Au-doped Ni/GDC as an Improved Cathode Electrocatalyst for H2O Electrolysis in SOECs

Abstract The present work deals with the comparison between single electrolyte supported Solid Oxide Electrolysis Cells that comprise either a 3 wt.% Au-Ni/GDC or a Ni/GDC steam/hydrogen electrode. Specifically, their electrochemical performance was investigated for the H 2 O electrolysis reaction by varying the p H 2 O/ p H 2 ratio (from 1 to 9), the operating temperature (800-900 °C) and the applied current. Physicochemical characterization was also performed both in the form of powders and as half cells with ex-situ and in-situ techniques, such as SEM, BET, XPS and TGA, including specific measurements in the presence of H 2 O. Different structural and activity properties were observed for each cermet, where the cell comprising the 3Au-Ni/GDC electrode exhibited better electrochemical performance, especially at 850 °C and above, having lower polarization resistance. This improvement is ascribed to the formation of a surface Ni-Au solid solution, which causes weaker interaction of H 2 O and of the resulting adsorbed O ads species with the modified cermet. The outcome is an electrode with a lower degree of surface oxidation and increased “three phase boundaries” length, where the charge transfer and electrode processes are enhanced for the H 2 O electrolysis reaction.