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We discovered dislocations in the electrical double layer (EDL) in a room-temperature ionic liquid (RTIL) by direct 3D atomic force microscopy (AFM) imaging with molecular resolution. This unexpected discovery sheds new light on complex dynamics of solid-liquid interfaces and provides insight into their electrochemical behavior.
Scientific Achievement
Significance and Impact
- The unexpected discovery of topological defects in RTILs within the EDL at a carbon (graphite) surface fundamentally changes our conceptual understanding of the EDL and helps explain anomalous observations, e.g. slow charge/discharge dynamics of electrochemical capacitors. This also necessitates new theoretical models of the EDL, allowing for lateral topological defects parallel to electrode-electrolyte interfaces.
Research Details
- 3D force mapping was performed on highly oriented pyrolytic graphite (HOPG) in Emim+ Tf2N- RTIL using atomic force microscopy.
- Dislocation-type defects in the RTIL were observed spanning 50-80 nm.
- Statistical analysis allowed for a qualitative measure of the degree of order in the ionic liquid structure as a function of distance to the surface.
- An increase in disorder is observed throughout the defects.
- Molecular dynamics simulations reveal that step-edge defects on the carbon surface result in only short range changes in the RTIL