Hydrogenated Amorphous TiO_2-x and Its High Visible Light Photoactivity

Hydrogenated crystalline TiO₂ with oxygen vacancy (O_V) defect has been broadly investigated in recent years. Different from crystalline TiO₂, hydrogenated amorphous TiO_2-x for advanced photocatalytic applications is scarcely reported. In this work, we prepared hydrogenated amorphous TiO_2-x (HA-TiO_2-x) using a unique liquid plasma hydrogenation strategy, and demonstrated its highly visible-light photoactivity. Density functional theory combined with comprehensive analyses was to gain fundamental understanding of the correlation among the O_V concentration, electronic band structure, photon capturing, reactive oxygen species (ROS) generation, and photocatalytic activity. One important finding was that the narrower the bandgap HA-TiO_2-x possessed, the higher photocatalytic efficiency it exhibited. Given the narrow bandgap and extraordinary visible-light absorption, HA-TiO_2-x showed excellent visible-light photodegradation in rhodamine B (98.7%), methylene blue (99.85%), and theophylline (99.87) within two hours, as well as long-term stability. The total organic carbon (TOC) removal rates of rhodamine B, methylene blue, and theophylline were measured to 55%, 61.8%, and 50.7%, respectively, which indicated that HA-TiO_2-x exhibited high wastewater purification performance. This study provided a direct and effective hydrogenation method to produce reduced amorphous TiO_2-x which has great potential in practical environmental remediation.