Fabrication and electrochemical modelling of 8YSZ and GDC10 freeze tape cast scaffolds for solid oxide cells (SOCs)

The morphology of electrodes in Solid Oxide Cells (SOCs) has a great impact on their mechanical stability during operation as well as transport properties and kinetics, which in turn affect electrode and cell performance. This study proposes a new experimental procedure based on the freeze tape casting technique for the manufacturing of graded porous electrodes for SOCs and analyses how the main processing parameters shape the final electrode microstructure. The use of water-based freeze tape casting has enabled the effective fabrication of hierarchical porous ionic backbones featuring the typical porosity of functional and supporting electrodes in a single tape. The porous samples are morphologically characterized by Environmental Scanning Electrode Microscopy (ESEM), X-Ray Computed Tomography (X-Ray CT) and computational tools to retrieve their microstructural characteristics. Subsequently, for the first time according to the authors knowledge, a Computational Fluid Dynamic (CFD) model has been developed to compare the gas transport properties of conventional spongy-like to graded porous electrodes of planar SOCs. The results presented strongly suggest that hierarchical porous electrodes enable higher performance by decreasing the voltage concentration losses and boosting the gas transfer within the electrode diffusion channels.