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 wit...