| Abstract
| - In situ electrochemical IR spectroscopy data, obtained on a Pt thin-film electrode in 0.5 M H2SO4 solutionin an attenuated total reflection configuration (ATR-FTIRS), show an anomalous, reversible blue-shift of theIR peak frequency of linearly bound adsorbed CO with decreasing potential in the H-upd potential range,together with an increase in band intensity. This phenomenon, which is observed only at coverages ≤0.3monolayers and becomes more pronounced with decreasing COad coverage, is explained by a potential-induced island formation in the CO adlayer at low potentials. The phase transition is driven either indirectlyby coadsorption of H-upd or directly by a potential-induced change in the COad−COad interaction energies.
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