Platinum working electrode

Does the platinum working electrode serve as the cathode or the anode in this analysis ... 

The Kad Fischer jack on the back of most pH meters, used to monitor Kad Fischer titrations, suppHes a constant regulated current to the cell, which can consist of two identical (platinum) working electrodes. The voltammograms shown in Figure 9 illustrate the essential features of this technique. The initial potential difference, AH, is small because both redox forms of the sample coexist to depolarize the electrodes. The sample corresponds to the wave on the right-hand (cathodic) side of each figure and is therefore easily oxidized. The titrant is represented by the wave on the left-hand (anodic) side and is therefore easily reduced. Halfway to the end point the potential difference,, remains small, but at the end point the potential difference,... 

Figure 3.6-1 The electrochemical window of 76-24 mol % [BMMIM][(CF3S02)2N]/Li [(Cp3S02)2N] binary melt at a) a platinum working electrode (solid line), and b) a glassy carbon working electrode (dashed line). Electrochemical window set at a threshold of 0.1 mA cm. The reference electrode was a silver wire immersed in 0.01 m AgBp4 in [EMIM][BF4] in a compartment separated by a Vicor frit, and the counter-electrode was a graphite rod.

Figure 2.18 Cyclic vollammograms of a Pt working electrode immersed in aqueous perchloric acid (in the absence of CO) showing the oxidation peaks of adsorbed CO for different degrees of coverage 0. The scan rate was 50 mV s 1. The adsorption was effected by exposing the platinum working electrode to CO-saturated electrolyte for a sufficient length of time to give the coverage required. From Bcdcn et al. (1985).

This system was subsequently investigated by Christensen et at. (1990) also using in situ FTIR, who observed identical product features (see Figure 3.48). In order first to compare directly the IR spectrum of oxalate generated in situ, the authors took advantage of the surface reactivity of Pt and the poor diffusion of species to and from the thin layer. Thus, a solution of oxalic acid in the electrolyte was placed in the spectroelectrochemical cell, the potential of the platinum working electrode stepped to successively lower values and spectra taken at each step. The spectra were all normalised to the reference spectrum collected at the base potential of 0 V vs. SCE. As a result of the deprotonation of adventitious water ... 

Various plutonium materials are dissolved in acidic media and then fumed with sulfuric acid. In a 0.5 M sulfuric acid electrolyte, plutonium is reduced to Pu(III) at a platinum working electrode maintained at 0.310 V relative to a saturated calomel electrode. Plutonium (III) is oxidized to Pu(IV) at 0.670 V for the coulometric measurement. This work supports manufacturing, stock pile reduction, and pilot programs for making nuclear fuels from the stockpile. 

Table 2 Formal electrode potentials (V vs. SCE, at 25° C) and peak-to-peak separation (mV) for the couple [Fe(t]5-C5H5)2]/[Fe(t]5-C5H5)2] in different solutions. Platinum working electrode (measured in our laboratory)...

Figure 4 Cyclic voltammograms recorded at different scan rates of a CH2Cl2 solution of 1,1 bis( diphenylphosphino)-2-[ -(((l-hydroxy-2-phenyl) amino) me thylboro-nate) ethyl]ferrocene. Platinum working electrode. Supporting electrolyte [NBu4][C104] (0.2 mol dm 3)...

Figure 9 Cyclic voltammogram of [V(phen)23+JJ03SCF3)2 in CH2Cl2 solution. Platinum working electrode. Scan rate 0.5 V s 1...

Figure 109 Typical cyclic voltammetric behaviour of a few Ni(II)-tetrazamacrocycles in MeCN solution. Platinum working electrode...

Figure 6.14 Cyclic voltammogram obtained for a multiple-electron-transfer system, where a thin film of sputtered V2O5 on a platinum working electrode has been immersed in an electrolyte solution of propylene carbonate containing LiCI04 (1.0 mol dm ). From Cogan, S. F., Nguyen, N. M Perrotti, S. J. and Rauh, R. D Electroctromism in sputtered vanadium pentoxide , SPIE, 1016, 57-62 (1989). Reproduced by permission of the International Society for Optical Engineering (SPIE).

