Chemical reaction controlled synthesis of Cu2O hollow octahedra and core-shell structures

Uniform hollow octahedra of Cu2O were successfully synthesized by the facile room-temperature chemical reaction of copper acetate and N2H4 without using any surfactant. The growth mechanism of the hollow octahedra and the solution environment in the chemical reaction were investigated. The chemical reactions from Cu2+ to Cu(OH)(4)(2-) and finally to Cu2O can be done within <2 s. In this reaction system, N2H4 served as an alkali and reducing agent. Acetate ions, Ac-, can serve as buffer, act as counterions, and Ac- are coordinated to the Cu2O particle surface. The hollow-octahedron@nanoparticles-aggregate core@shell structures were synthesized by the introduction of NH4+ cations. The core@shell structures show a higher capacity and better cycling stability than the hollow octahedra as lithium-ion battery anodes because the core@shell structures can endure large volume changes during electrochemical reactions and nanoparticles with small sizes can shorten the diffusion path of the Li+ ions and electrons. As supercapacitors, the core@shell structures have a higher specific capacitance than that of the hollow octahedra.