Long Term Durability Investigation of Cu-Doped La₂NiO₄ Oxygen Electrodes in Solid Oxide Electrolysis Cells

State-of-the-art oxygen electrodes in SOECs, lanthanum strontium cobalt iron oxide (LSCF) and lanthanum strontium cobalt oxide (LSC), contain strontium. Undesired reactivity and migration of Sr cations during long-term operation was found to be detrimental to the electrochemical performance as they triggered formation of multiple oxide phases, including insulating phases and electrode or barrier layer delamination. Developing alternative electrodes that are devoid of Sr is very important for long-term operation of SOECs. In this work, we synthesized and evaluated properties of La 2 NiO 4 -based compositions with a Ruddlesden-Popper structure. The Cu-doped La 2 NiO 4 compositions made of nano-size particles exhibited an enhanced electrochemical performance when tested in SOECs during steam electrolysis for hydrogen production. Long-term durability of these electrodes was studied using planar Ni-YSZ electrode-supported cells with an active area of 1.5 (button cells) and 13 cm 2 (2.5 cm x 5 cm cells). Compared to the Sr-containing electrodes, the La 2 Ni 0.8 Cu 0.2 O 4 (LNCuO-20) demonstrated lower degradation rate at 1.3 Volt resulting in a current density over 1 A/cm 2 at 750⁰C. Chrome and sulfur tolerance of these electrodes during long term operation will be discussed as well.