Investigation of the Interaction Between Cu2-x S +So Coatings and Pd(II) Ions by Cyclic Voltammetry and X-ray Photoelectron Spectroscopy

Abstract

The interaction between Pd 2+ ions and Cu 2-x S coating formed by three cycles and containing ∼30 at.% of elementary S has been investigated by the methods of cyclic voltammetry and photoelectron spectroscopy (one cycle of coating formation includes treatment of the surface with Cu(I)+Cu(II) ammoniate solution, hydrolysis of the adsorbed copper compounds and sulphidation of copper oxygen compounds in Na 2 S n solution). After exposure of such a coating to Pd 2+ ions (1.7 mM PdCl 2 , pH=2), an exchange as well as a redox interaction between the coating components and Pd 2+ ions has been shown to occur Due to this the amount of copper in the coating decreases from 2 to 4 times and that ofsulphur from 1.5 to 5 times. The coating modified in such a way has been found to contain up to 75 at.% of palladium, ∼90% of it being in a metallic state. It has been determined that at the beginning S 0 is bound into a soluble compound: 2Pd 2+ + S 0 + 3H 2 O → 2Pd 0 + H 2 SO 3 + 4H + . The Cu 2 S present in the coating is considered to interact with Pd 2+ , with the formation of Pd 0 and CuPdS 2 , while CuS reacts most likely according to the reaction: CuS + 3Pd 2+ + 3H 2 O → 3Pd 0 + H 2 SO 3 + Cu 2+ + 4H + . The Cu 2-x S + S 0 coating formed on a dielectric and modified with Pd 2+ , contrary to the initial Cu 2-x S + S 0 coating, can be plated with copper from any electrolyte for copper deposition.