Structural Stability of NaCl and KCl Cleavage Surfaces in the BMIM-PF6 Ionic Liquid

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Ebru Cihan - , Single Molecule Machines (Junior Research Group) (cfaed) (Author)
  • Natalia Janiszewska - , Jagiellonian University in Kraków (Author)
  • Kamil Awsiuk - , Jagiellonian University in Kraków (Author)
  • Qingwei Gao - , Shanghai University of Electric Power (Author)
  • Rong An - , Nanjing University of Science and Technology, Shandong Laboratory of Yantai Advanced Materials and Green Manufacture (Author)
  • Ronen Berkovich - , Ben-Gurion University of the Negev (Author)
  • Enrico Gnecco - , Jagiellonian University in Kraków (Author)

Abstract

We have investigated the evolution of freshly cleaved NaCl(100) and KCl(100) surfaces exposed to the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) and repeatedly scraped using atomic force microscopy (AFM). The response of the two surfaces to the IL is completely different. On NaCl, the cleavage step edges are slightly eroded, and the surface is progressively smoothed by the AFM tip. These changes are accompanied by a continuous increase in the friction force. On KCl, a dramatic dissolution of the surface is observed immediately after bringing it into contact with the IL. The surface is then smeared along the fast scan direction in the area scratched by the tip and even beyond. An increase in the friction force is also observed but only in the beginning of the surface modification process. Crystallites (∼100–200 nm in size) are observed all over the unscratched areas of KCl but not of NaCl. This result is supported by molecular dynamics simulations and Raman spectroscopy, which indicate a much stronger interaction of the IL with the KCl surface and, respectively, the formation of a BMIM-PF6 solid phase on it. The analysis performed on the model systems presented here could be extended to other ionic crystal surfaces in contact with ILs, the possible degradation of which must be evaluated in view of their use in catalysis and energy storage applications.

Details

Original languageEnglish
Pages (from-to)13793-13799
Number of pages7
JournalLangmuir
Volume41
Issue number22
Publication statusPublished - 10 Jun 2025
Peer-reviewedYes

External IDs

Scopus 105006845813
ORCID /0000-0002-1747-3838/work/188860383
PubMed 40445222

Keywords