Mn- or Cu- substituted LaFeO 3 -based three-way catalysts: Highlighting different catalytically operating modes of La 0.67 Fe 0.8 M 0.2 O 3 (M=Cu, Mn)

• Published in: Applied catalysis. B, Environmental Environmental, 2021-11, Vol.296, p.120330, Article 120330
• Main Authors: Nandi, Shreya, Wu, Jiang Xiang, Simon, Pardis, Nuns, Nicolas, Trentesaux, Martine, Tougerti, Asma, Fonda, Emiliano, Girardon, Jean-Sébastien, Paul, Jean-François, Mamede, Anne-Sophie, Berrier, Elise
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical Sciences
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2021.120330

The present work aims at presenting our investigations on the redox behaviour of Cu-or Mndoped LaFeO 3-based perovskite powders under three-way catalysis (TWC) relevant conditions. Two distinct La-deficient catalysts of generic formula La 0.67 Fe 0.8 Mn 0.2 O 3 and La 0.67 Fe 0.8 Cu 0.2 O 3 denoted as Mn-dLFO and Cu-dLFO, respectively, were prepared based on the conventional citrate complexation route and systematically investigated using complementary characterisation techniques. This study has made it possible to highlight fundamentally different structures. In Cu-dLFO, most Cu 2+ cations are expelled from the LaFeO 3 perovskite lattice in the form of a segregated CuO phase. On the other hand, in the case of Mn-dLFO, majority of Mn 3+ cations are stabilised within the perovskite solid solution, while substantial iron exsolution in the form of an additional α-Fe 2 O 3 phase was evidenced. The evolution of both catalysts during CO-TPR using operando Raman revealed the formation of polycyclic aromatic hydrocarbons (PAHs) besides the relative structural stability of the LaFeO 3 lattice. The reduction of Mn 3+ to Mn 2+ , indirectly suggested by Raman analysis, is further supported by a quasi-in situ XPS study. The latter also evidenced the reduction of CuO to metal copper to a large extent in Cu-dLFO. In addition, a share of the α-Fe 2 O 3 phase present in Mn-dLFO is reduced to metal Fe 0 during CO oxidation, and is fully re-oxidised upon NO reduction. Our investigation thus evidences that both copper and manganese sites in Cu-dLFO and Mn-dLFO, respectively, are redox-active centres upon CO oxidation / NO reduction with, however, varying operating modes underpinned by their fundamentally different structures.