Preparation Of Porous Carbon Materials And Construction Of Electrochemical Sensors For Environmental Pollutants

As chemical raw materials,dihydroxybenzene isomers are widely used in dyes,cosmetics,pesticides,medicine and other fields.Because of its high toxicity,wide distribution,difficult degradation and bioaccumulation,it will cause environmental pollution after entering the ecological environment.It will enter the human body through direct or indirect ways,seriously endanger human health and threaten human life.In addition,pesticides are also important environmental pollutants,which are widely used in agricultural production and pose a potential threat to human life and health.The above environmental pollutants may cause irreversible harm to human body even at low concentration.Therefore,it is particularly important to establish a simple,rapid and highly sensitive new method for the detection of environmental pollutants.Electrochemical sensor is an important environmental monitoring method with the advantages of portable instrument,simple operation,time saving and high sensitivity.Its sensing performance is largely determined by the sensing interface,and the electrode needs to be modified to construct the sensing interface.In recent years,porous carbon has attracted extensive attention in the field of electrochemistry due to its low cost,good conductivity,large specific surface area,highly developed pore structure,easy surface functionalization and high reactivity.In this paper,three different electrochemical sensing interfaces were constructed based on porous carbon.The structural information of porous carbon was obtained by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,N₂physical adsorption desorption,Raman spectroscopy and X-ray diffraction（XRD）.Cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）were used to study the electrochemical properties of porous carbon materials.The structure-activity relationship between the structure of porous carbon materials and their electrochemical sensing properties was explored,and the mechanism of enhancing the electrochemical sensing properties was obtained.This paper has carried out the following work:1.A highly sensitive electrochemical sensor for simultaneous detection of dihydroxybenzene isomers was constructed based on 3D hierarchical porous carbon.In this work,sodium alginate（SA）was used as carbon precursor to prepare porous carbon by direct carbonization.A series of porous carbon materials with different structures（SA-T）were obtained at different carbonization temperatures.It was found that the prepared porous carbon materials was a 3D hierarchical porous carbon with microporous,mesoporous and macroporous structures.When carbonization temperature was 900℃,the specific surface area of SA-900 was as high as 1572.4m²·g^-1.N,N-dimethylformamide（DMF）was used as the dispersant of 3D hierarchical porous carbon materials to prepare a homogeneous dispersed suspension,which was modified on the surface of glassy carbon electrode（GCE）to construct electrochemical sensing interface and used for simultaneous detection of catechol（CC）,isophthalic acid（RC）and hydroquinone（HQ）.Under the optimized conditions,the detection limits of the sensor for simultaneous detection of CC,RC and HQ are0.0303μM,0.3193μM and 0.0183μM,respectively.2.Preparation of carbon materials based on chitosan assisted by different auxiliary agents and construction of high sensitive electrochemical sensor for simultaneous detection of dihydroxybenzene isomers.In this work,chitosan（CS）was used as carbon precursor,and three kinds of auxiliary agents（Na Cl,Na OH,Na₂CO₃）were used to assist chitosan to prepare carbon materials.It was found that the structure of the carbon materials（CS-Na Cl）prepared by Na Cl assisted chitosan was not much different from that of the carbon materials derived from chitosan itself,while the introduction of Na OH and Na₂CO₃made the carbon materials derived from chitosan have microporous,mesoporous and macroporous structures,and the specific surface areas reached 632.3 m²·g^-1（CS-Na OH）and 781.8 m²·g^-1（CS-Na₂CO₃）,respectively.The electrochemical sensing interface（CS-Na₂CO₃/GCE）based on CS-Na₂CO₃has excellent electrocatalytic properties for CC,RC and HQ,with detection limits of 0.0168μM,0.2904μM and 0.0121μM,respectively.3.Preparation of intrinsic defect porous carbon based on carbon nitrogen bond breaking and construction of carbendazim electrochemical sensor.In this work,N-doped porous carbon（N-PC）was prepared by using 1,10-phenanthroline as nitrogen source and carbon source,and Na₂CO₃as auxiliary agent.Then the carbon nitrogen bond was broken at high temperature to form defect sites,and the intrinsic defect porous carbon（D-PC）was obtained.It was found that the specific surface area of D-PC was 1508.9 m²·g^-1.Compared with N-PC(732.0 m²·g^-1),it increased significantly.After high temperature treatment,the carbon content of D-PC is as high as 99.06%.In the analytical application of carbendazim,D-PC/GCE showed better electrochemical sensing performance than N-PC/GCE,with a linear range of0.01-1.00μM and a detection limit of 0.0061μM.