The role of Cu(II) in the process of forming non-stoichiometric copper sulphide coatings by a chemical route

The composition of non-stoichiometric copper sulphide (Cu) coatings obtained during the interaction of Cu(II) with Na 2 S n (n = 1-4) has been investigated by cyclic voltammetry in 0.05 M H 2 SO 4 solution. The overall reaction has been shown to correspond to the equation. 4 Na 2 S 0 + 2 Cu(OH) 2ad →Cu 2 S ad + (4n-3) S 0 ad + 4 NaOH + 2 Na 2 S in which S o /Cu = (4n 3 1/2). Such a stoichiometry of reaction has been explained by the formation of an intermediate the adsorbed Cut II) polysulphide (Na 2 CuS n ) or a polynuclear complex (Na 2 Cu 2 S and its decomposition in simultaneous intramolecular redox reaction between Cu(II) and S 2 . When increasing n from I to 4/2-x) increases from 1.91 to 1.99 approximately.