Preparation And Photocatalytic Properties Of Copper Oxide And Multi Heterojunction Materials With Controllable Morphology

In the past ten years,the application of cuprous oxide（Cu₂O）as a visible light active semiconductor in the field of photocatalysis and photoelectrochemical has increased significantly.However,because the redox potential of C_u2O is located between its band gap,self-photoreduction or self-photooxidation will inevitably occur during lighting.In view of its serious photo-corrosion problem,various effective strategies have been implemented to enhance the photostability of Cu₂O,the common point is to improve the charge transfer from Cu₂O to reactants or other catalysts to avoid charge accumulation in particles.In this paper,we prepared Cu₂O with different morphology and particle size and combined Cu₂O with other semiconductors to construct heterojunction structure to explore the effective method of separating electrons or holes from Cu₂O photocatalyst,inhibit the self-photolysis of Cu₂O and improve the photocatalytic performance.The main research contents and results are as follows:1.Cu₂O with a specific polyhedral morphology was synthesized through a hydrothermal method by reducing a complex of Cu Cl₂·2H₂O and Na OH with ascorbic acid（AA）.Effects of the dosage of sodium hydroxide and AA,and the reaction temperature were investigated on the morphology,particle size and photocatalytic performance of Cu₂O nanocrystallites.The results show that the morphology changed from truncated octahedral to six-corners-{111}truncated octahedral along with the increasing molar ratio of Na OH/Cu Cl₂.The preferential growth rates of the{111}and{110}faces affected by the concentration of[Cu（OH）₄]^2-resulting in the morphological evolution.The sufficient AH₂ has an etching effect to form a quasi-spherical Cu₂O structure.The highly-truncated octahedral Cu₂O with the dominant{110}faces has higher adsorption and also photocatalytic activity under visible light.It’s proposed that the{110}faces of Cu₂O microcrystals possess higher photocatalytic activity than{111}faces,and are even more active than the{100}faces.2.A novel ternary nanocomposite of Cu₂O-ZnO/g-C₃N₄ was synthesized for the first time.The ZnO/g-C₃N₄ binary composite material was prepared by the Co-firing method first,and then the Cu₂O-ZnO/g-C₃N₄ ternary nanocomposite material（CZg-x,x=0.05g,0.1g,0.5g）containing different masses of ZnO/g-C₃N₄ was synthesized by the hydrothermal method.For comparison,Cu₂O-ZnO and Cu₂O-g-C₃N₄ binary nanocomposites were prepared at the same time.SEM,EDS,TEM,FTIR,XRD and XPS results show that the CZg ternary composite material was successfully prepared.The degradation ability of CZg-0.1g ternary composites to methyl orange（MO）under visible light is approximately 3.7 times higher than that of g-C₃N₄/Cu₂O,8.4 times higher than that of Cu₂O,and 18.7 times higher than that of ZnO/Cu₂O.DRS results show that the band gap of CZg-0.1g is 2.1e V,which can absorb visible light in the wavelength shorter than 590 nm.PL results reveal the recombination rate of electron-hole pairs is low.In addition,through free-radical capture experiment,it is determined that the reason for the enhanced photocatalytic activity of CZg ternary composites is the increase in redox potential and the separation of effective electrons and holes caused by carrier transfer in the p-n junction and Z-scheme.