Desolvation of Ions in Subnanometer Pores and Its Effect on Capacitance and Double-Layer Theory

John Chmiola , Céline Largeot (1) , Pierre-Louis Taberna (1) , Patrice Simon (1) , Yury Gogotsi

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

The study of charged solid–liquid interfaces, manifested as “double layers”, represents a problem of both practical and scientific importance. Double layers are present in all electrolyte solutions and have been traditionally studied using planar noble-metal electrodes and mercury drops. However, in the ionic channels in cells or the small-diameter pores of electrochemical double-layer capacitors (EDLCs),ions are in a very confined situation, which is different from that of a planar solid/electrolyte interface. By using nanoporous carbon with pores smaller than the size of an ion and a single associated solvent molecule, we show that the implicit assumption that double layers are governed only by ion/ electrode charge separation may be short-sighted. Other factor may play a more dominant role than previously thought, for example, increasing the confinement of the ions leads to an increase in the capacitance. Including the effect of partially desolvating ions in the current double-layer theory could lead to a better understanding of the behavior of ions in confined environments.

Mots clés: electrochemistry; ion pairs; nanostructures; porosity; solvation

Domaines: Matériaux

John Chmiola, Céline Largeot, Pierre-Louis Taberna, Patrice Simon, Yury Gogotsi. Desolvation of Ions in Subnanometer Pores and Its Effect on Capacitance and Double-Layer Theory. Angewandte Chemie International Edition, 2008, 47 (18), pp.3392-3395. ⟨10.1002/anie.200704894⟩. ⟨hal-03578220⟩