| AVS 65th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Thursday Sessions |
| Session HC+SS-ThM |
| Session: | In-situ Analysis of Heterogeneously Catalyzed Reactions |
| Presenter: | Benjamin Hagman, Lund University, Sweden |
| Authors: | B. Hagman, Lund University, Sweden A. Posada-Borbón, Chalmers University of Technology, Gothenburg, Sweden A. Schaefer, Chalmers University of Technology, Gothenburg, Sweden C. Zhang, Lund University, Sweden M. Shipilin, Stockholm University, Sweden N.M. Martin, Chalmers University of Technology, Gothenburg, Sweden E. Lundgren, Lund University, Sweden H. Grönbeck, Chalmers University of Technology, Gothenburg, Sweden J. Gustafson, Lund University, Sweden |
| Correspondent: | Click to Email |
Due to the urgent problem of global warming, there is a need to reduce the release of the greenhouse gas CO2 into the atmosphere. A potential approach to limit the CO2 release is to convert it into useful chemical products, such as methanol [1]. However, the recycling of CO2 is a challenging task as the molecule is rather inert, which makes it difficult to activate for reduction and subsequent hydrogeneration. The most used metal for this activation is Cu, and a fundamental understanding of how CO2 interacts with Cu surfaces would promote the development of new catalysts for the reduction of CO2 [2].
We have studied the CO2 interaction with both Cu(100) and stepped Cu(911) surfaces at elevated CO2 pressures using Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS). APXPS gives us the ability to probe the changes of the surface during the chemical reaction. In our case, we see that CO2 chemisorbs on the surface and dissociates to O and CO, of which CO desorb, while the atomic oxygen remains on the surface.
For the Cu(100) surface, we observe that the rate of oxygen uptake from CO2 dissociation is constant until the atomic oxygen coverage approaches 0.25 ML, where the rate decreases. After 0.25 ML the rate remains constant until a saturation appears as the oxygen coverage approaches 0.5 ML. Density Functional Theory (DFT) calculations indicate that CO2 can adsorb and dissociate on both the terraces and steps on Cu(100), however, the dissociation is expected to take place mainly on the step as the barrier for the dissociation is lower at such sites. The atomic oxygen, from the dissociation at the step, is expected to diffuse away from the step to the terrace, leaving the number of active sites constant, and explaining the constant oxygen uptake rate. Both the experiment and DFT calculations indicate that the atomic oxygen from the dissociation of CO2 poisons the adsorption and dissociation of CO2 at an oxygen coverage above 0.25 ML, however, we believe that the step can remain active after 0.25 ML.
To confirm the role of the steps on Cu(100), we have also studied the interaction of CO2 and Cu(911). We observe the CO2 adsorption is significantly facilitated by the presence of the steps on the Cu(911) surface as compared to the flat Cu(100). The effect of the facilitated CO2 adsorption on the subsequent dissociation will be discussed.
References:
[1] W. Wang, et al., Chem. Soc. Rev., 40 (2011), pp. 3703-3727
[2] M. D. Porosoff, et al., Energy Environ. Sci., 9 (2016), pp. 62-73.