| Abstract: | Previously reported experiments from our laboratory showed that soot oxidation by oxygen atoms at 298 K was dominated by large net oxygen atom adsorption on this soot. The adsorbed oxygen was stable at 298 K; at elevated temperatures, this oxygen desorbed entirely as carbon monoxide and carbon dioxide. Here, we describe experiments using electron microscopy and nitrogen adsorption measurements to characterize the as-collected soot, soot loaded with varying amounts of adsorbed oxygen, and this oxygen-loaded soot that has been thermally degassed. The electron micrographs show small changes in the soot except at very long oxygen-atom exposure times, for which significant carbon gasification has occurred. The nitrogen adsorption measurements show large increases in the micropore structure of soot on thermal desorption of the adsorbed oxygen. These results confirm our earlier conclusion that oxygen atom adsorption occurs throughout the soot particles, not just on the surface. These data further show that thermal desorption (of CO and CO2) occurs from within the soot particles and does not result from migration of the chemisorbed oxygen to the soot surface. |
