Atomic-Scale View at the Segregation of Alkali Metals toward the KTaO3(001) Perovskite Surface

Aji Alexander, Michele Reticcioli (Corresponding author), Llorenç Albons, Jesús Redondo, Marco Corrias, Igor Píš, Zhichang Wang, Viktor Johánek, Josef Mysliveček, Cesare Franchini, Dominik Wrana (Corresponding author), Martin Setvin

Publications: Contribution to journalArticlePeer Reviewed

Abstract

Perovskites exhibit outstanding performance in applications such as photocatalysis, electrochemistry, or photovoltaics, yet their practical use is hindered by the instability of these materials under operating conditions, specifically caused by the segregation of alkali cations toward the surface. The problem arises from the bulk strain related to different cation sizes, as well as the inherent electrostatic instability of perovskite surfaces. Here, we focus on atomistic details of the surface-driven process of interlayer switching of alkali atoms at the inorganic perovskite surface. We show that the (001) surface of KTaO3 cleaved at room temperature contains equally populated TaO2 and KO terminations, while the uncompensated polarity of these terminations promotes diffusion of KO from the subsurface toward the topmost surface layer at temperatures as low as 200 °C. This effect is directly probed at the atomic scale by Atomic Force Microscopy and the chemical properties of the resulting surfaces are investigated by the adsorption of CO and H2O. The experiments indicate that KO segregation is associated with the formation of K and O vacancies in the near-surface region, which is further supported by depth-dependent X-ray Photoelectron Spectroscopy measurements and Density Functional Theory calculations. Our study shows that the KO segregation influences the surface reactivity both toward CO and water, which was probed at the atomic scale.
Original languageEnglish
Pages (from-to)70010-70019
Number of pages10
JournalACS Applied Materials and Interfaces
Volume16
Issue number50
Early online date10 Dec 2024
DOIs
Publication statusPublished - 18 Dec 2024

Austrian Fields of Science 2012

  • 103018 Materials physics
  • 103020 Surface physics

Keywords

  • cation segregation
  • KTaO3
  • scanning probe microscopy
  • perovskites
  • solid oxide fuel cells
  • ORR
  • photoelectron spectroscopy
  • density functional theory
  • KTaO

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