Micro gravimetric and voltammetric study of Zn underpotential deposition on platinum in alkaline medium

Author(s)

Calegaro, M. L. ; Miwa, D. W. ; Machado, S. A. S. ; Santos, Mauro Coelho dos ^[4]

• Document type: Journal article
• Source: Surface Science; v. 579, n. 1, p. 58-64, Mar. 2005.
• Field of knowledge: Physical Sciences and Mathematics - Chemistry

Abstract

The microgravimetric and voltammetric responses of a polycrystalline Pt electrode in 0.1 mol L-1 NaOH solution in the presence and the absence of 1.6 x 10(-4) Zn2+, at 0.1 V s(-1) were analyzed. During the positive potential sweep, the water molecules are progressively substituted by OH- ions, prior to NO formation. The voltammetric charges obtained under the Zn-ads dissolution peaks suggest that 0.7 monolayers are deposited, with each Zn ad-atom occupying one active site and transferring two electrons. The total loss of mass due to the dissolution of the Zn ad-layer was 136.6 ng cm(-2) and the mass increase due to NO formation was found to be only 12 ng cm(-2) less than the theoretical ones, 157.5 and 37.4 ng cm(-2), respectively, indicating that both processes are overlapped. In this way it is proposed that an adsorbed by-layer of Zn and OH- ions is formed. (AU)