Platinum electrodes electrodeposition

Poly crystalline silver layer electrodeposited on a polycrystalline platinum electrode. 

Simultaneous and continuous measurements of extracellular pH, potassium K+, and lactate in an ischemic heart were carried out to study lactic acid production, intracellular acidification, and cellular K+ loss and their quantitative relationships [6, 7], The pH sensor was fabricated on a flexible kapton substrate and the pH sensitive iridium oxide layer was electrodeposited on a planar platinum electrode. Antimony-based pH electrodes have also been used for the measurement of myocardial pH in addition to their application in esophageal acid reflux detection. 

D.M. Zhou, H.X. Ju, and H.Y. Chen, Catalytic oxidation of dopamine at a microdisc platinum electrode modified by electrodeposition of nickel hexacyanoferrate and Nafion. J. Electroanal. Chem. 408, 219-223 (1996). 

Platiniini electrodes were cleaned chemically first in aqua regia for 20 min. and then electrochemically by sweeping the potential from 30 mV to 1600 mV repeatedly in 3 M stdiuric add. Ruthenitim (IQ) nitrosylmtrate, (Ru(N0)(N03)3), Johnson Matthey) aqueous solution was added to the electrolyte to obtain 0.01 M ruthenium. Then, ruthenium was electrodeposited on platinum electrodes at a constant potential, 0.05V, for 10 s. 

M. S. El-Deab, and T. Ohsaka, Electrocatalysis by nanoparticles Oxygen reduction on gold nanoparticles-electrodeposited platinum electrodes, J. Electroanal. Chem. 553, 107-115 (2003). 

It is desirable to measure R (and thus G) at a high frequency in order to reduce Xc to a negligible value compared to R. Unfortunately, other complications arise if the frequency is increased above a few kilohertz, and therefore other means must be devised to decrease Xc. A commonly used remedy is to increase the surface area and thus the capacitance of the electrodes as much as possible. A 100-fold area increase is obtained by platinizing the electrodes, that is, electrodepositing a layer of platinum black onto the platinum electrodes, usually from a solution of chloroplatinic acid [8]. 

Photoelectrochemical reactions of hydrated microcrystalline Chi a electrodeposited on platinum electrodes have been studied by Fong and co-workers (72,73,74,75). The experiments were perfomed in short circuit electrochemical cells. In aqueous electrolytes... 

It is interesting to conclude this section with an example that, in a sense, brings the chapter full circle. The metallization of plastic materials used as metal substitutes is a process with actual and future commercial potential. Usually, plastics are plated after appropriate sensitization by an electroless process which involves reduction of metal ions (e.g. Ni2+, Cu2+) by chemical rather than electrical means.19 There seems no reason why the reducing agent should not be incorporated in the polymer and Murray and his collaborators101 have demonstrated that copper, silver, cobalt and nickel may each be electrodeposited on to films of [poly-Ru(bipy)2(4-vinylpyridine)2]2+ coated on to platinum electrodes. The metal reductions are mediated by the Ru1 and Ru° states of the polymer. 

An in depth study of the deposition mechanism was carried out by Sun et al. who studied the 1 1 [EMIMJCl/ZnCf system at various temperatures on glassy carbon (GC), nickel and platinum electrodes [106], The GC electrode required the largest overpotential for deposition. The stripping process showed a single peak on GC, whereas on Ni two oxidation processes were observed, separated by ca. 0.6V. Itwas proposed that the more positive oxidation process corresponded to the dissolution of an intermetallic compound formed during electrodeposition. 

Chlorostannate and chloroferrate [110] systems have been characterized but these metals are of little use for electrodeposition and hence no concerted studies have been made of their electrochemical properties. The electrochemical windows of the Lewis acidic mixtures of FeCh and SnCh have been characterized with ChCl (both in a 2 1 molar ratio) and it was found that the potential windows were similar to those predicted from the standard aqueous reduction potentials [110]. The ferric chloride system was studied by Katayama et al. for battery application [111], The redox reaction between divalent and trivalent iron species in binary and ternary molten salt systems consisting of 1-ethyl-3-methylimidazolium chloride ([EMIMJC1) with iron chlorides, FeCb and FeCl j, was investigated as possible half-cell reactions for novel rechargeable redox batteries. A reversible one-electron redox reaction was observed on a platinum electrode at 130 °C. 

