Study On Doping Modification And Performance Of Cu₂O Photocatalytic Materials

With the rapid development of dyeing and printing industry,a large amount of dyestuff wastewater is produced.There are some problems existing in the traditional physical and chemical treatment methods,such as incomplete treatment results,high cost of treatment equipment and materials.However,the application of photocatalytic technology in the treatment of wastewater has the advantages of low cost,strong treatability,clean and pollution-free,which provides a good idea for the refractory toxic organic dyestuff wastewater.As a kind of photocatalyst,the semiconductor material Cu₂O has the advantages of low cost,non-toxic,simple in structure and easy to obtain,and changeable energy band gap.Therefore,it has a broad application foreground in the field of photocatalysis.Although Cu₂O has good visible light induction performance,it still has certain defects that cannot be ignored,such as light corrosion,rapid recombination of photo-generated electron-hole,and insufficient stability of organic degradation performance.In order to avoid these shortcomings of Cu₂O,Cu₂O is modified to further improve the photocatalytic capacity and it is applied to dyestuff wastewater which is difficult to treat to solve the environmental pollution of the dyestuff wastewater.Therefore,in the study,the Cu₂O material is doped and modified to prepare a composite photocatalytic material with excellent performance for the treatment of organic dyestuff wastewater.In this paper,a S-doped Cu₂O composite photocatalyst with excellent performance was studied.Cubic Cu₂O was prepared by simple glucose reduction method,and then the S element was introduced by adding thiourea for modification.The analysis of XRD and TEM showed that nano Cu9S5 was formed,and finally a hollow spherical Cu₂O@Cu9S5 catalyst was obtained.Compared with pure Cu₂O,the Cu₂O@Cu9S5composite photocatalyst had a good absorption effect on the wavelength of 300～800 nm,and its visible light utilization was significantly enhanced.In the treatment experiment of dye simulated pollutant methyl orange（MO）,Cu₂O@Cu9S5 showed the dual performance of adsorption and degradation,and the comprehensive removal efficiency of MO reached more than 95%.The analysis of optical and electrochemical properties of Cu₂O@Cu9S5 showed that Cu₂O/Cu9S5 formed a heterostructure,which reduced the band gap,made the electron hole pair more easily activated,and decreased the recombination rate of electron hole and increased the carrier density.The modified Cu9S5 can reduce the resistance of carrier migration,which made the carriers separated quickly and improved the photocatalytic performance.The Analysis of the catalytic mechanism of MO degradation catalyzed by Cu₂O@Cu9S5 photocatalyst revealed that the superoxide anion radical（·O₂^-）and photogenerated hole（h⁺）generated by Cu₂O@Cu9S5 under visible light excitation played a major role in the degradation of MO,which decomposed organic MO into small molecular compounds.The order of degradation ability of active ions produced in the process of MO degradation was:·O₂^->h+>·OH.On the whole,the novel hollow bifunctional material Cu₂O@Cu9S5 prepared by S-doped Cu₂O had excellent photocatalytic performance,which had potential application value in the treatment of toxic dyestuff wastewater.In order to further improve the photocatalytic performance of Cu₂O,La/S,Bi/S and Zn/S Co-doping modification of Cu₂O was carried out.On the premise of preparing Cu₂O·S material by hydrothermal method,double element doped composite photocatalysts:La-Cu₂O·S,Bi-Cu₂O·S and Zn-Cu₂O·S were successfully prepared by impregnation method.In the study of MO treatment,the removal rate of MO by Zn-Cu₂O·S was 100%,and the performance was further improved.The improvement of the performance of Zn-Cu₂O·S material was attributed to the formation of Zn O,which was an n-type semiconductor.It combined with Cu₂O·S to form p-n heterostructure composite photocatalyst,which effectively promoted the separation of photogenerated electron hole pairs,thus improving the photocatalytic performance of the material.