Electrocatalysis systems, design

Electrodes. At least three factors need to be considered ia electrode selection as the technical development of an electroorganic reaction moves from the laboratory cell to the commercial system. First is the selection of the lowest cost form of the conductive material that both produces the desired electrode reactions and possesses stmctural iategrity. Second is the preservation of the active life of the electrodes. The final factor is the conductivity of the electrode material within the context of cell design. An ia-depth discussion of electrode materials for electroorganic synthesis as well as a detailed discussion of the influence of electrode materials on reaction path (electrocatalysis) are available (25,26). A general account of electrodes for iadustrial processes is also available (27). 

Significant (and even spectacular) results were contributed by the group of Norskov to the field of electrocatalysis [102-105]. Theoretical calculations led to the design of novel nanoparticulate anode catalysts for proton exchange membrane fuel cells (PEMFC) which are composed of trimetallic systems where which PtRu is alloyed with a third, non-noble metal such as Co, Ni, or W. Remarkably, the activity trends observed experimentally when using Pt-, PtRu-, PtRuNi-, and PtRuCo electrocatalysts corresponded exactly with the theoretical predictions (cf. Figure 5(a) and (b)) [102]. 

A newly-designed photoelectrocatalytic (PEC) reactor for CO2 reduction, which combines photocatalysis by Ti02 and electrocatalysis by carbon nanotubes (CNT), has recently been proposed (Fig. 7) [152]. A proton-conductive Nafion membrane connects the Ti02 and CNT. Irradiation of the combined system of nano-structured Ti02 deposited on a metal Ti electrode with Pt modified CNT deposited on carbon sheet caused water splitting to H2 and O2. A half-cell for the cathodic electrode, i.e., Pt or Fe modified CNT electrode, produces various organic molecules such as 2-propanol due to electrocatalytic reduction of CO2 on the electrode. The proposed PEC reactor is incomplete in its present state. However, these systems are expected to couple water splitting and CO2 reduction, and thus it may establish a new artificial photosynthetic system. 

Integrated systems refer to heterogeneous films on electrodes designed to contain a mixture of constituents with different functions. For instance, electrocatalysis of organics were successfully achieved with the incorporation of catalytic monomers in carbon paste matrix. Examples are oxidations of alcohol by ruthenium 0x0 complex [59] and ascorbic acid by catechol or aminophenol [60], p-phenylenediamine, or tetramethyl-p-phenylenediamine [61], and Prussian blue [62]. A CME prepared... 

It is evident therefore that it is now possible to characterize electrode-solution interfaces at the molecular level fundamental measurements can be made on systems of practical importance. The significance of the development of these methods (as well as of other new methods in the pipeline ) lies at least in part in the scope this gives for the design and selection of appropriate conditions for electrocatalysis, synthesis, corrosion inhibition, metal plating, operation of battery systems etc. 

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