Investigation of the interaction between Co sulfide coatings and Cu(I) ions by cyclic voltammetry and XPS

Abstract

The interaction between the Co sulfide coating formed on a glassy carbon electrode and Cu(I)-ammonia complexes solution was investigated by cyclic voltammetry in 0.1 M KClO4, 0.1 M NaOH and 0.05 M H2SO4 solutions. It was determined that, after treating the cobalt sulfide coating formed by two deposition cycles with Cu(I)-ammonia complexes (0.4 M, pH 8.8–9.0, τ=180 s, T=25±1°C), an exchange occurs between the coating components and Cu(I). Copper(I) substitutes 75% of the Co(III) compounds present in the coating (~1.81×10–7 mol cm–2) because of Cu2O (1.36×10–7 mol cm–2) formation. The rest of the Co(II) and Co(III) sulfide compounds are also replaced by copper with formation of Cu2– x S with a stoichiometric coefficient close to 2 (~1.9). After modifying the cobalt sulfide coatings with Cu(I) ions, the total amount of metal (Co+Cu) increases, owing to the sorption of Cu(I) compounds. In addition, the number of deposition cycles decreases from 3 to 1.5 [1 cycle involves cobalt sulfide layer formation and 0.5 cycle is attributed to modifying by Cu(I) ions]. The coatings modified in the above-mentioned manner may be successfully used for plastic electrochemical metallization as Cu2– x S coatings formed by three deposition cycles.