An integrated absorption and electrolysis process to H2S treatment using alkaline ionic liquids aqueous solution

Abstract

The electrolytic oxidation of H₂S is a promising energy conversion technology for hydrogen production and the removal of this environmental pollutant. Additionally, the anode oxidation reactions offer the added advantage of obtaining valuable chemicals. Here, a series of alkaline ionic liquids ([DBNH]IM, [DBUH]IM, [DBNH][1,2,4-triaz], [NH₄Cl][MEA], and [ChCl][MEA]) aqueous solutions were used as absorbents and anolytes for absorption-electrolysis cycles with pristine carbon cloth to enhance H₂S absorption and electrolysis, coupling with efficient HER. [DBNH]IM-based electrolyte exhibited higher H₂S trapping capacity primarily due to its ability in H₂S absorption and modulation effect. Under constant potential electrolysis at 1.2 V vs RHE applied for 12 h, the maximum hydrogen production rate reached 1150 μmol h⁻¹. Even after three cycles, the hydrogen production rate in [DBNH]IM-based system remained at approximately 185 μmol h⁻¹. The anodic sulfur product can be separated from the electrolyte by bubbling CO₂; solid product was confirmed to be α-sulfur as high as 99.207%. In summary, the obtained electrolyte demonstrates effective decomposition of H₂S while simultaneously producing clean hydrogen and sulfur in a sustainable way.