Probing Acid–Base Properties of Anatase TiO2 Nanoparticles with Dominant {001} and {101} Facets Using Methanol Chemisorption and Surface Reactions

In the present study, we investigate the surface acid–base properties of anatase TiO 2 nanomaterials with dominant {101} and {001} facets via methanol titrations. Two anatase nanoparticles, TiO 2 (101) and TiO 2 (001), with well-defined morphology are prepared. TiO 2 (101) is predominantly enclosed by the {101} facets (>90%), and TiO 2 (001) contains ∼46% {001} facets and ∼54% {101} facets. Upon adsorption of methanol at 423 K, diffuse reflectance infrared Fourier transform spectroscopy measurements show that both molecular and dissociative adsorption occur on TiO 2 (101), while dissociative adsorption dominates on TiO 2 (001). During methanol temperature-programmed desorption, TiO 2 (001) mainly generates the acid–base product dimethyl ether and thermal cracking products CO and H 2, as anticipated. In contrast, substantial amounts of formaldehyde and methane also desorb from TiO 2 (101), suggesting strong participation of surface defects (e.g., oxygen vacancies).