Electrochemical Investigation of Bi-Fe Alloy Thin Films Prepared by Electrodeposition

The electrodeposition of Bi, Fe, and Fe-Bi alloy from an acetate solution at pH 6.50 on a glassy carbon electrode at ambient temperature was studied using cyclic voltammetry, chronoamperometry, and scanning electron microscopy (SEM). The solutions prepared for alloy coating deposition consisted of CH3COOH, Bi5H9N4O22, FeSO4·7H2O, (NH4)2SO4, Na3C6H5O7·2H2O, H3BO3, and NH4OH. The results showed that the simultaneous deposition of Fe and Bi was facilitated by the complexing action of Na3C6H6O7 and NH4OH, effectively reducing the difference in the reduction potentials of the two metals. Cyclic voltammetry results indicate that the deposition processes are diffusion-controlled, with diffusion coefficients for Bi3+ and Fe2+ calculated as 1.17×10-4 and 4.97×10-7 cm² s-1, respectively. Based on dimensionless curves and the Scharifker and Hills theory, the nucleation mechanism analysis revealed that Fe2+ undergoes progressive nucleation, while Bi3+ and the Bi3+-Fe2+ system transition from instantaneous to progressive nucleation. Surface morphological analysis by SEM of Bi, Fe, and Fe–Bi electrodeposits, performed at 10 and 60-second intervals, further corroborates the conclusions derived from dimensionless plots and the Scharifker and Hills theory. These findings provide valuable insights into these electrochemical systems' nucleation and growth behavior. Keywords: electrodeposition, iron-bismuth alloy, diffusion, nucleation mechanism, nuclei growth