Electrochemical oxidation index

Table 23. Comparison of the Electrochemical Oxidation Index (EOI) at Pt/Ti and Sn02- Anodes (ABB-Anode) with organic substances [45a, 287, 288]...

The Electrochemical Oxidation Index (EOI), which is the average value of the current efficiency during the oxidation, is determined from the ICE using the relationship (Comninellis and Pulgarin 1991) ... 

Table 2.5 Initial electrochemical oxidation index (EOI) determined for the various test substances using Pt and Sn02 anodes (Stucki et al. 1991)...

From the Instantaneous Current Efficiency (ICE) - time curve (Fig. 1) an average value can be calculated and defined as the Electrochemical oxidation Index (EOI)... 

In this work, the parameters Electrochemical Oxidation Index (EOI) and Electrochemical Oxygen Demand (EOD), involved in the electrochemical treatment of organic pollutants, are presented [1-6]. From these parameters, both the degree of oxidation (X) and the average oxidation state of carbon (Ox) in the wastewater can be calculated during treatment [6]. 

The Electrochemical Oxidation Index (EOI) expresses the average current efficiency for the oxidation of organics and is a measure of the ease of electrochemical oxidation of the target organic compound (or the wastewater under investigation) on the investigated anode material under the experimental conditions used. 

In this context see also Refs. [83a, 83b]. Comninellis and Plattner [287,287a, 288] have developed a simple method for estimating the facility of the electrochemical oxidation of organic species based on a newly defined electrochemical oxidizability index (EOI) and the degree of oxidation using the electrochemical oxygen demand (EOD). Electrochemical oxidizability index for various benzene derivatives obtained at Pt/Ti and Sn02-ABB-anodes are listed in Table 23. 

Figure 16.1. The energy level of carbon monoxide molecules, and the formation of metal-carbon monoxide bonding [449]. (Reprinted from Grgur BN, Markovic NM, Lucas CA, Ross PN. Electrochemical oxidation of carbon monoxide from platinum single crystals to low temperature fuel cells catalysis. Part 1 carbon monoxide oxidation onto low index platinum single crystals. J Serb Chem Soc 2001 66 785-97. With permission from the Serbian Chemical Society.)...

Several aromaticity indices (bond lengths, bond orders, Jug and Francois s aromaticity index) indicate that, despite the nonplanarity of the five-membered ring in 2,5-diphenylthiophene-l-oxide (108), this compound is intermediate in aromaticity between the corresponding thiophene 107 and the nonplanar 1,1-dioxide 109 (Scheme 48).149 The theoretical calculations were supported by experimental electrochemical data.150... 

Refs. [i] http /lwww.seca.doe.gov [ii] http //www.spice.or.jp/ fisher/ sofc.html descript [iii] http //www.pg.siemens.com/en/fuelcells/sofc/ tubular/index.cfm [iv] Weissbart J, Ruka R (1962) J Electrochem Soc 109 723 [v] Park S, Vohs JM, Gorte RJ (2000) Nature 404 265 [vi] Liou J, Liou P, Sheu T (1999) Physical properties and crystal chemistry of bismuth oxide solid solution. In Processing and characterization of electrochemical materials and devices. Proc Symp Ceram Trans 109, Indianapolis, pp 3-10 [vii] Singhal SC (2000) MRS Bull 25 16 [viii] Matsuzaki Y, Yasuda I (2001) J Electrochem Soc 148 A126 [ix] Ralph JM, Kilner JA, Steele BCH (1999) Improving Gd-doped ceria electrolytes for low temperature solid oxide fuel cells. In New Materials for batteries and fuel cells. Proc Symp San Francisco, pp 309-314... 

There are many substances which would appear to be good candidates for LC-EC from a thermodynamic point of view but which do not behave well due to kinetic limitations. Johnson and co-workers at Iowa State University used some fundamental ideas about electrocatalysis to revolutionize the determination of carbohydrates, nearly intractable substances which do not readily lend themselves to ultraviolet absorption (LC-UV), fluorescence (LC-F), or traditional DC amperometry (LC-EC) [2], At the time that this work began, the EC of carbohydrates was more or less relegated to refractive index detection (LC-RI) of microgram amounts. The importance of polysaccharides and glycoproteins, as well as traditional sugars, has focused a lot of attention on pulsed electrochemical detection (FED) methodology. The detection limits are not competitive with DC amperometry of more easily oxidized substances such as phenols and aromatic amines however, they are far superior to optical detection approaches. 

Weaver, M.J., Zou, S., and Tang, C. (1999) A concerted assessment of potential-dependent vibrational frequencies for nitric oxide and carbon monoxide adlayers on low-index platinum-group surfaces in electrochemical compared with ultrahigh vacuum environments structural and electrostatic implications. Journal of Chemical Physics, 111, 368-381. 

SCHEME 2.5 Wroblowa s oxygen electroreduction mechanism with electrochemical rate constants k3 forthe direct reduction to water, k2 and k 2 for the parallel electrochemical reduction and oxidation of adsorbed hydrogen peroxide, k3 for the electrochemical decomposition of hydrogen peroxide to water, k4 for the chemical catalytic decomposition of hydrogen peroxide to oxygen, and ks and fc 5 for the parallel adsorption/desorption of the adsorbed hydrogen peroxide. The species with the super index and ° are located at the interface and in the bulk of the solution, respectively. The sub index ads refers to the adsorbed state, and the term dif symbolizes the diffusion to the bulk of the solution and vice versa. 

Current voltage correlations measured for the Butler-Volmer equauon (Eq. 9.2), describe mathematically the current-voltage correlation for a reversible electrochemical reaction, for instance, the anodic oxidation of hydrogen (index a) and cathodic hydrogen evolution (index c). 

A detector is used to monitor the separation proeess and the response is direetly proportional to the concentration. The detector can be based on variable wavelength UV/ visible light, fluorescence, polarimetry, electrochemical behavior (for materials that ean be readily oxidized), electrical conductivity, refractive index and more recently, the highly successful mass spectrometer. 

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