Electrolytic cell–assisted polyoxometalate based redox mediator for H2S conversion to elemental sulphur and hydrogen

Abstract

This study proposed a novel electrolytic cell–assisted redox system based on lacunary-type polyoxometalate, which can simultaneously remove hydrogen sulphide (H2S), recover elemental sulphur, and produce hydrogen. In this redox system, H2S is oxidised into elemental sulphur by using polyoxometalate ([Sm(PMo(VI)11O39)2]−11), which is reduced to corresponding heteropoly blue (reduced polyoxometalates [Sm(PMo(IV)11O39)2]−55). Furthermore, heteropoly blue is electrochemically oxidised back into polyoxometalate on the anode surface, and hydrogen is produced on the surface of the cathode in an electrolytic cell. The experimental results indicated that a 94.8% H2S removal efficiency, and 77.9% sulphur recovery efficiency were achieved under optimum conditions. H2S was effectively converted to elemental sulphur in the proposed system. Moreover, Optical and electrochemical characterisations demonstrated that the structures of the lacunary-type polyoxometalate could be well-maintained at pH 5, which was most favourable for H2S removal. Notably, clean energy hydrogen could be produced in polyoxometalate regeneration process. This innovative system—combining H2S waste conversion to elemental sulphur, electrochemical regeneration of redox mediators, and hydrogen production and thus providing environmental benefits and significant economic value—may have future applications in commercial technology.