Facile preparation of Cu2O microcrystals with morphologies of octahedron, half circular and rectangular plates by anodic dissolution of bulk Cu in alkaline aqueous solutions

In this work, a facile electrochemical route i.e., anodic dissolution of bulk Cu at 2.0 V or more (vs. SCE) in a NaOH solution containing NH₂OH·HCl, was introduced for the synthesis of clean Cu₂O microcrystals (Cu₂O MCs) with morphologies of octahedron, half circular plate, etc. The bulk Cu electrode can be facilely dispersed into Cu(OH)₄²⁻ in alkaline solutions with the help of intense O₂ releasing. In the presence of reductive NH₂OH·HCl, Cu(II) was quickly reduced to Cu(I). Due to the concentration gradient of Cu(I) and OH⁻ resulting from the electrochemical reaction and the selective adsorption of OH⁻ on different crystal facets, half circular plate Cu₂O MCs were for the first time, synthesized. By changing the NaOH concentration or applied potential, octahedron and rectangular plate Cu₂O MCs could also be obtained. Scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) techniques, etc. were used to characterize the oxides. The Cu₂O MCs were phase-pure cubic Cu₂O. This electrochemical route is simple, basically green and can be used to synthesize Cu₂O MCs with different morphologies.