How defects in lanthanum iron manganite perovskite structures promote the catalytic reduction of NO by CO

• Published in: Materials today chemistry 2024-01, Vol.35 (C), p.101910, Article 101910
• Main Authors: Mohammadi, Asghar, Thurner, Christoph W., Haug, Leander, Bekheet, Maged F., Müller, Julian T., Gurlo, Aleksander, Hejny, Clivia, Nezhad, Parastoo Delir Kheyrollahi, Winkler, Daniel, Riedel, Wiebke, Penner, Simon
• Format: Article
• Language: English
• Subjects: Defects; In situ X-ray diffraction; In situ X-ray photoelectron spectroscopy; Nitrogen oxide abatement
• ISSN: 2468-5194; 2468-5194
• DOI: 10.1016/j.mtchem.2024.101910

Adjusting the defect level during synthesis of A- and B-site deficient lanthanum iron manganite (LFM) perovskites shows that non-stoichiometry can beneficially influence the catalytic reactivity to N2 in the reduction of NO by CO on noble metal-free LFM-based perovskites. Optimal steering of La deficiency and the associated redox chemistry to reduce the near-surface regions during catalytic operation at low temperatures is the key factor. Surface enrichment by reducible B site cations and a proper design of structural defects resulting from the optimum introduction of La defects exclusively cause in-situ reduction of surface-near regions by CO oxidation, as well as formation of oxygen vacancies for enhanced NO and N2O reactivity. Excess doping with defects causes structural instability and continuous supply of oxygen from the catalyst bulk to the surface at elevated temperatures. Introduction of B site vacancies leads to surface enrichment by non-reducible lanthanum cations, causing suppressed catalyst activity undercutting even stoichiometric LFM. [Display omitted] •Non-stoichiometry increases the catalytic deNOx reactivity in LFM perovskites.•Optimum steering of La deficiency important for redox chemistry.•Overdoping with La - associated defects leads to structural instability.•B site vacancies cause surface enrichment by non-reducible La cations.