Solid Oxide Steam Electrolyzer: Gas Diffusion Steers the Design of Electrodes

Abstract

The hydrogen production by SOECs coupled with renewable energy sources is a promising route for the sustainability hydrogen economy. Multiphysics computing simulations appear to be the most efficient approaches to analyze the coupled mechanisms of SOEC operation. Using a relevant model, it is possible to predict the electrical behavior of solid oxide electrodes considering the current collector design. The influences of diffusion and grain diameter on cell performances can be investigated through 2D simulations, current–voltage characteristics, and current source distribution through electrodes. The simulation results emphasize that diffusion is linked to a relocation of the reaction away from the interface electrolyte/electrode, in the volume of the cathode. Furthermore, the current collector proves itself to be a great obstacle to gas access, inducing underneath it a shortage of steam. Inducing gradients of grain diameters in both anode and cathode drives the current sources to occur close to the electrode/electrolyte interface, thus decreasing ohmic losses and facilitating gas access. This approach shows the crucial importance of cathode microstructure as this electrode controls the cell response.