Transition Metal Elements as Ni/GDC Dopants for the H_2O Electrolysis Process in SOECs: Fe-Ni vs Au-Mo-Ni Interaction

摘要

The present study focuses on the effect of transition metal elements as dopants of the commercial NiO/GDC powder for the Solid Oxide H_2O electrolysis. Specifically, the experimental comparison is between Au, Mo and Fe doping. Comparative electrocatalytic measurements with I-V curves and Electrochemical Impedance Spectra (EIS) analysis are presented in the range of 800-900°C between electrolyte-supported cells with Ni/GDC, 3Au-3Mo-Ni/GDC and 2Fe-Ni/GDC, as the fuel electrode. In summary, the cell comprising the ternary 3 Au-3Mo-Ni/GDC electrode performed significantly better while 2wt% Fe-Ni/GDC proved to be not successful. The superior performance of the Au-Mo-Ni ternary sample is primarily ascribed to the enrichment of the surface with Au and of the bulk phase with Mo, through the formation of Ni-Au-Mo solid solution. The involved elements modify the physicochemical properties of the electrode, improving the: (i) H_2O re-oxidation rate, (ii) electronic conductivity and (iii) electrochemical interface. In regards to the Fe-doping, it is worth to be stressed that there are key preparation/modification parameters, which can tune the properties of Fe-Ni/GDC as a promising SOEC fuel electrode.