Electrocatalysis hydrogen peroxide

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. 

Anson FC, Ni CL, Saveant JM. 1985. Electrocatalysis at redox polymer electrodes with separation of the catalytic and charge propagation roles. Reduction of dioxygen to hydrogen peroxide as catalyzed by cobalt(II) tetrakis(4-A-methylpyridyl)porphyrin. J Am Chem Soc 107 3442. 

Fig. 18b.9. Example cychc voltammograms due to (a) multi-electron transfer redox reaction two-step reduction of methyl viologen MV2++e = MV++e = MV. (b) ferrocene confined as covalently attached surface-modified electroactive species—peaks show no diffusion tail, (c) follow-up chemical reaction A and C are electroactive, C is produced from B through irreversible chemical conversion of B, and (d) electrocatalysis of hydrogen peroxide decomposition by phosphomolybdic acid adsorbed on a graphite electrode.

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]. 

The ZnO/eosinY hybrid films were prepared by cathodic electrodeposition from a hydrogen peroxide oxygen precursor in chloride medium [484,] and the role of reduced eosin bound to ZnO in the electrocatalysis was discussed. 

Moreover, the conductivity, and hence the catalytic decomposition of hydrogen peroxide, has been observed to influence the stability of the oxygen electrode. The stability of phthalocyanine catalysts is a decisive factor for the practical applicability of organic catalysts in fuel cells operating in an acid medium. This is therefore a very important observation. The observed disturbance of the delocalization of the n electrons (rubiconjugation) in Fe-polyphthalocyanines, in addition to the correlation between conductivity on the one hand, and electrocatalysis and catalytic decomposition of hydrogen peroxide on the other, leads to a special model of the electroreduction of oxygen on phthalocyanines. The model... 

Table 5. Activities of some metal chelates in the catalytic decomposition of hydrogen peroxide and in electrocatalysis with an oxygen cathode 38>...

Figure 4-6. (A) A close-up view of the active site of yeast cytochrome c peroxidase showing the residues in the distal pocket at which hydrogen peroxide is reduced to water. Overlaid on the structure of the wild type enzyme are the positions of residues in the W51F mutant (tryptophan is replaced by phenylalanine). (B) Voltammograms of a film of wild type CcP on a PGE electrode, obtained in the absence and presence of H2O2 at ice temperature, pH 5.0. The electrode is rotating at 200 rpm, but the catalytic current in this case continues to increase as the rotation rate is increased therefore under these conditions the electrocatalysis is diffusion controlled and few facts are revealed about the enzyme s chemistry. For the W51F mutant, the signal due to the reversible two-electron couple and the catalytic wave are both shifted >100 mV more positive in potential compared to the wild-type enzyme. Reproduced from ref. 46 and 47 with permission.

The concentration of hydrogen peroxide can be measured directly using amperometric detection. A change in H2O2 concentration in the medium appears as a variarion in the output current. The quantified parameters are m nitude of the sensor response, response time, and current response. It is desirable to measure signals in conditions when the linear relationship exists between the current value and the analyte concentration. At that point, the reactions are considered to be in steady state when pseudoequilibrium occurs between the species close to the sensor and their consumption at the indicative electrode. One of the serious problems associated with measurement of complex analytes is the possible interference of the redox species present in the sample. Several methods have been reported which aimed at reducing level of interference. These methods include use of perm-selective coatii, use of artificial mediators, or selective electrocatalysis. The use of mediators or selective electrocatalysis helps to lower the detection potential to the level when the majority of interferii species are electroinactive. ... 

Santhosh, R, Manesh, K M., Lee, K R, and Gopalan, A. I. (2006). Enhanced electrocatalysis for the reduction of hydrogen peroxide at new multiwall carbon nanotube grafted polydiphenylamlne modified electrode. Electroanalysis, 18, pp. 894-903. 

Chan, R.J., Y.O. Su, and T. Kuwana (1985). Electrocatalysis of oxygen reduction. 5. Oxygen to Hydrogen peroxide conversion by cobalt (It) tetrakis (V-methyl-4p5ridyl) porphyrin. Inorg. Chem. 24, 3777-3784. 

Sayed SM, Jtittner K (1983) Electrocatalysis of oxygen and hydrogen peroxide reduction by UPD of bismuth on poly- and mono-crystalline gold electrodes in acid solutions. Electrochim... 

Electroreduction of hydrogen peroxide was carried out by montmorillonite clay incorporating Ru(NH3)g Electrocatalysis by polypyridine Os and Ru complexes... 

A potentiometric electrode based on direct mediatorless bio-electrocatalysis for determination of choline and butyryl-choline is developed. The electrode consists of a carbon based material and enzymes peroxidase and choline oxidase co-immobilized on the electrode surface. Choline oxidase catalyzes the reaction of choline oxidation accompanied with hydrogen peroxide formation. Hydrogen peroxide acts as a substrate of the enzyme peroxidase. 

Modification of PANI-coated electrodes with metal tetrasul-fonated phthalocyanines (MeTSPc), where the metal is cobalt or iron, resulted in significant changes in the electrocatalysis of the reduction of diojygen [504]. Obviously, insertion of the MeTsPc into the polymer occurs [505]. This was supported in an investigation by Coutanceau et al. by the results of in situ UV-vis spectroscopy. The role of the polymer in the mechanism and the kinetics of dioxygen electroreduction seemed to be somewhat difficult to elucidate. Insertion of CoTsPc resulted in a positive shift of the onset of dioxygen reduction. The two-electron pathway that results in hydrogen peroxide as a reduction product remains. 

Mashazi P, Mugadza T, Sosibo N, Mdluli P, Vilakazi S, Nyokong T (2011) The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines. Talanta 85 2202-2211... 

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