Ni/ZrO 2 catalysts are widely used in many reactions such as CO/CO 2 methanation and reforming of acetic acid. The kind of ZrO 2 phase plays a vital role in the catalytic properties of Ni/ZrO 2 catalysts that depend on the interface between zirconia and supported Ni particles. Periodic density functional theory was applied to systematically investigate the interaction of a single Ni atom and Ni n (n ¼ 2-4) clusters with cubic ZrO 2 (c-ZrO 2 ) (111), monoclinic ZrO 2 (m-ZrO 2 ) (À111), and tetragonal ZrO 2 (t-ZrO 2 ) (101) surfaces. Adsorption of the Ni atom and all Ni n (n ¼ 2-4) clusters on zirconium dioxide surfaces was kinetically and thermodynamically preferred. Adsorption of Ni n clusters on the m-ZrO 2 (À111) surface is more stable than that on the t-ZrO 2 (101) surface, and the t-ZrO 2 (101) surface is more stable than the c-ZrO 2 (111) surface. The aggregation ability of Ni n clusters on different ZrO 2 surfaces and the isolated clusters follow the trend m-ZrO 2 (À111) < t-ZrO 2 (101) < c-ZrO 2 (111) < isolated cluster. Therefore, Ni n clusters can have a better dispersion and can inhibit aggregation due to the support. What is more, the single-phase ZrO 2 was synthesized and loaded with an equivalent content of active Ni components. The experimental results obtained by X-ray photoelectron spectroscopy analysis support the hypothesis that has been deduced.

CO oxidative coupling to dimethyl oxalate (DMO) on Pd(111), Pd-Cu(111) and Pd-Al(111) surfaces was systematically investigated by means of density functional theory (DFT) together with periodic slab models and micro-kinetic modeling. The binding energy results show that Cu and Al can be fine substrates to stably support Pd. The favorable pathway for DMO synthesis on these catalysts starts from the formation of two COOCH intermediates, followed by the coupling to each other, and the catalytic activity follows the trend of Pd-Al(111) > Pd(111) > Pd-Cu(111). Additionally, the formation of DMO is far favorable than that of dimethyl carbonate (DMC) on these catalysts. The results were further demonstrated by micro-kinetic modeling. Therefore, Pd-Al bimetallic catalysts can be applied in practice to effectively enhance the catalytic performance and greatly reduce the cost. This study can help with fine-tuning and designing of high-efficient and low-cost Pd-based bimetallic catalysts.

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