| Summary: | The validity of the electrochemical series for metal sulfides decomposition in their standard state has been tested experimentally at 1500 K for La₂S₃, Cu₂S, MoS₂, and ReS₂ in a molten electrolyte with the following molar composition: (BaS)₅₄₋(Cu₂S)₃₁₋(La₂S₃)₁₅ (electrolyte B). Voltammetry measurements indicated the presence of faradaic reactions in the investigated electrolyte with and without the addition of MoS₂ and/or ReS₂. Electrolysis experiments showed that the addition of La₂S₃ to BaS-Cu₂S increases the faradaic efficiency for liquid copper production with respect to a previously studied (BaS)₅₄₋(Cu₂S)₄₆ electrolyte, and enabled isolation of elemental sulfur as the anodic product. Electrochemical measurements suggested the need to take into account the activity of dissolved Cu₂S in order to explain the observed cell voltage during electrolysis. Electrolysis in the presence and absence of ReS₂ and/or MoS₂ confirmed their relative stability as predicted by assuming decomposition in their standard states. Analysis of the metal products electrowon from an electrolyte containing Cu₂S, MoS₂, and ReS₂ indicated the simultaneous production of solid and liquid phases with nonequilibrium compositions.
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