Effect of sulfur impurity on the stability of cubic zirconia and its interfaces with metals

Based on the density functional theory (DFT), we evaluate the effect of sulfur impurity on the stability of cubic zirconia (c-ZrO2) and its interfaces with metals (Ni, Cu). It is observed that, at low concentration, sulfur atoms have the tendency to locate at the zirconia surface, while at high concentration (similar to 23.0 wt%), homogeneous ZrOS structure can be obtained. We further predict that sulfur impurity in c-ZrO2 induces a reduction of the wettability between metals (Cu, Ni) and c-ZrO2. Thus, for Cu(011)/ZrO2(011) and Ni(011)/ZrO2(011) interfaces, the predicted reductions of the work of separations are up to 53%. This may have significant effect on the degradation of solid oxide fuel cell (SOFC) performance, when sulfur-containing fuels are used. The computational schemes developed in this study are useful for the search for more sulfur-tolerant metal/ceramic anode systems.