OS1610 Theoretical study on the effect of surface adsorbate on Ni surface diffusion
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To predict the long-term durability of solid oxide fuel cell (SOFC) anode, it is important to determine the surface diffusion coefficient of Ni. Although the effect of surface adsorbed species on surface diffusion is well known by both experimental and theoretical work, the available data for Ni surface diffusion assuming SOFC operating condition is not sufficient to simulate microstructural evolution. To understand the effect of surface adsorbed species on surface diffusion, it is important to identify the stable movable species on the surface. Therefore, we calculated the formation energy of Ni_nX_m cluster (X=H, O, and S) on Ni(111) surface by using density functional theory (DFT) calculation. In this study, the contribution of surface adsorbates to cluster formation energy is calculated by using energy gain of surface adsorbates by attaching to form cluster as a reference to binding energy on clean surface. From our calculation results, it is found that Ni_3S_3 cluster could be promising stable cluster and this is in agreement with experimental observation. For hydrogen NiH could be dominant cluster, while for oxygen NiO or Ni_3O are favorable on the Ni(111) surface. To analyze the detailed effect of surface adsorbed species on the Ni surface, we have to perform more precise calculation and to consider the temperature effect s.
