Specific and high-affinity adsorption of volatile organic compounds on titanium dioxide surface

Area of Science:

• Surface science
• Environmental chemistry
• Catalysis

Background:

• The interaction between metal oxides and volatile organic compounds (VOCs) is crucial for environmental and catalytic processes.
• Previous studies indicated selective adsorption of atmospheric carboxylic acids on TiO2 (rutile (110)) surfaces, despite their low concentrations.

Purpose of the Study:

• To investigate the adsorption behavior of common VOCs on rutile (110) surfaces using in situ sum-frequency vibrational spectroscopy.
• To compare the adsorption mechanisms of formic acid, acetic acid, and formaldehyde on rutile (110) with those on fused silica.

Main Methods:

• In situ sum-frequency vibrational spectroscopy (SFVS) was employed.
• The study focused on the interaction of rutile (110) with formic acid, acetic acid, and formaldehyde.
• Adsorption on fused silica was also examined for comparative analysis.

Main Results:

• SFVS spectra for adsorbed formic acid, acetic acid, and formaldehyde on rutile (110) showed a broad resonance near 2950 cm-1.
• This resonance suggests a bridging bidentate adsorption configuration for these molecules on the rutile surface.
• In contrast, fused silica exhibited a molecular monodentate adsorption, with aliphatic carbons as dominant adventitious species.

Conclusions:

• Rutile (110) surfaces facilitate bridging bidentate adsorption of common atmospheric VOCs like carboxylic acids and formaldehyde.
• The adsorption behavior differs significantly from that observed on fused silica, highlighting the importance of the metal oxide surface.
• Understanding these interactions is key for advancing environmental remediation and catalytic applications involving VOCs.