The Effect of Co Incorporation on the CO Oxidation Activity of LaFe_1−xCo_xO₃ Perovskites

• Main Authors: Maik Dreyer, Moritz Krebs, Sharif Najafishirtari, Anna Rabe, Klaus Friedel Ortega, Malte Behrens
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Catalysts
• Subjects: perovskite; CO oxidation; DRIFTS; lanthanum; iron; cobalt
• Online Access: https://www.mdpi.com/2073-4344/11/5/550

Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe_1−xCo_xO₃ perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N₂ physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which continued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H₂-temperature programmed reduction (H₂-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents.