Electrocatalytic approach

Considerably less work has been reported on an electrocatalytic approach to modeling cytochrome P-450 utilizing an electrochemically reduced metalloporphyrin (Fe or Mn) in the presence of... 

Last but not least, from the process improvement point of view, a research group at Sepracor led by Yun Gao has developed an extremely effective electrocatalytic version of the catalytic AD process (see Section 6D.2.2) [37]. As symbolized in Figure 6D.3, this electrocatalytic approach to AD appears to be ideal. Enantiomerically pure diols arise from electricity, water, and olefins compounds, with hydrogen gas and a little water over the dam as the only byproducts. 

A case has been (X2.) made for a mechanistic commonality between gas/solid and electrocatalytic approaches to similar reactions such as the interaction of hydrogen molecules or CO with Pt surfaces. Unsupported Ru has exceptional activity for methanation and Fischer-Tropsch type gas/solid reactions (121. The electrochemical formation of CH has only been observed on Ru and not with other materials such as Pt, Mo, C, Pd, Ag, Os, Ni, GaAs, GaP, and Si (14.) Evidently the exceptional character of Ru in gas phase reactions is carried over in electrochemical systems. It is useful to discuss our electrochemical results vis it vis what is known about the gas/solid methanation reaction. However the formation of CH from CO (15.) rather than CO2 (16.), is much better characterized. 

We are able to give a thermodynamic basis for the distinction between catalytic and electrocatalytic approach to a given system. In the case of catalytic hydrogenation H2 and should be considered as components of the system. In contrast to this, treating the system in terms of electrocatalysis and electrons have to be considered as components. 

Attachment Strategies It has been shown that a film of adsorbed laccase will exchange electrons directly with a PGE electrode, leading to electrocatalytic O2 reduction, but the adsorbed film is very unstable [Blanford et al., 2007]. Several approaches have been employed to generate films of laccase that are stable for many days and show higher electrocatalytic current density. 

Figure 17.6 Redox hydrogel approach to immobilizing multiple layers of a redox enzyme on an electrode, (a) Structure of the polymer, (b) Voltammograms for electrocatalytic O2 reduction by a carbon fiber electrode modified with laccase in the redox hydrogel shown in (a) (long tether) or a version with no spacer atoms in the tether between the backbone and the Os center (short tether). Reprinted with permission fi om Soukharev et al., 2004. Copyright (2004) American Chemical Society.

Special electrochemical sensors that operate on the principle of the voltammetric cell have been developed. The area of chemically modified solid electrodes (CMSEs) is a rapidly growing field, giving rise to the development of new electroanalytical methods with increased selectivity and sensitivity for the determination of a wide variety of analytes [490]. CMSEs are typically used to preconcentrate the electroactive target analyte(s) from the solution. The use of polymer coatings showing electrocatalytic activity to modify electrode surfaces constitutes an interesting approach to fabricate sensing surfaces useful for analytical purposes [491]. 

A new approach to improve the performance of solar devices using natural pigments is to employ carbon nanotube (CNT)-based counter-electrodes. As previously reported, the excited dye transfers an electron to Ti02 and so it acquires a positive charge. Then, the cationic molecule subtracts an electron from the counterelectrode which is transported by the electrolyte. This reaction is usually catalyzed by means of conductive and electrocatalytically active species for triiodide reduction of carbon coatings. CNTs have a high superficial area, which represents a very... 

Modified electrodes containing cyclam derivatives have been prepared. The approach utilizing cyclam incorporated in Nafion film on a carbon electrode shows that the catalytic efficiency of the system is much lower than observed when the catalyst is adsorbed on the mercury. With electrodes prepared following the Langmuir Blodgett technique, only the electrode materials that allow the orientation of the monolayer so that the tail points to the substrate were found to be electrocatalytically active.165... 

A way to circumvent the first problem is to ensure that all of the active material is present at the electrode surface. That is, employ a chemically modified electrode where a precursor to the active electrocatalyst is incorporated. The field of chemically modified electrodes Q) is approaching a more mature state and there are now numerous methodologies for the incorporation of materials that exhibit electrocatalytic activity. Furthermore, some of these synthetic procedures allow for the precise control of the coverage so that electrodes modified with a few monolayers of redox active material can be reproducibly prepared. Q)... 

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. 

On the basis of the combined weight of the above results, we believe that bifunctional electrocatalytic properties may be operative for both MOR and ORR on the AuPt bimetallic nanoparticle catalysts depending on the nature of the electrolyte. For ORR in acidic electrolyte, the approaching of both the reduction potential and the electron transfer number for the bimetallic catalyst with less than 25%Pt to those for pure Pt catalyst is indicative of a synergistic effect of Au and Pt in the catalyst. For MOR in alkaline electrol)he, the similarity of both the oxidation potential and the current density for the bimetallic catalyst with less than 25%Pt to those for pure Pt catalyst is suggestive of the operation of bifunctional mechanism. Such a bifunctional mechanism may involve the following reactions ... 

Investigations of enzyme-catalyzed direct electron transfer introduce the basis for a future generation of electrocatalysts based on enzyme mimics. This avenue could offer new methods of synthesis for nonprecious metal electrocatalysts, based on nano-structured (for example, sol—gel-derived) molecular imprints from a biological catalyst (enzyme) with pronounced and, in some cases, unique electrocatalytic properties. Computational approaches to the study of transition state stabilization by biocatalysts has led to the concept of theozymes . " ... 

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