Self-Driven Photoelectrochemical Splitting of H2S for S and H2 Recovery and Simultaneous Electricity Generation.

A novel, facile self-driven photoelectrocatalytic (PEC) system was established for highly selective and efficient recovery of H2S and simultaneous electricity production. The key ideas were the self-bias function between a WO3 photoanode and a Si/PVC photocathode due to their mismatched Fermi levels and the special cyclic redox reaction mechanism of I-/I3-. 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 I3- by photoholes or hydroxyl radicals, H2S was oxidized to S by I3-, and I3- was then reduced to I-. Meanwhile, H+ was efficiently converted to H2 in the photocathode region. In the system, H2S was uniquely oxidized to sulfur but not to polysulfide (Sxn-) because of the mild oxidation capacity of I3-. High recovery rates for S and H2 were obtained up to ∼1.04 mg h-1 cm-1 and ∼0.75 mL h-1 cm-1, respectively, suggesting that H2S was completely converted into H2 and S. In addition, the output power density of the system reached ∼0.11 mW cm-2. The proposed PEC-H2S system provides a self-sustaining, energy-saving method for simultaneous H2S treatment and energy recovery.