Results electrode

There was a clear difference between the target and the nontarget samples in their DPV responses when the resulting electrodes were operated or treated under... 

In addition to the use of composite anodes and cathodes, another commonly used approach to increase the total reaction surface area in SOFC electrodes is to manipulate the particle size distribution of the feedstock materials used to produce the electrodes to create a finer structure in the resulting electrode after consolidation. Various powder production and processing methods have been examined to manipulate the feedstock particle size distribution for the fabrication of SOFCs and their effects on fuel cell performance have also been studied. The effects of other process parameters, such as sintering temperature, on the final microstructural size features in the electrodes have also been examined extensively. 

Due to the important relationship between particle size of starting powders and resulting electrode microstructure and corresponding performance, much work has been performed to modify the particle size and morphology of the starting powders used in SOFC processing. Additional methods have been investigated to better control the microstructure and properties of fuel cell components, which are discussed in more detail in Section 6.2. 

Numerous bisthiols have been observed to form spontaneously multilayers on gold and silver on the basis of the oxidative formation of disulfides.15-27 Nonetheless, most of these compounds lack electroactive character, with few notable exceptions.23,27 In principle, the introduction of redox centers at the core of these molecules and their subsequent assembly into multilayers can be exploited to generate electroactive films. The concentration of redox centers within the resulting electrode coatings, as well as their thickness, can be significantly larger than those possible with electroactive thiols such as 1-4 (Fig. 7.1).11 14 In addition, the transition from electroactive monolayers to electroactive multilayers can translate into a significant enhancement in stability and a much more effective protection of the electrode surface. 

The electrode material also may be manipulated to achieve more specific or more reliably controlled performance. Specific catalysts for desired reactions may be incorporated into the electrode material or bound to the surface of the electrode. A present example is the coating of a carbon or other inert electrode with a polymer film impregnated with a mercuric salt. The resulting electrode is catalytic for reduction of metals, such as Pb2+, that are soluble in mercury. This is an area of research that could pay off through qualitative improvements in accuracy, precision, and response time. 

Note particularly that film electrodes make it economically practical to use very expensive materials as electrodes because of the very small quantities required to form the film. For example, a platinum film of 300 nm thickness and 1 cm2 cross-sectional area contains 640 pg of platinum. A macroscopic wire electrode of the same surface area constructed with 26-gauge platinum wire (0.4 mm diameter, 7.9 cm long) contains 210 mg of platinum, or 330 times as much platinum. At a price of 60/g, the cost of the platinum in the film ( 0.04) is much lower than the cost of the wire ( 12.80). Despite the great reduction in raw materials cost, the resulting electrode may not actually be proportionally less expensive than bulk platinum for small numbers of film electrodes, due to significantly greater fabrication costs. However, when produced on a large scale, costs of film electrodes may be dramatically lower. 

In one approach crown ethers (31) or (32) are mixed with PVC and a plasticizer such as o-ni-trophenyl octyl ether in THF to give a membrane on evaporation of the solvent. Discs may then be cut and incorporated into electrodes. The resulting electrodes show good selectivity for thallium(I) and are useful in the measurement of thallium concentrations.88... 

Place the above mixture (7 pL) onto the working electrode area and allow to dry for 45 min at room temperature. The resulting electrode should be yellow in colour. 

Direct binding of the ion-selective component to the electrode has also been studied. For example, graphite combined with an antimony compound has been screen printed and the resultant electrodes shown to give selective responses to sulphide ion in simulated wastewater samples (0.01-0.7 mM sulphide) with high stability to repeated testing and low interference from other compounds [31]. 

Cadogan et al. [73] deposited polypyrrole onto platinum from a variety of solutions and found the resultant films to be anion sensitive but very unselec-tive. When polypyrrole was deposited from NaN03 solution, however, the resultant electrode gave near-Nernstian responses to nitrate ion in the range 0.5-0.0005 M with selectivities of about 20 over other lipophilic ions such as iodide and perchlorate [74]. Similar electrodes could be fabricated via a screen-... 

The turnover number, kT, reflects the redox activity of the immobilized cells. The resulting electrode current is given by Faraday s law ... 

Cyclic voltammetric measurements on the resulting electrodes clearly show the presence of the complexes, and, from Ej, values for the RuIII/II couples, that they survive the attachment procedure with their characteristic redox properties intact. XPS (X-Ray... 

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