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Solid oxide electrolysis cells (SOECs) are promising due to high electrolysis efficiency, but at high operating temperature T_OP ≥ 800 °C, they suffer from component inter-diffusion and particle agglomeration; selection of a sealant is also difficult. One way to avoid these problems is to decrease their T_OP. However, operation at intermediate T_OP ∼650 °C limits SOEC efficiency due to high overpotential at the air electrode. We use La₂NiO_4+δ (LNO) as an air electrode (anode) of an SOEC and compare its electrochemical performance and stability with those of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) in high-humidity H₂ atmosphere (80% H₂O + 20% H₂) at T_OP = 650 °C. LNO and LSCF anodes are screen-printed on a Gd_0.2Ce_0.8O_2−δ (GDC)/Y_0.16Zr_1.84O_2−δ (8 mol % yttria-stabilized zirconia, YSZ) bilayer electrolytes of fuel-electrode (cathode) supported cells. At open circuit condition, LSCF shows slightly smaller …