The surface chemistry of Cu (100) in HCl solutions as a function of potential: a study by LEED, Auger spectroscopy and depth profiling

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The surface chemistry of Cu (100) in HCl solutions has been examined by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and Auger depth profiling (ADP). Electrochemistry was conducted in an antechamber directly coupled to an UHV surface analysis instrument. (2 1 2 ×2 1 2 R45° LEED pattern formed in HCl regardless of potential or Cl− concentration. The extent of Cl adsorption from 1 mM HCl varied only slightly with potential. Immersion of a Cl-coated electrode into 1 mM H 2SO 4 at a series of potentials showed more clearly the reductive desorprion of Cl at potentials negative of −0.31 V (vs. Ag/AgCl). Sulfate adsorption at negative potentials resulted in a Cu(100)(2× 2)-SO 2− 4 structure. Anodic polarization of the electrode in 10 mM HCl resulted in streaks in the 2 1 2 ×2 1 2 R45° LEED pattern due to formation of CuCl islands on the (2 1 2 ×2 1 2 R45° -Cl surface. CuCl island formation was verified by depth profiling.