Preparation Of Graphene Microspheres And Its Application In The Detection Of Sulfur Dioxide In Ionic Liquids

Sulfur dioxide（SO₂）is a common air pollutant,which is an important indicator to evaluate whether the atmosphere is polluted.At present,there has many SO₂ detection methods including chromatography,differential absorption spectrometry,spectrophotometry,fluorescence method and electrochemical method,among which electrochemical method is widely used because of its good selectivity and excellent repeatability,and high ppm detection accuracy.However,at present,the electrochemical detection of SO₂ is mainly to detect sulfite(SO₃^2-).In order to construct an electrochemical sensor for directly detecting SO₂ gas,it is necessary to choose a suitable absorption solvent.Room-temperature ionic liquids have attracted extensive attention in SO₂ capture and have been used as absorbents due to their advantages including of very low vapor pressure,high thermal stability and high chemical stability,and non-volatile characteristics.Three-dimensional graphene can effectively prevent the agglomeration of lamellar graphene,give full play to the excellent performance of a single graphene,and facilitate the full contact between analytes and graphene and amplify electrochemical signals.Therefore,the electrochemical sensor based on three-dimensional graphene materials can detect and quantitatively analyze SO₂ in ionic liquids.In this paper,two-dimensional graphene oxide（2D-GO）was prepared into three-dimensional graphene oxide（3D-GO）by spray drying technology.Graphene microspheres were prepared by direct spray drying of lamellar graphene oxide and lamellar graphene oxide（GO）mixed with carbon black microspheres（CB）,and they were reduced.The electrochemical detection performance of these two materials for SO₂ in ionic liquids was investigated.It mainly includes the following research contents:（1）Three-dimensional electrochemical sensor for reducing graphene oxide and sulfur dioxide.Three-dimensional graphene oxide（3D-GO）was obtained by spray drying with GO solution as precursor,and then it was reduced by high-temperature calcination to obtain 3D-r GO.The morphology and structure of the obtained 3D-r GO were analyzed and characterized by SEM,FTIR,XRD and BET.The results showed that"wrinkled paper"3D-r GO was obtained after spray drying and calcination of GO,with a diameter of 1～4μm.Compared with 3D-GO/GCE and GCE,the mass transfer and conductivity of 3D-r GO/GCE were greatly improved by modifying this material on the surface of 3 mm glassy carbon electrode.The detection range of SO₂ sensor is 1000～5500 ppm,and the detection limit is 570.19 ppm（S/N=3）.Besides,the sensor exhibited good repeatability,reproducibility and stability.（2）Sulfur dioxide electrochemical sensor with reduced graphene oxide and carbon black composite microspheres.The 3D-GO/CB composite microspheres were obtained by using the mixed solution of GO and CB as precursor,homogenizing to make the size of microspheres more uniform and spray drying.Furthermore,a spherical composite was sympathized after introduction of CB in GO,which provides more conductive channels and larger specific surface area,and the diameter of3D-GO/CB is about 3μm.3D-GO/CB was modified on the surface of 1 mm glassy carbon electrode by drop coating method,and then it was reduced by electrochemical reduction method to obtain 3D-r GO/CB/GCE electrochemical sensor.The conductivity of the sensor is greatly improved,and it shows excellent electrocatalytic performance when detecting SO₂ in[EMIM][Tf O]solution.The linear range is 100～3500 ppm,and the detection limit is 52.3ppm（S/N=3）.The sensor has good repeatability,reproducibility and stability,which provided a broad application prospect for the electrochemical detection of SO₂ in ionic liquids.