Research On Effect Of Heterojunction Construction And Doping On Photocatalytic Performance Of Bismuth Materials

In recent years,the treatment of organic pollution has become one of the focal issues due to the increasing environmental pollution.Compared with traditional organic pollutant treatment methods,semiconductor photocatalysis technology is a new type of green pollution-free environmental treatment technology,which has low cost and no secondary pollution.Bismuth vanadate(BiVO4),bismuth molybdate(Bi2MoO6)and bismuth tungstate(Bi2WO6)are three typical bismuth-base semiconductor photocatalytic materials with good photocatalytic properties.However,it still has problems of narrow visible light response range and high electron-hole pair recombination rate.Therefore,the research on the modification of bismuth materials has been widely concerned by many scholars.In this paper,Bi2MoO6,BiVO4 and Bi2WO6 are modified by heterojunction construction and elemental doping to improve the visible light photocatalytic performance.The main contents of this paper are as follows:(1)The Eu-CN-BVO heterojunction photocatalysts with different ratios of g-C3N4 coupling and Eu3+doping were prepared by solvothermal method using ethylene glycol.The photocatalytic activities of the photocatalysts were evaluated by using the organic dye Rhodamine B(RhB).When the addition amount of g-C3N4 was 0.5 g and the doping ratio of Eu was 0.08%,the 8Eu-5CN-BVO composite exhibited the highest photocatalytic activity,and the degradation rate of RhB was 98%.The phase compositions,morphologies and photocatalytic activities of the samples were characterized by the XRD,SEM,TEM/HRTEM,EDS-Mapping,XPS,FT-IR,UV-Vis DRS and PL.The characterization results showed that the Eu-CN-BVO composites presented the three-dimensional bidirectional dendritic structures.After g-C3N4 coupling,it formed heterojunction structures with BiVO4.After Eu3+doping,it introduced impurity levels,which can be used as electron capture.The synergistic effect of g-C3N4 coupling and Eu3+doping effectively inhibited the combination of electrons and holes and significantly improves the photocatalytic activity of BiVO4.In addition,the five recycling experiments confirmed that the prepared photocatalysts had good stability.The trapping experiments illustrated the action of three main active species were in the order of ·O2->h+>·OH during the photocatalytic degradation of RhB.(2)The Bi2MoO6 samples were synthesized by solvothermal method using ethanol and ethylene glycol.Then,the g-C3N4/Bi2MoO6 composites were prepared via precipitation calcination.Finally,the Pd/CN/BMO photocatalysts with different coupling and doping ratios were prepared by photoreduction method.The photocatalytic activities of the photocatalysts were evaluated by using the organic dye RhB.When the compounding amount of g-C3N4 was 10%and the doping amount of PdCl2 was 0.002 g,the 2Pd/10CN/BMO composites exhibited the highest photocatalytic activity.The degradation rate of RhB was 97%,4.85 times of pure BMO.The phase compositions,morphologies and photocatalytic performances of the samples were characterized by the XRD,SEM,TEM/HRTEM,EDS-Mapping,XPS,FT-IR,UV-Vis DRS and PL.The results showed that the Pd/CN/BMO photocatalysts presented three-dimensional h ollow flower-like microsphere structures.After g-C3N4 coupling,it formed heterojunction structures with Bi2MoO6,which promoted the separation of electron-hole pairs effectively.After Pd doping,the light absorption performance of the composites were enhanced due to the SPR effect.The synergistic effect of g-C3N4 coupling and Pd doping improved the photocatalytic performance of the Bi2MoO6 significantly.In addition,the five recycling experiments confirmed that the prepared photocatalysts had good stability.The trapping experiments illustrated the action of three main active species were in the order of ·O2->h+>·OH during the photocatalytic degradation of RhB.(3)The ternary CN/Sm-BWO heterojunction photocatalysts with different ratios of g-C3N4 coupling and Eu3+doping were prepared by hydrothermal method.The photocatalytic activities of the photocatalysts were evaluated by using the organic dye RhB.When the doping ratio of Sm was 0.1%and the addition amount of g-C3N4 was 15 mL,the 15CN/0.1Sm-BWO presented the highest photocatalytic activity.The degradation rate of RhB was as high as 98%.The phase compositions,morphologies and photocatalytic performances of the samples were investigated by the XRD,SEM,TEM/HRTEM,EDS-Mapping,XPS,FT-IR,UV-Vis DRS and PL.The results showed that the CN/Sm-BWO photocatalysts had three-dimensional square sheet structures.After Sm doping,part of Sm3+replaced Bi3+in Bi2WO6,which provided electron traps for photogenerated electrons.After g-C3N4 coupling,it formed heterojunction structures with Bi2WO6,which effectively promoted the separation of electron-hole pairs.The synergistic effect of g-C3N4 coupling and Sm doping enhanced the photocatalytic activity of Bi2WO6 significantly.In addition,the five recycling experiments confirmed that the prepared photocatalysts had good stability.The trapping experiments illustrated the action of three main active species were in the order of ·O2->h+>·OH during the photocatalytic degradation of RhB.