Correlation between the thickness of NiFe2O4 and hydrogen production performance for solid oxide electrolysis cells

Abstract

This study investigates the influence of cathode thickness on the performance of solid oxide electrolysis cells with 20% H2O–80% N2 at 800 °C. NiFe2O4 (NFO) was used as the cathode material. The thickness of the cathode was controlled to be approximately 10–70 μm. NFO can be considered as a mixed electron and oxide-ion conductor because the cell performance changes with its thickness. Furthermore, the ohmic and polarization resistances decreased significantly when the cathodic thickness increased to 30 μm. The performance improvement was because of the increase in conduction networks. In addition, the electrochemical reaction area increases to lower polarization resistances. However, with a cathodic thickness of 30–70 μm, the ohmic resistance increased significantly because the conduction paths became longer from the current collector to the reaction area. In addition, the polarization resistance increased slightly owing to the difficulty in gas diffusion.