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Hierarchical TiO2 Microspheres: Synergetic Effect of {001} and {101} Facets for Enhanced Photocatalytic Activity

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Abstract

Well-faceted nanocrystals of anatase TiO2 with specific reactive facets have attracted extraordinary research interest due to their many intrinsic shape-dependent properties. In this work, hierarchical TiO2 microspheres consisting of anatase nanosheets or decahedrons were synthesized by means of a facile hydrothermal technique; meanwhile, the percentage of {001} facets can be tuned from 82 to 45 %. Importantly, by investigating the photo-oxidation reactions for .OH radical generation and photoreduction reactions for hydrogen evolution, the TiO2 microspheres consisting of nano-decahedrons with 45 % {001} facets show superior photoreactivity (more than 4.8-times) compared to the nanosheets with 82 % {001} facets. By analyzing the results of scanning electron microscopy (SEM), photoluminescence (PL) and first-principles density functional theory (DFT) calculations, a model of charge separation between the well-formed {001} and {101} facets is proposed, and the enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges among the crystal facets co-exposed.

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