Synthesis And Photocatalytic Properties Of Cuprous Oxide Micro-crystals And Their Composites Via Flux Method

Cuprous oxide (Cu2O), a p-type semiconductor with a direct band gap of2.17eV,can be excited by visible light with the wavelength from400nm to800nm. In theory,photoelectric efficiency can reach20%. Because of its unique electronic and opticalproperties, Cu2O has attracted abundant attention for its applications in solar energyconversion, gas sensors, photocatalytic degradation of organic pollutants and so on.As we all know, many properties of cuprous oxide micro-crystals are highlydependent on its shape and size. Thus it is important to look for an easy way whichcan implement morphology-controlled synthesis of Cu2O particles.In this study, cuprous oxide micro-crystals have been synthesized via a simpleflux method. We have systematically researched the parameters of reaction (includingreaction time and reaction temperature) which can affect the shape of Cu2O crystals.Also, the growth mechanism and the corresponding photocatalytic properties of Cu2Ohave been studied. Cu2O/Cu composites have been prepared of by using the samemethod and the related properties have been researched. The main contents are asfollows:(1) Cuprous oxide micro-crystals were successfully synthesized by a simple fluxroute without any organics. The morphology of Cu2O nanocrystals was mainlyinfluenced by the reaction time and the reaction temperature. The results show thatwhen the reaction time was fixed, the reaction temperature controlled the growth rates of different crystalline faces of Cu2O by interacting with these faces. When thereaction time is2h and the reaction temperature rises from250°C to650°C. themorphology of cuprous oxide micro-crystals have been changed from octahedron、{110}-truncated octahedron to rhombic dodecahedron. When the reaction timeincreases from2h to6h, and the reaction temperature are kept at650°C, themorphology of the obtained samples changes from rhombic dodecahedron to{111}-truncated rhombic dodecahedral.(2)We have investigated photocatalytic activities of as-prepared Cu2O particleswith different morphologies via the photodegradation of MO(methyl orange) solutionunder visible light irradiation. The order of photocatalytic activity of Cu2O withdifferent morphologies was as follows: rhombic dodecahedron>{111}-truncatedrhombic dodecahedral>{110}-truncated octahedron> octahedron. Cu2O rhombicdodecahedra exhibit exceptionally good photocatalytic activity because the {110} faceis likely more positively charged compared to the {111} face according to relatedliterature.(3)Cu2O/Cu composite has been achieved through one pot synthesis in solid fluxreaction. By scanning electron microscopy, Cu2O/Cu composites are composed ofrhombic dodecahedron Cu2O crystallites and Cu microspheres, which themicrospheres are closely attached to the surface of the rhombic dodecahedron.Moreover, the Cu2O/Cu composite showed much better photocatalytic activity thanindividual Cu2O in photocatalytic degradation of methyl orange solution. Thestructure of Cu2O/Cu composite enhances charge transportation, which separates theelectron-hole pairs. Therefore, the quantum efficiency is improved and the catalyticactivity effectively is increased.