Density Functional Theory Study of CO Adsorption and Dissociation on Molybdenum(100)

Abstract

The adsorption of CO on Mo(100) has been calculated for several adsorption states at four surface coverages using density functional theory (DFT). Dissociation of CO on Mo(100) has been investigated for two surface coverages: 0.25 and 0.5 monolayer (ML). A full analysis of the vibrational frequencies of CO was performed, to determine whether structures are stable adsorption states or transition states. Results show that CO adsorbs molecularly on the Mo(100) surfaces up to coverages of 0.5 ML at 4-fold hollow sites with the molecular axis tilted away from the surface normal by 55−57° and dissociates easily with activation energies ranging from 0.45 to 0.56 eV, leading to energy gains of −1.71 and −0.59 eV at 0.25 and 0.5 ML, after dissociation, respectively. The adsorption energy of the CO molecule at 0.25 ML is −2.64 eV with a C−O stretching vibration of 1062 cm-1. Increasing the CO surface concentration leads to a lower C−O stretching frequency of 958 cm-1, which is remarkable, and it is in conflict with the Blyholder model and previous experimental observations for CO on transition-metal surfaces. Furthermore, calculations reveal that reported CO desorption peaks in literature, thought to be due to recombination of carbon and oxygen, are more likely due to molecular desorption of CO at the 4-fold hollow position with a tilted geometry. This conclusion is supported by the low recombination energies calculated (one-third of that described in literature).

Biomass hydrodeoxygenation catalysts innovation from atomistic activity predictors

“…On the bcc(100) surfaces, the adsorption of oxygen occurs preferentially on the hollow sites of Fe(100) and on the bridge sites of Mo (100) and W(100). This is in agreement with previous computational studies [149][150][151][152].…”

“…On the bcc(100) surfaces, the adsorption of oxygen occurs preferentially on the hollow sites of Fe(100) and on the bridge sites of Mo(100) and W(100). This is in agreement with previous computational studies [148][149][150][151]. The hollow sites were identified as the most stable positions for oxygen adsorption on the (110) surfaces of Fe and W while the long bridge position is most favourable on Mo (110).…”

Synthesis of Hollow Pt-Ni Nanoboxes for Highly Efficient Methanol Oxidation

“…Briefly, calculations were performed by including plane-waves with a kinetic energy below or equal to 400 eV. A projector-augmented wave (PAW) method, which essentially combines the accuracy of all-electron methods and the computational simplicity of the pseudopotential approach 49 , was used to describe the electron-ion interaction for Pt, Ni, C and O atoms 50 . For CO molecule was calculations a cubic unit cell of 10 × 10 × 10 Å 3 was used.…”

CO dissociation induced by adsorbed oxygen and water on Ir(111)

“…A fundamental understanding of CO dissociation on transition metals is important for Fischer-Tropsch synthesis (FTS). 1 The FTS process, which produces hydrocarbons from CO and hydrogen, has received widespread attention as an alternative to petroleum. 2 Thus, adsorption and dissociation of CO have been investigated experimentally and theoretically on group-VIII transition metals (Fe, 3 Pt, 4 Ni, 5 Co, 6 Rh, 7 Ru, 8 and Pd 9 ) and non-VIII group transition metals (Mo, 10 W, 11 Ag, 12 and Cu 13 ).…”