Three-dimensional microstructural characterization of solid oxide electrolysis cell with Ce 0.8 Gd 0.2 O 2 -infiltrated Ni/YSZ electrode using focused ion beam-scanning electron microscopy

CeO2-based surface modification is established as an effective strategy for improving the electrochemical performance of solid oxide electrolysis cells (SOECs), but the relevant mechanism has not been fully explored yet. Here, we employ focused ion beam-scanning electron microscopy to examine the microstructural evolution of bare nickel-based yttrium-stabilized zirconia (Ni/YSZ) electrode (reference cell) and Gd-doped CeO2 (CGO)-infiltrated Ni/YSZ electrode (optimized cell) before and after 100-h durability test. The initial current density of the optimized cell was 1.16 A cm−2 (at 1.3 V), which was 1.5 times larger than that of the reference cell. The voltage of the reference cell degraded dramatically due to a 1.16% reduction in the volume fraction of Ni, while the optimized cell showed a negligible degradation with a minor change in the volume fraction of Ni. It was confirmed that CGO nanoparticles formed a protective layer on the Ni surface during the electrolysis process, which prevented further evaporation of Ni. Overall, the infiltration of CGO into traditional Ni/YSZ electrode prevented decrease in the triple-phase boundary density and reduced the resistance by providing additional active sites for hydrogen evolution reaction. We believe that this work provides an efficient strategy for developing high-performance and long-term stable SOECs.