Underpotential Deposition in the Nanoscale

O. A. OVIEDO, O. A. PINTOS, C. F.A. NEGRE, M. M. MARISCAL, C. G. SÁNCHEZ AND E. P. M. LEIVA

Congreso; 63 annual meeting of the International Society of Electrochemistry; 2012

Electrosorption of metal ions on foreign substrates at potentials more positive than the reversible Nernst deposition potential, known as underpotential deposition (upd), allows surface control of metal coverage by straightforward application of a potential difference. The possibility of using upd to control the shape of Au-NPs has been explored by Personik et al. [1] but recent experiments developed by Compton and co-workers [2] show that remarkable size effects occur when nanoparticle size is reduced below 50 nm, where the upd phenomenon seems to vanish. Such a curious transition from upd to overpotential deposition has also been predicted by calculations [3,4]. In the present work, we report on recent advances in the theoretical modelling of upd on free NPs [5,6]. We discuss this problem in three different contexts: 1) theoretical approach: from a nanothermodynamic formalism up to a statistical mechanical model; 2) atomistic simulation: using different Monte Carlo simulation techniques, from simple gas models up to continuum simulations in the grand canonical ensemble; 3) experimental feasibility: by means of a state-of-the art quantum mechanical atomistic model, we simulate the plasmon spectra of nanoparticles in different conditions. We discuss the electrochemical decoration of Au, Ag and Pd nanoparticles by different foreign metals. It is found that depending on precursor nanoparticle size and shape, controlled decoration may be achieved in undersaturation or oversaturation conditions. Multilayer deposition is also considered, with the finding that this phenomenon is also size dependent, in agreement with experimental measurements. [1] M.L. Personick, M.R. Langille, J. Zhang, and C.A. Mirkin, Nano Lett. 11 (2011) 3394. [2] F.W. Campbell, Y. Zhou and R.G. Compton, New Journal of Chemistry, 34, (2010), 187. F.W. Campbell and R.G. Compton, Int. J. Electrochem. Sci., 5 (2010) 407. Y. Zhou, N.V. Rees, and R.G. Compton, ChemPhysChem, 12, (2011), 2085. [3] O. A. Oviedo, E. P. M. Leiva and M. M. Mariscal, Phys. Chem. Chem. Phys., 10 (2008) 3561. [4] O. A. Oviedo, M. M. Mariscal and E. P. M. Leiva. Phys. Chem. Chem. Phys. 12 (2010) 4580. [5] O.A. Oviedo, C.F.A. Negre, M.M. Mariscal, C.G. Sánchez, E.P.M. Leiva. Electrochemistry Communications 16 (2012) 1-5. [6] “Metal Clusters and Nanoalloys: From Modeling to Applications”, Nanostructure Science and Technology. Springer. ISBN 978-1-4614-3267-82012. In press.