The development of efficient and recoverable catalysts is essential for advancing carbon dioxide utilization technologies and improving the sustainability of catalytic processes. Magnetic iron oxide-based composites supported on carbon materials are particularly promising due to the combination of catalytic activity, structural stability, and the possibility of magnetic separation from the reaction medium. The aim of this study was to produce potassium-modified magnetic iron oxide composite catalysts based on Fe₃O₄ and CoFe₂O₄ on carbon supports and to study the influence of synthesis conditions and composition on their phase composition and structural characteristics. Based on a comparative analysis of the obtained data, the catalyst composition was optimized and a preliminary assessment of their application in CO₂ hydrogenation was conducted. Potassium-modified magnetic iron-containing composites supported on carbon nanotubes (CNTs) and coconut shell activated carbon (AC) were synthesized via coprecipitation and vortex electromagnetic field (VEF) synthesis followed by thermal treatment and evaluated as promising materials for CO₂ utilization processes. The influence of synthesis parameters, including pH, Fe²⁺/Fe³⁺ molar ratio, coprecipitation temperature, and calcination temperature, on the structural, phase, and magnetic properties of the catalysts was studied. Structural analysis confirmed the formation of Fe₃O₄ and CoFe₂O₄ spinel phases. The optimal calcination temperature of 673 K ensured the formation of a well-crystallized Fe₃O₄ phase with sufficiently high saturation magnetization, whereas a further increase in temperature resulted in partial oxidation of Fe₃O₄ with the formation of Fe₂O₃. Optimal synthesis conditions were determined ensuring uniform deposition of Fe₃O₄ nanoparticles measuring 10–100 nm on carbon supports. It was found that CoFe₂O₄-based composites possess high coercivity but are characterized by lower catalytic activity in the CO₂ hydrogenation reaction: the maximum CO₂ conversion for CoFe₂O₄–K/CNTs was 59% at 600 °C, which is lower than that of the studied iron oxide composites. Synthesis using VEH (vortex electromagnetic homogenizer) improved particle dispersion and catalytic performance, increasing apparent CO₂ conversion from 51% to 54% at 450 °C. Methane formation was more pronounced at intermediate temperatures, whereas at temperatures above 500 °C the product distribution shifted toward CO, indicating the increasing contribution of the reverse water–gas shift (RWGS) reaction. It was shown that optimization of the synthesis parameters made it possible to obtain magnetic composites with controlled structural-phase and magnetic properties, and the combination of high dispersion, structural stability and magnetic activity makes the synthesized composites promising catalysts for carbon dioxide hydrogenation processes.

Background/Objectives: The synthesis process of Vanadium Pentoxide (V2O5) with organic dyes like acid blue and acid yellow molecules was carried out utilizing the simple precipitation procedure with distilled water as the solvent. To understand more about the composition of the materials, the required characteristics were done on the synthesized samples. Methods: Initially, Powder X-ray diffraction (PXRD) investigation was done on the samples to analyze their amorphous nature. The Images from the Scanning Electron Microscope (SEM) revealed that the synthesized samples have a micro-rod-like structure. The occurrence of functional groups in both synthesized molecules was analyzed using a Fourier-Transform Infrared Spectroscopy (FTIR) study. Findings: The study revealed the presence of a peak at 3408 cm-1, which is caused by stretching vibrations in the N-H group, a peak at 2853 cm-1, which is characteristic of CH3, a peak at 1630cm-1, which relates to the presence of the group-N = N, and a peak at 1040 cm-1, which is characteristic of the C-N group. Additionally, to verify the dielectric nature of the synthesized powder samples, their cut-off wavelength, 245 nm for V2O5 with acid blue dye, and 363 nm for V2O5 with acid yellow dye, can be seen in the UV-vis-NIR absorption spectra. The photoluminescence spectrum displayed red light at Eg=1.7 eV for V2O5 with acid blue molecule and at Eg=1.6 eV for V2O5 with acid yellow molecule. Novelty: The novelty of this study is to test the suitability of V2O5 molecules with acid blue and V2O5 molecules with acid yellow as the best materials for utilization in optoelectronic devices, which is not addressed in existing studies. Keywords: Simple precipitation method, Powder X­ray diffraction (PXRD), Scanning Electron Microscope (SEM), Fourier­Transform Infrared Spectroscopy (FTIR), Photoluminescence, UV­ vis­NIR