Titanium(iv) oxide having a copper co-catalyst: a new type of semihydrogenation photocatalyst working efficiently at an elevated temperature under hydrogen-free and poison-free conditions

Abstract

A copper-loaded titanium(IV) oxide photocatalyst exhibited perfect selectivity in hydrogenation of alkynes to alkenes in an alcohol solution at 298 K under hydrogen-free and poison-free conditions. A slight elevation in the reaction temperature to 323 K greatly increased the reaction rate with the selectivity being preserved and the formation of an H₂ by-product being suppressed. The apparent activation energy of 4-octyne semihydrogenation was determined to be 54 kJ mol⁻¹, indicating that the rate determining step of this photocatalytic reaction was not an electron production process but a thermocatalytic hydrogenation process under light irradiation.