Preparation And Photocatalytic Degradation Of All-solid Z-type Heterojunctions Based On Cheap Organic Carbon Sources

At present,the problem of water pollution caused by organic wastewater and heavy metal ions needs to be solved.Compared to the traditional techniques,the photocatalytic technology has the characteristics of wide application range,strong treatment efficiency,mild reaction conditions and clean pollution.The performance of photocatalysts is an important factor that restricts the photocatalytic degradation of pollutants.However,in the photocatalytic reaction of traditional heterojunction composites,there are some problems,such as semiconductor material level mismatch,expensive electronic medium,low efficiency of photogenerated electron and hole separation,low photocatalytic efficiency and poor stability.Therefore,it is necessary to design and prepare a new heterostructure photocatalytic system to overcome the above problems.Therefore,in this paper,n?Bi₂O₃ and p?Co₃O₄ materials are used in the cheap D113 as organic carbon source mediated by electron flow to form Z-type transport chain,to construct the all-solid Z-type heterojunction Bi₂O₃-Co₃O₄@C.It increases the separation efficiency of photogenerated electrons and holes,improves the photocatalytic activity of pollutants,and has good recycling performance and certain stability.（1）The source and harm of wastewater,the development and application of photocatalytic technology are introduced,the structural properties and application of Z-type heterojunction are described,and the significance and content of the research are introduced.The synthetic route of all solid Z-type heterojunction Bi₂O₃-Co₃O₄@C is summarized.The mechanical design principle of the hydrothermal reactor in the experiment and the feasibility of its application in this study are also studied.The mapping of methylene blue,Rhodamine B,tetracycline and hexavalent chromium ions was completed.（2）The optimal reaction conditions are explored through the investigation of reaction time,reaction temperature,reaction feed ratio and other factors.The structure and morphology of Bi₂O₃-Co₃O₄@C were confirmed by XRD,FT-IR,TEM,XPS,Raman and other testing techniques.Optical tests showed that Bi₂O₃-Co₃O₄@C exhibited the strongest UV-visible light absorption capacity compared with Bi₂O₃@C,Co₃O₄@C and Bi₂O₃@Co₃O₄,and PL and electrochemical tests showed that it had the best photogenerated electron-hole separation efficiency.（3）The mechanical device of photocatalytic system was designed and built.The photocatalytic performance of Bi₂O₃-Co₃O₄@C is tested,The degradation rates of methylene blue,rhodamine B,tetracycline and hexavalent chromium ions with an initial concentration of 20 mg/L can reach 100%,47.52%,94.28%and 100%under natural light for 2 h under the action of Bi₂O₃-Co₃O₄@C.Under light（λ>420 nm）for2 h,the degradation rates reached 78.31%,30.41%,66.15%and 100%.The optimal turn over frequency（TOF）of Bi₂O₃-Co₃O₄@C for pollutant degradation was 2.5h^-1.After 5 cycles,the degradation efficiency of methylene blue remained at 91.46%.The all-solid Z-type heterostructure and electron flow of Bi₂O₃-Co₃O₄@C are verified by DFT theoretical calculation of VASP code.The mechanism of photocatalysis was also analyzed.In summary,this paper successfully designed a carbon-mediated all-solid Z-type heterojunction Bi₂O₃-Co₃O₄@C,and has a good removal efficiency for methylene blue,rhodamine B,tetracycline and hexavalent chromium ions in wastewater.The photocatalytic degradation mechanism and electron transfer process were studied by DFT calculation and test results.