Self-Driven Photoelectrochemical Splitting of H 2 S for S and H 2 Recovery and Simultaneous Electricity Generation

A novel, facile self-driven photoelectrocatalytic (PEC) system was established for highly selective and efficient recovery of H 2 S and simultaneous electricity production. The key ideas were the self-bias function between a WO 3 photoanode and a Si/PVC photocathode due to their mismatched Fermi levels and the special cyclic redox reaction mechanism of I – /I 3 – . Under solar light, the system facilitated the separation of holes in the photoanode and electrons in the photocathode, which then generated electricity. Cyclic redox reactions were produced in the photoanode region as follows: I – was transformed into I 3 – by photoholes or hydroxyl radicals, H 2 S was oxidized to S by I 3 –, and I 3 – was then reduced to I – . Meanwhile, H + was efficiently converted to H 2 in the photocathode region. In the system, H 2 S was uniquely oxidized to sulfur but not to polysulfide (S x n- ) because of the mild oxidation capacity of I 3 – . High recovery rates for S and H 2 were obtained up to ∼1.04 mg h –1 cm –1 and ∼0.75 mL h –1 cm –1, respectively, suggesting that H 2 S was completely converted into H 2 and S. In addition, the output power density of the system reached ∼0.11 mW cm –2 . The proposed PEC-H 2 S system provides a self-sustaining, energy-saving method for simultaneous H 2 S treatment and energy recovery.