Template-free Fabrication of Nano-sized Cu_2O Hollow Spheres, Sheets and Octahedrons in Cu-citrate System and their Morphology-dependent Semiconductor Type

摘要

Nano-sized cuprous oxide (nano-Cu_2O) materials with different morphologies such as hollow spheres, two-dimensional (2D) sheets and octahedrons were synthesized using a simple hydrothermal method in a Cu-citrate complex solution by making small adjustments to the solution's pH value under alkaline conditions. The morphology of the Cu_2O was observed using scanning electron micros-copy (SEM) and high resolution transmission electron microscopy (HRTEM). The crystalline features of the materials were characterized by X-ray diffraction (XRD). The formation mechanism related to these materials was also discussed. The photoelectrochemical experiments showed that the hollow Cu_2O structure synthesized under a pH range of 8-11 exhibited n-type semiconductor characteristics. Alternatively, solid octahedral Cu_2O formed in the presence of strong alkaline conditions (i.e. pH greater than or equal to 12) and exhibited p-type behavior. The nanosheet Cu_2O possesses the same n-type semiconductor properties as hollow spherical Cu_2O and displays a larger photo-response. This indicated that nanosheet Cu_2O is a promising material for photoelectric applications.