Electrochemical triangle

Reaction (1.2) is an example of a reduction reaction. Reduction reactions are also called cathodic reactions. So, alternatively, one can define corrosion as anodic reactions that are occurring at the anode. Thus, three main conponents of any electrochemical corrosive reaction are the anode, the cathode, and the solution in which corrosion occurs. This solution is called the electrolyte, and water is always an integral part of it. One may show these components as three comers of an electrochemical triangle (see Figure 1.1). 

The electrochemical triangle implies that for corrosion to happen, all three components must be available and interactive. It follows that any method to be implemented to solve a corrosion problem must try to remove at least one of the sides of the triangle. This point will be discussed in more detail later. 

Figure 11.4. Effect of the mole fraction, XIro2, of Ir02 in the Ir02-Ti02 catalyst film on the rate of C2H4 oxidation under open-circuit conditions (open circles) and under electrochemical promotion conditions (filled circles) via application of 1=200 pA T=380°C, Pc2h4=015 kPa, Po2=20 kPa. Triangles indicate the corresponding electrochemical promotion rate enhancement ratio p values.22,29...

The formation of colloidal sulfur occurring in the aqueous, either alkaline or acidic, solutions comprises a serious drawback for the deposits quality. Saloniemi et al. [206] attempted to circumvent this problem and to avoid also the use of a lead substrate needed in the case of anodic formation, by devising a cyclic electrochemical technique including alternate cathodic and anodic reactions. Their method was based on fast cycling of the substrate (TO/glass) potential in an alkaline (pH 8.5) solution of sodium sulfide, Pb(II), and EDTA, between two values with a symmetric triangle wave shape. At cathodic potentials, Pb(EDTA)2 reduced to Pb, and at anodic potentials Pb reoxidized and reacted with sulfide instead of EDTA or hydroxide ions. Films electrodeposited in the optimized potential region were stoichiometric and with a random polycrystalline RS structure. The authors noticed that cyclic deposition also occurs from an acidic solution, but the problem of colloidal sulfur formation remains. 

Figure 8.13 In situ electrochemical SXS characterization of PtsNi) 11) and Pt(l 11) surfaces (a)XRV measurements forPtsNitlll) at the (0, 0, 2.7) (filled squares) andPt(lll)at (1, 0, 3.6) (open triangles) (b) surface coverage by underpotentially deposited hydrogen (Hupd) and hydroxyl species (OHad) calculated from the cyclic voltammograms (c) segregation profile ascertained from the SXS measurements. (Reprinted with permission from Stamenkovic et al. [2007a]. Copyright 2007. American Association for the Advancement in Science.)...

Figure4. Comparison of UHV and in situ electrochemical data. Solid and dotted lines correspond to the potential drop across the inner layer for the Br/H20 and Cl / H2O systems at a Ag 110 electrode. Full circles correspond to the change in work function of a Ag l 10 surface with Br and water to complete the inner layer (taken from figure 3 c). Open triangles correspond to similar work function data for the Cl / H2O system on Ag l 10. ...

Figure 5. Calculated ternary phase diagram for EC/PC/ DMC as expressed in the form of a composition triangle plane. The dotted lines represent the isotherms with 10 K intervals with 300 K marked. (Reproduced with permission from ref 167 (Figure 12). Copyright 2003 The Electrochemical Society.)...

Fig. 6.97. Some techniques used in the study of isotherms (a) Electrochemical quartz crystal microbalance mass change (AW) vs. quantity of electricity (AG) [Au, 0.1 M HCI04 (a), and 0.05 MH2S04 ( )] and anion coverage vs. electrode potential [poly-Au (open symbols), and Au(111) (dark symbols) HS04 (circles) and CI04 (triangles)]. Reprinted from H. Uchida, N. Ideda, and M. Watanabe, J. Electroanal. Chem. 42 , copyright 1997, Figs. 3 and 5, with permission of Elsevier Science.) (b) Specular reflection method reflectivity change vs. potential [Au, HCI04 with Nal (b) and (c) 0...

