Surface chemistry of TiO connecting thermal catalysis and photocatalysis.

Chemical reactions catalyzed under heterogeneous conditions have recently expanded rapidly from traditional thermal catalysis to photocatalysis due to the rising concerns about sustainable development of energy and the environment. Adsorption of reactants on catalyst surfaces, subsequent surface reactions, and desorption of products from catalyst surfaces occur in both thermal catalysis and photocatalysis. TiO catalysts are widely used in thermal catalytic and photocatalytic reactions. Herein we review recent progress in surface chemistry, thermal catalysis and photocatalysis of TiO model catalysts from single crystals to nanocrystals with the aim of examining if the surface chemistry of TiO can bridge the fundamental understanding between thermal catalysis and photocatalysis. Following a brief introduction, the structures of major facets exposed on TiO catalysts, including surface reconstructions and defects, as well as the electronic structure and charge properties, are firstly summarized; then the recent progress in adsorption, thermal chemistry and photochemistry of small molecules on TiO single crystals and nanocrystals is comprehensively reviewed, focusing on manifesting the structure-(photo)activity relations and the commonalities/differences between thermal catalysis and photocatalysis; and finally concluding remarks and perspectives are given.