Improved electrocatalytic properties of strontium-doped lanthanum nickelate cathodes by infiltrating samarium-doped ceria

Ce 0.8 Sm 0.2 O 1.9 oxygen-ion conductor was infiltrated into the backbone of pre-prepared porous La 1.8 Sr 0.2 NiO 4+δ electrode to enhance the electrocatalytic properties of the electrode for oxygen reduction reaction. The phase structure, microstructure, and electrocatalytic properties of the infiltrated electrodes were investigated in comparison with the pristine La 1.8 Sr 0.2 NiO 4+δ electrode. The Ce 0.8 Sm 0.2 O 1.9 infiltrated into the porous electrode backbone appeared as nano-sized particles deposited on La 1.8 Sr 0.2 NiO 4+δ grains. The primary steps of the electrode reaction were facilitated to varying extents with the assistance of oxygen vacancies in the Ce 0.8 Sm 0.2 O 1.9 . As a result, the overall reaction kinetics of the infiltrated electrodes was accelerated. The oxygen vacancy-assisted acceleration effect was leveled off at a Ce 0.8 Sm 0.2 O 1.9 loading of around 10 vol%. The leveling-off behavior was explained with respect to the microstructural evolution of the electrodes with increasing Ce 0.8 Sm 0.2 O 1.9 loading. The 10 vol% Ce 0.8 Sm 0.2 O 1.9 infiltrated electrode achieved appreciably improved electrocatalytic properties. Compared with the pristine La 1.8 Sr 0.2 NiO 4+δ electrode, the polarization resistance (~0.25 Ω cm 2 ) and overpotential (~53 mV at 200 mA cm −2 ) of the infiltrated electrode at 800 °C were reduced by ~40% and ~45%, respectively, while the exchange current density (~190 mA cm −2 ) was enhanced by ~66%.