Electrocatalytical reduction oxygen

Alt H, Binder H, Sandstete G (1973) Mechanism of the electrocatalytic reduction of oxygen on metal chelates. J Catal 28 8-19... 

Toda T, Igarashi H, Watanabe M. 1998. Role of electronic property of Pt and Pt alloys on electrocatalytic reduction of oxygen. J Electrochem Soc 145 4185-4188. 

El-Deab MS, Ohsaka T. 2002b. An extraordinary electrocatalytic reduction of oxygen on gold nanoparticles-electrodeposited gold electrodes. Electrochem Commun 4 288-292. 

Gadamsetti K, Swavey S. 2006. Electrocatalytic reduction of oxygen at electrodes coated with a bimetallic cobalt(II)/platinum(II) porphyrin. J Chem Soc Dalton Trans 5530. 

DR. DAVID STANBURY (Rice University) With regard to the problem of the electrocatalytic reduction of oxygen, I have attempted to formalize some ideas regarding the constraints of thermodynamics in order to elucidate the probable character of cobalt complexes which may catalyze the oxygen electrode via binuclear peroxo-bridged intermediates. The following gross mechanism is presupposed ... 

For the study of the electrocatalytic reduction of oxygen and oxidation of methanol, our approach to the preparation of catalysts by two-phase protocol " provides a better controllability over size, composition or surface properties in comparison with traditional approaches such as coprecipitation, deposition-precipitation, and impregnation. " The electrocatalytic activities were studied in both acidic and alkaline electrolytes. This chapter summarizes some of these recent results, which have provided us with further information for assessing gold-based alloy catalysts for fuel cell reactions. 

The electrocatalytic activity of the nanostructured catalysts was investigated for electrocatalytic reduction of oxygen and oxidation of methanol. Several selected examples are discussed in this section. The results from electrochemical characterization of the oxygen reduction reaction (ORR) are first described. This description is followed by discussion of the results from electrochemical characterization of the methanol oxidation reaction (MOR). 

M. M. Maye, N. N. Kariuki, J. Luo, L. Han, P. Njoki, L. Wang, Y. Lin, H. R. Naslund, and C. J. Zhong, Electrocatalytic reduction of oxygen Gold and Gold-platinum nanoparticle catalysts prepared by two-phase protocol. Gold Bull. 37, 217-223 (2004). 

Electrocatalytic Reduction of Dioxygen The electrocatalytic reduction of oxygen is another multi-electron transfer reaction (four electrons are involved) with several steps and intermediate species [16]. A four-electron mechanism, leading to water, is in competition with a two-electron mechanism, giving hydrogen peroxide. The four-electron mechanism on a Pt electrode can be written as follows ... 

Two examples are selected to describe and discuss the electrocatalytic reduction of di oxygen, the first one with a TMSP [161] and the second one with a sandwich-type complex [162]. The discussion reflects the questions encountered also with usual plenary POMs. 

Summarizing the state of the art for the electrocatalytic reduction of oxygen the following statements can be made. 

One such reaction that has been studied is the electrocatalytic reduction of oxygen directly to water.25,27 The electrocatalysts for this process are often based on metal porphyrins and phthalo-cyanins. Thus a graphite electrode whose surface was modified by the irreversible adsorption of a cofacial dicobalt porphyrin dimer was able to reduce oxygen under conditions where the reduction did not occur on the bare electrode itself. Similarly, a catalytic chemically modified electrode for the oxidation of chloride to chlorine has been prepared28 where the active catalyst was reported to be a ruthenium dimer, [(bipy)2(OH)RulvORuvO(bipy)2]4+, which was reduced to the corresponding [Rum-RuIV] dimer during the reaction. 

However, for some electrocatalytic reactions, such as the electrooxidation of alcohols, aldehydes or acides, and also the electro reduction of oxygen, lead adatoms can exhibit a promoting effect (3-7). Moreover, lead can change the selectivity in the case of electrocatalytic reductions of nitrocompounds (8), whereas it inhibits the adsorption of hydrogen on platinum (9,10),... 

PPy films modified by platinum catalyst particles were also considered for electrocatalytic reactions (oxygen reduction and methanol oxidation) by Hepel et al. [41], The incorporation of a PtCl anion was performed during the electropolymerization of pyrrole and monitored by the electrochemical quartz crystal microbalance (EQCM) technique, allowing us to evaluate the amount of platinum obtained after reduction of the PPy/PtCl film. 

The study of the electrocatalytic molecular oxygen reduction [85-88] on a new class of materials—Chevrel cluster compounds MoeVg (V=Se, S, or Te) [89] see Figure 1(d)—led to the development of the chalcogenide clusterlike compound (Ru cSe ). Figure 1(d) depicts the structure in which one can recognize the clustering... 

Chemically modified electrodes resulting from the attachment of quinones, phenantroline, dipyridyl complexes, and N4 complexes, from the development of polymer-coated carbon materials, and from electrodes modified by enzymes have been specifically designed for the electrocatalytic reduction of molecular oxygen (OERR). Carbon materials with immobilized hydroquinone have also been utilized to accelerate the electrochemical oxidation of molecular hydrogen. 

Electrocatalytic Reductions Table 13 gathers the main electrocatalytic processes triggered by POMs dissolved in solution. The electrocatalytic reductions of di oxygen, hydrogen peroxide and of several NOx including nitrite, nitric oxide, and nitrate are selected for a more detailed description. 

Oxygen Electrocatalytic Properties Oxygen Reduction. Figure 8 compares steady-state polarization curves for the electroreduction of Op on a typical pyrochlore catalyst, Pb2(Rui.42Pbo.53)06.5 15 w/o platinum on carbon. The latter was considered representative of conventional supported noble metal electrocatalysts. The activities of both catalysts are quite comparable. While the electrodes were not further optimized, their performance was close to the state of the art, considering that currents of 1000 ma/cm could be recorded, at a relatively moderate temperature (75 C) and alkali concentration (3M KOH). Also, the voltages were not corrected for electrolyte resistance. The particle size of the platinum on the carbon support was of the order of 2 nanometers, as measured by transmission electron microscopy. 

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