Electrochemistry of the nickel-cyanide system at mercury electrodes: Part I. Adsorption and electrode reactions of nickel cyanide

For compositions such that Ni²⁺ and Ni(CN)^2?₄ can co-exist, there is very strong adsorption of Ni(CN)₂ on mercury electrodes. The electrochemical characteristics of this adsorption are quantitatively accounted for by a Frumkin isotherm, with an adsorption constant, β=(4.1±0.2)×10⁶ mol^?2 dm⁶, and a positive (attraction) constant, A=3.9±0.1. The surface layer appears to consist of strongly interacting NiNi(CN)₄ units. The most probable model of surface equilibria involves direct co-adsorption of Ni²⁺ and Ni(CN)^2?₄ from the bulk on mercury. Electroreduction of an adsorbate proceeds with the uptake of one electron per NiNi(CN)₄ unit.