Hydrogen Sulfide Splitting into Hydrogen and Sulfur through Off-Field Electrocatalysis.

Hydrogen sulfide (H 2 S), a toxic gas abundant in natural gas fields and refineries, is currently being removed mainly via the Claus process. However, the emission of sulfur-containing pollutants is hard to be prevented and the hydrogen element is combined to water. Herein, we report an electron-mediated off-field electrocatalysis approach (OFEC) for complete splitting of H 2 S into H 2 and S under ambient conditions. Fe(III)/Fe(II) and V(II)/V(III) redox mediators are used to fulfill the cycles for H 2 S oxidation and H 2 production, respectively. Fe(III) effectively removes H 2 S with almost 100% conversion during its oxidation process. The H + ions are reduced by V(II) on a nonprecious metal catalyst, tungsten carbide. The mediators are regenerated in an electrolyzer at a cell voltage of 1.05 V, close to the theoretical potential difference (1.02 V) between Fe(III)/Fe(II) and V(II)/V(III). In a laboratory bench-scale plant, the energy consumption for the production of H 2 from H 2 S is estimated to be 2.8 kWh Nm -3 H 2 using Fe(III)/Fe(II) and V(II)/V(III) mediators and further reduced to about 0.5 kWh Nm -3 H 2 when employing well-designed heteropolyacid/quinone mediators. OFEC presents a cost-effective approach for the simultaneous production of H 2 and elemental sulfur from H 2 S, along with the complete removal of H 2 S from industrial processes. It also provides a practical platform for electrochemical reactions involving solid precipitation and organic synthesis.