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-/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, H2S 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, H2S 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 similar to 1.04 mg h(-1) cm(-1) and similar to 0.75 mL h(-1) cm(-1), respectively, suggesting that H2S was completely converted into H-2 and S. In addition, the output power density of the system reached similar to 0.11 mW cm(-2). The proposed PEC-H2S system provides a self-sustaining, energy-saving method for simultaneous H2S treatment and energy recovery.