Nanocomposite electrodes for high current density over 3 A cm^-2 in solid oxide electrolysis cells

Solid oxide electrolysis cells can theoretically achieve high energy-conversion efficiency, but current density must be further increased to improve the hydrogen production rate, which is essential to realize widespread application. Here, we report a structure technology for solid oxide electrolysis cells to achieve a current density higher than 3 A cm^-2, which exceeds that of state-of-the-art electrolyzers. Bimodal-structured nanocomposite oxygen electrodes are developed where nanometer-scale Sm_0.5Sr_0.5CoO_3-δ and Ce_0.8Sm_0.2O_1.9 are highly dispersed and where submicrometer-scale particles form conductive networks with broad pore channels. Such structure is realized by fabricating the electrode structure from the raw powder material stage using spray pyrolysis. The solid oxide electrolysis cells with the nanocomposite electrodes exhibit high current density in steam electrolysis operation (e.g., at 1.3 V), reaching 3.13 A cm^-2 at 750 °C and 4.08 A cm^-2 at 800 °C, corresponding to a hydrogen production rate of 1.31 and 1.71 L h^-1 cm^-2 respectively.