Stable Cu-Doped La₂NiO_4+δ Oxygen Electrodes for Solid Oxide Electrolysis Cells

A high-temperature solid oxide electrolysis cell (SOEC) technology is making significant progress toward commercialization, aiming to offer an efficient and cost-competitive path to hydrogen production from water. Improvements in the performance and durability of SOECs are still needed to extend the device's life. Strontium surface segregation in state-of-the-art Sr-containing oxides, lanthanum strontium cobalt iron oxide (LSCF) and lanthanum strontium cobalt oxide (LSC), and Sr reactivity with air gas impurities, such as chromium (Cr) and sulfur (S), leading to secondary phase formation suppresses the electrode activity. Developing Sr-free oxygen electrodes would alleviate these issues and improve the long-term device operation. In this work, we investigated the performance and stability of copper-doped La₂NiO_4+δ compositions with the Ruddlesden-Popper structure for oxygen evolution reaction (OER) using small- and large-area planar electrode-supported SOECs. Cells with the La₂Ni_0.8Cu_0.2O_4+δ (LNCuO-20) demonstrated a current density of up to 1.2 A/cm² at 750 °C at 1.3 V when operated in 90% steam in hydrogen versus air for over 1000 h. The materials' scalability and applicability for practical devices were validated by using 13 cm² active area cells.