(178f) Water Adsorption Behavior On Unique Titanium Dioxide Polymorph (TiO2-B) Facets

Titanium dioxide (TiO2) processes the promising perspective in many applications, such as solar cell, photocatalysis, catalyst support, water splitting devices and sensors etc. TiO2-based materials received enormous expectation in solving or easing the environmental challenges and energy crisis. Surface chemical and physical properties play a dominate role in most fields, such as biology, materials science, catalysis etc. It is well accepted that surfaces with high reactivities are extraordinary important both from scientific and technological viewpoint. Current investigations focus on three main crystallographic forms of TiO2, rutile, anatase and brookite. But there is another polymorph of TiO2 named TiO2-B in ambient conditions, which has been rarely studied since it was identified in 1980s. To advance the basic understanding this polymorph of TiO2, we present ab initio calculations to reveal the structure and electronic properties of TiO2-B crystal.

Water is a most common molecule in nearly all the application fields of TiO2. H2O molecules are also widely adopted to probe the surface chemistry of various metal oxides. Water adsorption or dissociation on different surfaces is one of the most important issues for understanding and controlling functionality of metal oxide materials. Moreover, we studied water adsorption behaviors on TiO2-B facets, (001) and (100), to elaborate the chemi-/physic- properties. Water distinct adsorption behaviors on two surfaces, (001) and (100) are identified. Dissociative adsorption of water is quite favored, even at monolayer coverage on TiO2-B (100). Whereas, molecular adsorption of water is the most favorable state on TiO2-B (001), regardless of the coverage. Thus, we reported that another surface of the forth TiO2 polymorph, TiO2-B (100), would be probably very reactive as anatase (001) or rutile (011)-2x1, on which dissociation of water is also favored. These results highligh surface control during the synthesis process of the catalyst, it is another key issue for improving the catalysis performance.