Electrodes technology for

Davenport, J.R. and Jabro, J.D. (2001) Assessment of hand held ion selective electrode technology for direct measurements of soil chemical properties. Commun. Soil Sci. Plant Anal, 32, 3077-3085. 

The use of intermittent BD arrangements employing timers and electrical conductivity electrodes has been standard technology for at least 25 years. Nevertheless, problems still occur that may be attributable to the use of electrodes unsuitable for the temperatures involved or inadequate electrode cleaning and maintenance. 

A series of primary zinc-air cells are developed with capacity ranging from 100 Ah to 3300 Ah and nominal currents ranging from 2 A to 50 A. Technologies for the production of the air electrodes, porous zinc electrodes and for the assembling of the cells are elaborated. Some of the developed zinc-air cells are in production since 1981. 

Ion-selective electrode research for biomedical analysis is no longer the relatively narrow, focused field of identifying and synthesizing ionophores for improved selectivity and the integration of ion-selective electrodes into clinical analyzers and portable instruments. These efforts have matured now to such an extent that they can teach valuable lessons to other chemical sensing fields that are just emerging technologies. 

The technology for making single crystal ball electrodes is inexpensive and well developed [223, 224], Wire of the noble metals Au and Pt can be melted in a hydrogen oxygen flame. By careful manipulation of the flame on the ball, it can be recrystallized repeatedly to form a perfect single crystal. The crystals have a set of flat spots, [111] planes, which develop on the surface. These facets feature some of the... 

Electrochemical infrared spectroscopy can be used on all kinds of electrodes and for all substances that are IR active. It is particularly useful for the identification of reaction intermediates, and has been used extensively for the elucidation of the mechanisms of technologically important reactions. A case in point is the oxidation of methanol on platinum, where linearly bonded = C = O (i.e., CO bonded to one Pt atom) has been identified as an intermediate Figs. 15.7 and 15.8 show EMIRS [6c] and IRRAS [8] spectra of this species. Near 2070 cm-1 the EMIRS spectrum shows the typical form produced by a peak that shifts with potential. This shift can be followed in the IRRAS spectrum... 

As in the case with PAFC s, voltage obtained from an AFC is affected by ohmic, activation, and concentration losses. Figure 4-7 presents data obtained in the 1960 s (18) which summarizes these effects, excluding ohmic losses, for a catalyzed reaction (0.5-2.0 mg noble metal/cm ) with carbon-based porous electrodes for H2 oxidation and O2 reduction in 9 N KOH at 55-60 C. The electrode technology was similar to that employed in the fabrication of PAFC electrodes. Performance of AFC s with carbon-based electrodes has not changed dramatically since these early results were obtained. 

The data in Table 6-1 provide a chronology of the evolution in cell component technology for MCFCs. In the mid-1960s, electrode materials were, in many cases, precious metals, but the technology soon evolved to the use of Ni-based alloys at the anode and oxides at the cathode. 

The SPE technology solves some problems but it poses others. In particular, the strong acid environment developed on the membrane calls for a complete change of electrode materials from those used in the conventional alkaline electrolysis. More specifically, especially the requirements for electrode materials for O2 evolution are stringent since the anodic conditions are especially aggressive for corrosion problems. 

As discussed above, Pt is the reference electrode material for H2 evolution since it is the most active elemental cathode. H2 is formed on Pt with a Tafel slope of 30-40 mV, the lowest ever observed for this reaction. Its cost makes this metal unsuitable for routine applications. In fact, cathode materials traditionally used in technology have long been iron or mild steel in acidic solution and Ni in (strongly) alkaline solution. Steel can also be used in moderately basic solution. 

Bio-Electrics, Incorporated, has developed the Electrofrac Detoxification System to treat hazardous contaminants in soil. The system, which was developed from gasification research, uses electrodes placed in soil to heat the site. There are potential applications of this technology for removal of volatile organic compounds (VOCs), pyrolysis of non-VOCs, treatment of organic residues, and in situ vitrification of soils and asbestos. There have been bench-scale tests of the technology for remediation applications. 

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