Gopinath et al. describe the reduction of U(VI) to U(IV) at an activated platinum electrode in 1 M H2SO4 for the coulo-metric determination of uranium [63]. The platinum working electrode is chemically and electrochemically oxidized and then electrochemically reduced to produce a surface that is more active toward uranium... 

Figure 2.10 Differential pulse voltammetry profiles obtained at a platinum working electrode in a MeCN solution 5 x 1 4 in [Et3Bn]Cl and 0.1M in [Bu4N]C104. Dashed line, 3 M in the [Cun(ll)Nin](ClC>4)4 complex salt solid line, 1CT3M in both the [Cui1[(12)](C1C>4)2 and [NiI1[(ll)](C104)2 complex salts.

Electrodes. - For the in situ generation of radical ions by electrolysis, several kinds of electrolytic cells have been utilised. In most cases, platinum working electrodes are the working electrodes. However, several alternative materials have been introduced for electrochemical studies. Possibly, they can be valuable for ESR spectroscopists. 

Diffusion control constant flux mode. Table P.3 contains the potential transient data obtained on a platinum working electrode (against SHE) immersed in an aqueous solution of 0.1 M ferric perchlorate and 1.0 M ammonium perchlorate. The experiment was carried out at a constant current of 10 mA/cm2, and the diffusion coefficient of both reactant and product is assumed to be 10 5 cm2/s. 

In electrogravimetry [19], the analyte, mostly metal ions, is electrolytically deposited quantitatively onto the working electrode and is determined by the difference in the mass of the electrode before and after the electrolysis. A platinum electrode is usually used as a working electrode. The electrolysis is carried out by the con-trolled-potential or the controlled-current method. The change in the current-potential relation during the process of metal deposition is shown in Fig. 5.33. The curves in Fig. 5.33 differ from those in Fig. 5.31 in that the potentials at i=0 (closed circles) are equal to the equilibrium potential of the M +/M system at each instant. In order that the curves in Fig. 5.33 apply to the case of a platinum working electrode, the electrode surface must be covered with at least a monolayer of metal M. Then, if the potential of the electrode is kept more positive than the equilibrium potential, the metal (M) on the electrode is oxidized and is dissolved into solution. On the other hand, if the potential of the electrode is kept more negative than the equilibrium potential, the metal ion (Mn+) in the solution is reduced and is deposited on the electrode. 

Jackson et al. [26] set miniaturized, battery-powered, high-voltage power supply conditions in NCE for the separation of dopamine and catecholamines with electrochemical detection. The authors varied platinum working electrode voltage from 25 to 200 V/cm for achieving low limits of detection. 

Another type of thin film device consists of four 0.5 x 0.5 mm2 platinum working electrodes and a Ag/AgCl reference electrode made on a 0.3 mm glass carrier. The enzymes were immobilized onto the working electrodes in a photo crosslinked pHEMA membrane and additionally covered by a diffusion limiting and a catalase containing top layer [77]. 

Scheme 5. Scheme of electrochemical ion transport with redox-active crown ether. W W2 mini-grid platinum working electrodes. C C2 platinum plate counter electrodes. R1, R2 saturated calomel reference electrodes. 

Shi et al. [70] were the first to demonstrate the use of an air and moisture stable ionic liquid, [C4mim][PF,s], for the electrochemical synthesis of poly(thiophene), grown onto a platinum working electrode by potentiodynamic, constant potential or constant current techniques. The use of growth potentials between 1.7 and 1.9 V (vs. Ag/AgCl) reportedly gave smooth, blue-green electroactive films, whereas potentials above 2 V resulted in film destruction by overoxidation. 

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