Thermodynamic analysis on metal selenides electrodeposition

Fundamental thermodynamic features of metal selenides electrodeposition have been investigated in this paper. Based on thermodynamic calculation, the reaction equilibriums and potential–pH formulas of Me–Se–H2O system at 298 K are obtained, and the general potential–pH diagram of this system is drawn for the first time. The potential–pH diagram for some typical selenides is also presented. The analysis results show that the electrodeposition of metal selenides generally proceeds under weak acidic conditions (pH 1–3) via Kroger mechanism, and the deposition potential should be more positive than that of individual metal ions. It is also found that for different metal selenides, the deposition potential and pH ranges are different. Usually, the more positive the standard redox potential of the metal element is, the more positive the deposition potential of selenide corresponds to, and the broader the optional pH range can be.

► General potential–pH diagram of Me–Se–H2O system is plotted for the first time.
► Some general thermodynamic laws of metal selenides electrodeposition are analyzed.
► Potential–pH diagrams of some typical Me–Se–H2O systems are drawn.