Platinized platinum — Metallic platinum covered with a rough large-surface-area platinum coating. The very well-developed metal surface results in a Pt -> electrode of a large true area that is relatively nonpolar-izable. A platinized platinum electrode can be obtained by cathodic -> electrodeposition of a rough Pt deposit at Pt-metal electrode from a solution consisting of chloro-platinic acid (3%), lead acetate (0.025%), and hydrochloric acid (ca. 1%) The name of this electrodeposited coating -r platinum black comes from deep black color and dull surface of the deposit. In fact, the dark black color appears when lead is used as an additive. When pure... 

Using a different approach, the research gronps of Fabre and Freund have synthesized boronate-functionalized conjugated polymers, which serve as electrochemical sensors. For example, a conjugated redox-active film of polypyrrole (174) was electrodeposited onto a platinum electrode from acetonitrile solution. Addition of fluoride anions led to a new redox system that showed an anodic shift relative to polypyrrole itself, which was attributed to fluoride binding to the boronate group. A related poly(aniline boronic acid) (175) was also reported and studied for saccharide detection. " ... 

Figure 25. Polarization curves for copper electrodeposition on the cylindrical platinum electrodes treated by copper electrodeposition under the same conditions shown in Fig. 24a-c. Reprinted from ref. 8 with permission of Elsevier.

Electrodeposition Processes Hasse et al. [366] have used in situ AFM for the detection of silver nucleation at the three-phase junction of the type metal-sUver halide-electrolyte solution. At this phase boundary, electrochemical reduction of submicrometer size silver halide crystals immobilized on the surface of gold and platinum electrodes took place. Following nucleation, the reaction advanced until the entire surface of the silver halide crystals was covered with 20 atomic layers of silver. Then, reduction was terminated. The obtained silver layer could be oxidized and the next layer of silver halide crystals became accessible for further reduction. 

In an analytical laboratory, electrodeposition is used to determine how much material is in a solution by selectively depositing it on an electrode. The electrode is weighed before and after, and the percentage determined based on the sample weight. You could determine the concentration of chromium in the above solution by taking a small aliquot and depositing the chromium onto a weighed platinum electrode. 

Solutions containing the metal, most commonly in nitric acid, will deposit the metal on a platinum electrode by electrodeposition. Polonium metal is deposited spontaneously from such solutions on to metals such as silver or nickel. The metal can be sublimed off such support metals at low pressures. Thermal decomposition of polonium sulfide also yields the metal. In much the same way as tellurium, the metal can be obtained from its solutions by the action of reducing agents such as hydrazine, tin(II) ion, titanium(III) ion, and dithionite. Such metal precipitates appear as gray-black powders. Thin foils, silvery in color, have been prepared by vacuum sublimation of the metal. 

A different approach to the preparation of preferentially oriented surfaces on polycrystalline systems has been demonstrated by Sumino and Shibata. In References 57-59 it has been shown that a fast-cycling treatment is not required for obtaining deposits with preferential orientation. A platinum electrode with a single-crystal (100) surface was obtained by annealing a thin platinum film electrodeposited on a polycrystalline platinum foil. 

F. Chao, M. Costa, and C. Tian, Different steps in electrodeposition of poly(3-methylthio-phene) films on platinum-electrodes studied by ellipsometry, SEM and AFM techniques. Synth. Met., 53,127 (1993). 

N. Hernandez, J.M. Ortega, M. Choy, and R. Ortiz, Electrodeposition of silver on a poly (o-aminophenol) modified platinum electrode, J. Electroanal. Chem., 515, 123-128 (2001). 

---