inner layer (compact layer)

in electrochemistry
https://doi.org/10.1351/goldbook.I03049
The region between the outer Helmholtz plane and the interface.
Source:
PAC, 1983, 55, 1251. 'Interphases in systems of conducting phases (Provisional)' on page 1261 (https://doi.org/10.1351/pac198355081251)