The region in which non-specifically adsorbed ions are accumulated and distributed by the contrasting action of the electric field and thermal motion. Counter and co-ions in immediate contact with the surface are said to be located in the Stern layer. Ions farther away from the surface form the diffuse layer or Gouy layer.
See also: interfacial double-layer
Sources:
PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 618 (https://doi.org/10.1351/pac197231040577)
PAC, 1983, 55, 1251. 'Interphases in systems of conducting phases (Provisional)' on page 1261 (https://doi.org/10.1351/pac198355081251)