UV photoinduced reduction of water to hydrogen in Na2S, Na2SO3, and Na2S2O4 aqueous solutions

Hydrogen was produced by ultraviolet (UV) light irradiation (>200 nm) in an Na2S aqueous solution without photocatalysts. Water (protons) appeared to be directly reduced to hydrogen by excited electrons produced in photon abs orption with sulfide ions (S2-). The maximum quantum efficiency for hydroge n formation, 8.9%, was obtained in a 25 mmol dm(-3) Na2S solution. Marked a mounts of hydrogen were produced under UV light irradiation in the aqueous solutions of SO32- and S2O42- ions. S2- ion absorption began at 290 nm, SO( 3)(2-)at 275 nm, and S2O42- at 400 nm. Hydrogen hardly formed at all, howev er, in SO42-, I-, and SCN- solutions. (C) 1999 Elsevier Science S.A. All ri ghts reserved.