SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100)

Published

January 3, 2024

Author(s)

Thomas P. Moffat, David Raciti, Angela R. Hight Walker, Eric J. Cockayne, John Vinson, Kathleen Schwarz

Abstract

Shell-isolated Nanoparticle Enhance Raman Spectroscopy (SHINERS) and Density Functional Theory (DFT) are used to probe Cl- adsorption and the order-disorder phase transition associated with the c(2×2) Cl- adlayer on Cu(100) in acid media. A two-component Cu-Cl) vibrational band centered near 260 cm-1 ± 1 cm-1 is used to track the potential dependence of Cl- adsorption. The potential dependence of the dominant 260 cm-1 component tracks the coverage of the fluctional c(2×2) Cl- phase on terraces in good agreement with the normalized intensity of the c(2×2) superstructure rods in prior surface x-ray diffraction (SXRD) studies. As the c(2×2) Cl- coverage approaches saturation a second Cu-Cl) component mode emerges between 290 cm-1 and 300 cm-1 that coincides with the onset and stiffening of step faceting where Cl- occupies the three-fold hollow sites to stabilize the metal kink saturated Cu <100> step edge. Formation of the c(2×2) Cl- adlayer is accompanied by strengthening of O-H stretching modes for non-hydrogen bonded water at 3600 cm-1 and an increase in hydronium concentration evident in the flanking H2O modes at 3100 cm-1. Polarization of the water molecules and enrichment of hydronium arise from the combination of Cl- anionic character and lateral templating provided by the c(2×2) adlayer consistent with SXRD studies. At negative potentials Cl- desorption occurs followed by development of a sulfate sS=O) band. Below -1.1 V vs Hg/HgSO4 a new 200 cm-1 mode emerges which may align with hydride formation and surface reconstruction reported in electrochemical scanning tunneling microscopy studies.

Citation

Journal of the American Chemical Society

Pub Type

Journals

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Keywords

Cu(100), Raman Spectroscopy, SHINERS, chloride adsorption, water structure, electrochemistry, copper

Citation

Moffat, T. , Raciti, D. , Hight Walker, A. , Cockayne, E. , Vinson, J. and Schwarz, K. (2024), SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100), Journal of the American Chemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956720 (Accessed October 19, 2024)