The sulfur poisoning properties of the nickel/oxygen-enriched yttria-stabilized zirconia (denoted as Ni/YSZ + O) with or without interface O vacancy are studied using the first-principles method based on density functional theory. The effects of the extra O atom at the subsurface vacancy of Ni/YSZ are focused. It is found that S at the Ni/YSZ + O can diffuse easily away from the interface oxygen to the top Ni layer sites. With the formation of O vacancy at the Ni/YSZ + O interface (denoted as Ni/(YSZ + O)-O-v), the adsorbed S prefers to diffuse back to the Ni/YSZ interface O vacancy. Compared with Ni/YSZ-O-v, the Ni/(YSZ + O)-O-v can effectively not only weaken the S adsorption at the interface O vacancy site, but also improve the diffusion of S out of the interface O vacancy. Therefore, the Ni/YSZ + O can help to alleviate the sulfur poisoning at the interface O vacancy site as compared with the Ni/YSZ. (C) 2015 Elsevier B.V. All rights reserved.