Effect of the Composition of LaFe1 – xСоxO3 (x = 0–1) Perovskites on Catalytic Activities in the Reactions Involving Oxygen

Abstract

The catalytic activity of LaFe_{1 – x}Co_xO₃ perovskites obtained by the Pechini method was studied in reactions of high-temperature decomposition of N₂O, oxidation of CH₄ and CO. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), adsorption and temperature-programmed hydrogen reduction (H₂-TPR). The obtained single-phase solids with a specific surface area (S_BET) of 6.1–9.7 m²/g are porous aggregates of 10 nm to 1 micron in pore size, consisting of dendrite-like agglomerates. It has been shown that the increase in Co content leads to increase of the amount of weakly bound oxygen in perovskites. Analysis of the relationship between the activity of LaFe_{1 – x}Co_xO₃ perovskites and the amount of weakly bound oxygen revealed a good correlation for the entire range of compositions only for the N₂O decomposition reaction; a limited correlation (up to x = 0.6) for the CO oxidation reaction and the absence of such a correlation for the CH₄ oxidation reaction. The influence of key stages of reaction mechanisms affecting activity is discussed. The advantage of using the Pechini method for the preparation of high active N₂O decomposition catalysts was revealed.