Density functional theory study of dopant effect on sintering in the anode of solid oxide fuel cell

Sintering of Ni particles in the Ni/Y-doped ZrO₂ anode is a major obstacle to the widespread use of solid oxide fuel cell. In this study, we investigated the dopant effect on the diffusion of a Ni atom on the ZrO₂ surface with dopants (Y and Al) by density functional theory calculations in order to inhibit the sintering. The most stable adsorption sites of the Ni atom on the Al-doped and Y-doped ZrO₂ surfaces are the vicinity of the twofold-coordination oxygen atom and the vicinity of an oxygen vacancy, respectively. It is found that the most stable adsorption energy on the Al-doped ZrO₂ surface is larger than that on the Y-doped ZrO₂ surface. The analysis of diffusion path based on the potential energy surfaces of the Ni atom on the two surfaces shows that the energy barrier for the diffusion of the Ni atom on the Al-doped ZrO₂ surface is larger than that on the Y-doped ZrO₂ surface. The diffusion of the Ni atom on the Al-doped ZrO₂ surface is more difficult than that on the Y-doped ZrO₂ surface. This is because the Ni atom strongly bound to the twofold-coordination oxygen atom and the Ni atom is constrained in the Al-doped ZrO₂ surface. Thus, the Ni sintering on the Al-doped ZrO₂ surface is inhibited compared to that on the Y-doped ZrO₂ surface.