Establishing redox flow batteries with polyoxometalates-based redox couples for enhanced hydrogen sulfide splitting

The valorization of hydrogen sulfide (H₂S) through its dissociation into hydrogen and elemental sulfur presents a promising route for converting hazardous waste into valuable commodities. Here, we report a novel redox flow battery (RFB) system employing polyoxometalate-based redox couples that achieves highly efficient H₂S conversion. The anodic H₅[PMo₂VMo₁₀VIO₄₀]/H₃[PMo₁₂VIO₄₀] system demonstrates three critical advantages over conventional Fe²⁺/Fe³⁺ mediators: (1) minimal membrane crossover, (2) high volumetric capacity (more than 3.5 times), and (3) rapid reaction kinetics (k₀ = 0.022 cm s⁻¹). When coupled with the cathodic H₄[SiW₁₂VIO₄₀]/H₆[SiW₁₀VIW₂VO₄₀] system, this design demonstrates 90% faradaic efficiency for simultaneous H₂ and sulfur production. The synergistic combination of these redox mediators establishes a sustainable platform for toxic H₂S conversion while enabling scalable hydrogen production and sulfur recovery.