A Three-Dimensional Microstructure-Scale Simulation of a Solid Oxide Fuel Cell Anode—The Analysis of Stack Performance Enhancement After a Long-Term Operation

Abstract

In this research, we investigate the connection between an observed enhancement in solid oxide fuel cell stack performance and the evolution of the microstructure of its electrodes. A three dimensional, numerical model is applied to predict the porous ceramic-metal electrode performance on the basis of microstructure morphology. The model features a non-continuous computational domain based on the digital reconstruction obtained using focused ion beam scanning electron microscopy (FIB-SEM) electron nanotomography. The Butler–Volmer equation is used to compute the charge transfer at reaction sites, which are modeled as distinct locally distributed features of the microstructure. Specific material properties are accounted for using interpolated experimental data from the open literature. Mass transport is modeled using the extended Stefan–Maxwell model, which accounts for both the binary, and the Knudsen diffusion phenomena. The simulations are in good agreement with the experimental data, correctly predicting a decrease in total losses for the observed microstructure evolution. The research supports the hypothesis that the performance enhancement was caused by a systematic change in microstructure morphology.

Microstructure Evolution in a Solid Oxide Fuel Cell Stack Quantified with Interfacial Free Energy

“…The relationship between the phase distribution of the postdegradation microstructures and their electrochemical performance was discussed in our previous paper [5] for a similar planar SOFC stack. In that case, the reduction of the cell's overpotential was observed due to the decrease of pore tortuosity-a development predicted by several PFM-based analyses reported on in the literature.…”

“…Understanding the SOFC microstructure evolution is aided by empirical studies involving long-term stack performance experiments, combined with the analysis of microstructure changes which occurred over during the experiments. Monaco et al [1] conducted X-ray holotomography-based microstructure analyses for Solid Oxide Cells operating for periods ranging from 1000 h to 15,000 h. Brus et al performed two independent long performance tests in which an enhancement, rather than deterioration of performance was observed [2][3][4][5].…”

Thin Solid Film Electrolyte and Its Impact on Electrode Polarization in Solid Oxide Fuel Cells Studied by Three-Dimensional Microstructure-Scale Numerical Simulation

“…The cell analyzed for the purpose of this study is composed of a Ni-YSZ anode, a YSZ electrolyte, and an LSCF-GDC cathode. The microstructure reconstructions discussed in this paper are taken from our previous study [21,27]. The parameters of each electrode are discussed in Table 1.…”

“…More details regarding the mathematical, and the numerical model have been provided in our previous papers [19,21].…”

“…The cross-electrode interactions are present if there exists a difference between the performance predicted by a model which assumes uniform current flow through the electrolyte, and the model in which no such assumption is made. Previously we have constructed and validated a model of this type, using it for the purpose of analyzing heterogeneity [19,20], and aging phenomena [21]. However, in these studies, the electrodes were investigated individually.…”