The growth of Nin clusters and their interaction with cubic, monoclinic, and tetragonal ZrO2 surfaces–a theoretical and experimental study

Abstract

Ni/ZrO₂ catalysts are widely used in many reactions such as CO/CO₂ methanation and reforming of acetic acid. The kind of ZrO₂ phase plays a vital role in the catalytic properties of Ni/ZrO₂ 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 = 2–4) clusters with cubic ZrO₂ (c-ZrO₂) (111), monoclinic ZrO₂ (m-ZrO₂) (−111), and tetragonal ZrO₂ (t-ZrO₂) (101) surfaces. Adsorption of the Ni atom and all Ni_n (n = 2–4) clusters on zirconium dioxide surfaces was kinetically and thermodynamically preferred. Adsorption of Ni_n clusters on the m-ZrO₂(−111) surface is more stable than that on the t-ZrO₂(101) surface, and the t-ZrO₂(101) surface is more stable than the c-ZrO₂(111) surface. The aggregation ability of Ni_n clusters on different ZrO₂ surfaces and the isolated clusters follow the trend m-ZrO₂(−111) < t-ZrO₂(101) < c-ZrO₂(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 ZrO₂ 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.