Chemistry of CCl4 on Fe3O4(1 1 1)-(2 × 2) surfaces in the presence of adsorbed D2O studied by temperature programmed desorption

Temperature programmed desorption (TPD) was used to study surface reactions of Fe3O4(1 1 1)-(2 × 2) sequentially exposed, at ∼100 K, to vapor-phase D2O and CCl4. Previous TPD and XPS results have indicated that in the absence of D2O, CCl4 dissociatively adsorbs on Fe3O4(1 1 1) producing chemisorbed Cl and CCl2. Subsequent heating of the surface results in abstraction of lattice iron and oxygen atoms and causes them to desorb as FeCl2 and OCCl2, respectively. This study shows that when this Fe3O4 surface is exposed only to D2O, TPD measures a rich surface chemistry with multiple desorption events extending as high as ∼800 K, indicating dissociative adsorption of D2O on the Fe3O4(1 1 1) surface. After sequential exposure to D2O and then CCl4, the production of FeCl2 and OCCl2 from adsorbed CCl4 is suppressed, indicating that D2O fragments block the surface reactive sites.