7.3 Reactivity of CO with Iron Oxides
103
A
B
C
Fig. 7.4 A A typical mass distribution produced for iron oxide anionic clusters. The first iron oxide
in each series is labelled according to Fe n O m
− , where (n, m) with subsequent peaks in the series
have one additional oxygen atom. B The ground state geometries of O 2 , CO, FeO 1–3 , and Fe n O m
−
clusters. The bond lengths are given in Angstroms and the superscripts indicate the spin multiplicity.
The arrows indicate the spin polarization at the Fe atoms for the Fe 2 O m
− clusters. The Mulliken
charges are marked below each atom. C Graphs of the dissociation energy associated with removing
an O atom or O 2 subunit from (a) FeO n
− and (b) Fe 2 O n
− . (c) Graph of the dissociation energy
associated with removing Fe or FeO n from Fe 2 O n
− clusters
comparison, the breaking of Fe–Fe bonds in the dimer clusters Fe 2 O n
− could mainly
occurred at higher energies or under multiple collision conditions [22].
Figure 7.5 shows the reactivity of FeO 2
− , FeO 4
− , Fe 2 O 3
− and Fe 2 O 6
− with CO,
where the reactant and product signals change as a function of increasing CO pressure. These cluster stoichiometries, especially FeO 2
− and Fe 2 O 3
− which both are
composed of one more oxygen atom than the number of iron atoms, were found to be
the most efficient iron oxide anions by following the CO oxidation reaction channel.
Theoretical studies showed that the atomization energy of CO and CO 2 are 11.63 and
17.97 eV, respectively, that is, the formation of CO 2 is energetically feasible in cases
where it takes less than 6.34 eV to remove an O atom from the cluster, providing no
insurmountable reaction barriers to prevent the formation of CO 2 . The presence of
Fe n O m−1
− products (mass-selected reaction from Fe n O m
− ) suggested that oxygen
103
A
B
C
Fig. 7.4 A A typical mass distribution produced for iron oxide anionic clusters. The first iron oxide
in each series is labelled according to Fe n O m
− , where (n, m) with subsequent peaks in the series
have one additional oxygen atom. B The ground state geometries of O 2 , CO, FeO 1–3 , and Fe n O m
−
clusters. The bond lengths are given in Angstroms and the superscripts indicate the spin multiplicity.
The arrows indicate the spin polarization at the Fe atoms for the Fe 2 O m
− clusters. The Mulliken
charges are marked below each atom. C Graphs of the dissociation energy associated with removing
an O atom or O 2 subunit from (a) FeO n
− and (b) Fe 2 O n
− . (c) Graph of the dissociation energy
associated with removing Fe or FeO n from Fe 2 O n
− clusters
comparison, the breaking of Fe–Fe bonds in the dimer clusters Fe 2 O n
− could mainly
occurred at higher energies or under multiple collision conditions [22].
Figure 7.5 shows the reactivity of FeO 2
− , FeO 4
− , Fe 2 O 3
− and Fe 2 O 6
− with CO,
where the reactant and product signals change as a function of increasing CO pressure. These cluster stoichiometries, especially FeO 2
− and Fe 2 O 3
− which both are
composed of one more oxygen atom than the number of iron atoms, were found to be
the most efficient iron oxide anions by following the CO oxidation reaction channel.
Theoretical studies showed that the atomization energy of CO and CO 2 are 11.63 and
17.97 eV, respectively, that is, the formation of CO 2 is energetically feasible in cases
where it takes less than 6.34 eV to remove an O atom from the cluster, providing no
insurmountable reaction barriers to prevent the formation of CO 2 . The presence of
Fe n O m−1
− products (mass-selected reaction from Fe n O m
− ) suggested that oxygen