Active site density and reactivity for the photocatalytic dehydrogenation of 2-propanol an TiO2 (110)

By combining molecular beam experiments at 350 K with low temperature experiments on an immobile adlayer, we determine the fraction of surface sites active for the photocatalytic dehydrogenation of 2-propanol to acetone to be 0.08 on a fully oxidized surface. We also find that the reaction probability at these sites is essentially unity. The presence of oxygen vacancies (approximate to 0.1 monolayer) increases the fraction of active sites to 0.15 without changing the reaction probability, reaction kinetics, or product distribution. From this, we conclude that only sites which can bind O-2 strongly are active for the reaction. Candidates for such sites include steps and kinks on fully oxidized surfaces and oxygen lattice vacancies on reduced surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.