Chloromethane surface chemistry on Fe3O4(1 1 1)-(2 × 2): A thermal desorption spectrometry comparison of CCl4, CBr2Cl2, and CH2Cl2

The surface chemistry of CBr2Cl2 on the Fe3O4(1 1 1)-(2 × 2) selvedge of single-crystal α-Fe2O3(0 0 0 1) has been investigated using temperature programmed reaction and desorption (TPR/D) measurements. The spectra obtained in this case show that strong chemisorption occurs and that a series of adsorbed halogenated reaction products are present. By comparison, studies of the adsorbed phase of CH2Cl2 show that only physisorption occurs. The TPR/D spectra of CBr2Cl2 show that dissociative formation of CCl2 followed by its reaction with lattice oxygen is central to the monolayer reaction chemistry in this chloromethane. The branching ratios of the various desorbed products are compared with those obtained from CCl4 adsorbed on the same (2 × 2) surface.