Crowding and anomalous capacitance at an electrode-ionic liquid interface observed using operando X-ray scattering

Miaoqi Chu, Mitchell Miller, Pulak Dutta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Room temperature ionic liquids are widely recognized as novel electrolytes with properties very different from those of aqueous solutions, and thus with many potential applications, but observing how they actually behave at electrolytic interfaces has proved to be challenging. We have studied the voltage-dependent structure of [TDTHP]+[NTF2]- near its interface with an electrode, using in situ synchrotron X-ray reflectivity. An anion-rich layer develops at the interface above a threshold voltage of +1.75 V, and the layer thickness increases rapidly with voltage, reaching ~6 nm (much larger that the anion dimensions) at +2.64 V. These results provide direct confirmation of the theoretical prediction of "crowding" of ions near the interface. The interfacial layer is not purely anionic but a mixture of up to ~80% anions and the rest cations. The static differential capacitance calculated from X-ray measurements shows an increase at higher voltages, consistent with a recent zero-frequency capacitance measurement but inconsistent with ac capacitance measurements.

Original languageEnglish (US)
Pages (from-to)175-180
Number of pages6
JournalACS Central Science
Volume2
Issue number3
DOIs
StatePublished - Mar 23 2016

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

Fingerprint

Dive into the research topics of 'Crowding and anomalous capacitance at an electrode-ionic liquid interface observed using operando X-ray scattering'. Together they form a unique fingerprint.

Cite this