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 H2O electrolysis reaction by varying the pH2O/pH2 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 H2O. 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 H2O and of the resulting adsorbed Oads 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 H2O electrolysis reaction.