Figure 9 Cl2 plasma beam maximum ion energy. Circles = 27 MHz triangles = 100 kHz solid = Cl2+ open = Cl+.20 Reprinted by permission of the publisher. The Electrochemical Society, Inc.

Figure 5. Plot of the logarithm of the competition ratio (ratio of products formed via trapping by acetonitrile and water, respectively) versus percentage water in the solution. Filled circles, p-xylene open circles, o-xylene triangles, hexamethylbenzene. Solid lines, electrochemical reaction broken lines, solvolysis of ArCHjOTs.

Fig. 2.2S. A comparison of the potential dependence for the electrochemical oxidation of NADH at a poly(aniline)/poly(vinylsulfonate)-coated electrode. (fccu,[site]Ds /AwM). and the second-order rate constant for the homogeneous oxidation of NADH by a range of two-electron mediators, k2- The open symbols correspond to homogeneous oxidation by ortho. , and para, O, substituted quinones and diaminobenzenes. the filled triangles. , are the...

Fig. 2.9 Electrochemical degradation of 100-ppm phenol as a function of charge passed for different electrode materials, i = 10 mA cm-2, (a) Phenol removal (b) TOC removal (filled square) Ti/Ru02 (filled triangle) Ti/Sb-Sn-Ru02 (filled circle) Ti/Sb-Sn-Ru02-Gd (open square) Ti/Pb02 and (open circle) Pt. Reprinted from Feng and Li (2003), Copyright (2003), with permission from Elsevier...

Figure 4.36. Normalized resistivity (open points) and conductivity (solid points) profiles for Pt/C cathodes with (triangles) and without (circles) Nafion impregnation [8], (Reproduced by permission of the authors and of ECS—The Electrochemical Society, from Lefebvre MC, Martin RES, Pickup PG. Characterization of ionic conductivity within proton exchange membrane fuel cell gas diffusion electrodes by impedance spectroscopy.)...

Figure 15.3 Current-voltage characteristics of n-GaAs in BP-AICU containing 0.2 M ferrocene and 0.02 M ferricinium chloride Single crystal n-GaAs (triangle) polycrystalline n-GaAs (circle). The light intensity in these experiments was 100 mW cm [10]. (Reprinted by permission of the Publisher, The Electrochemical Society).

Oxygen surface coiiceiitiatlon of the Ni(lll) dosed with O2 calculated from AES spectra In percent ( ) versus O2 exposure In L. Shown In the figure also are oxygen surface concentrations of Ni(111) pre-covered with CO-c(4x2) prior to O2 exposure (O) and transfer into the auxiliary chamber ( ). The triangle Indicates the oxygen concentration alter a bare Nl(lll) was exposed Co electrochemical environment und then transferred back Co Che main chamber. 

Central Laboratory for Electrochemical Power Sources, Bulgaria, S.E.A. Tudor, Politecnico di T orino, BritejEuram Project BE97—4085, Task 3 Improvements in negative plate performance. Annual Report 1 January 1999 to 31 December 1999, Advanced Lead-Add Battery Consortium, Research Triangle Park, NC, USA, 2000. 

Figure 24. Effect of the composition of the IrOj-TiOa/YSZ catalyst films on the rate of C2H4 oxidation under open-circuit (open circles) and electrochemical promotion (full circles) conditions. Triangles indieate the corresponding rate enhancement ratio (p) value. Experimental conditions as in Figure 23. Reprinted from Ref. with permission from Academic Press.

Fig. 7.22 Pressure-composition isotherms (squares) for (a) Gd, (b) Mgo.sGdoj and (c) Mgo.62Gdo.38 alloys as determined electrochem-ically. The corresponding normalized transmission at 1.85eV (triangles) is also shown. (1 bar= 10 Pa) (From Di Vece et al. (2002), Ref [93].)...

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