A high performing perovskite cathode with in situ exsolved Co nanoparticles for H₂O and CO₂ solid oxide electrolysis cell

La_0.5Ba_0.5Mn_1-xCo_xO_3-δ (x < 0.4) with a perovskite structure is studied as a cathode material for solid oxide electrolysis cells. The exsolution of metallic Co from the perovskite in a reducing atmosphere is in situ investigated. Co improves the electrical conductivity of La_0.5Ba_0.5MnO_3-δ in a reducing atmosphere, and facilitates the oxygen exchange reaction on the cathode surface. The cathode with in situ exsolved Co nanoparticles shows a high activity for both H₂O and CO₂ electrolysis. At 1.3 V, a single cell supported by a La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ electrolyte layer achieves H₂O electrolysis current densities of 0.46 and 1.01 A cm^-2 at 700 and 800 °C, respectively. A high CO₂ electrolysis current density of 0.88 A cm⁻² is also obtained with the same cell at 1.2 V and 850 °C with a Faradaic efficiency exceeding 90 %. The cathode exhibits a high stability for H₂O and CO₂ electrolysis. The co-electrolysis of H₂O and CO₂ with the cathode is also studied.