Reversible Solid Oxide Cells, a key technology for the future energy scenario: the role of the air electrode

With the widespread diffusion of renewable energy sources (RES), the conversion of excess power into fuels and chemicals is considered one of the most promising schemes in the future energy scenario. However, RES applicability relies on energy levelling systems, able to balance their intrinsic intermittent nature [1]. In this context the future impact of reversible Solid Oxide Cells (rSOCs) is unquestionable [2]. The rSOCs operating temperature makes the energy conversion very efficient and not dependent on critical raw materials. On the other hand, this operating condition is responsible of fast degradation processes. The current trend focuses on decreasing their operation temperature to mitigates the negative effects of thermal cycles on system long term reliability. However, this temperature lowering reduces the electrode kinetics. Particularly sensitive to this aspect is the kinetics of the oxygen reaction at SOC air electrode, which has a big impact on the overall system losses. This paper recalls some results of the authors on SOC air electrodes obtained with well-known perovskite electrocatalysts like manganites [3, 4] and cobaltites [5] that thanks to original processing procedures show enhanced electrochemical activity and improved stability. From this starting point, recent findings on cobalt-free ferrites will be presented focusing also on the electrode architectures as a central key point to fruitfully exploit material properties and to manage their constrain.