Electrochemical valorization of H₂S in natural gas to sulfate under mild conditions.

Abstract

H₂S capture and valorization from polluted natural gas offer environmental and resource recovery benefits, but current approaches produce moderate-value sulfur with intensive carbon footprint. Herein, we develop an electrochemical deep oxidation method that converts H₂S from polluted natural gas into value-added K₂SO₄ using in-situ cathodically generated H₂O₂. We first validate this concept using commercial H₂O₂ and then in-situ generated H₂O₂ in H-cell, revealing the importance of high H₂O₂ concentration for deep H₂S oxidation, especially sluggish S₂O₃^2--to-SO₃^2- conversion. We then showcase its application potential in 4-cm² and then 100-cm² flow reactor with high interfacial H₂O₂ concentration and large current, with the latter achieving H₂S removal (100,000 ppm to <15 ppm), >70% K₂SO₄ selectivity, and 100-h stable operation. Life-cycle assessment and techno-economic analysis confirm the strategy's sustainability advantages and economic viability. We finally extend this method to produce a 1.4 wt% H₂SO₄ solution by modifying the flow reactor with a solid-electrolyte type.