Study On Structure And Photocatalytic Properties Of Cu₂O Nanocrystal Synthesized By Liquid-phase Reduction Method

With the rapid development of industry, the environmental pollution became one of the most urgent problems in society, meanwhile, the industrial waste water was the most important part of environmental pollution. Therefore it is very urgent to solve the purification problem of waste water. Many scientists take action to solve the water pollution problem, but it is not very effective in practical applications. Researchers commits to finding a continuable and efficient way of catalytic degradation of organic pollutant, which was extensively studied due to its low cost, non-toxic and recycled. The present problem was to found a stable photocatalytic semiconductor material which can make the best use of solar energy.Cu2O is p-type semiconductor material with a direct band gap (2.17eV). It can absorb the energy of visible light which accounts for more than40%in the total energy of sunlight, therefore it is a much efficient semiconductor material for using the energy of sunlight. Because of the electrons and holes generated by Cu2O not easily separated, Cu2O was oxidized easily and become CuO which have not photocatalytic performance. Scientists found two ways to solve the problem:decreasing the size of Cu2O particles make the probability of recombination of holes and electrons reduce, and Combining Cu2O with other semiconductor was in order to increase the transfer of holes and electrons. The main subject of the dissertation mainly investigated the preparation of Cu2O nanoparticles with different morphologies, the mechanism of its formation, the reasons of the formation of Cu2O with different morphologies and particle sizes and its photocatalytic effect.Nanospheres and octahedronal Cu2O was prepared from an aquous solution of copper acetate as the precursor and hydrazine hydrate as reductant by chemical precipitation method with no surfactant at room temperature, whose diameter was about70nm. Cu2O crystal structure was analyzed by X-ray diffraction (XRD) and the morphology was observed with scanning electron microscope (SEM).The reaction process showed that Cu2+was reduced into Cu2O by N2H4·H2O, then a part of Cu2O were reduced into Cu, and finally oxygen in the air under stirring entering into the solution oxidized Cu into Cu2O.After the morphology and microstructure characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis, we found that no impurity peak was observed. Moreover, we analyzed that the state of the precursor, hydrazine, sodium hydroxide, ethylene glycol and oxygen impact on the morphology, size and properties of Cu2O. When the molar ratio of sodium hydroxide and copper acetate was2:1, spherical Cu2O was obtained; while when the molar ratio of sodium hydroxide and copper acetate was4:1, octahedronal Cu2O was gained.The photocatalytic degradation performance of different morphologies and sizes of Cu2O under different preparation conditions was analyzed using Methyl orange solution. Size was the most critical factor affecting the photocatalytic degradation performance. In this experiment, spherical cuprous oxide particle whose size is about70run have good photocatalytic effect and the degradation efficiency is up to95.7%, while octahedral Cu2O only88%. The main reason was the particle size was small in order to reduce the probability of electron-hole recombination, therefore the photocatalytic performance was relatively good.