CuO/La0.5Sr0.5CoO3: precursor of efficient NO reduction catalyst studied by operando high energy X-ray diffraction under three-way catalytic conditions

Abstract

Substitution of critical raw materials such as platinum group metals in automotive catalysts is challenging. In this work we prepared a nanocomposite in which CuO nanoparticles are highly dispersed on a La_0.5Sr_0.5CoO₃ perovskite-type oxide. The behaviour and reactivity under three way catalyst conditions was monitored by operando time-resolved high-energy X-ray diffraction under oscillating rich/lean feed. The reducing environment converted CuO into Cu(0) in a two step process: Cu(II) to Cu(I) and to Cu(0), while the perovskite evolved to an oxygen deficient brownmillerite phase. These structural transformations are shown to be crucial for catalytic activity. The in situ generated Cu(0)/Cu(I)/brownmillerite nanocomposite is active for NO reduction above 300 °C, reaching 90% NO conversion at 450 °C. The effect of feed composition on the diffraction patterns was studied by Rietveld refinement in order to rationalize the experimental observations under TWC conditions.