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

1999; Elsevier BV; Volume: 128; Issue: 1-3 Linguagem: Inglês

10.1016/s1010-6030(99)00156-2

1873-2666

Kohjiro Hara, Kazuhiro Sayama, Hironori Arakawa,

Chemical and Physical Properties in 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 absorption with sulfide ions (S2−). The maximum quantum efficiency for hydrogen formation, 8.9%, was obtained in a 25 mmol dm−3 Na2S solution. Marked amounts of hydrogen were produced under UV light irradiation in the aqueous solutions of SO32− and S2O42− ions. S2− ion absorption began at 290 nm, SO32− at 275 nm, and S2O42− at 400 nm. Hydrogen hardly formed at all, however, in SO42−, I−, and SCN− solutions.