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Interaction of CO with Gold Under Gas Phase and Electrochemical Environments

preprint
submitted on 24.10.2020, 09:30 and posted on 27.10.2020, 10:10 by Sudarshan Vijay, Thomas Vagn Hogg, Johan Ehlers, Henrik Høgh Kristoffersen, Yu Katayama, Yang Shao-Horn, Ib Chorkendorff, Karen Chan, Brian Seger

We present a joint theoretical-experimental study of CO coverage on Au under both gas phase and electrochemical conditions. By analyzing temperature programmed desorption (TPD) spectra on (211) and (310) surface facets, we show that, under atmospheric CO pressure, the steps of both facets adsorb up to 0.7 ML coverage of *CO, while the terraces have close to zero coverage. We show this result to be consistent with density functional theory calculations of adsorption energies. Under electrochemical conditions on polycrystalline Au, we investigate the CO binding with in situ attenuated total reflection surface enhanced IR spectra (ATR-SEIRAS). We detect a CO band at 0.2V vs. SHE that disappears upon partial Pb underpotential deposition (facet selective), which suggests Pb blocks the CO adsorption sites. With Pb underpotential deposition on single crystals and theoretical surface Pourbaix analysis, we narrow down the possible adsorption sites of CO to open site motifs: (211) and (110) steps, as well as (100) terraces. Ab initio molecular dynamics simulations of explicit water at the Au surface, however, shows the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than steps in an electrochemical environment. The competition between water and CO adsorption can result in different binding sites for *CO on Au in gas phase and electrochemical environments.

Funding

VSUSTAIN project (9455)

Japan Society for the Promotion of Science (JSPS) KAKENHI Grant-in-Aid for Early-Career Scientists (19 K15360)

JSPS Open Partnership Joint Research Projects/Seminars (JPJSBP 120209925)

History

Email Address of Submitting Author

vijays@fysik.dtu.dk

Institution

Technical University of Denmark

Country

Denmark

ORCID For Submitting Author

0000-0001-8242-0161

Declaration of Conflict of Interest

No conflict of interets

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