Effective overpotential

Fig. 13. Schematic of (a) a straight pore, (b) the concentration profile of hydrogen established in the pores of Raney-nickel coating under operation condition (c) calculated distribution of H2 concentration, effective overpotential, and (d) current density in a pore (diameter of 2 nra).

The better understanding of the concept effective overpotential can be realized by taking into account the fact that the time of dendritic growth initiation depends on used deposition overpotentials. Increasing deposition overpotentials lead to decreasing times for... 

The Concept of Effective Overpotential Applied for Metal Electrodeposition Under an Imposed Magnetic Field... 

The application of the concept of effective overpotential for the case of the change of hydrodynamic conditions caused by magnetic field effects means that morphologies of nickel and copper deposits obtained under parallel fields (the largest magnetohydro-dynamic (MHD) effect) should be, at macro level, similar to those obtained at some lower overpotentials or potentials without imposed magnetic fields. This assumption can be confirmed by the following consideration ... 

Mechanism of Formation of the Honeycomh-Like Structure The Concept of Effective Overpotential ... 

The concept of effective overpotential is applicable for all cases where there is the change of the hydrodynamic conditions in the near-electrode layer, which can be induced by the agitation of electrolyte not only by evolving hydrogen but also by application of ultrasonic [11] and magnetic [12, 13] fields or simply by vigorous stirring of an electrolyte [14]. 

Nikolic ND, Popov KI, Pavlovic Lj J, Pavlovic MG (2006) The effect of hydrogen codeposition on the morphology of copper electrodeposits. I the concept of effective overpotential. J Electroanal Chem 588 88-98... 

Nikolic ND (2007) The effects of a magnetic field on the morphologies of nickel and copper deposits the concept of effective overpotential . J Serb Chem Soc 72 787-797... 

Of course, hydrogen evolution affects mechanism of formation of powder particles. The dendrites are formed without, as weU as with, a quantity of evolved hydrogen (the case of Cu) which was insufficient to achieve any effect on the hydrodynamic conditions in the near-electrode layer. Then, the electrodeposition process was primarily controlled by the diffusion of ions to the electrode surface, rather than the kinetic of the electrodeposition [5,6], The cauUflower-Uke particles are formed in the conditions of vigorous hychogen evoluticMi with the strong effect of evolved hydrogen on the hydrodynamic conditions in the near-electrode layer, and the concept of effective overpotential is proposed to explain formation of these particles [25, 35]. 

Finally, hychogen evolution becomes crucial factor determining the shape of powder particles of the group of the inert metals, and the concept of effective overpotential is applicable to explain the formation of these powder particles. Due to vigorous hychogen evolution, dendritic growth is almost completely inhibited. Analysis of the polarization curves for Co and Ni [12, 26, 30] showed that their... 

Anyway, the concept of effective overpotential can be summarized as follows when hydrogen evolution is vigorous enough to change hydrodynamic conditions in the near-electrode layer, then electrodeposition process occurs at some overpotential which is effectively lower than the specified one. This overpotential is denoted by effective overpotential of electrodeposition process. From morphological point of view, it means that morphologies of metal deposits become similar to those obtained at some lower overpotentials where there is no hydrogen evolution or it is very small. More about the formation of the honeycomb-like structure and the concept of effective overpotential can be found in [46, 52-61]. 

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