Adsorption of R-OH molecules on TiO2 surfaces at the solid-liquid interface

Area of Science:

• Computational Materials Science
• Surface Chemistry
• Physical Chemistry

Background:

• Titanium dioxide (TiO2) applications often involve solid-liquid interfaces, yet theoretical studies predominantly focus on gas-phase reactivity.
• Simulating solid-liquid interfaces is computationally challenging for ab initio methods like density functional theory (DFT).
• Understanding TiO2 surface interactions in aqueous environments is crucial for catalysis, photocatalysis, and sensing.

Purpose of the Study:

• To investigate the adsorption behavior of water, methanol, hydrogen peroxide, and formic acid on anatase (101) and rutile (110) TiO2 surfaces in aqueous solution.
• To evaluate the influence of a continuum solvation model and an explicit first water monolayer on adsorption energies and configurations.
• To compare the relative affinities of different molecules for TiO2 surfaces in a realistic liquid environment.

Main Methods:

• Employed density functional theory (DFT) with a continuum solvation model within a periodic boundary conditions framework.
• Simulated the interaction of H2O, CH3OH, H2O2, and HCO2H with anatase (101) and rutile (110) TiO2 surfaces.
• Analyzed various adsorption configurations, including the explicit inclusion of the first water monolayer.

Main Results:

• Molecular adsorption of water and methanol was found to be most stable in aqueous solution.
• The preferred adsorption configuration for hydrogen peroxide was surface-dependent.
• Formic acid exhibited a higher surface affinity than water, methanol, and hydrogen peroxide, while methanol and hydrogen peroxide showed poor adsorption.
• The explicit first water monolayer significantly influenced adsorbate stabilization.

Conclusions:

• The study highlights the importance of considering solvation effects and explicit water layers for accurate TiO2 surface reactivity predictions.
• Formic acid is identified as having a strong affinity for TiO2 surfaces in aqueous media, unlike methanol and hydrogen peroxide.
• The findings provide valuable insights for designing TiO2-based materials and processes in liquid environments.