Cathodic electrochemical deposition

Basol BB (1988) Electrodeposited CdTe and HgCdTe solar Cells. Sol Cells 23 69-88 Bhattacharya RN, Rajeshwar K, Noufi RN (1985) In situ preparation of p-Type CdTe thin films by cathodic electrodeposition. J Electrochem Soc 132 732-734 Llabres J (1984) In situ preparation of undoped p-Type CdTe by cathodic electrochemical deposition. J Electrochem Soc 131 464 65... 

More recently there has been some interest in producing molybdenum disulphide by electrochemical deposition. Much of this work has been aimed at producing large crystals for use as semi-conductors, but Ponomarev et al reported the production of highly-textured films with basal plane orientation by cathodic electrochemical deposition from tetrathiomolybdate solutions, followed by annealing at 550°C in argon. 

Figure 12.2 Scheme of the cathodic electrochemical deposition of sol-gel films. 

Sol-gel-derived silane-based materials have been proven as a suitable matrix for entrapment of bioactive species, due to biocompatibility of silica and the mild operating conditions. We recall that the solutions used for cathodic electrochemical deposition of silane-based sol-gel films are usually mild acidic (pH 3-6), and the deposition is achieved by electrochemically driving the inter- cial pH near the cathode to mild basic, about pH 8. This environment is favorable for maintaining the activity of biological species such as proteins, enzymes, and bacteria. Many researchers have reported the fabrication of biosensing films by co-electrodeposition of silane with different bioactive substances. The essence of the concept is to entrap bioactive substances within the sol-gel matrix during... 

Yufit V, Nathan M, Golodnitsky D, Peled E (2003) Thin-film lithium and lithium-ion batteries with electrochemically deposited molybdenum oxysulfide cathodes. J Power Sources 122 169-173... 

The electrolyte is made by in situ chlorination of vanadium to vanadium dichloride in a molten salt bath. Higher valent chlorides are difficult to retain in the bath and thus are not preferred. The molten bath, which is formed by sodium chloride or an equimolar mixture of potassium chloride-sodium chloride or of potassium chloride-lithium chloride or of sodium chloride-calcium chloride, is contained in a graphite crucible. The crucible also serves as an anode. Electrolysis is conducted at a temperature about 50 °C above the melting point of the salt bath, using an iron or a molybdenum cathode and a cathode current density of 25 to 75 A dnT2. The overall electrochemical deposition reaction involves the formation and the discharge of the divalent ionic species, V2+ ... 

In the fifth paper of this chapter on cathodes, an investigation of thin-film oxide-hydroxide electrodes containing Cr, Ni, and Co compounds was authored by N. Vlasenko et al. The thin-films were produced by electrochemical deposition from transition metal aqueous fluorine-containing electrolytes onto steel substrates. These thin-films were tested in Li coin cells. Electrochemical activity appears to scale with the amount of fluoride used in the deposition the larger concentration of fluoride in the bath, the greater the capacity. One Ni oxide-hydroxide film electrode showed greater than 175 mAh/g reversible capacity on the 50th cycle with excellent coulombic efficiency. 

We managed to obtain dense and solid thin films of 3d-metal oxides using the techniques of electrochemical deposition from aqueous fluorine-containing electrolytes. The films have been studied as a possible cathode material for secondary cells. The best samples show good cycle retention and acceptable specific capacity in the range of 180 mAh/g. They also feature a plateau of electrochemical potential at approximately 3,5 V, which is acceptable for present industrially produced electrochemical devices. 

One important type of complex mechanism in electrode reactions is a series of consecutive reactions. One example of this type is electrochemical deposition from complexed ions. In this case the electrochemical reaction is preceded by a chemical reaction. Another example is that of inclusion of cathodic hydrogen evolution. We discuss these two cases next. 

This method involves electrochemical deposition of the MPc onto CNT-modified electrode surface by repetitive cycling in a concentrated MPc solution (1 mM) within a specific potential window. The first cyclic voltammetric scan is usually similar to subsequent scans, indicating the formation of monomeric species only. Ozoemena et al [11] found that on certain occasions, as reported recently [11] during the electro-deposition of CoTAPc onto a basal plane pyrolytic graphite electrode (BPPGE) pre-modified with SWCNT, both cathodic and anodic waves may decrease continually and then stabilizes at a certain scan (a process known as electrochemical adsorption or simply called electrosorption ). 

