Oxygen standard reduction potentials

The standard potential for the anodic reaction is 1.19 V, close to that of 1.228 V for water oxidation. In order to minimize the oxygen production from water oxidation, the cell is operated at a high potential that requires either platinum-coated or lead dioxide anodes. Various mechanisms have been proposed for the formation of perchlorates at the anode, including the discharge of chlorate ion to chlorate radical (87—89), the formation of active oxygen and subsequent formation of perchlorate (90), and the mass-transfer-controUed reaction of chlorate with adsorbed oxygen at the anode (91—93). Sodium dichromate is added to the electrolyte ia platinum anode cells to inhibit the reduction of perchlorates at the cathode. Sodium fluoride is used in the lead dioxide anode cells to improve current efficiency. 

Several significant electrode potentials of interest in aqueous batteries are listed in Table 2 these include the oxidation of carbon, and oxygen evolution/reduction reactions in acid and alkaline electrolytes. For example, for the oxidation of carbon in alkaline electrolyte, E° at 25 °C is -0.780 V vs. SHE or -0.682 V (vs. Hg/HgO reference electrode) in 0.1 molL IC0 2 at pH [14]. Based on the standard potentials for carbon in aqueous electrolytes, it is thermodynamically stable in water and other aqueous solutions at a pH less than about 13, provided no oxidizing agents are present. 

What is the standard potential for the reduction of oxygen to water in (a) an acidic solution (b) a basic solution ... 

The above experimental data (Figs. 1 and 2) allow us to estimate the possibility for taking place the oxygen reduction process on PANI catalyst. If the special procedure is not taken to withdraw oxygen out of solution, PANI electrode in 1 M HC1 usually demonstrates a potential of about 0.6 V (SHE). In compliance with the Fig. 1 the position of the reduction peak might be at 0. 28 V. From the data of the standard potentials for the following reaction ... 

Extrapolation of the linear portion of the curves to the standard oxygen reduction potential gives the corresponding exchange current density, a measure of the equilibrium rate of the reaction [35]. The results are given in Table I. Within... 

The same method was also used to derive the standard potential for the concerted reduction of some endoperoxides, these values are also listed in Table 4. The BDE of endoperoxides is smaller than that for aeyclic peroxides, which is reasonable due to the added strain and the eelipsing interactions of the lone pairs on the oxygen. 

In type 2, the homogeneous redox reaction of the electrogenerated and regenerated redox catalyst consists of a chemical reaction. For oxidations, these reactions may be hydride ion or hydrogen atom abstraction, oxygen transfer, or an intermediate complex or bond formation. For reductions, hydride or car-banion transfer from a metal complex is often observed. In all these cases, very large potential differences between the standard potential of the substrate and the redox catalyst may be overcome. The selectivity can be very high and may... 

What is the standard potential for the reduction of oxygen to water in (a) an acidic solution (b) a basic solution (c) Is Mn04 more stable in an acidic or a basic aerated solution (a solution saturated with oxygen gas at 1 atm) Explain your conclusion. 

In acetonitrile, the valence band of Ti02 lies at about +2.4 V versus the standard calomel electrode and the conduction band lies at -0.8 V. The hole migrates to the surface where it oxidizes adsorbed olefin (oxidation potential = +1.4 V), producing a surface-bound cation radical. The electron also migrates to the surface where it is captured by adsorbed oxygen (reduction potential = -0.75 V), forming adsorbed superoxide. 

The two cathodic partner reactions in corrosion are hydrogen evolution and oxygen reduction. Consider the Electrochemical Series (for a full list, see The Handbook of Chemistry and Physics) and work out a rule that gives the standard reversible electrode potential, less negative than which (pH 7 and aMzt = lO 6 M) a metal will no longer have a tendency to corrode (a) in 1 M acid and (b) in 1 M alkali. (Bockris)... 

Moore then explained how mitochondria are biological fuel cells. The oxygen reduction taking place in a mitochondrion is exactly the same as in a standard fuel cell. Using several enzymes and only earth-abundant elements, the mitochondrion converts electrochemical potential to biochemical work with efficiency greater than 90 percent. This is a steady-state process in which protons are pumped across the membrane to maintain its electrical potential. If... 

Standard reduction potentials for reactions in biochemical systems are normally determined at pH = 7. From the discussion above, it can be seen that the corresponding potentials for the hydrogen and oxygen reduction reactions at this pH value are... 

Oxygen, from a thermodynamic point of view, is a strong oxidant if the reduction occurs in a more-or-less synchronous four-electron step (log K = 83.1 for equation 1). However, O2 is a much weaker oxidant if the first two-electron reduction sequence becomes operative only if the second reduction sequence (H2O2 H2O) is much slower (presumably because of the cleavage of the 0—0 bond) than the first one, the reaction 02 + 2H" +2e = H2O2 with a standard potential of only 0.69 V (log K = 23.5) determines the oxidizing ability of O2. This seems to be the case for the electronation of oxygen in many electrode systems. 

D25.12 Corrosion is an electrochemical process. We will illustrate it with the example of the rusting of iron, but the same principles apply to other corrosive processes. The electrochemical basis of corrosion that occurs in the presence of water and oxygen, is revealed by comparing the standard potentials of the metal reduction, such as... 

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