  In this paper we report on the reactivity of adsorbed cyanide deriving from
ligand release during metal electrodeposition from cyanocomplex solutions of
Au(I), Au(III), Ag(I) and Cu(I) in H2O and D2O. When CN is adsorbed at cathodic
potentials in excess of the HER threshold, metal-dependent reactivity can be
detected by SERS. Finite surface coverages with adsorbed CN at such cathodic
potentials can be obtained only if CN is delivered directly to the cathode
surface as by decomplexing of the cyanocomplexes of the metals undergoing
cathodic reduction. In Au(I) and Au(III) baths, Au-CN reacts with Au-H and is
hydrogenated to adsorbed CH2=NH and CH3-NH2. In Ag(I) baths, Ag-CN reacts with
Ag-H giving rise to polycyanogens. No reactivity of Cu-CN was found, under
otherwise identical conditions. Our conclusions are supported also by dedicated
DFT molecular computations.
