Vm. Golovenko et al., MASS-TRANSPORT IN ELECTROCHEMILUMINESCENT SOLUTIONS - CONVECTIVE MASS-TRANSFER IN ELECTROCHEMILUMINESCENCE CELLS, Russian journal of electrochemistry, 30(9), 1994, pp. 1036-1041
A theoretical study is presented of the electrochemiluminescence (ECL)
occurring in pseudomono-molecular electron-transfer reactions in cell
s with electrolyte convection effected by a rotating-disc electrode or
by pumping the active medium for potentiodynamic electrolysis. Solvin
g the convective mass-transport equations with appropriate initial and
boundary conditions yields the relationships that describe the coordi
nate and time distribution of the concentration of electrogenerated ra
dical cations A(+) of electrochemiluminophor (depolarizer) and, theref
ore, the concentration of ECL emitter (singlet-excited electrochemilum
inophor molecules) in terms of a unique relation between the two quant
ities. It was shown that fast subsequent chemical reactions of the ele
ctron transfer from electrochemically inactive species B (nucleophile)
to electrophilic species A(+), which are accompanied by emission of E
CL photons, occur within the kinetic reaction layer where the distribu
tion of species A(+) is virtually unaffected by convection. The transi
ent time required for attaining the steady-state state distribution of
the A(+) concentration was derived, and conditions under which diffus
ion and convective mass transfer become comparable were determined. Th
e relationship between the ECL intensity and the electrode rotation sp
eed (or the speed of pumped liquid) obtained in our model was noted to
be at odds with the relationships that were obtained earlier by Maloy
et al. A qualitative interpretation of the ECL experiments in cells w
ith convective mass transfer is presented.