Iridium nitrogen adsorption

Direct ammonia oxidation is well understood for platinum and some other noble metals [17]. The actual reactant is free ammonia (NH3) therefore more ammonia is oxidized at higher pH values. At low overpotentials, nearly all anrnuuiia is oxidized to N2 as the potential increases, some nitrate and nitrite are produced, and at even higher potentials, the electrodes are poisoned by nitrogen adsorption. Of all tested noble metal electrodes, those with platinum and iridium deposits exhibit a particularly high performance (see, e.g., [18]). Direct anunonia oxidation has also been reported for electrodes without noble metals. Two examples are BDD [12] or... 

Several types of nitrogen substituents occur in known dye stmetures. The most useful are the acid-substituted alkyl N-substituents such as sulfopropyl, which provide desirable solubiUty and adsorption characteristics for practical cyanine and merocyanine sensitizers. Patents in this area are numerous. Other types of substituents include N-aryl groups, heterocycHc substituents, and complexes of dye bases with metal ions (iridium, platinum, zinc, copper, nickel). Heteroatom substituents directly bonded to nitrogen (N—O, N—NR2, N—OR) provide photochemically reactive dyes. 

Whereas determination of chemisorption isotherms, e.g., of hydrogen on metals, is a means for calculating the size of the metallic surface area, our results clearly demonstrate that IR studies on the adsorption of nitrogen and carbon monoxide can give valuable information about the structure of the metal surface. The adsorption of nitrogen enables us to determine the number of B5 sites per unit of metal surface area, not only on nickel, but also on palladium, platinum, and iridium. Once the number of B5 sites is known, it is possible to look for other phenomena that require the presence of these sites. One has already been found, viz, the dissociative chemisorption of carbon dioxide on nickel. 

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