Carbon monoxide adsorption on platinum(111) doped with titanium oxide (TiO), iron oxide (FeO), zinc oxide, and iron and platinum ad-atoms. Molecular orbital study of carbon monoxide-dopant interactions

Abstract

An atom superposition and electron delocalization molecular orbital study shows the oxygen end of CO adsorbed on a cluster model of the Pt(l 11) surface is attracted by ir donation to empty d orbitals in Ti and Fe cations and an Fe ad-atom at an adjacent site. This attractive interaction causes tilting from normal and leads to decreases in the CO vibrational frequency of 3-400 cm™1. Adsorbed CO is not attracted toward the closed-shell d10 Zn2+ cation or toward the nearly closed-shell Pt ad-atom because the antibonding counterparts to the it donation orbitals are occupied in these cases. These results are related to the strong metal-support interaction literature by way of a brief review of that literature. The predicted tilting with CO frequency decrease supports Sachtler's conjecture to this effect, but it is suggested that it is still not certain that such CO bond weakening is a necessary or sufficient condition for Fischer-Tropsch selectivity.

Dry reforming of CH4 on Co/Al2O3 catalysts reduced at different temperatures

“…It was supposed that the appearance of this type of adsorbed CO could be an indication of the secondary interaction of CO with a neighboring cobalt atom, which should cause the lateral tilt of the CO. The occurrence of this interaction results in the significant lengthening of C O bond [31]. It means that in our cases the distance between the neighboring cobalt atoms is different when the catalysts were reduced at different temperatures.…”

C–O bond scission on “defect-rich and perfect” Pd(111)?

“…The influence of surface defects on these low-index surfaces cannot be fully ruled out though. The ability of CO to adopt a tilted geometry on early transition metals has been explained in terms of their ability to accept electrons (due to their d-electron-deficiency) [22]. In contrast to the above-mentioned metals, Pd has a filled d-band (4d 10 ) and CO adsorbs perpendicular on Pd(1 1 1) [23,24].…”

8 Surface vibrational spectroscopy on noble metal catalysts from ultrahigh vacuum to atmospheric pressure

“…The ability of CO to adopt a tilted geometry on early transition metals has been explained in terms of their ability to accept electrons (due to their d-electron-deficiency). 261 In contrast to the abovementioned metals, Pd has a filled d-band (4d 10 ) and CO adsorbs perpendicular on Pd (111). 97,257 It seems that also CO molecules adsorbed on sputter-induced defects are not enough tilted to provide the geometry required for CO dissociation (similar arguments also apply for methanol decomposition; see below).…”