Electrochemical oxygen reduction

The experimental activation energy extrapolated to zero current for the oxygen electrochemical reduction on platinum in acidic media is around 1 eV [42,43] and the experimental current density at... 

The conventional electrochemical reduction of carbon dioxide tends to give formic acid as the major product, which can be obtained with a 90% current efficiency using, for example, indium, tin, or mercury cathodes. Being able to convert CO2 initially to formates or formaldehyde is in itself significant. In our direct oxidation liquid feed fuel cell, varied oxygenates such as formaldehyde, formic acid and methyl formate, dimethoxymethane, trimethoxymethane, trioxane, and dimethyl carbonate are all useful fuels. At the same time, they can also be readily reduced further to methyl alcohol by varied chemical or enzymatic processes. 

Two techniques, electrochemical reduction (section IIl-C) and Clem-mensen reduction (section ITI-D), have previously been recommended for the direct reduction of isolated ketones to hydrocarbons. Since the applicability of these methods is limited to compounds which can withstand strongly acidic reaction conditions or to cases where isotope scrambling is not a problem, it is desirable to provide milder alternative procedures. Two of the methods discussed in this section, desulfurization of mercaptal derivatives with deuterated Raney nickel (section IV-A) and metal deuteride reduction of tosylhydrazone derivatives (section IV-B), permit the replacement of a carbonyl oxygen by deuterium under neutral or alkaline conditions. 

Three different methods have been discussed previously (sections III-C,III-D and IV-A) for the replacement of a carbonyl oxygen by two deuteriums. However, in the conversion of a 3-keto steroid into the corresponding 3,3-d2 labeled analog, two of the three methods, electrochemical reduction (section ni-C) and Raney nickel desulfurization of mercaptal derivatives (section IV-A), lead to extensive deuterium scrambling and the third method, Clemmensen reduction (section III-D), yields a 2,2,3,3,4,4-dg derivative. 

Nitroxides are iV, iV-disubsdnited nitric oxide radicals, the unpaired electron being delocalized between the nitrogen and oxygen The reduction of 2-methyl-2-nitropropane with sodium or electrochemically yields di-r-butyl nitroxide as the final product " Such nitroxide radicals are important for the snidy of a organic ferromagnet... 

The electrochemical reduction of oxygen usually proceeds via two well-separated two-electron steps. The first step corresponds to the formation of hydrogen peroxide ... 

However, no such catalysis was detected. The reason was that even very small amounts of iodide adsorbed on the platinum electrode strongly inhibited the electrochemical reduction of oxygen. A less dramatic but more instructive example was provided by Xiao and Spiro s study of the reaction... 

Bregoli LJ. 1978. The influence of platinum crystallite size on the electrochemical reduction of oxygen in phosphoric acid. Electrochim Acta 23 489-492. 

El Kadiri F, Fame R, Dmand R. 1991. Electrochemical reduction of molecular-oxygen on platinum single-crystals. J Electroanal Chem 301 177-188. 

Genies L, Eaure R, Durand R. 1998. Electrochemical reduction of oxygen on platinum nanoparticles in alkaline media. Electrochim Acta 44 1317-1327. 

El-Deab MS, Okajima T, Ohsaka T. 2003. Electrochemical reduction of oxygen on gold nano-particle-electrodeposited glassy carbon electrodes. J Electrochem Soc 150 A851-A857. 

Vassilev P, Koper MTM. 2007. Electrochemical reduction of oxygen on gold surfaces A density functional theory study of intermediates reaction paths. J Phys Chem C 111 2607-2613. 

BetteUieim A, Parash R, Ozer D. 1982. Catalysis of oxygen cathodic reduction by adsorbed iron(in)-tetra(A,A,A-trimethylanilinium)porphyrin on glassy carbon electrodes. J Electrochem Soc 129 2247. 

The electrochemical reduction of oxygen to form hydrogen peroxide is a very interesting process which has not suffered the expected development due to its... 

Sljukic B, Bank CE, Compton RG (2005) Exploration of stable sonoelectrocatalysis for the electrochemical reduction of oxygen. Electroanalysis 17 1025-1034... 

The catalytic layer of the air electrode is made from a mixture of the same hydrophobic material and porous catalyst [2]. It comprises hydrophobic zones through which the oxygen is transported in gas phase and zones containing catalyst where the electrochemical reduction of oxygen is taking place. It must be noted that the overall structure of the electrode is reproducible when various kinds of carbon-based catalysts are used. 

One of the main problems in the development of air gas-diffusion electrodes for metal-air cells is to find active and stable catalysts for the electrochemical reduction of oxygen. Carbon-based catalysts are mostly used, because of their highly developed surface area and capability for adsorption of 02, suitable morphology, chemical stability, good electric conductivity and comparatively low price. 

Iliev I., Gamburzev S., Kaisheva A., Gas-diffusion electrodes with transition metal macrocyclic catalysts for electrochemical reduction of oxygen, Proceedings of the 31 ISE Meeting 1980 Sept. 22 - 26, Venice, Italy, Vol. I, p. 286-288. 

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