| AVS 66th International Symposium & Exhibition | |
| Surface Science Division | Friday Sessions |
| Session SS+HC+PS-FrM |
| Session: | Planetary, Ambient, and Operando Environments |
| Presenter: | Jonathan Rodríguez-Fernández, Aarhus University, Denmark |
| Authors: | J. Rodríguez-Fernández, Aarhus University, Denmark Z. Sun, Aarhus University, Denmark E. Rattigan, Aarhus University, Denmark C. Martín, IMDEA Nanoscience, Spain E. Carrasco, IMDEA Nanoscience, Spain E. Pellegrin, ALBA Synchrotron Light Source C. Escudero, ALBA Synchrotron Light Source D. Ecija, IMDEA Nanoscience, Spain J.V. Lauritsen, Aarhus University, Denmark |
| Correspondent: | Click to Email |
Nanostructured cobalt oxides (CoOx) have proven to be interesting low temperature oxidation catalysts, for example for preferential oxidation (PROX) of carbon monoxide (CO). CoOx has been identified as one of the most active materials for CO oxidation showing activity down to temperatures as low as –800C1. However, the pure oxide catalyst seems to be strongly poisoned by water. Some studies indicate that combining CoOx with gold synergistically improves the catalytic performance and poisoning resistance2-3, but an understanding of this metal-oxide effect is lacking. To obtain an atomic scale understanding of the improved catalytic performance of combined Au-CoOx catalysts we have designed a model system where cobalt oxide nanoparticles are synthesized on an Au single crystal surface by physical vapor deposition in an oxygen environment 4-5.
Here, we significantly advance the mechanistic understanding of cobalt oxide nanocatalysts for CO oxidation by studying the surface chemistry of the model catalyst under operando conditions. We use powerful near ambient pressure techniques such as scanning tunneling microscopy (NAP-STM) and synchrotron X-ray photoelectron spectroscopy (NAP-XPS) to study CoOx nanoislands on Au(111) at mbar pressure in a CO/O2 gas mixture. From STM results, we find that the structure of the ~20nm wide monolayer cobalt oxide nanoislands is static during exposure to a mixture of CO and O2 gases at a pressure of 1.5 mbar. Under these conditions at room temperature, the nanoislands seem to exhibit activity towards CO oxidation, and we can detect CO, CO2 surface species by NAP-STM experiments and by analysis of the corresponding O1s and C1s core level NAP-XPS spectra. In addition, we study the morphological evolution by NAP-STM and the reactivity of the CoO nanoislands from RT to 3000C under operando conditions. At around 2000C, CO2 is found in gas phase and decreasing at the surface. Furthermore, to observe the influence of the substrate, we repeated the CoO nanoislands on Pt(111), obtaining similar reactivity results.
References:
1. Xie, X., et al., Nature 458 (2009): 746-749.
2. Cunningham, D. A. H., et al., Catal. Lett. 25 (1994): 257-264.
3. Liu, Y., et al., J. Catal. 309 (2014): 408-418.
4. Fester, J., et al., Nature Communications 8 (2017): 14169.
5. Walton, Alex S., et al., ACS Nano 9.3 (2015): 2445-2453.