Effect of the molecular structure on the adsorption of nitriles on Ag single crystal face electrodes: iso-valeronitrile vs. acetonitrile

The adsorption of iso-valeronitrile (IVN) on Ag single crystal face electrodes was studied by means of capacitance measurements at near zero frequency in aqueous 0.15 M NaClO4 as a supporting electrolyte solution. Experimental data have shown that adsorption increases in the sequence of crystal faces (1 1 0)<(1 0 0)<(1 1 1)<Hg. Differently from acetonitrile adsorption, the mode of adsorption of IVN is attributable to hydrophilic–hydrophobic interactions resulting in a squeezing-out mechanism. The crystal face sequence is governed by Ag–water interactions which are thus confirmed to vary in the order (1 1 0)>(1 0 0)>(1 1 1). Although never observed with Hg, below a critical value of the squeezing-out effect, neutral organic compounds are unable to displace the first layer of water molecules adsorbed on a solid metal surface.