Ultra-small yellow defective TiO2 nanoparticles for co-catalyst free photocatalytic hydrogen production

Blue TiO 2 (Ti 3+ defected TiO 2 ) nanoparticles have been intensively investigated for photocatalytic H 2 production. However, the Ti 3+ , with energy level ~1.0   eV below the conduction band , cannot initiate visible light driven H 2 production. Thus, Pt or NiO x is often used as a co-catalyst, which is economically unattractive and environmentally contaminative. In this paper, the ultra-small yellow TiO 2 nanoparticles (~3   nm) have been firstly synthesized without introducing any external dopants . The titanium vacancies (acceptor) and titanium interstitials (donor) that incorporated in the yellow TiO 2 are evidenced by various characterization techniques, and their formation mechanism is proposed. Photocatalytic evaluations indicate that the acceptor–donor defects play key roles in the catalytic process, not only initiating, but also promoting the visible light driven H 2 production. The improved activity is also evidenced by that the simulated solar light driven H 2 production for the yellow TiO 2 is ~3.7 fold comparing to that of the normal TiO 2 . A reasonable explanation is that the acceptor-donor defect associates form internal polarization for spontaneously separating photo-generated charge-carriers. The improved charge-carrier separation has been confirmed by photoluminescence spectra and photoluminescence emission decay profiles. Instead of the traditional TiO 2 based photocatalysts , the acceptor–donor defect engineered photocatalyst system offers a new approach for simultaneously initiating and promoting visible light driven co-catalyst free H 2 production.