Electrodeposition behaviour of antimony in H2SO4-NH4F-SbF3 solutions

Abstract

The electrodeposition of antimony is first investigated in H2SO4-NH4F-SbF3 solutions. In this study, linear scan voltammetry, cyclic voltammetry, chronoamperometry, chronopotentiometry and SEM-EDX techniques were utilized. The results suggested that the Sb3+ reduction takes place via a two-step reaction including a pre-conversion process. Linear scan voltammetric technique was used to identify the apparent transfer coefficient, exchange current density and apparent activation energy. The numbers of transfer electrons are calculated to be n1=1 and n2=2. For the first step reaction at 298K, α1 and i10 are 0.133 and 3.468×10-3A·cm-2, respectively. The pre-conversion reaction releases two F- ions and does not affect NH4+ ions. A series of cyclic voltammograms were recorded at different scan rates and indicate that the reduction of Sb3+ is an irreversible process that is controlled by diffusion. The diffusion coefficients of Sb3+ in H2SO4-NH4F-SbF3 electrolyte at different temperatures were calculated to be 1.051×10-5 cm2·s-1 (298K), 1.149×10-5 cm2·s-1 (303K), 1.257×10-5 cm2·s-1 (308K), 1.484×10-5 cm2·s-1 (313K), and 2.120×10-5 cm2·s-1 (318K). The apparent activation energies of Sb3+ reduction at different overpotentials were calculated as 16.932 kJ·mol-1 (-0.230 V), 16.696 kJ·mol-1 (-0.240 V), 16.274 kJ·mol-1 (-0.250 V), 16.195 kJ·mol-1 (-0.260 V), 15.802 kJ·mol-1 (-0.270 V), 15.502 kJ·mol-1 (-0.280 V), 15.244 kJ·mol-1 (-0.290 V), 14.964 kJ·mol-1 (-0.300 V), and 14.647 kJ·mol-1 (-0.310 V).