As an important metal oxide, anatase titanium dioxide has been widely investigated because of its many promising properties in catalysis and photocatalysis. The properties of anatase TiO 2 crystals are largely determined by external surfaces exposed. Many efforts have been made to improve the percentage of high-reactive facets like {001} facets of anatase TiO 2 to enhance its catalytic properties. This review reports the recent progress in designing and fabricating high-reactive facets dominated anatase TiO 2 via various strategies including traditional vapor phase epitaxial processes, hydrothermal/solvothermal methods, nonhydrolytic alcoholysis methods and high temperature gas phase reactions. Furthermore, focusing on (001) surface, the review also covers advances in the theoretic simulations of various high-reactive facets of anatase TiO 2 crystals. Finally, we offer a summary and some perspectives on the challenges and new directions for future research in this emerging frontier. 1. Introduction Metallic and semiconducting nanocrystals with tailored facets have always attracted intense interests in the last decade due to their many intrinsic shape-dependent properties, such as water splitting for hydrogen, solar cells, CO 2 reduction, gas sensors etc. 1-21 As one of the commonly available and most studied metal oxides, titanium dioxide (TiO 2) has been widely used as a pigment and in sunscreens, paints, ointments, toothpaste, and catalysis. 9 we have witnessed an exponential growth of research activities since Fujishima and Honda discovered the phenomenon of photocatalytic splitting of water on a TiO 2 electrode under ultraviolet (UV) light in1972. 22 Many promising applications have been developed
Metal nanoclusters (Au, Pt, Pd, Cu) encapsulated in channels of mesoporous ceria (mp-CeO(2)) were synthesized. The activation energies of water-gas shift (WGS) reaction performed at oxide-metal interfaces of metal nanoclusters encapsulated in mp-CeO(2) (M@mp-CeO(2)) are lower than those of metal nanoclusters impregnated on ceria nanorods (M/rod-CeO(2)). In situ studies using ambient-pressure XPS (AP-XPS) suggested that the surface chemistry of the internal concave surface of CeO(2) pores of M@mp-CeO(2) is different from that of external surfaces of CeO(2) of M/rod-CeO(2) under reaction conditions. AP-XPS identified the metallic state of the metal nanoclusters of these WGS catalysts (M@mp-CeO(2) and M/rod-CeO(2)) under a WGS reaction condition. The lower activation energy of M@mp-CeO(2) in contrast to M/rod-CeO(2) is related to the different surface chemistry of the two types of CeO(2) under the same reaction condition.
A new synthetic strategy was developed to prepare large-sized well-defined anatase TiO(2) nanosheets wholly dominated with thermodynamically unfavorable high-reactive {001} and {100} facets, which has a percentage of 98.7% and 1.3%, respectively. The as-prepared anatase TiO(2) nanosheets show a well-faceted morphology and have a large size in length (ca. 4.14 μm). The formation mechanism of the anatase TiO(2) nanosheets was also analyzed and investigated.
Many properties of dopants have been investigated to explore the key factor that influenced the CO oxidation activity of M-doped ceria (CeM). Nevertheless, these reports were controversial. Herein, the Pauling electronegativity (χP) of the M was presented as a convenient guide to screen a proper dopant for ceria. Kinetics results indicated that the T
10 (the temperature when CO conversion reached 10%) of CeM73 catalysts (Ce/M molar ratio was 7/3; M = Cu, Ti, Zr, and Tb) was linearly dependent on the χP of the M, which could adjust the amount of active lattice oxygen (A
OL). The A
OL was important to catalyst activity because lattice oxygen extraction was the rate-determining step in the overall reaction.
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