Spatially resolved electrochemical performance and temperature distribution of a segmented solid oxide fuel cell under various hydrogen dilution ratios and electrical loadings

Abstract

Inhomogeneous distributions are essential factors resulting in degradations of performance and durability of a solid oxide fuel cell (SOFC). In this work, effects of hydrogen dilution ratio and electrical loading on spatially distributed electrical performance and temperature of a segmented SOFC are investigated. Interpretations of local electrode processes and polarization resistances including ion transport, charge transfer, and gas diffusion during potentiostatic operation of the whole cell are obtained. The segment near the gas outlet has the worst initial performance owing to considerably large oxygen surface exchange and reaction overpotential. The temperature distribution obtained by spline interpolation of the experimental data demonstrates that diluting the fuel significantly decreases the average cell temperature at open circuit voltage, which indicates the parasitic combustion heat cannot be ignored. Strongly inhomogeneous distributions of current density and temperature in the cell are observed at low hydrogen ratio and operating voltage, which leads to locally harsh conditions near the gas outlet region. Furthermore, microstructure analysis reveals that the cathode segment adjacent to the gas outlet undergoes greater degradation resulting from oxygen depletion of the cell under low voltage. The results facilitate better understanding of the inhomogeneous electrochemical and temperature behaviors in different zones of a SOFC.