The Dynamic Nature of CO Adlayers on Pt(111) Electrodes. Issue 15 (18th February 2020)

• Record Type: Journal Article
• Authors: Wei, Jie; Amirbeigiarab, Reihaneh; Chen, Yan‐Xia; Sakong, Sung; Gross, Axel; Magnussen, Olaf M.
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 15(2020)
• Page Start: 6182
• Page End: 6186
• Publication Date: 2020-02-18
• Subjects: CO adlayer -- density functional theory -- scanning tunneling microscopy -- Pt(111) -- surface mobility; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201913412
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: CO adlayers on Pt(111) electrode surfaces are an important electrochemical system and of great relevance to electrocatalysis. The potential‐dependent structure and dynamics of these adlayers are complex and still controversial, especially in the CO pre‐oxidation regime. We here employ in situ high‐speed scanning tunneling microscopy for studying the surface phase behavior in CO‐saturated 0.1 m H2 SO4 on the millisecond time scale. At potentials near the onset of CO pre‐oxidation local fluctuations in the (2×2)‐CO adlayer are observed, which increase towards more positive potentials. Above 0.20 V (vs. Ag/AgCl), this leads to an adlayer where COad apparently reside on every top site, but still exhibit a (2×2) superstructure modulation. We interpret this observation as a dynamic effect, caused by a small number of highly mobile point defects in the (2×2)‐CO adlayer. As shown by density functional theory calculations, the CO lattice near such defects relaxes into a local (1×1) arrangement, which can rapidly propagate across the surface. This scenario, where a static (2×2) COad sublattice coexists with a highly dynamic sublattice of partially occupied top sites, explains the pronounced COad surface mobility during electrooxidation. Abstract : Adsorbed CO on Pt(111) electrodes can become highly mobile at the onset of pre‐oxidation, despite a high adsorbate surface density. Origin of this behavior is the formation of defects in the adlayer, which enable density fluctuations and by this rapid quasi‐collective CO transport.