Atomic and Electronic Edge Structures of Monolayer Ceria on Pt(111)

Zhichao Huang, Cheng Han,* Yi-Yang Sun,* Kai Wu,* and Wei Chen* 

Abstract

Ceria (CeO₂) on Pt(111) has been widely studied in model catalysis due to the strong interfacial interaction between CeO₂ and platinum (Pt). Although extensive studies have been conducted on monolayered CeO₂ islands on the Pt(111) surface, the atomic and electronic structures of the island edge are still elusive. Herein, density functional theory calculations are employed to simulate the CeO₂(111) surface, the CeO₂ monolayer on Pt(111), and their edges. It is found that unlike the outmost O−Ce−O layer of CeO₂(111), the CeO₂ layer on Pt(111) is negatively charged and has non-zero magnetic moments. For the CeO₂(111) surface, the stoichiometric-type edge is the most stable, and the atomic orders of two edges from outside in are O_s²⁻−Ce⁴⁺−O_i²⁻ and O_i²⁻−Ce⁴⁺−O_s²⁻. For the CeO₂/Pt(111) surface, however, only at high temperature and under ultra-high vacuum conditions, the most stable edge is the same as thatof CeO₂(111). Otherwise, an oxygen-rich edge will be formed, where the atomic orders of two edges from outside in are O_i²⁻−O_s²⁻−Ce⁴⁺ and O_i²⁻−Ce⁴⁺−O_s²⁻. Furthermore, the adsorption energy of the K ion on the O_i²⁻−O_s²⁻−Ce⁴⁺-type edge is lower thanthat on the O_i²⁻−Ce⁴⁺−O_s²⁻-type edge, indicating a stronger adsorbability of the O_i²⁻−O_s²⁻−Ce⁴⁺-type edge toward positivelycharged ions. The edge structures proposed here and the corresponding electronic properties provide an insight into the interaction between CeO₂ and the Pt surface, which helps to understand the catalytic mechanism on the CeO₂/Pt(111) surface.