La2Ni1−xCoxO4+δ (x = 0.0, 0.1 and 0.2) based efficient oxygen electrode materials for solid oxide electrolysis cells

The present study is focused on the development of alternative oxygen electrodes for Solid Oxide Electrolysis Cells (SOECs). Rare earth nickelates with general formula Ln 2 NiO 4+δ (Ln = La, Pr or Nd) have shown good performance as oxygen electrodes with various electrolytes. Among them, La 2 NiO 4+δ is most stable nickelate by itself however its electrochemical performance is lower compare to Pr 2 NiO 4+δ . Therefore, to further enhance the physico-chemical properties, electrochemical performance of La 2 NiO 4+δ as SOECs oxygen electrode, herein, we have performed the substitution of nickel with cobalt. Three compositions ( x = 0.0, 0.1 and 0.2) were mainly considered and completely characterized using several techniques. The symmetrical as well as single cells were then prepared and electrochemically characterized using DC- and AC-techniques in the temperature range 700–900 °C. The electrode reaction mechanism was also investigated by recording the impedance spectra at different p O 2 . With cobalt substitution, an improvement in electrochemical performance as well lower degradation rate is observed during long term SOEC operation at −1 A⋅cm −2 current density at 800 °C with 50% H 2 and 50% H 2 O feed gas mixture. • La 2 Ni 1-x Co x O 4+δ nickelates as O 2 -electrode materials for SOEC is reported first time. • These nickelates are stable and always over-stoichiometric in air/O 2 atmospheres. • Single cell with La 2 Ni 0.8 Co 0.2 O 4+δ oxygen electrode shows the best cell performance. • Lowest degradation is observed for La 2 Ni 0.8 Co 0.2 O 4+δ electrode under SOEC operation.