Dissociative adsorption of CCl4 on the Fe3O4(111)-(2×2) selvedge of α-Fe2O3(0001)

Molecular scale investigations of the reactivity of magnetite with formic acid, pyridine, and carbon tetrachloride

“…17b are Cl atoms, bound atop surface Fe tet1 sites. This interpretation is supported by XPS data suggesting that Cl mobility is confined to the temperature range $450-820 K, when FeCl 2 is observed as a desorbing species (Abib et al, 2003a). In addition, STM data presented by Rim et al (2003Rim et al ( , 2004 support this interpretation.…”

“…The final reaction shown above represents the desorption of FeCl 2 (Eq. (2d)) at temperatures in excess of 820 K. A later XPS study has revealed that the conversion of iron monochloride to iron dichloride occurs within a temperature range of 450-820 K (Abib et al, 2003a), indicating that Cl is mobile on Fe 3 O 4 (111) surfaces in this temperature range. It is unlikely that the mobile species evident in Fig.…”

“…Thus, it follows that at 298 K, OCCl 2 is the dominant desorbing species, which means that the CCl 2 intermediate must be mobile at the surface since this species is a prerequisite of phosgene desorption. The detection of surface bound CCl 2 but not OCCl 2 using XPS at 100 K indicates that the formation of the latter is a two-step process, with the formation of a carbonyl bond involving the CCl 2 intermediate and a surface oxygen requiring thermal activation (Abib et al, 2003a). It is proposed that the mobile population of adsorbates seen in Fig.…”

“…We believe that these are the first atomic resolution observations showing both mobile reaction intermediates and immobile reaction products on an iron oxide surface. Despite the lack of direct chemical information from STM experiments, it is possible to interpret our observations with the help of earlier temperature programmed desorption (TPD) and XPS investigations of CCl 4 adsorption on Fe 3 O 4 (111) surfaces (Abib et al, , 2003a. Abib et al (2002) have investigated the interaction of CCl 4 with a Fe 3 O 4 (111) selvage formed on a aFe 2 O 3 (0001) substrate using TPD analysis.…”

“…(2) represents the dissociative adsorption of CCl 4 , which has been shown to occur spontaneously on Fe 3 O 4 (111) at 100 K (Abib et al, 2003a). The dissociation of an individual CCl 4 molecule results in the adsorption of CCl 2 and 2Cl at the surface.…”