Absence of CO dissociation on Mo(112)

Area of Science:

• Surface Science
• Materials Science
• Computational Chemistry

Background:

• Understanding carbon monoxide (CO) adsorption and dissociation on metal surfaces is crucial for catalysis and materials science.
• The Mo(112) surface presents a unique stepped structure influencing adsorbate behavior.

Purpose of the Study:

• To investigate the adsorption sites, molecular orientations, and thermal dissociation of CO on the Mo(112) surface.
• To determine the energetic feasibility of CO dissociation and its implications for surface reactions.

Main Methods:

• Density-functional theory (DFT) calculations for binding energies, local densities of states, and vibrational frequencies.
• Monte Carlo simulations to interpret temperature-programmed desorption (TPD) spectra.
• Analysis of predicted photoemission signatures.

Main Results:

• Bridge-on-row sites are preferred for CO adsorption, with in-furrow sites occupied at higher coverages.
• CO adopts a tilted orientation (beta state) at low coverage and an upright one (alpha state) at high coverage.
• The estimated barrier for CO dissociation (2.8 eV) significantly exceeds the chemisorption energy (2.1 eV), rendering thermal dissociation improbable.

Conclusions:

• CO adsorption on Mo(112) is characterized by distinct states and orientations without significant thermal dissociation.
• TPD spectra can be explained by adsorption phenomena alone, without invoking dissociation.
• Photoemission studies can distinguish between chemisorbed CO and adsorbed oxygen atoms, confirming the absence of dissociation.