| AVS 66th International Symposium & Exhibition | |
| Surface Science Division | Monday Sessions |
| Session SS+HC-MoA |
| Session: | CO2, CO, Water, and Small Molecule Chemistry at Surfaces |
| Presenter: | Seth Shields, The Ohio State University |
| Authors: | S.J. Tjung, The Ohio State University Q. Zhang, The Ohio State University J.J. Repicky, The Ohio State University S. Yuk, The Ohio State University X. Nie, Dalian University of Technology S. Shields, The Ohio State University N. Santagata, University of Memphis A. Asthagiri, The Ohio State University J.A. Gupta, The Ohio State University |
| Correspondent: | Click to Email |
Copper oxide catalysts are promising candidates for reducing CO2 into useful fuels, such as ethanol, but the mechanism remains obscure. Studying the O-Cu(100) surface, which represents the initial transition of the oxidation of copper to copper oxide, and the adsorption process of CO2 has the potential to elucidate the CO2 reduction mechanism.
We performed a DFT/STM theoretical and experimental probe of the properties of CO2 adsorption on the O-Cu(100) surface. The Cu(100) surface was repeatedly sputtered with Ar+ and annealed at 550°C in an ultra-high vacuum chamber, and subsequent Auger spectroscopy revealed the lack of surface contamination. The O-Cu(100) surface was obtained by exposing the Cu(100) face to 10-6 mbar of oxygen for 5 minutes at 300°C. The sample was then cooled and transferred into an attached low temperature (5K) ultra-high vacuum (10-11 mbar) STM chamber.
The atomic resolution STM revealed the (2√2× √2) R45°O-Cu(100) reconstruction, in good agreement with the DFT calculations. The reconstruction consists of an O-Cu-O row structure separated by missing Cu rows. Additionally, there are two equivalent domains which result from nucleation along the [001] and [010] directions of the Cu(100). Differential conductance spectroscopy reveals an increase in the work function of the O-Cu(100) surface, and two additional unoccupied states generated by the oxygen atoms, in agreement with the DFT calculations.
CO2was adsorbed onto the O-Cu(100) surface via in situ dosing in the STM. The CO2 adsorbed exclusively between two oxygen atoms in the missing row reconstruction, which has the largest predicted adsorption energy. The lack of point defects on the surface indicates that the CO2 does not dissociate, and the CO2 molecules are easily disturbed by the tip under all tunneling conditions, which is consistent with the theoretically predicted low diffusion barrier.
This work acknowledges funding from the NSF (1809837).