Morphology Evolution of Cu<sub>2</sub>O from Octahedra to Hollow Structures

Octahedral Cu<sub>2</sub>O crystals with an edge length about 1 μm were synthesized by reducing a copper-citrate complex with glucose. The morphology and structure of Cu<sub>2</sub>O particles were greatly affected by the concentration of glucose, reaction temperature, and time. When the concentration of glucose increased from 0.6 to 1.6 M, the morphology of Cu<sub>2</sub>O could be changed from octahedral single crystals to spherical polycrystals. When the reaction time was prolonged from 6 to 36 h, solid Cu<sub>2</sub>O octahedra could be changed to a mixture of hollow Cu<sub>2</sub>O octahedra and irregular Cu particles. After removing Cu particles, pure Cu<sub>2</sub>O hollow octahedra could be obtained. The formation mechanism of hollow Cu<sub>2</sub>O octahedra was discussed. Similarly, hollow Cu<sub>2</sub>O spheres could also be obtained using this method. The prepared hollow octahedral Cu<sub>2</sub>O particles exhibited a higher photocatalytic activity for photodegradation of <i>p-</i>nitrophenol aqueous solution under visible-light illumination than other Cu<sub>2</sub>O particles with different morphologies (hollow spheres, solid octahedra, and solid spheres).