Reductions, hydrogen peroxide

The reaction in equation 55 occurs when there is insufficient hydrogen peroxide reductant in the absorber solution. Monitoring of the hydrogen peroxide concentration is important because is unstable in strong alkaline solutions, decomposing to water and oxygen. A small excess of sodium hydroxide is... 

Adzic RR, Markovic NM. 1982. Structural effects in electrocatalysis Oxygen and hydrogen peroxide reduction on single crystal gold electrodes and the effects of lead ad-atoms. J Electroanal Chem 138 443-447. 

Markovic NM, Tidswell IM, Ross PN. 1994. Oxygen and hydrogen peroxide reduction on the gold(lOO) surface in alkaline electrolyte the roles of surface structure and hydroxide adsorption. Langmuir 10 1-4. 

The kinetics of hydrogen peroxide reduction catalyzed by Prussian blue has been investigated [12, 113]. In neutral media the reaction scheme of H202 reduction has been found to be the following ... 

The electrochemical rate constants for hydrogen peroxide reduction have been found to be dependent on the amount of Prussian blue deposited, confirming that H202 penetrates the films, and the inner layers of the polycrystal take part in the catalysis. For 4-6 nmol cm 2 of Prussian blue the electrochemical rate constant exceeds 0.01cm s-1 [12], which corresponds to the bi-molecular rate constant of kcat = 3 X 103 L mol 1s 1 [114], The rate constant of hydrogen peroxide reduction by ferrocyanide catalyzed by enzyme peroxidase was 2 X 104 L mol 1 s 1 [116]. Thus, the activity of the natural enzyme peroxidase is of a similar order of magnitude as the catalytic activity of our Prussian blue-based electrocatalyst. Due to the high catalytic activity and selectivity, which are comparable with biocatalysis, we were able to denote the specially deposited Prussian blue as an artificial peroxidase [114, 117]. 

Prussian blue-based nano-electrode arrays were formed by deposition of the electrocatalyst through lyotropic liquid crystalline [144] or sol templates onto inert electrode supports. Alternatively, nucleation and growth of Prussian blue at early stages results in nano-structured film [145], Whereas Prussian blue is known to be a superior electrocatalyst in hydrogen peroxide reduction, carbon materials used as an electrode support demonstrate only a minor activity. Since the electrochemical reaction on the blank electrode is negligible, the nano-structured electrocatalyst can be considered as a nano-electrode array. 

Except for Prussian blue activity in hydrogen peroxide, reduction has been shown for a number of transition metal hexacyanoferrates. The latter were cobalt [151], nickel [152], chromium [150], titanium [153], copper [154], manganese [33], and vanadium [28] hexacyanoferrates. However, as was shown in review [117], catalytic activity of the mentioned inorganic materials in H202 reduction is either very low, or is provided by impurities of Prussian blue in the material. Nevertheless, a number of biosensors based on different transition metal hexacyanoferrates have been developed. 

A.A. Karyakin, E.E. Karyakina, and L. Gorton, The electrocatalytic activity of Prussian blue in hydrogen peroxide reduction studied using a wall-jet electrode with continuous flow. J. Electroanal. Chem. 456, 97-104 (1998). 

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]. 

R. Prabhakar, T. Vreven, M. J. Frisch, K. Morokuma and D. G. Musaev, Is the protein surrounding the active site critical for hydrogen peroxide reduction by selenoprotein glutathione peroxidase An ONIOM study, J. Phys. Chem. B, 110 (2006) 13608-13613. 

Figure 12 Proposed mechanism for hydrogen peroxide reduction catalyzed by D. vulgaris Rbr. (Reprinted with permission from Ref. 68. 2003 American Chemical Society)...

From a practical point of view, the performance of 02 cathode materials that display poor or no activity for hydrogen peroxide reduction, such as carbon in alkaline... 

Yet another important aspect that can shed light on the mechanism of dioxygen reduction is the ability of the adsorbed catalyst to reduce and/or chemically decompose hydrogen peroxide. For example, CoTPP and CoTPyP (and certainly bare OPG) display no activity for hydrogen peroxide reduction (n = 2) in the potential region of... 

The rate of hydrogen peroxide reduction important both as a lixiviatu and as an intermediate in oxygen reduction. The rate of H202 reduction is given by ihe aquation16... 

Hydrodesuifurization molybdenum catalysts, 1435 Hydrogen peroxide reduction... 

The electrochemical rate constants for hydrogen peroxide reduction have been found to be dependent on the amount of Prussian blue deposited, confirming that H2O2 penetrates the films, and the inner layers of the polycrystal take part in the catalysis. For... 

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