The Effect of Surface Geometry of Copper on Adsorption of Benzotriazole and Cl. Part I

Abstract

The adsorption of benzotriazole and Cl on low Miller index surfaces of copper and under-coordinated defects thereon was characterized using density functional theory calculations; the former is an outstanding corrosion inhibitor and the latter a corrosion promoter. We find that adsorption bonding of intact benzotriazole (BTAH), dehydrogenated benzotriazole (BTA⊙), and Cl becomes stronger as the coordination number of surface Cu atoms involved in the adsorption site decreases, whereas the adsorption energy of H—considered as a side-product of BTAH dehydrogenation—is rather insensitive to surface geometry. The Cl binds the strongest, and the binding energy ranges from −3.3 eV on Cu(111) to −3.9 eV on very low-coordinated defects, and BTA⊙ binds somewhat weaker, from −2.8 to −3.8 eV, whereas BTAH binds considerably weaker, from −0.6 to −1.3 eV. The bonding enhancement due to reduced coordination of surface Cu atoms is hence the strongest for BTA⊙, which indicates its ability to passivate the reactive under-coordinated surface sites. This bonding enhancement is also a principal reason for the formation of organometallic complexes of BTA⊙ on flat facets, such as the BTA–Cu–BTA complex or [BTA–Cu]n polymer. The role of solvent effects for the adsorption of considered species was also addressed, and approximate calculations reveal that the aqueous-phase adsorption of deprotonated BTA– is more exothermic than that of Cl–, mainly because the chloride anion is smaller and solvates considerably stronger in water than the BTA–.