A New Deep Hole-Trapping Site For Water Splitting On The Rutile Tio2(110) Surface

The mechanism of the water photooxidation reaction on the rutile TiO2(110) surface has been extensively discussed but still remains highly controversial. By ab initio many-body Green's function theory, we discover a new deep hole-trapping site 2Ti(6c)-O-br-O-Ti-5c which should be the key intermediate regulating the reaction. This site releases an O-2 molecule after capturing two holes, producing a bridging oxygen vacancy simultaneously. Accompanied by a huge Stokes shift, electron-hole recombination at this site emits light around 1.5 eV. These two phenomena can solve the long-standing mysteries of surface roughening and photoluminescence at 810 nm observed experimentally. We find that introducing Ti vacancies into rutile to turn it into a p-type conductor can make H2O dissociate directly at bridging oxygen, so that photooxidation efficiency may be elevated substantially.