STM and DFT studies of CO2 adsorption on Cu(100)-O surface

TL;DR

This study combines STM experiments and DFT calculations to investigate CO2 adsorption and diffusion on the Cu(100)-O surface, revealing weak binding and specific adsorption sites, with implications for surface chemistry understanding.

Contribution

It provides a detailed combined experimental and theoretical analysis of CO2 adsorption sites, energies, and diffusion barriers on Cu(100)-O, highlighting weak binding characteristics.

Findings

CO2 molecules sit between O atoms in the missing row reconstructed surface.

CO2 molecules are weakly bound and easily perturbed by the STM tip.

Adsorption energies and diffusion barriers indicate weak surface binding.

Abstract

We characterized CO2 adsorption and diffusion on the missing row reconstructed Cu(100)-O surface using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations with dispersion. We deposited CO2 molecules in situ at 5K, which allowed us to unambiguously identify individual CO2 molecules and their adsorption sites. Based on a comparison of experimental and DFT-generated STM images, we find that the CO2 molecules sit in between the O atoms in the missing row reconstructed Cu(100)-O surface. The CO2 molecules are easily perturbed by the STM tip under typical imaging conditions, suggesting that the molecules are weakly bound to the surface. The calculated adsorption energy, vibrational modes, and diffusion barriers of the CO2 molecules also indicate weak adsorption, in qualitative agreement with the experiments. A comparison of tunneling spectroscopy and DFT-calculated density of states shows that the primary change near the Fermi level is associated with changes to the surface states with negligible contribution from the CO2 molecular states.