Comparison of Perovskite Systems Based on AFeO3 (A = Ce, La, Y) in CO2 Hydrogenation to CO

CO₂ is the most cost-effective and abundant carbon resource, while the reverse water–gas reaction (rWGS) is one of the most effective methods of CO₂ utilization. This work presents a comparative study of rWGS activity for perovskite systems based on AFeO₃ (where A = Ce, La, Y). These systems were synthesized by solution combustion synthesis (SCS) with different ratios of fuel (glycine) and oxidizer (φ), different amounts of NH₄NO₃, and the addition of alumina or silica as supports. Various techniques, including X-ray diffraction analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, N₂-physisorption, H₂ temperature-programmed reduction, temperature-programmed desorption of H₂ and CO₂, Raman spectroscopy, and in situ FTIR, were used to relate the physicochemical properties with the catalytic performance of the obtained composites. Each specific perovskite-containing system (either bulk or supported) has its own optimal φ and NH₄NO₃ amount to achieve the highest yield and dispersion of the perovskite phase. Among all synthesized systems, bulk SCS-derived La–Fe–O systems showed the highest resistance to reducing environments and the easiest hydrogen desorption, outperforming La–Fe–O produced by solgel combustion (SGC). CO₂ conversion into CO at 600 °C for bulk ferrite systems, depending on the A-cation type and preparation method, follows the order La (SGC) < Y < Ce < La (SCS). The differences in properties between La–Fe–O obtained by the SCS and SGC methods can be attributed to different ratios of oxygen and lanthanum vacancy contributions, hydroxyl coverage, morphology, and free iron oxide presence. In situ FTIR data revealed that CO₂ hydrogenation occurs through formates generated under reaction conditions on the bulk system based on La–Fe–O, obtained by the SCS method. γ-Al₂O₃ improves the dispersion of CeFeO₃ and LaFeO₃ phases, the specific surface area, and the quantity of adsorbed H₂ and CO₂. This led to a significant increase in CO₂ conversion for supported CeFeO₃ but not for the La-based system compared to bulk and SiO₂-supported perovskite catalysts. However, adding alumina increased the activity per mass for both Ce- and La-based perovskite systems, reducing the amount of rare-earth components in the catalyst and thereby lowering the cost without substantially compromising stability.