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The first steps of H,S adsorption have been studied on polycrystalline copper samples, which are more relevant to industrial copper samples than to single-crystal surfaces. The tools for characterization are ultrahigh vacuum spectroscopic methods, such as x-ray photoelectron and ion scattering spectroscopies. The H,S adsorption on metallic copper and on the corresponding Cu,O and CuO oxides is dissociative and highly dependent on the chemical nature of the exposed surface rather than on the temperature, from room temperature up to 623 K. In our conditions, Cu" sulphidation deals with the top Cuo layer whereas two to three oxide surface monolayers are modified at H,S saturation. The results on oxides are interpreted by an oxygen/sulphur replacement mechanism following the dissociative adsorption. Contaminated copper surfaces by phenanthrene or H,O treatments are hardly sulphided. As far as surface reactivity is concerned, the adsorbed sulphide species have been shown to be quite strongly bound to the different surface states tested in this work: only oxidative treatments induce desorbing products at 623 K.

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