Brass Surface Nanochemistry: The Role of Alloying Cu with Zn

Abstract

For the first time the surface of brass (Cu−Zn alloy) and its chemistry have been characterized by scanning tunneling microscopy/spectroscopy at the subnanometer (atomic) scale. The comparative results obtained on Cu70Zn30(111) and Cu(111) single-crystal surfaces evidence the random distribution of Zn atoms substituted to Cu atoms at the extreme surface of brass, the Zn-depleted concentration in the topmost layer of the alloy and the associated modifications of the surface density of states. The initial stages of interaction with oxygen and sulfur highlight the role of Zn in the surface chemistry. The reactivity becomes governed by the chemical defects (Zn atoms) introduced by alloying. The nucleation mechanism and the nature of the surface oxide compounds are modified. Surface reconstruction is promoted in the reaction with sulfur, and S vacancies are introduced in the surface sulfide compounds. The data are relevant for the detailed understanding of the effect of alloying a noble or seminoble metal matr...