Hydrogenated Amorphous Titania with Engineered Surface Oxygen Vacancy for Efficient Formaldehyde and Dye Removals under Visible-Light Irradiation.

Hydrogenated crystalized TiO 2-x with oxygen vacant (O V ) doping has attracted considerable attraction, owing to its impressive photoactivity. However, amorphous TiO 2 , as a common allotrope of titania, is ignored as a hydrogenated templet. In this work, hydrogenated amorphous TiO 2-x (HAm-TiO 2-x ) with engineered surface O V and high surface area (176.7 cm 2 g -1 ) was first prepared using a unique liquid plasma hydrogenation strategy. In HAm-TiO 2-x , we found that O V was energetically retained in the subsurface region; in particular, the subsurface O V -induced energy level preferred to remain under the conduction band (0.5 eV) to form a conduction band tail and deep trap states, resulting in a narrow bandgap (2.36 eV). With the benefits of abundant light absorption and efficient photocarrier transportation, HAm-TiO 2-x coated glass has demonstrated superior visible-light-driven self-cleaning performances. To investigate its formaldehyde photodegradation under harsh indoor conditions, HAm-TiO 2-x was used to decompose low-concentration formaldehyde (~0.6 ppm) with weak-visible light (λ = 600 nm, power density = 0.136 mW/cm 2 ). Thus, HAm-TiO 2-x achieved high quantum efficiency of 3 × 10 -6 molecules/photon and photoactivity of 92.6%. The adsorption capabilities of O 2 (-1.42 eV) and HCHO (-1.58 eV) in HAm-TiO 2-x are both largely promoted in the presence of subsurface O V . The surface reaction pathway and formaldehyde decomposition mechanism over HAm-TiO 2-x were finally clarified. This work opened a promising way to fabricate hydrogenated amorphous photocatalysts, which could contribute to visible-light-driven photocatalytic environmental applications.