Study On Hydrogen Sulfide Gas Sensor Based On Ionic Liquid Electrolyte

Electrochemical sensors have the advantages of high sensitivity,good selectivity,and abundant electrolyte raw materials,which have attracted widespread attention.However,most of the electrochemical sensors currently on the market use water-based electrolytes.Water-based electrolytes have the disadvantages of being easy to dry in high temperature environment and easy to break in high humidity environment.Traditional electrochemical sensors are relatively large and 80%of the structure is used to hold the electrolyte.Therefore,it is not easy to realize the needs of modern applications of miniaturization and arraying.Therefore,it is important to explore new materials to improve electrochemical sensors.In recent years,ionic liquids have been widely used in electrochemical research due to their excellent physical and chemical properties.However,there are few studies on the application of ionic liquids to hydrogen sulfide electrochemical sensors.Therefore,in view of the shortcomings of hydrogen sulfide electrochemical sensor,this paper uses pure ionic liquid instead of traditional solvent to design a commercial ionic liquid gas sensor.Electrolytes from 14 ionic liquids were screened for potential applications in commercial hydrogen sulfide electrochemical sensors.Finally,the reaction process of hydrogen sulfide gas on the Pt electrode was tested and analyzed.The details are as follows:?1?The structure of the electrochemical gas sensor of ionic liquid is designed and fabricated.The principle and structure characteristics of the electrochemical gas sensor are mainly discussed.In this paper,porous gas diffusion electrode suitable for electrochemical gas catalytic reaction was prepared,and the electrode materials were characterized.Then,two kinds of sensor structures are made,which are suitable for commercial application and electrode process analysis.The test results show that the two sensor structures can meet the performance requirements of the target gas on the three-phase reaction interface of the working electrode.?2?An ionic liquid electrochemical H₂S gas sensor was developed.First of all,according to the properties of ionic liquid,such as conductivity,melting point and so on,combined with literature,14 kinds of ionic liquid were selected as electrolyte.It is found that the gas sensors with[BMIm][HSO₄],[TMBSA][HSO₄],[BSO₃HMIm][HSO₄]and[Pr SO₃HMIm][HSO₄]as electrolyte have high sensitivity to H₂S gas,and the sensitivity is above 100 n A/ppm.However,this kind of sensor has the common shortcomings,the current response signal can not reach a stable state,and the current signal has a negative recoil phenomenon when the sensor recovers.Combined with the sensor performance test results of cation[EMIm]⁺,It can be concluded that the sensitivity signal stability of the sensor is related to anions,which determine the sensitivity of the sensor.The baseline of all sensors moved up when the humidity increased.[EMIm][OAc]electrolyte sensor has the best sensitivity to H₂S.The sensitivity of the sensor is 418 n A/ppm,and the response time and recovery time are63 s and 65 s.At the same time,the sensor has high selectivity,good repeatability,stable signal,linear relationship between response current signal and H₂S concentration.Although,the sensitivity of the sensor is greatly affected by temperature in the environment higher than 0?.But the sensitivity of the sensor is stable at low temperature.Therefore,[EMIm][OAc]sensor is expected to replace the traditional water-based electrochemical sensor in low temperature environment.?3?The cyclic voltammetry was used to study the electrode reaction process of H₂S gas on a platinum electrode.First,the formula of the peak current is derived using Fick's law and Faraday's law.Second,the sensors were tested using cyclic voltammetry.It was found that the dissociation free electrochemical window of[EMIm][OAc]in nitrogen was-0.6 V?1.5 V.Analysis of the test results of cyclic voltammetry scans shows that H₂S molecules are oxidized to H⁺and S when the electrodes are anodic polarized during forward scanning.The reduction of S occurs during the flyback.H₂S is directly reduced to HS^-when the electrode undergoes cathodic polarization.Finally,the study uses cyclic voltammetry.The changes of H₂S concentration and sweep rate on the electrode were measured.The results show that in the diffusion controlled electrode process,the peak current of oxidation of substance on the electrode is directly proportional to the concentration of reactant in the solution.The sensitivity of hydrogen sulfide gas sensor based on[EMIm][OAc]as electrolyte is 366.2 n A/ppm.The oxidation peak current is proportional to???.