Numerical Modeling of Nickel-Impregnated Porous YSZ-Supported Anodes and Comparison to Conventional Composite Ni-YSZ Electrodes

Abstract

SOFC anodes fabricated by Ni-impregnation of porous YSZ support have a microstructure distinct from the much studied/modeled conventional Ni-YSZ composite anodes. The Ni-infiltrated anode forms a semi-continuous network of electron conducting Ni-phase on the YSZ support framework. In this study, the Ni phase was modeled as a two-dimensional film on the porous YSZ structure and percolation theory was utilized to evaluate the following features that are unique to Ni-impregnated YSZ anodes - (i) the electrical conductivity of a semi-continuous film of nickel formed on the YSZ support framework, and (ii) the active TPBs in a nickel impregnated system based on the semi-continuous nature of the nickel phase. The effect of Ni loading relative to the total pore volume on electronic conductivities and TPB densities is evaluated and compared to literature.

Formation, Performance, and Long-Term Stability of Nanostructured Ni-YSZ Thin Film Electrodes

“…Porosity generation in NiO-YSZ anodes upon reduction into Ni-YSZ has been commonly observed, ,− which is ascribed to the smaller molar volume of Ni than that of NiO. Since the NiO-YSZ films consisted of nanoparticles (Figure c,e), the porosity generated, due to the reduction of NiO to Ni, was also of nanoscale morphology (Figure d,f).…”

“…One alternative route reported for fabricating Ni-YSZ composite anodes is infiltration. ,− In this technique, a liquid precursor containing Ni cations is deposited onto a porous YSZ scaffold layer, which is then infiltrated into the porous structure through capillary action. The liquid Ni precursor in the scaffold is then decomposed to form solid NiO, the morphology of which depends strongly on the nature of the precursor .…”

A Mathematical Model for Prediction of Long-Term Degradation Effects in Solid Oxide Fuel Cells

“…Hardjo et al studied the degradation of anode electrical conductivity as a result of a decrease in the number of nickel particles and an increase in their size. 31,32 Although pore size is generally assumed to be constant in degradation models, changes in pore diameter over time can affect SOFC performance by altering the area of active regions, TPB density, and mass diffusivity at the anode. 5−8 The model by Divisek and Wilkenhoner was selected for calculation of anode pore size.…”

“…In addition to these factors, it is also important for degradation models to consider other consequences of nickel coarsening and oxidization, such as changes in pore size, degradation of anode electrical conductivity, and changes in area of active regions. Hardjo et al studied the degradation of anode electrical conductivity as a result of a decrease in the number of nickel particles and an increase in their size. , Although pore size is generally assumed to be constant in degradation models, changes in pore diameter over time can affect SOFC performance by altering the area of active regions, TPB density, and mass diffusivity at the anode. − The model by Divisek and Wilkenhöner was selected for calculation of anode pore size . Then, it was updated by the size of Ni particles after coarsening to measure the changes in the pore size.…”

A numerical study of infiltrated solid oxide fuel cell electrode with dual‐phase backbone

“…Several models for infiltrated SOFC electrodes have been proposed in the literature. Hardjo used a 2‐dimensional model to simulate the infiltration process of Ni‐infiltrated YSZ anodes and evaluated electronic conductivity and TPB length. One of their findings is that the TPB length reaches a maximum at around 15% infiltration loading before declining significantly.…”