Tin oxide surfaces. Part 18.—Infrared study of the adsorption of very low levels (20–50 ppm) of carbon monoxide in air on to tin (IV) oxide gel
Abstract
Three major types of surface species, unidentate carbonate, bidentate carbonate and carboxylate, are formed when tin(IV) oxide is exposed to dry air containing very low levels of CO(20–50 ppm). All three types appear to be formed immediately and simultaneously upon exposure to the CO–air mixtures, and the abundance of each continues to increase during the period of exposure. Little adsorption occurs at low oxide calcination temperatures when the surface retains a relatively high degree of hydroxylation, but abundances of the three surface species increase markedly at temperatures > 570 K, and appear to reach a maximum at calcination temperatures of ca. 590–610 K, declining thereafter. Although quite stable at lower temperatures, the surface bidentate carbonate and carboxylate slowly transform into surface unidentate carbonate at temperatures ![[gt-or-equal]](https://www.rsc.org/images/entities/char_2a7e.gif)
ca. 400 K under an atmosphere of dry air.
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