Fundamental aspects of lead electrodeposition processes: Nucleation and growth

Abstract

In this comprehensive study, the processes of nucleation and growth of lead from electrolytes of various kind and compositions have been analyzed. The processes of Pb nucleation were examined by the analysis of potentiostatic current transients, while the growth process was examined by the scanning electron microscopic (SEM) analysis of the obtained deposits. It was found that nucleation of lead follows Scharifker and Hills (SH) model based on the 3-D instantaneous nucleation with the diffusion controlled growth. Morphologies of lead particles starting from granules produced at the low overpotentials from the dilute electrolytes to very branchy dendrites at the higher ones were formed by the electrodeposition processes. The obtained surface morphologies were correlated with the corresponding polarization characteristics. It was found that regular hexagonal particles are formed by electrodeposition in the ohmic control, while irregular crystals denoted as precursors of dendrites and dendrites of various types (the needle-like, the primary (P) and the secondary (S) dendrites) were formed in the mixed ohmicdiffusion and diffusion controlled electrodeposition. The needle-like and primary (P) dendrites were primarily formed from the basic (nitrate), while the secondary (S) and the tertiary (T) dendrites were formed from the complex (acetate and hydroxide) electrolytes.

U ovoj sveobuhvatnoj studiji su analizirani procesi nukleacije i rasta olova iz elektrolita različite vrste i sastava. Procesi nukleacije olova su ispitani analizom potenciostatskih strujnih prelaza, dok procesi rasta su ispitani analizom olovnih taloga tehnikom skenirajuće elektronske mikroskopije (SEM). Nađeno je da nukleacija olova sledi Šarifkerov i Hilsov (SH) model koji se zasniva na 3-D trenutnoj nukleaciji praćenoj difuziono kontrolisanim rastom. Procesima elektrohemijskog taloženja su bile dobijene različite morfologije olovnih čestica, počev od granula dobijenih na malim prenapetostima iz razblaženih elektrolita do veoma razgranatih dendrita na višim prenapetostima. Dobijene morfologije su bile korelisane sa odgovarajućim polarizacionim karakteristikama. Nađeno je da su regularne heksagonalne čestice formirane taloženjem u omskoj kontroli, dok nepravilni kristali označeni kao prekursori dendrita i dendriti različitog oblika (igličasti, primarni (P) i sekundarni (S) dendriti) su bili formirani u mešovito omsko-difuziono i difuziono kontrolisanom taloženju. Igličasti i primarni (P) dendriti su prvenstveno formirani iz osnovnog (nitratnog), dok sekundarni (S) i tercijarni (T) dendriti su formirani iz kompleksnih (acetatnog i hidroksilnog) elektrolita.