Cu-substituted La2NiO4+δ as oxygen electrodes for protonic ceramic electrochemical cells

Abstract In order to overcome different tasks related to the thermal and chemical compatibility of functional solid oxide electrochemical cell materials, including those based on proton-conducting electrolytes, the search for new potential oxygen/steam electrodes is of great interest. In the present work, the Lа2Ni1–хCuxO4+δ (LNCx, x = 0. 0.1, 0.2 and 0.3) compounds, which constitute a class of Co-free and alkaline-earth elements (AEE)-free layered materials, were successfully synthesised and then studied as possible oxygen electrodes for protonic ceramic fuel cells. A complex of methods was used to comprehensively analyse the individual characteristics of LNCx (structural parameters, oxygen overstoichiometry, thermal expansion, total conductivity) as well as their properties in symmetrical and fuel cell architectures (polarisation resistance, performance). According to the obtained results, a slight degree of Ni with Cu substitution can be used for optimising the functional properties of LNCx, such as low sintering temperatures of cathode formation, low thermal expansion coefficients, good electronic conductivity and sufficient electrochemical activity (including under conditions of moisturised atmospheres). Therefore, the LNCx cathodes can be considered as one of the possible Co- and AEE-free candidates for intermediate-temperature protonic ceramic electrochemical cells.