Preparation Of Butylimidazole Ionic Liquid Mixed Electrolyte And Its Oxygen Sensitive Properties

Oxygen is a vital gas for human survival,lack of oxygen may cause suffocation or death,and it is easy to cause fire or explosion in high concentration oxygen.Electrochemical oxygen sensors are one of the most studied types of oxygen sensors.They play an important role in chemical,medical,military,energy and automotive fields.Room temperature ionic liquids（RTILs）have excellent physical and chemical characteristics such as negligible vapor pressure,wide electrochemical window,high thermal and electrochemical stability,low volatility and inherent conductivity.In this thesis,four imidazole-based ionic liquids were synthesized,and the synthesized ionic liquids were modified to obtain electrolytes with higher sensitivity,stronger oxygen sensitivity and higher stability.Ionic liquids 1-butyl-2,3-dimethylimidazole tetrafluoroborate（[BMMIM][BF₄]）and1-butyl-3-methylimidazole tetrafluoroborate（[BMIM][BF₄]）were synthesized by two-step and one-step methods,respectively.By comparing the electrochemical properties of the two ionic liquids,it is shown that[BMIM][BF₄]has better oxygen sensitivity.In order to enhance the robustness of oxygen sensing,Co Fe₂O₄ was prepared by co-precipitation method.Co Fe₂O₄ and ionic liquid[BMIM][BF₄]with different mass fractions were uniformly mixed to obtain an ionic liquid mixed electrolyte.It was found that the oxygen sensitivity and stability of the electrolyte Co Fe₂O₄/[BMIM][BF₄]added with 30%by mass of Co Fe₂O₄ were significantly improved,and the linear regression coefficient R² of oxygen concentration and reduction peak current was 0.9990.Two ionic liquids 1-butyl-2,3-dimethylimidazole hexafluorophosphate（[BMMIM][PF₆]）and 1-butyl-3-methylimidazole hexafluorophosphate（[BMIM][PF₆]）were synthesized by two-step method and one-step method,respectively.Electrochemical analysis results show that[BMIM][PF₆]has more excellent electrochemical performance.The flake Ni Co₂O₄/r GO was prepared by hydrothermal method.The mixed electrolyte obtained by blending it with ionic liquid[BMIM][PF₆]can significantly improve the response current and working stability of pure ionic liquid.The sensitivity of the oxygen sensor is 0.1087μA/[%O₂],and the linear regression coefficient of the reduction peak current calibration curve is 0.9995.After continuous cyclic voltammetry test,the reduction peak current still maintained 90%of the initial current value.Ag-Ni/r GO nanocomposites were prepared by a one-step reduction method and mixed with[BMIM][PF₆]for the study of electrochemical oxygen sensors.Compared with[BMIM][PF₆],the reduction peak current of Ag-Ni/r GO/[BMIM][PF₆]is significantly improved.The peak value of reduction current in pure oxygen was 42.09μA,the sensitivity was increased from 0.0440μA/[%O₂]to 0.1869μA/[%O₂],and the linear regression coefficient was 0.9997.After continuous cyclic voltammetry test,the reduction peak current still maintains 92%of the initial current value.The reduction peak current of Ag-Ni/r GO/[BMIM][PF₆]maintained 95.9%of the initial peak current value after 15 days.