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 nanosheets (denoted as G@mTiO2), 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 m(2)/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, an excellent high-rate capability, and long cycle life.

Excessive nutrients (N and P) are among the most concerned pollutants in surface and ground waters. Herein, we report nanoscale zero-valent iron supported on ordered mesoporous carbon (nZVI@OMC) for electrocatalytic reduction of nitrate (NO) to nitrogen gas (N). This material has a maximum removal capacity of 315 mg N/g Fe and nitrogen selectivity up to 74%. The Fe-C nanocomposite is prepared via a postsynthetic modification including carbon surface oxidation, in-situammonia prehydrolysis of iron precursor and hydrogen reduction. The synthesized materials have large surface areas (660-830 m/g) and small iron nanoparticles (3-9 nm) uniformly dispersed in the carbon mesochannels. The iron loading can be adjusted in the range of 0-45%. Results demonstrate that the reaction reactivity of electrocatalysis can be fine-tuned by manipulating iron nanoparticle size, degree of crystallization, as well as porous structure. Meanwhile, the small, uniform, and stable iron nanoparticle promotes fast hydrogen generation for rapid cleavage of the N-O bond. Furthermore, this material can maintain its high performance over repetitive experimental cycles. Results suggest a new approach for fast and eco-friendly nitrate reduction and a novel nZVI application.

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m g ), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free-standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well-defined pore diameters for highly efficient nanosize-based separation at the macroscale.

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