Search

For the direct reduction of CO2 and H2O in solid oxide electrolysis cells (SOECs) with cermet electrodes toward methane, a fundamental understanding of the role of elemental carbon as a key intermediate within the reaction pathway is of eminent interest. The present synchrotron-based in situ near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) study shows that alloying of Ni/yttria-stabilized-zirconia (YSZ) cermet electrodes with Cu can be used to control the electrochemical accumulation of interfacial carbon and to optimize its reactivity toward CO2. In the presence of syngas, sufficiently high cathodic potentials induce excess methane on the studied Ni/yttria-stabilized-zirconia (YSZ)-, NiCu/YSZ- and Pt/gadolinium-doped-ceria (GDC) cermet systems. The hydrogenation of carbon, resulting from CO activation at the triple-phase boundary of Pt/GDC, is most efficient. [ABSTRACT FROM AUTHOR]

Using a Cu-doped lanthanum manganite perovskite structure (LaCu 0.5 Mn 0.5 O 3- 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-NO x reaction mixtures involving NO, CO, O 2 and water. The beneficial interplay of Cu with the oxygen-deficient perovskite resulting from in situ exsolution during humid de-NO x treatments is strongly connected with the metallic Cu state enhancing the N 2 O 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. [Display omitted] • Metallic Cu state enhances N 2 O chemistry upon dry deNOx treatment. • Under humid conditions the Cu remains mainly oxidized. • Effect of the Pd alloying on deNO x reactivity in the presence of H 2 O. • Beneficial combined concept of Cu exsolution and noble metal impreganation. [ABSTRACT FROM AUTHOR]