Electrochemical Cu growth on MPS-modified Au(111) electrodes

Klaus Krug, Yung Fang Liu, Wen Hsiang Ho, Yuh-Lang Lee, Wei Ping Dow, Shueh Lin Yau

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Au(111) electrodes have been modified with self-assembled monolayers (SAM) of 3-mercapto-1-propanesulfonic acid (MPS) and used as a substrate for Cu electrodeposition. Aqueous plating solutions contained 0.1 M H 2SO 4, low Cu concentrations (≤80 μM), and, optionally, 1.4 mM Cl ions. The deposition process was characterized by cyclic voltammetry (CV) and in-situ scanning tunneling microscopy (STM) as a function of the electrode potential. At potentials positive of Cu growth (≥0.7 V Rhe), freshly modified electrodes are covered by an ordered (5√ 3 × √21) MPS adlayer (α) both in Cl-free and Cl-containing electrolytes. The α adlayer becomes disordered at more negative potentials prior to the onset of Cu deposition (≤0.65 V RHe). In the potential regime of Cu underpotential deposition (UPD) (≈0.2-0.65 V RHe), the surface morphology strongly depends on the presence of Cl. In the absence of Cl, a transient, ordered Cu/MPS adlayer phase (δ) forms via 2D growth and covers the entire Au(111) surface. Subsequently, the δ phase transforms into a disordered Cu/MPS phase (σC u) with small, embedded Cu islands. In Cl-containing electrolyte, a disordered Cu/MPS/Cl phase (γ) nucleates at Au step edges or surface defects and spreads laterally. Cu islands form simultaneously within the γ phase. Two-dimensional growth of these islands results in a pure Cu-UPD layer. Overpotential deposition (OPD) proceeds via layer-by-layer mode with second layer nucleations at surprisingly small critical coverages (θC ≤≤0.5). Our observations differ significantly from those in previous studies, demonstrating that the Cu growth behavior critically depends on the concentrations of MPS, Cu, and Cl at the interface.

Original languageEnglish
Pages (from-to)17507-17517
Number of pages11
JournalJournal of Physical Chemistry C
Volume116
Issue number33
DOIs
Publication statusPublished - 2012 Aug 23

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

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