Phase field simulation of anode microstructure evolution of solid oxide fuel cell through Ni(OH)2 diffusion

Abstract

Microstructure evolution in a solid oxide fuel cell anode is strongly affected by operating condition. The detailed mesoscale evolution mechanism under operating condition is still under debate. Here we develop a phase-field model to simulate microstructure evolution through formation and diffusion of gaseous Ni(OH)2. We studied the coarsening kinetics and redistribution of Ni under different steam distributions and compare it to that under pure hydrogen condition. The results suggest that although the presence of a steady gradient of steam leads to redistribution of Ni, Ni(OH)2 formation and diffusion do not significantly change the Ni coarsening rate under strictly humid conditions, contrary to commonly reported hypotheses. It is concluded that competing mechanisms other than Ni(OH)2 diffusion must be responsible for the experimentally observed Ni redistribution and enhanced coarsening under humid conditions.