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 TiO2 nanomaterials with dominant {101} and {001} facets via methanol titrations. Two anatase nanoparticles, TiO2(101) and TiO2(001), with well-defined morphology are prepared. TiO2(101) is predominantly enclosed by the {101} facets (>90%), and TiO2(001) contains similar to 46% {001} facets and similar to 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 TiO2(101), while dissociative adsorption dominates on TiO2(001). During methanol temperature-programmed desorption, TiO2(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 TiO2(101), suggesting strong participation of surface defects (e.g., oxygen vacancies).

Automated summary

This study investigates the surface acid-base properties of anatase TiO2 nanomaterials with {101} and {001} facets via methanol titrations. It was found that adsorption and desorption of methanol differ significantly between TiO2(101) and TiO2(001), with surface defects playing an important role in the reaction process.