Study On Morphology Control Of Cuprous Oxide Powders Synthesized In Aqueous Solution

Cuprous oxide(Cu₂O) is an important p-type semiconductor with a direct band gap of 2 eV,and has wide applications in solar energy conversion,gas sensors and catalysis due to its unique optical and electronic properties.Over the last decade,extensive efforts have been focused on the research and development of micro/nano powders with specific morphologies and structures in the powder industry because of their distinctive properties. Moreover,it has even been a research hotspot that preparation methods and technologies of Cu₂O micro/nano powders.Herein,new synthetic routes to Cu₂O micro/nano powders have been designed and the formation mechanisms of the final shapes have been discussed.Two kinds of product morphologies,ie.,core-shell structure and cube,have been obtained by two different synthetic routes as described below.Starting from the intermediate-template strategy,we have designed a surfactant-free tartaric acid assisted hydrothermal approach for preparing homogenous core-shell structured Cu₂O powders.The morphology and structure information of the as-grown crystals were characterized by Scanning Electron Microscope(SEM),energy dispersive X-ray(EDX) and X-ray powder diffraction(XRD).Furthermore,a formation mechanism has been revealed through the time-dependent experiments:(1) formation of intermediate microspheres;(2) reductive conversion of this template to Cu₂O;(3) inside-out Ostwald ripening of Cu₂O powders.As to Cu₂O,the core-shell structure is seldom reported.This intermediate template strategy not only can promote a better understanding of the designed synthesis of hollow-structured powders in aqueous solution,but help to make available functional powders in controllable morphologies.Uniform cubic Cu₂O micro powders have been synthesized via a hydrothermal method by reducing copper nitrate with formic acid,and the effect of Cl^- ions and PVP on the morphologies of the products are also investigated.The products were characterized by SEM and XRD.The results reveal that the final shape of the Cu₂O powders change from cube to edge-truncated cube with the adding of Cl^- ions into the initial solution.