Surface and interstitial Ti diffusion at the rutile TiO(2)(110) surface

Area of Science:

• Materials Science
• Surface Science
• Computational Chemistry

Background:

• Titanium dioxide (TiO2) is a crucial material in catalysis, electronics, and energy applications.
• The diffusion of titanium (Ti) ad-species on the TiO2(110) rutile surface significantly influences its growth and reactivity.
• Understanding Ti diffusion mechanisms is essential for controlling TiO2 properties and performance.

Purpose of the Study:

• To elucidate the fundamental mechanisms governing Ti ad-species diffusion on the stoichiometric TiO2(110) rutile surface.
• To identify the minimum energy pathways for Ti diffusion between surface and subsurface sites.
• To provide insights into the re-oxidation processes of non-stoichiometric TiO2 surfaces.

Main Methods:

• Employed complementary computational methodologies: density functional theory corrected for on-site Coulomb interactions (DFT + U).
• Utilized a charge equilibration (QEq) atomistic potential to accurately model atomic interactions.
• Identified minimum energy pathways for Ti ad-species diffusion.

Main Results:

• Diffusion of Ti from the surface to the subsurface (and vice versa) follows an interstitialcy exchange mechanism.
• This mechanism involves the exchange of surface Ti atoms with 6-fold coordinated Ti atoms located beneath the bridging oxygen rows.
• Diffusion of Ti within the subsurface layers also proceeds via an interstitialcy mechanism.

Conclusions:

• The interstitialcy exchange mechanism is the dominant pathway for Ti diffusion on the TiO2(110) rutile surface and within its subsurface.
• This detailed understanding of Ti diffusion is critical for advancing research on TiO2 growth, reactivity, and surface re-oxidation.
• The findings contribute to the rational design and application of TiO2-based materials.