M. Schwarz et al., TEMPERATURE-DEPENDENCE OF THE TAFEL SLOPE - THE REDUCTION OF BROMATE IN ALKALINE MEDIA, Journal of electroanalytical chemistry [1992], 361(1-2), 1993, pp. 193-201
The temperature dependence of the transfer coefficient of bromate redu
ction at pH > 12 is studied in several supporting electrolytes (0.1-1
M LiCl, NaCl, KCl, CsCl) in the temperature range 0-90-degrees-C at th
e dropping mercury electrode. The transfer coefficient is found to be
independent of temperature. The treatment of the raw current-potential
data includes correction for the ohmic drop in solution, calculation
of the activation controlled current density from the ratio I/I(d) thr
ough Koutecky's tabulated X values and diffuse-double-layer correction
according to Frumkin's theory. The Tafel lines are linear over four t
o six decades of activation current density. Strong emphasis is placed
on accuracy. A small but definite dependence of the transfer coeffici
ent on the cation of the supporting electrolyte is found (0.61, 0.64,
0.67 and 0.67 for Li+, Na+, K+ and Cs+ respectively). The diffuse doub
le-layer effects are suitably accounted for by Frumkin's theory. The c
orrected reaction rates for the individual electrolytes, except for Cs
Cl, are independent of ionic strength. A negative apparent enthalpy of
activation is observed with all electrolytes along the polarographic
wave.