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American Chemical Society, Nano Letters, 3(15), p. 2186-2193, 2015

DOI: 10.1021/acs.nanolett.5b00291

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General Strategy to Synthesize Uniform Mesoporous TiO<sub>2</sub>/Graphene/Mesoporous TiO<sub>2</sub> Sandwich-Like Nanosheets for Highly Reversible Lithium Storage

This paper is available in a repository.
This paper is available in a repository.

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Abstract

Uniform oxide deposition on graphene to form a sandwich-like configuration is a well-known challenge mainly due to their large lattice mismatches and poor affinities. Herein, we report a general strategy to synthesize uniform mesoporous TiO2/graphene/mesoporous TiO2 sandwich-like (denoted as G@mTiO2) nanosheets, which cannot be achieved by conventional one-pot synthetic methods. We show that by rational control of hydrolysis and condensation of Ti precursors in a slow way, GO sheets can be conformably coated by amorphous TiO2 shells, which then can be facilely transformed into the well-defined G@mTiO2 nanosheets by annealing. This amorphous-to-crystalline strategy conveniently allows bypassing strain fields that would inevitably arise if direct growth of mesoporous anatase shells on graphene. As distinct from the most common structures of graphene-based composites (mixed, wrapped or anchored models), the resultant materials display a uniform sandwich-like configuration: few-layer graphene conformably encapsulated by mesoporous TiO2 shells. This new G@mTiO2 nanosheet exhibits ultrathin nature (~ 34 nm), small size and high crystalline nanocrystals (~ 6 nm), high surface areas (~ 252 m2/g) and uniform mesopores (~ 3.4 nm). We further show that, the thickness of mesoporous TiO2 shells can be facilely adjusted as desired by controlling the ammonia content; and this facile strategy can be easily extended to design other oxide/graphene/oxide sandwich-like materials. More importantly, we showcase the benefits of the resultant G@mTiO2 nanosheets as anodes in lithium ion batteries: they deliver an extra high capacity of ~ 256 mAh/g, an excellent high-rate capability and long cycle life.