Enhanced performance of reversible solid oxide cells using high-surface-area nanostructured thin-film oxygen electrodes

Reversible solid oxide cells (rSOCs) are highly efficient electrochemical energy conversion devices which provide a promising pathway to green energy challenges. An essential factor for achieving high performance and enabling their commercialization is the selection of the oxygen electrode material, as it significantly impacts polarization resistance at intermediate-to-low temperatures (< 700 °C). La₂NiO_4+δ (L2NO4) stands out as a promising material due to its mixed ionic and electronic conductivity, high oxygen exchange activity and low activation energy. In this work, L2NO4 nanostructured thin films were first optimized in symmetrical cells reaching polarization resistance values as low as 0.07 Ω cm² at 600 °C. The films were then integrated into state-of-the-art commercial button cells and tested in both fuel cell (SOFC) and electrolysis (SOEC) modes revealing extremely high performance, with a power density of 1.2 and 1.3 W cm⁻² at 0.7 V at 670 and 725 °C, respectively, in SOFC mode, and a current density of 1.2 A cm⁻² at 1.3 V and 670 °C in SOEC mode. The superior efficiency compared to commercial cells emphasizes the nano-engineering strategy for enhancing performance while minimizing the use of critical raw materials. This is achieved by employing approximately 10–15 times less oxygen electrode material (g cm⁻²), a crucial factor for the sustainable development of these devices.