Photocatalytic Hydrogenation of Alkynes and Alkenes with Water over TiO2. Hydrogenation Accompanied by Bond Fission

Article abstract of DOI:10.1021/j150656a028

Photocatalytic reactions of alkynes and alkenes with water have been investigated over TiO2 powder.The major photoformed products are those formed by hydrogenation accompained by C=C or C<*>C bond fission.Oxidation products such as CO and CO2 are also formed.From the change in the product yields with the remaining amount of water adsorbed as well as the pressure of water vapor it is concluded that water molecules and not surface OH^- groups are responsible for the reaction and also that vacant sites for the alkyne (or alkene) adsorption are necessary for the occurrence of the reaction.The fission of the C=C or C<*>C bond observed with the hydrogenation is attributed to the interaction of the alkynes (or alkenes) with the trapped e^-(Ti³⁺) and h⁺(^.OH) pairs.It is suggested that a close association of photoformed electron and hole pairs plays a significant role in the bond fission.