Lead underpotential deposition on polycrystalline gold electrode in perchloric acid solution : A combined electrochemical quartz crystal microbalance and probe beam deflection study

• Published in: Journal of the Electrochemical Society 2001-03, Vol.148 (3), p.E105-E111
• Main Authors: HENDERSON, Mark J, BITZIOU, Eleni, HILLMAN, A. Robert, VIEIL, Eric
• Format: Article
• Language: English
• Subjects: Chemistry; Electrochemistry; Electrodeposition; Exact sciences and technology; General and physical chemistry; Study of interfaces
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1346610

A quantitative combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) analysis of Pb underpotential deposition (Pb sub upd ) in aqueous 0.1 mol dm exp -3 perchloric acid solution at polycrystalline gold was achieved by comparing the cyclic-voltammetric, - gravimetric, and -beam deflection responses. The refractive index responses (PBD) were commensurate with the large variation in index of refraction of Pb(CIO sub 4 ) sub 2 with change in concentration (30.5 cm exp 3 mol exp -1 ), demonstrating that the technique is remarkably sensitive to monitor the formation of submonolayers of Pb sub upd . In this work the current and mass variation signals were projected upon the beam deflection profile by using the mathematical tool of quantitative temporal convolution. We show that the overall process of Pb sub upd occurs in three distinct stages. The first stage consists of water ejection from gold. In the second stage, metal underpotential deposition is accompanied by OH sub ad displacement followed, in the last step, by water formation. The coupled diffusion coefficient of Pb(ClO sub 4 ) sub 2 transferring in 0.1 mol dm exp -3 HClO sub 4 solution was evaluated to be 6.25 x 10 exp -6 cm exp 2 s exp -1 .