Study On Preparation And Properties Of Ionic Liquid Electrolyte For Electrochemical Oxygen Sensor

Oxygen plays an important role in biological activities and industrial production.It is important for people's production and life to detect oxygen accurately and efficiently.Electrochemical gas sensors are considered to be the most promising detection method because of their high sensitivity,high selectivity,repeatability and low power consumption.The electrolytes of electrochemical gas sensors are mainly water-based electrolytes or organic solvents,which are easy to volatilize and leak,thus reducing the service life of the sensors.Ionic liquids?ILs?have excellent chemical properties such as low vapor pressure,wide electrochemical window and high chemical and thermal stability.In this paper,three kinds of ILs,imidazole,aluminium chlorate and pyrrolidone,were synthesized and modified to obtain electrochemical oxygen sensors with high stability and sensitivity.Imidazole IL 1-butyl-3-methyl-imidazole tetrafluoroborate?[BMIM]BF₄?was prepared by one-step method.The results of electrochemical tests showed that[BMIM]BF₄ had a response ability to oxygen,but the linear relationship between its response current and oxygen concentration was poor.In this paper,PVDF/[BMIM]BF₄ and PMMA/[BMIM]BF₄microporous electrolyte films were prepared by phase conversion method.The results show that the linear relationship between the response current and oxygen is enhanced by the addition of polymer.The linear regression coefficient of double-layer ionic liquid film?DLILF?obtained by superimposing two kinds of microporous film is 0.995,which can accurately measure oxygen content.Aluminum chlorate IL 1-butyl-3-methyl-imidazole ferric tetrachloride?[BMIM]FeCl₄?was synthesized by two-step method.It was found that the response current of[BMIM]FeCl₄ as electrolyte of electrochemical oxygen sensor was 103.9?A under pure oxygen,and the linear regression coefficient between the response current and oxygen concentration was 0.947,and the sensitivity of oxygen was 0.07.In order to improve its sensitivity,the sensitivity of electrochemical gas sensors was increased to 1.39 by adding chitosan?CS?to[BMIM]FeCl₄.Pyrrolidone IL N-butyl-N-methyl-2-pyrrolidone bromide?[C₄mpn]Br?was prepared by one-step method.The response current and sensitivity of the sensor were improved by adding silver-coated chitosan?Ag-CS?to the[C4mpn]Br,and the effects of different Ag-CS additions on the sensor were investigated.It is found that Ag-CS with mass ratio of 1%had the highest sensitivity?0.4?and response current?65.3?A in pure oxygen?.