Electrochemical Production of Hydrogen and Sulfur by Low-Temperature Decomposition of Hydrogen Sulfide in an Aqueous Alkaline Solution

Electrolysis of hydrogen sulfide to its constituents in a solution containing equimolar concentrations of NaOH and NaHS has been carried out at 80°C. In a double-compartment cell employing Nafion membrane as a separator, both crystalline elemental sulfur and high-purity hydrogen have been produced at high current efficiencies. Only minimal, if any, passivation of the anode by sulfur product was observed. According to solution composition, electrolysis could result in gas evolution at the anode, passivation of the anode by sulfur deposition, or oxidation of sulfide (S2–) or polysulfide (S) to sulfur oxyanions. However, in an optimized solution, electrolysis gave only anodic sulfur via bisulfide (HS–) and sulfide oxidation. Voltammetric and chronopotentiometric studies showed that sulfide, bisulfide, and polysulfide oxidation occurred at about the same potential