Construction Of Photoelectrochemical Sensors Based On Ti₃C₂ Mxene/Ms_1/2 （M=Cu,Zn,Sn） Nanocomposites For Detection Of Typical Heavy Metal Ions

In this thesis,preparing Ti₃C₂ MXene/CuS,Ti₃C₂ MXene/ZnS,and Ti₃C₂ MXene/SnS₂nanocomposites with different methods and used them as effective photosensitive materials to construct photoelectrochemical sensors,which successfully realized the sensitive detection of heavy metal ions in water.Specific research contents are as follows:1.The Ti₃C₂ MXene/CuS nanocomposites were prepared by solvothermal method and characterized by SEM,XRD,and XPS.The study on PEC properties shows that the introduction of Ti₃C₂ MXene could improve the PEC properties of Ti₃C₂ MXene/CuS nanocomposites.With the feeding mass ratio of Ti₃C₂ MXene to CuS was 1:5,which was labelled as Ti₃C₂ MXene_17%/CuS and had the strongest PEC response signal,and the PEC signal presented 5.8 times improvement compared with pure CuS.The presence of Ti₃C₂ MXene nanosheets could inhibit the charge recombination rate and improve the PEC performance of Ti₃C₂ MXene_17%/CuS nanocomposites.Based on Hg（II）photocurrent suppression principle,the Ti₃C₂ MXene_17%/CuS modified ITO sensor was successfully constructed to sensitive detection of Hg（II）.In the concentration range of 0.025μM～10μM,the PEC sensor showed good linearity for Hg（II）,and the detection limit was 0.01μM（S/N=3）.The PEC sensor has good selectivity and stability,which provides a simple and effective method for sensitive detection of Hg（II）in water.2.The Ti₃C₂ MXene/ZnS nanocomposites were prepared by physical adsorption method and it was successfully prepared,which was proved by XRD,XPS and SEM.The PEC performance study shows that the introduction of Ti₃C₂ MXene nanosheets could effectively improve the PEC performance of Ti₃C₂ MXene/ZnS nanocomposites.When the feed mass ratio of Ti₃C₂ MXene to ZnS was 1:45,the Ti₃C₂ MXene/ZnS(labelled as Ti₃C₂ MXene_2%/ZnS)has the strongest PEC response signal,and the PEC signal of that showed 307.3 times improvement compared with pure ZnS.With the Ti₃C₂ MXene_2%/ZnS modified ITO as working electrode and the basis of Cu（II）enhanced cathode photocurrent principle,the PEC sensor of Ti₃C₂ MXene_2%/ZnS was successfully used for Cu（II）sensitive detection.In the concentration range of 1.0μM～100μM and 0.5 m M～6m M,the PEC response signal showed a good linear relationship with the concentration of Cu（II）,and the detection limits were 0.25μM and 0.18 m M（S/N=3）.The constructed PEC sensor has good selectivity and stability,and effectively eliminate background interference in Cu（II）detection process,which has potential application prospect.3.The Ti₃C₂ MXene/SnS₂ nanocomposites were prepared by one pot hydrothermal method,and it was characterized by XRD,XPS and SEM to prove the successful preparation.Ultraviolet-visible diffuse reflection studies showed that with the adjustable band gap and excellent electrical conductivity of Ti₃C₂ MXene,it was helpful to improve the optical properties of Ti₃C₂ MXene/SnS₂nanocomposites.The PEC properties showed that the initial feeding quality of Ti₃C₂ MXene affected the PEC properties of the nanocomposites,and the prepared Ti₃C₂MXene/SnS₂nanocomposites(denoted as Ti₃C₂ MXene_0.4%/SnS₂)when the feeding mass ratio of Ti₃C₂ MXene to SnS₂ was 1:240 had the strongest PEC response signal,and the PEC signal of that presented 2.9times increase compared with pure SnS₂.With the Ti₃C₂ MXene_0.4%/SnS₂ modified ITO as working electrode and the basis of Cr（VI）suppression photocurrent principle,the PEC sensor constructed with Ti₃C₂ MXene_0.4%/SnS₂ was successfully used for Cr（VI）sensitive detection.In the concentration range of 1.0 p M～0.1 m M,the PEC response and with the concentration of Cr（VI）presented a good linear relationship,and detection limit was 0.51 p M（S/N=3）.The PEC sensor had good selectivity and stability,providing a simple and effective method for sensitive detection of Cr（VI）in water.In addition,Ti₃C₂ MXene_0.4%/SnS₂ nanocomposites showed excellent photocatalytic reduction efficiency for Cr（VI）because of the avoidances of lamellar accumulation and electron-hole recombination,and could reduce 90.2%Cr（VI）within 60 min.It provides a new catalyst for photocatalytic reduction of Cr（VI）.