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In this study, we successfully synthesized PrFeO 3 /CeO 2 -based nanocomposites with different mass contents of СeO 2 (0–18 wt%) via solution combustion with subsequent heat treatment in air. The results of EDXS and PXRD confirmed the presence of two phases in nanocomposites: a PrFeO 3 orthorhombic phase with an average crystallite size of 13.6–36.6 nm and a СeO 2 cubic phase in the form of an ultradisperse phase with an average particle size of 7.4–11.5 nm depending on the mass content of СeO 2. We characterized the morphology, porosity, and specific surface structure of the powders by scanning electron microscopy, transmission electron microscopy, and adsorption–structural analysis, which established the foam-like morphology of nanopowders with a predominantly mesoporous structure. The specific surface area varied in the range of 8.8–19.4 m2/g for different СeO 2 contents. We studied the optoelectronic properties of the nanocomposites with UV–visible diffuse reflection spectroscopy, which determined the values of the band gap of the PrFeO 3 phase actively absorbing radiation in the visible region (2.07–2.13 eV). Based on the adsorption–photocatalytic properties of the obtained nanocomposites, we established the presence of a synergistic effect from the addition of CeO 2 to PrFeO 3. We studied the adsorption capacity of the samples during the adsorption of methyl violet, and we analyzed the resulting adsorption isotherm in accordance with the Freundlich model. The obtained results indicated increased dye adsorption in the presence of CeO 2 , with the maximum value of K f = 45.7 observed at 15 wt%. We studied the photocatalytic Fenton-like activity of nanopowders during the degradation of methyl violet under the influence of visible light. We established he presence of a positive effect of CeO 2 additive. At 9 wt% content, the maximum photocatalytic reaction rate constant was reached at 0.056 min−1, which was previously unavailable for analogical Fenton-like photocatalysts based on REE orthoferrites. Based on the conducted studies, we propose a possible mechanism of the photo-Fenton-like decomposition of organic pollutants in the presence of PrFeO 3 /CeO 2 under the influence of visible light. The obtained nanocomposite materials were also characterized by high cyclic stability and the potential for magnetically controlled separation from the reaction solution, showing their potential as a basis for photocatalysts in wastewater treatment from dyes and other organic pollutants. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis and characterization of spherulite-like nanocrystalline titania with rutile structure (r-TiO2) are described herein. The r-TiO2 particles were synthesized via the convenient and low-cost hydrothermal treatment of TiO(C6H6O7) titanyl citrate. The r-TiO2 spherulites are micron-sized agglomerates of rod-shaped nanocrystals with characteristic sizes of 7(±2) × 43(±10) nm, oriented along (101) crystallographic direction, and separated by micropores, as revealed by SEM and TEM. PXRD and Raman spectroscopy confirmed the nanocrystalline nature of r-TiO2 crystallites. BET analysis showed a high specific surface area of 102.6 m2/g and a pore volume of 6.22 mm3/g. Photocatalytic performances of the r-TiO2 spherulites were investigated for the processes of methyl violet (MV) degradation in water and hydrogen evolution reaction (HER) in aqueous solutions of ethanol. The (MV) degradation kinetics was found to be first-order and the degradation rate coefficient is 2.38 × 10−2 min−1. The HER was performed using pure r-TiO2 spherulites and nanocomposite r-TiO2 spherulites with platinum deposited on the surface (r-TiO2/Pt). It was discovered that the r-TiO2/Pt nanocomposite has a 15-fold higher hydrogen evolution rate than pure r-TiO2; their rates are 161 and 11 nmol/min, respectively. Thus, the facile synthesis route and the high photocatalytic performances of the obtained nanomaterials make them promising for commercial use in such photocatalytic processes as organic contamination degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Series of PrFeO 3 nanopowders were synthesized via the solution combustion method. • Morphology and surface area of PrFeO 3 can be controlled by solution Ox/Red ratio. • PrFeO 3 nanopowders exhibit high efficiency toward photo-Fenton degradation of MV. • Photocatalytic activity is strongly affected by the presence of amorphous phase. Praseodymium orthoferrite nanopowders were synthesized by Red/Ox-controlled glycine-nitrate combustion followed by heat treatment. It was found that the temperature of PrFeO 3 formation from amorphous combustion products varied from 612 °C to 647 °C, depending on the initial reaction solution. The purity, crystallite size, morphology and specific surface area of ​​the samples were affected by the glycine-nitrate ratio (G/N). At nonstoichiometric G/N (more or less than 0.6), amorphous or low crystalline phases were formed. Also, at these ratios, nanopowders had the smallest crystallite size before (17.4–36.2 nm) and after (45.3–49.2 nm) heat treatment. All powders were characterized by developed porous morphology with a specific surface area of ​​2.9–11.9 m2/g and a band gap of 2.07–2.13 eV. The results of 57Fe Mössbauer spectroscopy confirmed magnetically ordered state of PrFeO 3 nanocrystals with 1 mol % of amorphous component, associated with the combustion mode of a glycine-nitrate solution. The photocatalytic activity of PrFeO 3 was evaluated by the rate of decomposition of methyl violet (MV) in the presence of peroxide under the action of visible light. [ABSTRACT FROM AUTHOR]