The mechanism and kinetics of Zn2+ electroreduction in the presence of octyltrimethylammonium bromide

Zn2+ electroreduction in the presence of octyltrimethylammonium bromide at a mercury electrode has been studied by voltammetric and impedance measurements in the range of 288–308 K. Kinetic data showed a two-step character of the electrode process and an inhibiting influence of octyltrimethylammonium bromide on Zn2+ electroreduction rate. Analysis of Tafel plots showed a change of electroreduction mechanism at a certain octyltrimethylammonium bromide concentration. Four models of electroreduction mechanisms were applied: two consecutive electron transfers (EE), ion transfer step followed by electron transfer (IE), ion transfer followed by adsorption (IA), and chemical step followed by electron transfer (CE). The results of investigations of Zn2+ reduction mechanism were combined with studies concerning activation energy for diffusion, standard reaction entropy, and activation enthalpy.