Electro-catalysts sensing

A different tact for the sensing of ammonia is the use of an electro-catalyst Table 16.2 overviews the various approaches which utilise metallic (and alloys and oxides thereof) micro- and nano-particles of various shapes and geometries. Platinum is the most commonly explored electro-catalyst for the electrochemical oxidation of ammonia and through its utilisation the slow kinetic rates and large overpotentials of the electrochemical oxidation are overcome. Ideally an effective electro-catalyst should satisfy a number of requirements, such as reasonable cost, high activity, minimum Ohmic loss and long-term stability which may of course... 

Clearly the majority of the electro-catalysts explored in Table 16.2 lend themselves to fuel cell applications. A key parameter to the success of the electrocatalytic sensing of ammonia involves the design of the catalyst. That is, a surface which gives rises to a large active surface area which also stabilises active intermediates and is of a composition to induce changes in the activation energy. The performance of the electro-catalyst is characterised by the mass activity (MA activity mass ) which is the current density (at a specific potential) normalised by the mass of the electro-catalyst which is related to the specific electrochemically active area (SSA area mass ) and the specific activity (SA activity area ) which is the current density normahsed by the electrochemically active surface area (ECSA) of the electro-catalyst. As such, the mass activity is the key parameter given by ... 

Applications of titania nanotube arrays have been focused up to now on (i) photoelectrochemical and water photolysis properties, (ii) dye-sensitized solar cells, (iii) photocatalysis, (iv) hydrogen sensing, self-cleaning sensors, and biosensors, (v) materials for photo- and/or electro-chromic effects, and (vi) materials for fabrication of Li-batteries and advanced membranes and/or electrodes for fuel cells. A large part of recent developments in these areas have been discussed in recent reviews.We focus here on the use of these materials as catalysts, even though results are still limited, apart from the use as photocatalysts for which more results are available. 

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

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