Performance and stability of Ruddlesden-Popper La2NiO4+δ oxygen electrodes under solid oxide electrolysis cell operation conditions

Ruddlesden-Popper La2NiO4+δ (LNO) oxygen electrodes were investigated under solid oxide electrolysis cell (SOEC) operation conditions. The electrochemical performance of LNO was measured in both solid oxide fuel cell (SOFC) and SOEC modes at 750 °C in air. The results suggest that LNO oxygen electrodes exhibit high electrochemical activity and the processes related to oxygen adsorption, dissociation and diffusion dominate the oxygen evolution reaction on the electrodes. Electrical conductivity relaxation (ECR) measurements imply that LNO shows better oxygen surface exchange performance than conventional LSM and LSCF electrodes, because of its special crystal structure with flexible non-stoichiometric oxygen. Significant performance degradation was observed during polarization at 500 mA cm−2 and 750 °C in the SOEC mode for 48 h. XRD and XPS results confirmed that high-order Ruddlesden-Popper La3Ni2O7 and La4Ni3O10 phases have great contributions to the performance degradation of LNO oxygen electrodes related to anodic current polarization at 500 mA cm−2 and 750 °C.