In situ growth of porous TiO2 with controllable oxygen vacancies on an atomic scale for highly efficient photocatalytic water splitting

Abstract

Oxygen vacancies play an important role in metal oxide semiconductors to improve the photocatalytic efficiency. Herein, we developed an effective method via atomic layer deposition to control the formation of oxygen vacancies in porous TiO₂ at a single atomic layer. X-ray photoelectron spectra and electron paramagnetic resonance spectra confirmed the different concentrations of oxygen vacancies which were formed by regulating the stoichiometric ratio of TiO₂. Time-resolved fluorescence decay spectra and photocurrent measurement results indicated that the oxygen vacancies accelerated the separation of charge carriers and prolonged the lifetime of electrons. As a result, the porous TiO₂ with abundant oxygen vacancies exhibited a much higher photocatalytic H₂ generation rate (3.41 mmol g⁻¹ h⁻¹), about 20 times that with fewer oxygen vacancies. Combined with density functional theory calculation, the introduced oxygen vacancies could introduce a defect level and delocalize charges around them, thus extending the light absorption region and promoting separation and transfer of photogenerated electrons and holes. This defect engineering not only opens up a way to manipulate the stoichiometric ratio at an atomic level, but also provides a flexible template to support single atom catalysts for energy conversion.