Preparation And Photocatalytic Activity Of Cuprous Oxide Micro/Nanocrystals

Cuprous oxide (Cu2O) is an conventional P-type semiconductor and has a direct band gap of 2.17 eV. Due to its unique optical and magnetic properties, Cu2O is a promising material with applications in solar energy conversion, negative electrode in lithium batteries, photocatalytic degradation of organic pollutants, magnetic storage and sensors, etc. Furthermore, Cu2O is non-toxic, readily available and easily prepared, which make it a research hotspot in recent years. It is generally known that morphology and size of micro/nano-crystallites often show significantly effects on their widely varying physical and chemical properties, many efforts have been devoted to the synthesis of uniform Cu2O micro/nano-crystallites with well-controlled morphology and size by various methods.In this paper, cuprous oxide was chosen as the research object, micro/nano cuprous oxide crystals with various shape and size were prepared by microwave assisted and hydrothermal method, respectively. The influence of reaction parameters on the morphology and size of cuprous oxide products was investigate by changing the reaction conditions. The cuprous oxide samples obtained under different conditions were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), FTIR and UV-vis diffuse reflectance spectroscopy, etc. The morphology evolution mechanism of products was discussed and the photocatalysis activities were investigated by degradation of methyl orange in simulated visible light.In microwave-assisted synthesis of cuprous oxide, the natural renewable resources starch was used as the reducing agent and dispersant. The process has the advantages of easy operation, low cost, mild reaction conditions and starting material cheap and easy to get. The results indicated that with the increase of OH- concentrations, the morphologies of products changed from spheres with a diameter of 100 nm, spheres with a diameter of 600 nm, octahedral with the edge length of about 800 nm, and truncated octahedrals with the edge length about 2-3 um. The morphology evolution mechanism of cuprous oxide was discussed through the selective adsorption of OH- on different crystal facets, the band gap of obtained samples was determined by UV-vis diffuse reflectance spectrum. The advantage of the microwave heating was testified by the comparing test. In addition, starch is proved to be able to control the particle size effectively and prevent products from conglomerating through steric-hinerance effect. By contrast the photocatalytic effect of the spherical, octahedral and truncated octahedral samples of cuprous oxide, we found that octahedral Cu2O showed the highest degradation rate of methyl orange of 94.5% after visible light irradiation for 3.5 hours.Synthesis of cuprous oxide by hydrothermal, using the natural biomacromolecule silk sericin as the reducing agent, explored the surfactant, the dosage of NaOH, hydrothermal temperature and time on the influence of the morphology and particle size. The research found that the addition of surfactant can control the size of products and prevent agglomeration effectively. When little of NaOH was added, the obtained products were a mixture of copper and cuprous oxide.With the increase of NaOH, the morphology of cuprous oxide products varied from 1D linetype to 3D polyhedron. Under low supersaturation condition, products tend to grown into lines. Hydrothermal reaction temperature also had an influence on the morphology and component of products,120℃ was turn out to be the optimum temperature to synthesis cuprous oxide.