Dioxygen electrocatalytic reduction

ELECTROCATALYTIC REDUCTION AND ACTIVATION OF DIOXYGEN 9.10.7.1 Electrocatalytic Four-electron Reduction of Dioxygen... 

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 ... 

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

Electrocatalytic Reduction of Dioxygen and Hydrogen Peroxide These two processes must be emphasized because reduction of dioxygen, and eventually hydrogen peroxide, features the usually claimed pathway for reoxidation of reduced POMs after the participation of the latter in oxidation processes. As a consequence, electrocatalysis of dioxygen and hydrogen peroxide reduction is a valuable catalytic test with most new POMs [154, 156,161]. 

A key step in the macrocyclic-mediated homogeneous electrocatalytic reduction of dioxygen involves encounters between the two species within the electrolyte region immediately adjacent to the electrode surface (see step a in Scheme 3.3). Hence, the course of the process will depend on the relative concentrations, or, more precisely, the fluxes, to be denoted hereafter as njp/Oj" of the mediator and dioxygen. 

Scheme 3.6 Mechanism for the FeTMPyP-mediated electrocatalytic reduction of dioxygen.

Electrocatalytic reduction of dioxygen and hydrogen peroxide in the presence ofMn2Fe2X4 (X = P or As). 685... 

C. Coutanceau, M.J. Croissant, T. Nappom, and C. Lamy, Electrocatalytic reduction of dioxygen at platinum particles dispersed in a polyaniline film, Electrochim. Acta, 46, 579-588 (2000). 

Ricard, D., B. Andrioletti, B. Boitrel, and M. L Her (1999). Electrocatalytic reduction of dioxygen to water by tren-capped porphyrins, functional models of cytochrome c oxidase. Chem. Commun. 1523-1524. 

Salimi, A. and M. Ghadermazi (2001). Electrocatalytic reduction of dioxygen on a glassy carbon electrode modified with adsorbed cobaloxime complex. Anal. Sci. 17, 1165-1170. 

Liu, S.-Q., J.-Q. Xu, H.-R. Sun, and D.-M. Li (2000). me5 o-Tetrakis(4-V-benzylpyridyl)porphyrin and its supramolecular complexes formed with anionic metal-oxo cluster Spectroscopy and electrocatalytic reduction of dioxygen. Inorg. Chim. Acta 306, 87-93. 

El Mouahid, O., C. Coutanceau, E.M. Belgsir, P. Crouigneau, J.M. Leger, and C. Lamy (1997). Electrocatalytic reduction of dioxygen at macrocycle conducting polymer electrodes in acid media. J. Electroanal. Chem. 426, 117-123. 

Collman J, Omg LL, Tyvoll DA (1995) Electrocatalytic Reduction of Dioxygen to Water by Iridium Porphyrins Adsorbed on Edge Plane Graphite Electrodes Inorg Chem 34(6) 1311-1324... 

D Souza F, Hsieh Y, Deviprasad GR (1998) Four-electrrai electrocatalytic reduction of dioxygen to water by an ion-pair cobalt porphyrin dimer adsorbed on a glassy carbon electrode. Chem Commun 9 1027-1028... 

Two examples are selected to describe and discuss the electrocatalytic reduction of dioxygen, 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. 

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