State Key Lab of Nonferrous Metals & Processes , General Research Institute for Nonferrous Metal , Beijing 100088 , China.
Nano Lett. 2018 Mar 14;18(3):1668-1677. doi: 10.1021/acs.nanolett.7b04680. Epub 2018 Feb 20.
Grain boundaries (GBs) can be used as traps for solute atoms and defects, and the interaction between segregants and GBs is crucial for understanding the properties of nanocrystalline materials. In this study, we have systematically investigated the Pt segregation and Pt-oxygen vacancies interaction at the ∑3 (111) GB in ceria (CeO). The Pt atom has a stronger tendency to segregate to the ∑3 (111) GB than to the (111) and (110) free surfaces, but the tendency is weaker than to (112) and (100). Lattice distortion plays a dominant role in Pt segregation. At the Pt-segregated-GB (Pt@GB), oxygen vacancies prefer to form spontaneously near Pt in the GB region. However, at the pristine GB, oxygen vacancies can only form under O-poor conditions. Thus, Pt segregation to the GB promotes the formation of oxygen vacancies, and their strong interactions enhance the interfacial cohesion. We propose that GBs fabricated close to the surfaces of nanocrystalline ceria can trap Pt from inside the grains or other types of surface, resulting in the suppression of the accumulation of Pt on the surface under redox reactions, especially under O-poor conditions.
晶界（GBs）可以作为溶质原子和缺陷的陷阱，而偏析体与 GBs 的相互作用对于理解纳米晶材料的性质至关重要。在这项研究中，我们系统地研究了在 CeO 中的∑3（111）GB 处的 Pt 偏析和 Pt-氧空位相互作用。Pt 原子具有比（111）和（110）自由表面更强的倾向向∑3（111）GB 偏析，但倾向比（112）和（100）弱。晶格畸变在 Pt 偏析中起主导作用。在 Pt 偏析的 GB（Pt@GB）处，氧空位优先在 GB 区域的 Pt 附近自发形成。然而，在原始 GB 处，氧空位只能在贫氧条件下形成。因此，Pt 向 GB 的偏析促进了氧空位的形成，它们的强相互作用增强了界面结合力。我们提出，在纳米晶 CeO 的表面附近制造的 GB 可以从晶粒内部或其他类型的表面捕获 Pt，从而抑制在氧化还原反应下，特别是在贫氧条件下，Pt 在表面上的积累。
