Electroreduction of benzyl chloride on silver-based electrode materials in acetonitrile media: the role of water and of Ag surface

Electroreduction of benzyl chloride on silver-based electrode materials in acetonitrile media: the role of water and of Ag surface O. Lugaresi, A. Minguzzi, C. Locatelli, S. Rondinini, A. Vertova Dipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano, via Golgi, 19 20133 Milano - Italy, tel. +39-02-50314216, fax+39-02-503 14203, ottavio.lugaresi@.unimi.it The remarkable electrocatalytic activity of silver is well documented in the literature [1] and recently, the combination of electrochemical, spectroscopic and theoretical studies [2], using benzyl chloride (BzCl) as model organic compound, has demonstrated that the reduction pathway implies the formation sequence of silver-substrate/product adducts, starting from a weakly adsorbed benzyl chloride-Ag specie, followed by the strongly adsorbed benzyl radical-Ag and benzyl anion-Ag species. The last ultimately desorbing to give the final reaction products. In this context the present contribution discusses the effect on the voltammetric signal of the presence of small amounts of water in the acetonitrile used as solvent. The source of proton from water may affect the normal reaction pathway and change the electrode activity. This provokes significant variations in electrode currents and potentials even at very low water content, thus providing an internal diagnostic signal for the quality of the solvent. This has immediate application to the comparison between electrode materials (e.g., massive silver, silver nanocubes and Ag-nanocubes supported on carbon) prepared by different procedures, and allows to evidence the effects of the morphology and size of silver particles on their electroactivity. [1] S. Rondinini, A. Vertova, "Electroreduction of Halogenated Organic Compounds", in Electrochemistry for the Environment, Ch. Comninellis, and G. Chen, (Eds.), Springer, 2010, DOI 10.1007/978-0-387-68318-8 [2] Yi-Fan Huang, De-Yin Wu, An Wang, Bin Ren, Sandra Rondinini, Zhong-Qun Tian, and Christian Amatore "Bridging the Gap between Electrochemical and Organometallic Activation: Benzyl Chloride Reduction at Silver Cathodes", J. Amer. Chem. Soc. 2010, 132, 17199-17210; DOI: 10.1021/ja106049c