Electrocatalytic enhancement of CO methanation at the metal-electrolyte interface studied by in situ X-ray photoelectron spectroscopy

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.