Stability of Excess Electrons Introduced by Ti Interstitial in Rutile TiO₂(110) Surface

Abstract

The surface chemistry of rutile TiO2(110) has long been ascribed to surface bridging oxygen vacancies (VO) and accompanying excess electrons. However, recently there has been debate whether titanium interstitials (Tiint), a subsurface defect, participates in the surface reactions of TiO2(110). We used a combination of ab initio molecular dynamics and static density functional theory calculations to systematically investigate the spatial distribution of excess electrons introduced by Tiint. We found that these excess electrons form polarons and that the most stable structure had one polaron located at the Tiint site, and the other three at second-layer Ti sites below five-coordinate Ti sites. This behavior of Tiint providing excess electrons to the near-surface region is similar to that of VO, which suggests that Tiint may contribute to the surface chemical reactions of TiO2(110).

On the Charge State of Titanium in Titanium Dioxide

“…This is of particular interest in the case of redox processes in TiO 2 systems; for example the assignment of oxidation states obtained in doped TiO 2 is done off the assumed +4 oxidation state in pure TiO 2 . [55][56][57] Our results suggest that, in principle, further oxidation at the Ti centers is possible. Conversely follows that oxygen could be further reduced, oxygen redox activity is a known effect occurring e.g.…”

Intrinsic intermediate gap states of TiO2 materials and their roles in charge carrier kinetics

“…In addition to V O species, the Ti(i) is another main chemical entity causing e-polaron states [192][193][194][195]. In recent research, a DFT + U ab initio molecular dynamics (AIMD) and a static DFT were adopted to investigate the localization of Ti(i)-induced electrons at Ti lattice sites, as shown in Fig.…”

“…In recent research, a DFT + U ab initio molecular dynamics (AIMD) and a static DFT were adopted to investigate the localization of Ti(i)-induced electrons at Ti lattice sites, as shown in Fig. 10(A) [195]. It was seen by them that the average lifetime of an electron at a specific Ti site is around 0.1 ps.…”

The Development of Non-Enzymatic Glucose Biosensors Based on Electrochemically Prepared Polypyrrole–Chitosan–Titanium Dioxide Nanocomposite Films

“…The proposed mechanism of glucose oxidation on TiOOH is as follows [32,33,34,35,36,37]:2TiO 2 + C 6 H 12 O 6 (Glucose) → 2TiOOH + C 6 H 10 O 6 (Gluconolactone). 2Ti(IV) + C 6 H 12 O 6 (Glucose) → 2Ti(II) + C 6 H 10 O 6 (Gluconolactone) + H 2 O 2 . C 6 H 10 O 6 (Gluconolactone) + H 2 O → 2H + + C 6 H 12 O 7 (Gluconate). 2Ti(II) → 2Ti(IV) + 2e − .…”

“…On the basis of the reported glucose oxidation and the findings of this study, TiOOH-modified electrodes mediated the heterogeneous redox reactions, and the Ti(IV) species was subsequently regenerated, which mimicked the enzymatic oxidation reactions. The proposed mechanism of glucose oxidation on TiOOH is as follows [ 32 , 33 , 34 , 35 , 36 , 37 ]: 2TiO 2 + C 6 H 12 O 6 (Glucose) → 2TiOOH + C 6 H 10 O 6 (Gluconolactone). 2Ti(IV) + C 6 H 12 O 6 (Glucose) → 2Ti(II) + C 6 H 10 O 6 (Gluconolactone) + H 2 O 2 .…”