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

Download Paper

Local Download

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 13, 2025)