The cadmium electrodeposition on the solid cadmium electrode from the sulfate medium was investigated [217]. The following kinetic parameters were obtained cathodic transfer coefficient a = 0.65, exchange current density Iq = 3.41 mA cm , and standard rate constant kg = 8.98 X 10 cm s . The electrochemical deposition of cadmium is a complex process due to the coexistence of the adsorption and nucleation process involving Cd(II) species in the adsorbed state. 

In the case ofn-Ge(lll) substrates, surface states affect electrochemical deposition of Pb [319]. At high cathodic potentials, the deposition occurs by instantaneous nucleation and diffusion-controlled three-dimensional growth of lead clusters. Comparing H- and OH-terminated n-Ge(lll) surfaces, the nucleation is more inhibited at n-Ge(lll)-OH, which can be explained by the different densities of Ge surface free radicals, being nucleation sites. In this case, nucleation site density is about 1 order of magnitude lower than that for n-Ge(lll)-H. 

U(III) species and a second three-electron reduction to give U(0) metal. The first reduction, U(IV)/U(III) couple, is elec-trochemically and chemically irreversible except in hexamethylphosphoramide at 298 K where the authors report full chemical reversibility on the voltammetric timescale. The second reduction process is electrochemically irreversible in all solvents and only in dimethylsulfone at 400 K was an anodic return wave associated with uranium metal stripping noted. Electrodeposition of uranium metal as small dendrites from CS2UCI6 starting material was achieved from molten dimethylsulfone at 400 K with 0.1 M LiCl as supporting electrolyte at a platinum cathode. The deposits of uranium and the absence of U CI3, UCI4, UO2, and UO3 were determined by X-ray diffraction. Faradaic yield was low at 17.8%, but the yield can be increased (55.7%) through use of a mercury pool cathode. 

As a result of that reductive process, a deposit of copper metal (denoted in Eq. 2.2 by s for solid ) is formed on the carbon electrode surface. The prominent anodic peak recorded in the reverse scan corresponds to the oxidative dissolution of the deposit of copper metal previously formed. The reason for the very intense anodic peak current is that the copper deposit is dissolved in a very small time range (i.e., potential range) because, in the dissolution of the thin copper layer, practically no diffusion limitations are involved, whereas in the deposition process (i.e., the cathodic peak), the copper ions have to diffuse through the expanding diffusion layer from the solution to the electrode surface. These processes, labeled as stripping processes, are typical of electrochemically deposited metals such as cadmium, copper, lead, mercury, zinc, etc., and are used for trace analysis in solution [84]. Remarkably, the peak profile is rather symmetrical because no solution-like diffusive behavior is observed. 

Plasma electrochemical reactions have been studied by chemists for a surprisingly long time, with the first report on cathodic metal deposition at the free surface of a liquid electrolyte with free electrons from a plasma dating back to 1887 [1], long before the plasma state had been named by Langmuir in 1928 [2], A short survey of past work with more conventional liquid electrolytes is also included in this chapter. 

The electrochemical method is also used for the synthesis of fullerene derivatives, among them C6o fullerene salts with alkali metals crystallized at the cathode [11, 12]. No evidence on the electrochemical deposition of fullerenes on the electrodes from organic solvents is available although this method for producing fullerene coatings on metals is of indubitable practical interest. 

The activities of CNTs have been evaluated by Girishkumar et al. [7] using ex situ EIS. Their study was conducted in a three-compartment electrochemical cell using a GDE electrode (a carbon fibre paper coated with SWCNTs and Pt black as an anode or cathode). Electrophoretic deposition was used to deposit both the commercially available carbon black (CB) for comparison and the SWCNT onto the carbon Toray paper. Commercially available Pt black from Johnson Matthey was used as the catalyst. In both cases, the loading of the electrocatalyst (Pt), the carbon support, and the geometric area of the electrode were kept the same. EIS was conducted in a potentiostatic mode at either an open circuit potential or controlled potentials. 

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