关键词: 镍, 二氧化锆, 模型催化剂, X射线光电子能谱, 紫外光电子能谱

Abstract:

The growth mode, electronic structure, and thermal stability of Ni nanoparticles on thin ZrO₂(111) film surfaces were investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy electron diffraction. Stoichiometric ZrO₂(111) thin films with thickness of 3 nm were epitaxially grown on a Pt(111) single-crystal surface. The results indicate that the growth of Ni vapor deposited on thin ZrO₂(111) films follows two-dimensional growth up to 0.5 ML (monolayer), followed by threedimensional growth (i.e., the Stranski-Krastanov growth mode). The Ni 2p_3/2 binding energy (BE) increases with decreasing Ni coverage. We used the Auger parameter method to differentiate the contributions to this BE shift from the initial-state and final-state effects. The main contribution to the Ni 2p core level BE shift is made by the final-state effect. However, at low Ni coverages, the initial-state effect also contributes. This suggests that at the initial stage of Ni growth on the ZrO₂(111) surface, Ni and ZrO₂ interact strongly, leading to charge transfer from Ni to the ZrO₂ substrate, with the appearance of partially positively charged Ni_δ+. Thermal stability studies of Ni/ZrO₂(111) model catalysts with two different coverages (0.05 and 0.5 ML) indicate further oxidation of Ni to Ni₂₊ and concurrent diffusion of Ni into the ZrO₂ substrate at elevated temperatures. These findings provide an atomic-level fundamental understanding of the interactions between Ni with ZrO₂, which is essential for identifying the structures of real ZrO₂-supported Ni catalysts.

Key words: Nickel, Zirconia, Model catalyst, X-ray photoelectron spectroscopy, Ultraviolet photoelectron spectroscopy