Structural and Electrochemical Investigation of Anode-Supported Proton-Conducting Solid Oxide Fuel Cell Fabricated by the Freeze Casting Process

Abstract

Hierarchically oriented macroporous NiO–BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY7) anode-supporting layer (ASL) was developed using the freeze casting technique. The resulting freeze-cast structure was analyzed through scanning electron microscopy and X-ray computed tomography. A thin layer of BZCY7 was utilized as a proton-conducting electrolyte, whereas La_1.9Sr_0.1Ni_0.7Cu_0.3O_3−δ –gadolinium-doped ceria 10% Gd (LSNC–GDC10) was employed and evaluated as cathode layer. The performance of the cell was assessed by means of electrochemical impedance spectroscopy and I–V–P curves at various temperatures. Furthermore, as a point of comparison, a cell with an ASL was prepared using the dry pressing method, incorporating 20 wt.% graphite as a pore-forming agent. The freeze-cast anode-supported cell demonstrated a polarization resistance of 1.45 Ω cm² at 550°C and 0.29 Ω cm² at 750°C. Maximum achieved power densities were 0.189 and 0.429 W cm⁻² at 550 and 750°C, respectively. For the cell fabricated by the dry pressing method, the maximum power densities were 0.158 and 0.397 W cm⁻² at 550 and 750°C, respectively. Additionally, the tortuosity factor of the anode layer and the gas diffusion streamline in the direction of solidification were determined by using 3D X-ray tomography imaging and subsequent image processing.