Photocatalytic hydrogen evolution from aqueous hydrazine solution over precious-metal/anatase catalysts

Abstract

Aqueous hydrazine solution has been photocatalytically decomposed over precious-metal/anatase catalysts yielding only H₂, N₂ and NH₃. H₂/N₂(molar ratio of H₂ evolved to N₂ evolved) is usually ca. 1 and does not depend on the reaction conditions (pH, metal, reactant concentration). However, the value is > 1 when another hole scavenger (CH₃OH) is present. N₂/NH₃ is ca. 0.5 and does not change in the presence of CH₃OH. On the basis of these results, the reaction scheme is considered to be as follows: the electrons photoexcited into the conduction band of anatase are consumed through H₂ formation and the positive holes generated in the valence band are consumed through the simultaneous formation of N₂ and NH₃. The dependence of the reaction rate on the concentration of N₂H₄ and on the metal suggests that the rate-determining step is the formation of H₂ over the metal.