Organic species fuel cell

Interest in fuel cells has stimulated many investigations into the detailed mechanisms of the electrocatalytic oxidation of small organic molecules such as methanol, formaldehyde, formic acid, etc. The major problem using platinum group metals is the rapid build up of a strongly adsorbed species which efficiently poisons the electrodes. 

Release rates of exudates from phytoplankton range from 0 to 80% of carbon fixed. These rates are dependent on species composition, physiological state, nutrient deficiency, temperature, and Ught limitation. Some evidence suggests that exudation is a mechanism for release of excess organic matter from cells when nutrient availability is too low to enable their usage as metabolic fuel. 

Nature over billions of years has already realized in the leaf a highly complex machinery that utilizes sunlight to oxidize water and produce electrons/protons used in a different part of the cell to reduce CO2, although not to fuels, but to the elements (carbohydrate, lipid, and other organic species) necessary for plant life and growing. The photosynthesis machinery is composed of elements for light... 

A further interesting effect discovered in our laboratories is that the addition of low levels of a second component, or dopant ion, can lead to significant increases in the ionic conductivity [6, 30, 31]. Typically these dopant species, for example, Li, OH , and H" ", are much smaller than the organic ions of the matrix, and since the relaxation times characterizing the motion of these ions are more rapid than those of the bulk matrix itself, these materials may represent a new class of fast ion conductor. The dopant ion effect can be used to design materials for specific applications, for example, Li+ for lithium batteries and H /OH for fuel cells or other specific sensor applications. Finally, we have recently discovered that this dopant effect can also be apphed to molecular plastic crystals such as succinonitrile [32]. Such materials have the added advantage that the ionic conductivity is purely a result of the dopant ions and not of the solvent matrix itself. 

The relatively slow rate of hydrocarbon fuel cell oxidations prompted an intensive examination of the adsorption characteristics of organic reactants in the 1960s. Because of the low potential for the development of hydrocarbon fuel cells, such studies have largely subsided today and no modern surface analysis techniques have been applied to characterize intermediates. Conventional adsorption studies of carbonaceous species have been reviewed repeatedly (7, 9-12, 100 -, therefore, we summarize here only some essential adsorption features for fuel cell and selective electrocatalytic oxidations. 

Electrocatalysis is a heterogeneous process that involves the adsorption and the chemisorption of reactants or intermediates at the interface. These phenomena are encountered, for example, in fuel cells (FCs) or in organic electrosynthesis. The electrocatalytic activity of a given electrode for a certain reaction may be characterized by the current density at a chosen potential, which is proportional to the specific activity, when referred to the effective active surface. As shown in Figure 21.2, the role of a heterogeneous catalyst is to adsorb the electro-reactive species (reactant and intermediate) and transform it to another compound that can more readily undergo the desired... 

A literally nanoarchitectured electrode was reported by Owen et al. [64,65], who electrodeposited nickel/nickel oxide, which is regarded an electrochemi-cally extremely important material whenever applications like fuel cells, the electrolysis of water, batteries or catalysts for the electrochemical hydrogenation of organic species are concerned. Mesoporous nickel electrodes have been electrodeposited by reduction of a nickel(II) solution dissolved within the aqueous... 

In accordance with this historical background, the main goal in the fuel cell oriented research is not changed, i.e., to overcome the blocking effects of the poisoning species by modification of the electrodes. Thus, the study of the behavior of binary catalysts and electrodes modified by metal adatoms or by organic species " remained in the center of interest. 

Methanol Fuel Cells The electrooxidation and dissociation of small organic molecules such as methanol on Pt-based electrodes is one of the most extensively studied systems in terms of both fundamental and applied research in surface (interfacial) electrochemistry (see also Chapter 3.5). It involves a very complex reaction occurring in many steps and various kinds of surface (interfacial) species, including reactants, intermediates, poisons, supporting electrolytes and even solvent... 

Electrochemical cells (electrolysers, batteries and fuel cells) require separators, which allow a flow of specific ionic charges but prevent the transfer of chemical species which remain located either in the cathodic or in the anodic compartment. Among the various separators of electrochemical cells, the ion permeable organic membranes are also used for separation processes such as dialysis and electrodialysis. 

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