Recovery of hydrogen from hydrogen sulfide by indirect electrolysis process

Recovery hydrogen from hydrogen sulfide is an effective way of utilizing exhaust gas. In this paper, removal of hydrogen sulfide by indirect electrochemical process was studied using acidic aqueous solution of Fe3+/Fe2+ as the electrochemical intermediate. Solid polymer electrolyte was applied to hydrogen production by indirect electrolysis of H2S, in which the anode was graphite cloth, the cathode was the platinized graphite cloth, and the membrane was proton exchange membrane. The results of electrolysis experiments showed the relationship of current density as a function of electrolytic voltage at constant flow rate of electrolyte, temperature, and electrolyte composition. The effect of the cathode liquid velocity on current density was small. When the flow rate of anode electrolyte was greater than 200 L/hr., the current density tended to be stable. When [Fe3+]>0.20 mol/L, the concentrations of Fe2+ and Fe3+ ions in the anode solution had no significant impact on the current density. The current density gradually increased with temperature. In the electrolytic process of hydrogen production, the Fe2+ ions diffused from the anode to the cathode. The amount of diffusing Fe2+ ions gradually increased with time. The effect of Fe2+ ions diffusion from anode to cathode on hydrogen production was discussed.