A highly active and durable electrode with in situ exsolved Co nanoparticles for solid oxide electrolysis cells

Abstract

This work demonstrates that a double perovskite Sr2Fe1.3Co0.2Mo0.5O6-δ (SFCM) with exsolved Co nanoparticles has enhanced the reaction activity and durability of solid oxide electrolysis cells (SOECs) for electrolysis of H2O, CO2 or CO2–H2O mixture. The Co nanoparticles are in situ exsolved from the parental SFCM in 10% H2–90% N2, as confirmed by analyses of XRD, XPS, TEM and SEM, and they can keep stable in the atmosphere of 50% CO2–50% H2 or 50% CO2–50% CO. The cells with a configuration of SFCM‖La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM)‖SFCM demonstrate excellent electrochemical performances in electrolysis. For example, polarization resistances of the electrolyzer are as low as 0.24 Ω cm2 in 50% H2O-50% H2 under open-circuit voltage. In addition, the cells for CO2/H2O co-electrolysis at 800 °C shows a reasonable durability at different current densities of 0.3, 0.6, 0.9, 1.2, 1.5, 1.8 A cm−2, and 1.0 A cm−2 for ~110 h s. Electrochemical impedance spectroscopy and distributed relaxation time analysis indicates that electrode surface exchange and diffusion are the rate-limiting steps in the electrolysis of CO2/H2O, and the resistances of these steps can be significantly decreased by the in situ exsolved Co nanoparticles from SFCM electrode, thereby providing higher activity and better stability.