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

Abstract

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)₄²⁻ 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.