Oxygen-Vacancy-Driven Orbital Reconstruction at the Surface of TiO₂ Core–Shell Nanostructures

Abstract

Oxygen vacancies and their correlation with the electronic structure are crucial to understanding the functionality of TiO2 nanocrystals in material design applications. Here, we report spectroscopic investigations of the electronic structure of anatase TiO2 nanocrystals by employing hard and soft X-ray absorption spectroscopy measurements along with the corresponding model calculations. We show that the oxygen vacancies significantly transform the Ti local symmetry by modulating the covalency of titanium–oxygen bonds. Our results suggest that the altered Ti local symmetry is similar to the C 3v , which implies that the Ti exists in two local symmetries (D 2d and C 3v ) at the surface. The findings also indicate that the Ti distortion is a short-range order effect and presumably confined up to the second nearest neighbors. Such distortions modulate the electronic structure and provide a promising approach to structural design of the TiO2 nanocrystals.

Operando Identification of Dynamic Photoexcited Oxygen Vacancies as True Catalytic Active Sites

“…57−59 The unpaired electrons in the intermediate state are easily excited due to the d−d transition, making the material display excellent activity. 60−62 However, as discussed before, the electron-rich surface drives the adsorption of molecules on the surface through electron transfer under dark conditions, 57,63 as evidenced by the O 2 − signal detected before the reaction (Figure 1a). Therefore, the electron transfer mechanism is deduced in Figure 4a.…”

“…From the perspective of electronic and orbital levels (Figure a), the introduction of Vo makes the excess electrons transfer to the Ti 3d orbital, which lowers the orbital energy level from the conduction band, forming an intermediate state. − The unpaired electrons in the intermediate state are easily excited due to the d–d transition, making the material display excellent activity. − However, as discussed before, the electron-rich surface drives the adsorption of molecules on the surface through electron transfer under dark conditions, , as evidenced by the O 2 – signal detected before the reaction (Figure a). Therefore, the electron transfer mechanism is deduced in Figure a.…”

Sunlight-Responsive Titania–Hydrated Tungsten Oxide Heteronanoparticles/Paper-Based Color-Switching Film for Solar Ultraviolet Radiation Monitors

“…The selected area electron diffraction (SAED) pattern shows the coexistence of TiO 2–x and WO 3 ·0.33H 2 O in the THTO heteronanoparticles (Figure S3). , The high-resolution TEM (HRTEM) image of the THTO heteronanoparticles shows lattice spacings of 0.352 and 0.184 nm (Figure b), which are attributed to the (101) plane of TiO 2 and the (400) plane of WO 3 ·0.33H 2 O, respectively. The structure characterization results demonstrate the formation of THTO heteronanoparticles with nanoscale interfacial contact, which is consistent with previous results.…”

Aliovalent Ta-Doping-Engineered Oxygen Vacancy Configurations for Ultralow-Voltage Resistive Memory Devices: A DFT-Supported Experimental Study

“…XAS is employed to investigate the local coordination chemistry of the Ta-doped and the undoped TiO 2 systems. This is important as formation of oxygen vacancies significantly transforms the local symmetry of Ti by the modulation of covalence of Ti–O bonds . Here, XAS spectra near the Ti L-edge and O K-edge, as shown in Figure a,b, respectively, were recorded in the total electron yield mode.…”

“…This is important as formation of oxygen vacancies significantly transforms the local symmetry of Ti by the modulation of covalence of Ti−O bonds. 22 Here, XAS spectra near the Ti Ledge and O K-edge, as shown in Figure 2a,b, respectively, were recorded in the total electron yield mode. The XAS spectrum at the Ti L-edge [Figure 2a] reflects the transitions of Ti 2p core electrons to the Ti 3d state, that is, the conduction band (CB).…”