Studies of nickel electrocrystallization on platinum ultramicroelectrodes

Abstract

A eletrocristalização de níquel foi estudada sobre ultramicroeletrodo (UME) de platina. O comportamento dos transientes de corrente indicou um processo de nucleação instantânea sob controle cinético. A aplicação do modelo de Abyaneh mostrou que os núcleos crescem com uma geometria do tipo calota esférica, possuindo valores diferentes para as constantes de velocidade no sentido paralelo e per pen dic u lar à superfície. As constantes de velocidade para o crescimento de núcleos no sentido paralelo variaram de 5,97 x 10-7 a 1,92 x 10-7 mol cm-2 s-1 , com o aumento do potencial de-0,57 a-0,63 V, enquanto que as correspondentes constantes no sentido per pen dic u lar apresentaram valores em torno de 1,44 x 10-7 mol cm-2 s-1. As relações en tre estas forneceram os ângulos de contato, cujos valores aumentaram de 27,5 a 87,6 graus. Finalmente, o número de núcleos formados aumentou com o potencial, de 0,43 x 10 7 a 379,09 x 10 7 cm-2. The electrocrystallization of nickel was stud ied on a plat i num ultramicroelectrode (UME). The be hav iour of the cur rent tran sients pointed to an in stan ta neous nu cle ation pro cess un der kinetic con trol. The ap pli ca tion of Abyaneh's model showed that nu clei grow in a spher i cal cap ge om e try with dif fer ent val ues for both rate con stants in the par al lel and per pen dic u l ar di rections. The par al lel rate con stants for nu clei growth var ied from 5.97 x 10-7 to 1.92 x 10-7 mol cm-2 s-1 by in creas ing the step po ten tial from-0.57 to-0.63 V, while the per pen dic u lar rate constant re mained con stant around 1.44 x 10-7 mol cm-2 s-1. The re la tion ships be tween these two con stants give the con tact an gles of the crys tal lites, whose val ues also in creased with po t en tial from 27.5 to 87.6 de grees. Finally, the num ber of nu clei formed on the sur face in creased with po ten tial from 0.43 x 10 7 to 379.09 x 10 7 cm-2 .

Analysis of the initial stages of electrocrystallization of Fe, Co and Fe-Co alloys in chloride solutions

“…This method of obtaining kinetic information of the nucleation process has been used extensively for a wide variety of systems. [22][23][24][25][26][30][31][32][33][34] Some of the non-dimensional plots obtained with the experimental and theoretical data are shown in Figure 4. It is clear from this figure that Fe deposition on Pt follows very close the theoretical response for an instantaneous nucleation, over the measured potential range.…”

Ultramicroeletrodos. Parte II: construção e aplicações

“…núcleos mostrou-se controlado por transferência eletrônica, o modelo de Abyaneh 38 desenvolvido para eletrodos convencionais revelou-se bastante satisfatório 39 .…”

Simulation of 3D Electrochemical Phase Formation: Mixed Growth Control

“…However, the calculated values of the number density of nuclei, the nucleation rate, and the growth rate can significantly differ from those obtained by the electron microscopy [ 2 , 11 , 12 , 13 , 14 , 15 ] due to the use of numerous approximations, which consider the mutual influence of nuclei through the overlap of neighboring nuclei or their diffusion zones; other reasons for the discrepancies are discussed in [ 16 ]. An exact solution to the overlap problem can be found only for the case of kinetically controlled growth [ 17 , 18 ], which is relatively rarely realized under ordinary conditions of electrodeposition [ 19 , 20 ]. The growth of a new phase can often occur under mixed (charge transfer and diffusion) control [ 21 , 22 , 23 , 24 , 25 , 26 ].…”