Interaction Mechanism and Electronic Dynamics between Defects and Hydrogen Atoms in TiO2 Thin Films

Hydrogen is one of the main hazards to the safety of material service; as a common material in the petrochemical industry, titanium alloy, with its surface nano thickness oxide film (TiO2), has excellent hydrogen resistance, and it is generally believed that the destruction of its surface structure causes hydrogen damage of titanium alloy, which can be a key obstacle to the safety and service life of hydrogen equipment. However, the unquantitatively explained phenomenon of defects interacting with hydrogen atoms in TiO2 films has hindered the mechanistic revelation of the hydrogen-blocking properties of oxide films as well as the development and practical application of surface protection technologies. In this study, based on the semiconducting properties of TiO2 membranes themselves, the hydrogen–microscopic defect structure interaction mechanism in two typical TiO2 crystal types, i.e., rutile and anatase, has been quantitatively described from the microscopic level of electron–hole complexation. In this research work, time-of-flight-secondary ion mass spectrometry (ToF-SIMS) was used to qualitatively characterize the spatial distribution of H atoms in TiO2 membranes after different prefabricated defects and prefilled with hydrogen, and time-resolved photoluminescence spectroscopy was used to geometrically and quantitatively characterize and analyze the kinetic behaviors of electron–hole complexes in TiO2 membranes with different defects. This investigation demonstrates that the concerted interaction between hydrogen atoms and defects present within TiO2 films modifies the electronic band configuration, thereby inducing notable variations in the electron–hole recombination lifetimes. The study of the microscopic mechanism of H-defect interactions in oxide films based on the electron–hole complex mechanism presented in this work opens up new ideas and provides valuable insights into the mechanism of hydrogen-blocking failure of oxide films.