We evaluated the Ni-based catalyst surface properties during possible transformation pathways between its metallic, oxide, and carbide phases, causing catalytic deactivation. The study uses density functional theory (DFT) calculations to determine thermodynamics and reaction mechanisms of elementary reactions, and the ratings concept is introduced previously as an evaluation tool for the dry reforming reaction of methane (DRR) catalyst. The results for carbon atom adsorption strength and activation energy of higher coke formation (2C* ⇄ C–C* + *) suggest that on metallic surfaces, coke formation would be easy on the (111) facet but suppressed on the (100). Likewise, the carbide surface exposing metal atoms strongly binds to carbon and easily forms higher coke. In contrast, the oxide of Ni exhibits coke-resistant properties as it weakly adsorbs carbon. Finally, a ternary contour plot featuring metallic/oxide/carbide phases of Ni on the (111) facet was employed for identifying surface compositions, yielding highly reactive and stable DRR catalysts through a microkinetics model. It is found that, to become coke-resistant, the surface should contain less than 10% of carbide, whereas more than 75% of metallic surface is needed for the catalyst to be out of the coke formation zone, and to enter the coke removal zone, up to 80% of the metallic surface is required.

中文翻译：

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甲烷干重整过程中镍基催化剂演变的计算研究

我们评估了镍基催化剂在其金属，氧化物和碳化物相之间可能发生转化的路径中引起催化失活的表面性能。该研究使用密度泛函理论（DFT）计算来确定基本反应的热力学和反应机理，并且之前引入了评级概念作为甲烷（DRR）催化剂干重整反应的评估工具。较高的焦炭形成（2C *（C–C * + *）的碳原子吸附强度和活化能的结果表明，在金属表面上，焦炭的形成在（111）面上较为容易，而在（100）面上则受到抑制。同样，暴露于金属原子的碳化物表面与碳牢固结合并容易形成更高的焦炭。相反，Ni的氧化物由于弱吸附碳而具有耐焦炭性。最后，采用三重轮廓图，其特征为（111）面上的Ni的金属/氧化物/碳化物相用于识别表面成分，并通过微动力学模型产生高反应性和稳定的DRR催化剂。已发现，要变得耐焦化，表面应包含少于10％的碳化物，而要使催化剂脱离焦炭形成区并进入除焦，则需要金属表面的75％以上区域，最多需要80％的金属表面。