Historical development of double layer models
The earliest model of the electrical double layer is usually attributed to Helmholtz (1879). Helmholtz treated the double layer mathematically as a simple capacitor, based on a physical model in which a single layer of ions is adsorbed at the surface.
Later Gouy and Chapman (1910-1913) made significant improvements by introducing a diffuse model of the electrical double layer, in which the potential at a surface decreases exponentially due to adsorbed counter-ions from the solution.
The current classical electrical double layer is the Gouy-Chapman-Stern model, which combines the Helmholtz single adsorbed layer with the Gouy-Chapman diffuse layer. Important approximations used in this model are:
- Ions are effectively point charges
- The only significant interactions are coulombic
- Electrical permittivity is constant throughout the double layer
- The solvent is uniform at the atomic scale
See also:
