When copper is not enough: Advantages and drawbacks of using copper in de-NOx reactions over lanthanum manganite perovskite structures

Abstract

Using a Cu-doped lanthanum manganite perovskite structure (LaCu0.5Mn0.5O3-δ), we show how Pd addition following different synthesis approaches (sol-gel vs. impregnation) allows to overcome the oxidation limitation of Cu in realistic de-NOx reaction mixtures involving NO, CO, O2 and water. The beneficial interplay of Cu with the oxygen-deficient perovskite resulting from in situ exsolution during humid de-NOx treatments is strongly connected with the metallic Cu state enhancing the N2O chemistry. The beneficial catalytic properties of metallic Cu can be preserved by adjustment of the Pd amount, as evidenced by combined in situ X-ray photoelectron spectroscopy and catalytic experiments following the main reactions of the de-NOx reaction network, including water-gas shift reaction and CO oxidation. The concept of impregnation with a noble metal and simultaneous exsolution with Cu yields a reactive Cu(Pd)/perovskite interface and provides a first step towards the economization of the noble metal content at the surface in future works.