In-situ observation of halogenated species adsorption onto Ag electrode by XANES, EXAFS and FEXRAV

Organic halides are at the basis of fundamental and applied studies in electrochemistry because of their present (and past) wide usage in a large variety of applications, ranging from herbicides/fungicides/pesticides in agriculture and woods disinfestations, to thermal and mechanical fluids, to solvents in commerce, industry and housework. Electrochemical methods have proven to be highly effective in the detoxification of wastes, since unlike conventional physico-chemical techniques (e.g. thermal degradation or chemical oxidation) they provide mild reaction conditions, avoiding the secondary pollution effects chained to the reagents excess, and are easily adapted even to small-scale treatments. This became particularly true after the discovery of Ag as a powerful catalyst for the electrochemical dehalogenation of organic halides [1-2]. However, the reasons behind the exceptional activity of Ag are still not completely clear, although the most recent evidences underlined the role of adsorption of the molecule on silver in the case of benzylchloride electroreduction [3]. This is why a fine study on the Ag chemical surroundings (particularly the nature of the adsorption of reactants and products) under reaction conditions is at the basis of the present work. Here we present a study of adsorption of Br- ions onto silver nanoparticles (3-5 nm diameter) characterized in-situ by X-Ray Absorption Spectroscopy (XAS) at the Br-K edge