Synthesis Of MoS₂ Composite Photocatalysts And Its Photocatlytic Degradation On Organic Pollutant

In the face of increasing environmental pollution,the search for efficient means of degrading organic pollutants has become a key issue.Compared with the microbial method with a long degradation cycle and the electrocatalysis treatment with large energy consumption,it is currently a major research hotspot to use abundant and non-polluting solar energy and convert it into valuable chemical energy,which can effectively achieve the purpose of degrading pollutants.In consideration of the energy of photocatalysis is small,the excited photo-generated electrons and holes are easy to recombine,and the efficiency in utilizing the light is low,which cannot be used in real practical applications.Therefore,it is necessary to prepare a catalyst,which not only has high utilization of light absorption and easy to be excited by visible light,but also is not prone to recombination of electron and holes and can degrade pollutants efficiently during the reaction process.As a typical transition metal sulfide,MoS₂ is a two-dimensional sheet material with graphene-like structure.It has rich edge active sites,adjustable band gap and high light absorption,and it is a new type of photocatalytic material.However,problems such as agglomeration caused by van der Waals forces between layers,poor conductivity,easy recombination of electrons and holes limit its development.On this basis,two or more materials will be compounded to construct a multi-element heterojunction.By changing the loading amount,the surface morphology of the material is controlled,the utilization rate of light absorption can be improved,and the transfer of photo-generated electron and holes is promoted,thereby improving the photocatalytic performance.The specific research contents are as follows:（1）Using MoS₂ as a substrate,the ternary composite visible light catalyst Cu/r GO/MoS₂（CRM）was successfully prepared by hydrothermal and chemical methods,and the effect of different proportions of Cu on catalyst performance was studied.We found that the 30% mass ratio of Cu（CRM-30）has the best light response,and adding a small amount of H₂O₂ can basically remove the organic dye Rh B within 5 minutes,and the material can maintain stability after multiple cycles of use.（2）On these basis,in order to construct a photocatalyst for the efficient degradation of antibiotics,we used C₃N₄ as the substrate,MoS₂ and Bi₂WO₆ were formed as a binary heterojunction firstly and used as a cocatalyst.In the pre-polymerization process,the morphology of the material could be controlled according to the load of MoS₂/Bi₂WO₆（BM）.SEM,TEM,XRD and other methods were used to determine the formation of heterojunction and BM load on the substrate C₃N₄ steadily.The study found that when the load of BM is 0.002 g,the catalyst CN-BM2 degrades more than 98% of the antibiotic sulfamethoxazole within 1 hour under visible light,and the degradation efficiency can reach 97.7% after 5 cycles of recycling.The ternary heterojunction formed between compounds could effectively prolong the lifetime of electrons and accelerated the separation of electron and holes.Through the discussion of active radicals,it was found that superoxide radicals（·O₂^-）and holes（h⁺）play a major role.（3）In order to further improve the degradation performance of the photocatalyst,the potential two-dimensional material black phosphorus（BP）with a certain band gap was used to replace the wide band gap Bi₂WO₆,and the preparation method was improved on the basis of the previous one.Through the one-step calcination method,C₃N₄,MoS₂ and BP formed a large specific surface area and porous ternary compound C₃N₄/BP/MoS₂（CBM）.When the MoS₂ loading was 0.002 g,it had the optimal catalytic effect.Under pure visible light irradiation,the antibiotic ciprofloxacin hydrochloride could degrade to 84.2% within 1 hour under the acidic condition of p H=5.Under the neutral condition of p H=7,the antibiotic ciprofloxacin hydrochloride could be completely degraded within 1 hour.Through PL,PC and EIS proved that CBM has excellent photoelectric performance,and can make the photo-generated carriers separate quickly and the coincidence rate is low.From the quenching experiment,it was found that the degradation of ciprofloxacin depends on h⁺ instead of ·OH or ·O₂^-.The degradation rate remained basically unchanged after 5 cycles of use,indicating that the catalyst had good cycling stability.