A New Approach to the Electrochemical Decomposition of Aqueous Hydrogen Sulfide Solution into Sulfur and Hydrogen Gas

Abstract

A new approach to the electrochemical decomposition of aqueous hydrogen sulfide solution into elemental sulfur and hydrogen gas has been proposed; this approach can be used to get rid of anode passivation caused by sulfur precipitated on the anode surface. After all sulfides, including S 2– , HS – and H2S in the anodic compartment, have been mostly converted into polysulfide ions, hydrogen sulfide gas is bubbled through the anolyte until the pH of the solution remains approximately constant. Sulfur is removed from the reaction mixture, which is then returned to the anode compartment where the unreacted sulfides and undecomposed lower polysulfide ions continue to undergo electrolysis into polysulfide ions, and then their decomposition by H2S gas again takes place. This cyclic process will lead to a high current efficiency with which aqueous H2S is electrochemically decomposed into sulfur and hydrogen gas without anode passivation. Results of both equilibrium calculations and experiments show the viability of this new approach.