UV-ATR Spectroscopy Study of the Speciation in Aqueous Polysulfide Electrolyte Solutions

The distribution of species, dissolution of sulfur as polysulfide and oxoanions in aqueous polysulfide electrolytes at room temperature was investigated. The dissociation of sodium sulfide in water produces equal molar concentrations of OH- and HS- ions. The addition of elemental sulfur produces a variety of speciation in this polysulfide electrolyte. In this study the formation of oxidised sulfur species by the reaction of elemental sulfur with the large quantity of OH- ions present in the Na2S aqueous sulfide solution was investigated. The adopted UV-ATR technique shows a much better response down to the 200nm region. The UV-ATR spectra of pure aqueous solutions of sodium thiosulfate, sulfate and sulfite were recorded and compared with the spectra of aqueous polysulfide electrolytes to report the presence of oxoanions.