Theoretical charge density−potential isotherms have been derived
for anodic monolayers of honeycomb,
square, and triangular lattice geometry on the basis of the Ising
lattice model. For mercury sulfide
monolayers at the mercury/electrolyte interface, the charge−potential
isotherms have been measured in
the temperature region between 279 and 313 K. The critical
temperature of the monolayer was indicated
by a sudden change in the isotherm shape. From the critical
temperature, the lateral interaction energy
of the molecules in the HgS monolayer has been directly calculated.
On the basis of the Ising lattice gas
model, these isotherms can be theoretically well described with a
low-temperature series expansion of the
degree of coverage with respect to the activity of the solution phase
species. The adsorption energy and
number of electrons involved in the electrode reaction obtained are
practically independent of temperature.