Insights into the effects of surface/bulk defects on photocatalytic hydrogen evolution over TiO2 with exposed {001} facets.

This paper describes the effects of defect distribution on energy band structure and the subsequent photocatalytic activity over TiO 2 with exposed {001} facets as the model catalyst. Our results show that only surface oxygen vacancies (V o ’s) and Ti 3+ centers in TiO 2 can be induced by hydrogenation treatment, whereas the generation of bulk V o ’s and Ti 3+ species depends on the thermal treatment in nitrogen. Both the surface and bulk defects in TiO 2 can promote the separation of electron-hole pairs, enhance the light absorption, and increase the donor density. The presence of surface and bulk defects in TiO 2 can not change the valence band maximum, but determine the conduction band minimum. Surface defects in TiO 2 induce a tail of conduction band located above the H + /H 2 redox potential, which benefits the photocatalytic performance. However, bulk defects in TiO 2 generate a band tail below the H + /H 2 potential, which inhibits hydrogen production. Thus, the change of band gap structure by defects is the major factor to determine the photocatalytic activity of TiO 2 for hydrogen evolution. It is a new insight into the rational design and controllable synthesis of defect-engineered materials for various catalytic processes. [ABSTRACT FROM AUTHOR]