Monoethanolamine Adsorption on TiO₂(110): Bonding, Structure, and Implications for Use as a Model Solid-Supported CO₂ Capture Material

We have studied the adsorption of monoethanolamine (MEA, HO(CH 2 ) 2 NH 2 ), a well-known CO 2 capture molecule, on the rutile TiO 2 (110) surface using a combined experimental and theoretical approach. X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and scanning tunneling microscopy measurements indicate that MEA adsorbs with the oxygen atom of the hydroxyl group and the nitrogen atom of the amine group bonded to adjacent 5-fold coordinated Ti-sites (Ti(5f)) in the Ti-troughs, leading to a saturation coverage of 0.5 ML at room temperature. Density functional theory calculations confirm that this adsorption configuration is the most stable one with an adsorption energy of 2.33 eV per MEA molecule. The bonding of MEA to TiO 2 (110) is dominated by local donor–acceptor bonds between the oxygen and nitrogen atoms of the MEA molecule and surface Ti(5f) sites. Hydrogen bonds between adjacent MEA molecules stabilize the adsorption structure at saturation coverage. The implications of this bonding configuration for the use of MEA/TiO 2 (110) as a model CO 2 capture material will be discussed.