J. Ennis et al., EFFECTIVE SURFACE-CHARGE FOR SYMMETRICAL ELECTROLYTES IN THE PRIMITIVE MODEL DOUBLE-LAYER, Electrochimica acta, 41(14), 1996, pp. 2115-2124
The asymptotic behaviour of the ion density distributions at a charged
planar interface in contact with a symmetric electrolyte is analysed
using the dressed ion theory of Kjellander and Mitchell. This gives a
rigorous way of defining an effective surface charge for such a double
layer, ie the surface charge that an ion ''sees'' at a large distance
from the interface. Numerical calculations of this effective surface
charge are performed using the anisotropic hypernetted chain approxima
tion for 1:1 and 2:2 electrolytes over a wide range of surface charges
. For monovalent ions we observe a saturation of the effective charge
when the real charge is increased-except for high concentrations and l
arge ions. For divalent ions we observe a reversal in the sign of the
effective surface charge as the actual surface charge increases. This
reversal is related to an over-compensation of the bare surface charge
in the first layer of counterions and the formation of an adjacent co
lon layer. Copyright (C) 1996 Published by Elsevier Science Ltd