CO2 adsorption on TiO2(101) anatase: a dispersion-corrected density functional theory study

Area of Science:

• Materials Science
• Surface Chemistry
• Computational Chemistry

Background:

• Titanium dioxide (TiO2), particularly the anatase (101) surface, is a key material in photocatalysis and heterogeneous catalysis.
• Understanding the adsorption, diffusion, and dissociation mechanisms of small molecules like carbon dioxide (CO2) on TiO2 is crucial for designing efficient catalytic processes.

Purpose of the Study:

• To investigate the adsorption, diffusion, and dissociation pathways of CO2 on the pristine and defective anatase (101) surface.
• To identify stable adsorption configurations and determine the energetic barriers for CO2 surface diffusion and dissociation.
• To explore the role of surface defects, such as oxygen vacancies and interstitial Ti atoms, in modulating CO2 reactivity.

Main Methods:

• Dispersion-corrected density functional theory (DFT) calculations were employed to model CO2 interactions.
• Various surface sites and defect configurations on the anatase (101) surface were systematically analyzed.
• Energetics of adsorption, diffusion barriers, and dissociation pathways were computed.

Main Results:

• On the oxidized anatase (101) surface, the most stable CO2 adsorption site is a tilted molecule at a five-fold coordinated Ti site.
• Surface diffusion of CO2 is facile, with low activation barriers, primarily occurring along Ti rows via a cartwheel motion.
• Surface defects (bridging oxygen defects, interstitial Ti atoms, subsurface oxygen vacancies) significantly enhance CO2 binding, favoring bent configurations and promoting exothermic dissociation with low barriers (< 21 kcal/mol).

Conclusions:

• Surface defects on anatase (101) play a critical role in enhancing CO2 adsorption strength and facilitating its dissociation.
• The identified defect sites offer promising avenues for the catalytic activation of CO2.
• Further research is needed to develop regeneration mechanisms for these defects to enable sustained CO2 catalytic conversion.