A Novel Green TiO₂ Photocatalyst with a Surface Charge-Transfer Complex of Ti and Hydrazine Groups

The optical property of TiO₂ plays an important role in its various and promising photocatalytic applications. Previous efforts in improving its optical properties include doping with various metal and/or non-metal elements, coupling with other colorful semiconductors or molecules, and hydrogenating to crystalline/disordered core/shell nanostructures. Here, we report a beautiful green TiO₂ achieved by forming the charge-transfer complex of colorless hydrazine groups and surface Ti⁴⁺ , which extends the optical absorption into the near infrared region (≈1100 nm, 1.05 eV). It shows an enhanced photocatalytic performance in hydrogen generation under simulated sunlight, and degradation of organic pollution under visible light due to an impurity state (about 0.28 eV) resulting in fast electron-hole separation and injection of electrons from the ligand to the conduction band of TiO₂ . This study demonstrates an alternative approach to tune the optical, impurity state and photocatalytic properties of TiO₂ nanoparticles and we believe this will spur a wide interest in related materials and applications.