Preparation Of Cu/Cu₂O-based Composite Materials And Their Applications In The Fields Of Adsorption And Photocatalysis

Dyes have brought significant social and economic benefits,but at the same time they have also caused serious water pollution.Adsorption and photocatalysis are effective methods for the treatment of dyes.The preparation of materials with both adsorption and photocatalysis properties will greatly improve the efficiency of dye treatment.In this thesis,26-facet Cu/Cu₂O composite material is prepared and its adsorption capacity for methyl orange(MO)is studied.At the same time,CQDs/Cu₂O(abbreviated as CQDs/0TD)and CQDs/Cu/Cu₂O(abbreviated as CQDs/3TD)composite materials are prepared.And their photocatalytic degradation ability of MO is also investigated.(Carbon quantum dots are abbreviated as CQDs,the reduction product under the addition of n×0.00075 mol thiourea dioxide is defined as n TD,the Cu₂O generated by a reduction is abbreviated as 0TD)In the first part,the preparation process of 26-facet Cu/Cu₂O composite and its adsorption capacity for MO are studied.The 26-facet Cu/Cu₂O composites are prepared by a two-step liquid-phase reduction method.Firstly,26-facet Cu₂O was prepared by using glucose as the reducing agent,and then the Cu/Cu₂O composite was obtained by secondary reduction with thiourea dioxide(TD)as the reducing agent.The formation mechanism of Cu/Cu₂O composites with different morphologies was analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that with the increase of the amount of TD,the reduction product changes from 26-facet Cu₂O to 26-facet Cu₂O@Cu core-shell structure composite,and the core-shell structure gradually cracks with the further increase of TD amount.In addition,the control experiment results confirm that the core-shell structure 26-facet Cu₂O@Cu composite corresponding to the 1TD has the best adsorption performance.The adsorption kinetics and thermodynamic analysis confirm that the adsorption in this thesis conform to the pseudo-first-order kinetics and the Freundlich isotherm model.Combined with X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),Zeta potential,it is confirmed that the adsorption originates from the electrostatic adsorption between positive charges and anionic dyes and the maximum adsorption capacity can reach 498 mg/g.Repeated experimental results show that when Na OH is used as the desorbent,the adsorption rate of 1TD to MO is over 60%after three adsorption-desorption cycles,and it has good adsorption stability.In the second part,the preparation technology of CQDs/0TD and CQDs/3TD and the photocatalytic degradation ability of MO is studied.First,CQDs were synthesized by electrochemical method,and then CQDs/0TD and CQDs/3TD materials were synthesized by ultrasonic method.The materials were characterized by UV-vis spectrophotometer,XRD,FTIR,SEM and TEM,and the results show that CQDs are successfully dispersed on the surface of Cu₂O and Cu/Cu₂O.Comparing the photocurrent test results of different materials,it is found that the order of photocurrent density is 0TD<CQDs/0TD?3TD<CQDs/3TD.It is speculated that the introduction of Cu and CQDs can accelerate the separation of photogenerated electrons and holes.It is conducive to the increase of photocurrent.The experimental results of the photocatalytic degradation of MO with different materials show that the photocatalytic degradation of MO with CQDs/3TD is better than that of 3TD,and the photocatalytic degradation of MO with 0TD is better than CQDs/0TD.This topic provides some ideas for the preparation of materials with both adsorption and photocatalytic properties.