Probing Acid–Base Properties of Anatase TiO<sub>2</sub> Nanoparticles with Dominant {001} and {101} Facets Using Methanol Chemisorption and Surface Reactions
Yiqing Wu, Feng Gao, Huamin Wang, Libor Kovařík, Berlin Sudduth, Yong Wang
Abstract
In the present study, we investigate the surface acid-base properties of anatase TiO<sub>2</sub> nanomaterials with dominant {101} and {001} facets via methanol titrations. Two anatase nanoparticles, TiO<sub>2</sub>(101) and TiO<sub>2</sub>(001), with well-defined morphology are prepared. TiO<sub>2</sub>(101) is predominantly enclosed by the {101} facets (> 90%), and TiO<sub>2</sub>(001) contains ~46% {001} facets and ~54% {101} facets. Upon adsorption of methanol 423 K, DRIFTS measurements show that both molecular and dissociative adsorption occurs on TiO<sub>2</sub>(101), while dissociative adsorption dominates on TiO<sub>2</sub>(001). During methanol TPD, TiO<sub>2</sub>(001) mainly generates acid-base product dimethyl ether and thermal cracking products CO and H<sub>2</sub>, as anticipated. In contrast, substantial amounts of formaldehyde and methane also desorb from TiO<sub>2</sub>(101), suggesting strong participation of surface defects (e.g., oxygen vacancies).