A SERS Investigation of Cyanide Adsorption and Reactivity during the   Electrodeposition of Gold, Silver and Copper from Aqueous Cyanocomplexes   Solutions
  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. 
Benedetto Bozzini, Lucia DUrzo, Claudio Mele, Vincenzo Romanello