This work focuses on increasing the quantum efficiency in titania photosynthetic (photosplitting of water) and photocatalysts for photocatalytic (oxidation of acetaldehyde) reactions by synthesizing controlled anatase nanocrystals with a shoebox-like shape. In general, anatase crystals have tetragonal dipyramid shapes (see figure). All of the {101} surfaces have the same property, because they are symmetrically identical. The elongated anatase crystals are synthesized through topological replacement (or transformation) of titanate display shoebox-like shapes with crystal forms of {100} and {001} (see figure). The {001} and {100} surfaces have different physical/chemical properties because they are not symmetrically related. The difference will enhance the electron-hole separation generated by photons and therefore enhance the quantum efficiency of photocatalytic reactions. In addition, both {001} and {100} surfaces have higher energies than normal {101} surfaces, which increases surface reactivity of the anatase. The shape-controlled anatase crystals display enhanced reactivity for both photosplitting of water and photocatalytic oxidation of organic pollutants (such as volatile organic compounds in air) using renewable solar energy. The results have important implications for enhancing the photocatalytic activity of titania for environmental remediation, increasing the quantum efficiency in photovoltaic solar cells and other photoassisted processes.
Lab talk
Jan 30, 2008
Investigation of the nanostructured rutile and anatase plates for improving photosplitting of water
The emergence of nanoscience and nanotechnology has made it possible to purposefully manipulate material structures at nanometer scales and has greatly advanced our understanding of how these nanoscale structures give rise to novel physical and chemical properties not seen in bulk materials. Both physical and chemical properties of nanocrystals can be tuned by controlling their sizes, shapes and architectures.
About the author
Dr Huifang Xu is an interdisciplinary scientist in the Department of Geology & Geophysics and Materials Science Program of the University of Wisconsin, Madison. One of his research interests is shape- and size-controlled crystals for environmental clean up and hydrogen production from water. Professor Xu and his colleagues are organizing a nanocrystal frontier symposium of “Crystal Shape Control and Shape Dependent Properties Across Length-scales” for the coming MRS Spring Meeting.