  Uncovering microstructure evolution mechanisms that accompany the long-term
operation of solid oxide fuel cells is a fundamental challenge in designing a
more durable energy system for the future. To date, the study of fuel cell
stack degradation has focused mainly on electrochemical performance and, more
rarely, on averaged microstructural parameters. Here we show an alternative
approach in which an evolution of three-dimensional microstructural features is
studied using electron tomography coupled with topological data analysis. The
latter produces persistent images of microstructure before and after long-term
operation of electrodes. Those images unveil a new insight into the degradation
process of three involved phases: nickel, pores, and yttrium-stabilized
zirconium.
