Mechanism of electrodeposition

In practical terms, large-scale cracking in the produced films, detrimental to photoelectric applications, was the main drawback of the above method. In order to prevent the appearance of cracks, propylene carbonate (PC) has been used as a solvent, with encouraging results [51]. The mechanism of electrodeposition of CdS in PC solutions containing Cd(II) ions and elemental sulfur has been studied by performing cyclic voltammetry at stationary Pt and Au electrodes [52]. 

Szabo JP, Cocivera M (1988) Mechanism of electrodeposition of cadmium selenide from SeS03 solution. Can J Chem 66 1065-1072... 

Baranski AS, Fawcett WR (1984) The mechanism of electrodeposition of cadmium sulfide on inert electrodes from diethylene glycol solutions. J Electrochem Soc 131 2509-2514... 

Rodrigues S, Munichandraiah N, Shukla AK (1998) A cyclic voltammetric study of the kinetics and mechanism of electrodeposition of manganese dioxide. J Appl Electrochem 28 ... 

There are four types of fundamental subjects involved in the process represented by Eq. (1.1) (1) metal-solution interface as the locus of the deposition process, (2) kinetics and mechanism of the deposition process, (3) nucleation and growth processes of the metal lattice (M a[tice), and (4) structure and properties of the deposits. The material in this book is arranged according to these four fundamental issues. We start by considering the basic components of an electrochemical cell for deposition in the first three chapters. Chapter 2 treats water and ionic solutions Chapter 3, metal and metal surfaces and Chapter 4, the metal-solution interface. In Chapter 5 we discuss the potential difference across an interface. Chapter 6 contains presentation of the kinetics and mechanisms of electrodeposition. Nucleation and growth of thin films and formation of the bulk phase are treated in Chapter 7. Electroless deposition and deposition by displacement are the subject of Chapters 8 and 9, respectively. Chapter 10 contains discussion on the effects of additives in the deposition and nucleation and growth processes. Simultaneous deposition of two or more metals, alloy deposition, is discussed in Chapter 11. The manner in which... 

Oxide electrodes have been observed to be almost immune from poisoning effects due to traces of metallic impurities in solution [99]. This is undoubtedly due primarily to the extended surface area. It can be anticipated that the calcination temperature must have a sizable effect. But in addition, a different mechanism of electrodeposition must be operative. Chemisorption on wet oxides is usually weak because metal cations are covered by OH groups [479]. As a consequence, underpotential deposition of metals is not observed on Ru02, although metal electrodeposition does takes place. However, electrodeposited metals give rise to clusters or islands and not to a monomolecular layer like on Pt. Therefore, the oxide active surface remains largely uncovered even if metallic impurities are deposited [168]. Thus, the weak tendency of oxides to adsorb ions, and its dependence on the pH of the solution is linked to their favorable behavior observed as cathodes in the presence of metallic impurities. 

The mechanism of electrodeposition or electrocrystallization28 29 involves, as a first step, the reduction of a cation on the substrate surface (aided by an applied potential or current) to form an adatom, and its migration over the surface to an energetically favourable site. Other atoms of the electrodeposit aggregate with the first, forming the nucleus of a new phase. The nucleus grows parallel and/or perpendicular to the surface. Clearly, a number of nuclei can form and grow on the surface. When all the electrode surface is covered with at least a monolayer, deposition is on the same metal rather than on a different metal substrate. As is to be expected, the formation of the first layers determines the structure and adhesion of the electrodeposit. 

---