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

Abstract

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 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.