Abstract
Potential step experiments were carried out with a Au disc electrode in alkaline sodium borohydride solutions of varying concentrations and temperatures. Analysis of the current transients for the full timescale enabled the delimitation of the domains where diffusion, electron transfer, and mixed control prevail. Chronoamperometric measurements in the diffusion controlled region led to current transients exhibiting Cottrellian behaviour, from which accurate diffusion coefficients, D, were estimated. Arrhenius plots of D allowed determination of the diffusion activation energies, Ed, and maximum diffusion coefficients, D0. Chronocoulometric measurements generated Anson plots from which the kinetic rate constants, k, and charge transfer activation energies, Ect, were calculated. Analysis of the current densities in conditions of infinite mass transfer led to Tafel plots from which exchange current densities, i0, transfer coefficients, α, standard rate constants, ks, and standard activation energies for charge transfer, Ect0, were determined. Purely charge transfer regimes were never observed for the studied applied potentials.