Investigation of the mechanism of photocatalytic alcohol dehydrogenation over Pt/TiO2 using poisons and labelled ethanol

Abstract

Poisoning experiments using pyridine, piperidine, aqueous ammonia, phenol and 2-nitrophenol show that both acid and base sites are involved in the room-temperature photocatalytic dehydrogenation of alcohols (liquid propan-1-ol being chosen for the tests) over a Pt/TiO₂ catalyst. The dominant role is played by the base sites, since an acid of the strength of 2-nitrophenol suffices to cancel dehydrogenation, whereas the basic substances only decrease its rate. An additional piece of information on the dehydrogenation mechanism is obtained from the use of gaseous 2,2,2-[²H₃] ethanol at 263 K which provides evidence that the β-deuterium atoms are not abstracted, whereas at 295 K an isotopic exchange between the products, H₂and 2,2,2-[²H₃]ethanal, subsequently occurs.