L. Blum et al., KINETIC-THEORY OF PHASE-TRANSITIONS AT ELECTRODE SURFACES - THE VOLTAMMOGRAM, Journal of electroanalytical chemistry [1992], 379(1-2), 1994, pp. 35-41
In recent papers we investigated the equilibrium statistical mechanics
of phase transitions at electrode interfaces. We derived the adsorpti
on isotherm theta = A(z, u)/[1 + A(z, u)]n which both z and u are func
tions of molecular parameters and the applied potential, which satisfi
es correct scaling to any desired accuracy. Implicit in our model is t
he approximation that each transition is treated as a single adsorbate
onto a sublattice of the available adsorption sites. This form can be
extended to include reaction and diffusion kinetics. We discuss the c
ases with diffusion (small bulk concentration) and without diffusion (
large bulk concentration). For the latter our model is solved mathemat
ically, and we obtain explicit formulae for the shifts of the peaks in
terms of the overall kinetic reaction constants. Asymptotic formulae
for slow scanning rates are given. We discuss the case of Cu/Au(111) u
nderpotential deposition (UPD) which is treated as a sequence of three
uncoupled phase transitions. Phenomenological rate constants are deri
ved fitting the theory to the experiments of Kolb and coworkers.