Mechanism of improved electrochemical performance of anode-supported solid oxide fuel cells by mesostructural modification of electrode–electrolyte interface

Abstract

The mechanism whereby structural modification on the mesoscale order (10–100 μm) improves the electrochemical performance of anode-supported solid oxide fuel cells (SOFCs) is elucidated. After preparing two types of anode-supported SOFC having different electrode–electrolyte interfacial areas, we carry out their structural analyses and electrochemical characterization. Next, we develop a two-dimensional (2D) numerical model in which the structures of the cells are implemented and then verify its validity by comparing experimental and simulation results. It is found that the structural features in the mesoscale-modified cell, such as interfacial area enlargement and thickness inhomogeneity, cause nonuniform distributions of physicochemical quantities that contribute to electrochemical reactions. Consequently, the decreases in the ohmic and activation overpotentials of the mesoscale-modified cell relative to the flat cell are respectively larger and smaller than those estimated under the assumptions that the ionic and charge-transfer current densities are uniformly distributed in a cell. Moreover, the ionic current density distribution has a strong nonuniformity at a high current density, leading to a large relative decrease in ohmic loss. Furthermore, the cell overpotential is more reduced at a higher current density; thus, the mesostructural modification of anode-supported SOFCs can lead to a higher cell performance.