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.