Shape evolution and size-controllable synthesis of Cu2O octahedra and their morphology-dependent photocatalytic properties

Octahedral Cu2O crystals with tunable edge length were synthesized by reducing copper hydroxide with hydrazine without using any surfactant. Systematic experiments were carried out to investigate the factors which impact on the morphology and size of the products. The molar ratios of the reagents (NH3:Cu2+ and OH-:Cu2+) determined the morphology and size of the corresponding products via affecting the coordination between NH3 and Cu2+. It is demonstrated that the ratio of growth rate along < 111 > versus < 100 > was varied by adjusting the molar ratio of NH3 to Cu2+, thus Cu2O crystals with different morphologies such as spheres, cubelike, and octahedra were obtained. The edge lengths of octahedra can be easily tuned from 130 to 600 nm by adjusting the molar ratio of OH- to Cu2+. It is an effective and facile method for the controlled synthesis of octahedral Cu2O. The obtained octahedral Cu2O particles show improved ability on adsorption and photodegradation of methyl orange compared with cubic Cu2O particles.