Strontium Free Cu-Doped La₂NiO₄ Oxides as Promising Oxygen Electrodes for Solid Oxide Electrolysis Cells

In this work, strontium-free copper-doped nickelates, La 2 Ni 1-x Cu x O 4 (x=0.1-0.3), were synthesized using solid state synthesis method and tested as potential oxygen electrodes in solid oxide electrolysis cells (SOEC). Similar to the parent compound, the Ruddlesden-Popper (RP) La 2 NiO 4 oxide, the Cu-doped compositions were confirmed to crystallize with tetragonal crystal structure with I 4/ mmm space group. The electrochemical performance of La 2 Ni 1-x Cu x O 4 electrodes was studied using Ni-YSZ electrode-supported button cells in SOEC mode and compared to the state-of-the-art (La 0.6 Sr 0.4 ) 0.95 Co 0.0.8 O 3-δ (LSCF)-doped ceria composite electrodes. Electrochemical tests were conducted at 750 o C with the Ni-YSZ hydrogen electrode exposed to 50% steam in hydrogen. The polarization resistance of SOEC with the La 2 Ni 0.8 Cu 0.2 O 4 (LNCuO-20) electrode was lower than that with LSCF. LNCuO-20 showed stable current density output over 800 hours tested, while cell with LSCF showed more degradation.