Synthesis of ultrasmall metal nanoparticles and continuous shells at the liquid/liquid interface in Ouzo emulsions

Herein, we report a novel method to synthesize metal nanoparticle-shells (NP-shells) and continuous shells at the liquid/liquid interface, via an interfacial reaction in an Ouzo emulsion. Ouzo emulsions spontaneously form submicronic droplets with a narrow size distribution, without any energy-intensive process. The Ouzo system in this work comprises water, tetrahydrofuran (THF) and butylated hydroxytoluene (BHT), and forms BHT-rich droplets (∼100 nm). The addition of a reducing agent (NaBH₄) in the aqueous phase, and of a metal precursor (AuPPh₃Cl and/or Pd(PPh₃)₂Cl₂) in the BHT-rich droplets, results in the formation of Au nanoparticles (AuNPs), continuous Pd shells, or bimetallic shells, at the interface of the droplets. Control over the NP-shell size was achieved by the addition of a water-soluble polymer during the synthesis, which in turn leads to smaller NP-shells.

Hierarchical porous NiCo2O4 nanosheet arrays directly grown on carbon cloth with superior lithium storage performance

Binary metal oxides have been explored as advanced candidates in lithium-ion battery (LIB) anodes due to their high specific capacity. Herein, the hierarchical structures of porous NiCo₂O₄ nanosheets directly grown on a conductive carbon cloth substrate (3D NCO-PSA/CC) were obtained by a facile in situ synthetic strategy. When applied as a binder-free LIB anode, it exhibited satisfactory performance with a high discharge capacity (a first discharge capacity of 2090.8 mA h g^-1 and a stable capacity of 1687.6 mA h g^-1 at 500 mA g^-1), superior rate capacity (discharge capacity of 375.5 mA h g^-1 at 6000 mA g^-1) and excellent reversibility (coulombic efficiency of approximately 100%). The outstanding performances should be attributed to the 3D porous structures, nanosheets and good conductivity of NCO-PSA/CC that could not only ensure the rapid transport of Li⁺ ions and electrons but also remit the huge volume change during lithiation/delithiation processes. Undoubtedly, the present facile and effective strategy can be extended to other binary metal-oxide materials for use as high-performance energy storage and conversion devices.

Complex Hollow Nanostructures: Synthesis and Energy-Related Applications

Hollow nanostructures offer promising potential for advanced energy storage and conversion applications. In the past decade, considerable research efforts have been devoted to the design and synthesis of hollow nanostructures with high complexity by manipulating their geometric morphology, chemical composition, and building block and interior architecture to boost their electrochemical performance, fulfilling the increasing global demand for renewable and sustainable energy sources. In this Review, we present a comprehensive overview of the synthesis and energy-related applications of complex hollow nanostructures. After a brief classification, the design and synthesis of complex hollow nanostructures are described in detail, which include hierarchical hollow spheres, hierarchical tubular structures, hollow polyhedra, and multi-shelled hollow structures, as well as their hybrids with nanocarbon materials. Thereafter, we discuss their niche applications as electrode materials for lithium-ion batteries and hybrid supercapacitors, sulfur hosts for lithium-sulfur batteries, and electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. The potential superiorities of complex hollow nanostructures for these applications are particularly highlighted. Finally, we conclude this Review with urgent challenges and further research directions of complex hollow nanostructures for energy-related applications.

Magneto-acceleration of Ostwald ripening in hollow Fe3O4 nanospheres

The magnetic field-induced acceleration of the Ostwald ripening process was demonstrated firstly in the formation of hollow Fe₃O₄ nanospheres.