DRS results it was found that band gap value is equal to 2.05 eV and 2.16 eV for h-YbFeO3/o-YbFeO3 and o-YbFeO3 samples, correspondently, providing strong visible-light absorption of the samples. It was shown that the electron structure of 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 is realized in a higher photocatalytic activity of the h-YbFeO3/o-YbFeO3 nanocomposite as compared to pure o-YbFeO3 in the process of 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 photocatalytic decolorization of MV over heterojunction nanocomposite was proposed to explain its high activity in the Fenton-like process.