Depth-direction analysis of nickel depletion in a Ni–gadolinia-doped ceria hydrogen electrode after steam electrolysis operation

We have examined the initial-stage degradation of a Ni–gadolinia-doped ceria (GDC) cermet hydrogen electrode prepared on GDC buffer layer stabilized-zirconia electrolyte supported cell during steam electrolysis operation at 800 °C. With use an air reference electrode, IR-free potential E and ohmic resistance side (RH2-side) were recorded. After −1.0 A cm−2 for 211 h, RH2-side increased appreciably, by 36 %, while value was nearly unchanged. It found via depth-direction analysis with focused ion beam-scanning microscopy that remaining percentage Ni decreased to ca. 60 % in between 1 3 µm from top layer, followed further decrease 42 0.5 µm. Since this suggests significant cathodic polarization within thin reaction zone, enlargement together stabilization contacting GDC, could be essential mitigate such degradation.