Oxygen Sensing Performance Of Amperomectric Oxygen Sensor Based On Bitrifluoromethyl Sulfonimide Ionic Liquid

Amperometric sensors are widely used in the detection of oxygen concentration due to their good reliability,reproducibility,low power consumption,and feasibility of miniaturization.As a kind of electrolyte material,ionic liquids possess merits like low volatility,proper conductivity,and wide electrochemical windows.However,limited by the low mobility of ionic liquids,sensors using pure ionic liquids as electrolytes usually have lower response currents when used for oxygen detection.In this paper,carbon-based materials with high electrochemical activity and large specific surface area are added to ionic liquids,to form a composite system containing ionic liquid and carbon-based material.The above system is assembled into a micro sensor,the ionic liquid acts as an electrolyte,and the carbon-based material promotes the oxygen reduction reaction on the electrode surface,so as to improve the sensing performance of the ionic liquid-based amperometric sensor oxygen.The specific research contents are as follows:1-ethyl-2,3-dimethylimidazol bis（trifluoromethyl sulfonyl）imide[Emmim][TFSI]was prepared by a traditional two-step method.It was proved by cyclic voltammetry（CV）tests that the ionic liquid-based sensor showed a certain response to different concentrations of oxygen.Theα-Fe₂O₃/r GO composite was synthesized via hydrothermal method,and was mixed with ionic liquid to form the composite systemα-Fe₂O₃/r GO/[Emmim][TFSI].The current responses of sensors based on[Emmim][TFSI],α-Fe₂O₃/[Emmim][TFSI]andα-Fe₂O₃/r GO/[Emmim][T-FSI]were compared by CV,and the results show thatα-Fe₂O₃/r GO/[Emmim][TFSI]exhibited the largest response current,indicating that the combined effect ofα-Fe₂O₃ and r GO improves the response of the assembled sensor.The sensitivity of the composite system-based sensor to different oxygen concentrations is 0.1041μA/[%O₂],and the linear correlation coefficient R²of oxygen reduction peak current to concentration is 0.9997.To explore the detection performance of imidazolium-based ionic liquid sensor to oxygen,1-butyl-2,3-dimethylimidazolium bis（trifluoromethyl sulfonyl）imide[Bmmim][TFSI]was prepared.The CV test proves that the pure ionic liquid[Bmmim][TFSI]sensor has a certain response ability to different concentrations of oxygen.To improve the sensing response to oxygen,transition metal-based N-doped porous carbon electrochemical catalysts for oxygen reduction Cu-N/C were prepared by calcining Cu-doped ZIF-8 precursors.The Cu-N/C was mixed with ionic liquid[Bmmim][TFSI]to obtain four composite systems Cu-N/C/[Bmmim][TFSI]s.The responses of sensors based on Cu-N/C/[Bmmim][TFSI]compound systems to oxygen are significantly increased relative to that of pure ionic liquid.For oxygen concentrations ranging from 0%to 100%,sensor based on 6%Cu-N/C/[Bmmim][TFSI]has good sensitivity and long-term response recovery ability,and the sensitivity value reached0.1678μA/[%O₂],with good stability obtained.In order to investigate the influence of electrochemical materials with special structures on improving the oxygen sensitivity performance of ionic liquid sensors.Co-N/C microcube electrochemical catalyst with hollow interior was prepared by precipitation and carbonization methods.Co-N/C microcubes obtained at different temperatures were mixed with ionic liquid1-butyl-1-methylpyrrolidine bis（trifluoromethyl sulfonyl）imide[C₄mpyrr][TFSI]to obtain three combined systems.CV tests illustrated that the sensing performance of Co-N/C/[C₄mpyrr][TFSI]s are significantly enhanced,the response of pure ionic liquid sensor to20%oxygen is 2.22μA,and the current values of Co-N/C-600/[C₄mpyrr][TFSI],Co-N/C-700/[C₄mpyrr][TFSI]and Co-N/C-800/[C₄mpyrr][TFSI]are 7.57,8.68 and 7.59μA,respectively.Under oxygen concentrations ranging from 0%to 100%,the sensor based on the complex system Co-N/C-700/[C₄mpyrr][TFSI]exhibits enhanced oxygen detection ability,the sensitivity was 0.1545μA/[%O₂],and the linear correlation between the response current and the oxygen concentration is 0.9991.To further study the sensitive properties of ionic liquids based on different cations to oxygen,and the effects on ionic liquid oxygen sensor performance of metal/metal oxide nitrogen-doped carbon nanotube composite materials,a phosphine-based ionic liquid trihexyltetracylate phosphine bis（trifluoromethyl sulfonyl）imide[P_14,6,6,6][TFSI]and Co particles encapsulated in carbon nanotube/zinc cobaltate nitrogen-doped carbon Co/Zn Co₂O₄@NC-CNTs were synthesized.Pure ionic liquid[P_14,6,6,6][TFSI]has a certain response performance to different concentrations of oxygen,and the sensitivity is 0.0721μA/[%O₂].It was found that Co/Zn Co₂O₄@NC-CNTs/[P_14,6,6,6][TFSI]-15 sensor has the largest response current t of 4.85μA to 20%oxygen among four complex systems.The assembled microsensor exhibits a good linear relationship between response current and the concentration with a linear regression coefficient of 0.9996,and the sensitivity of the assembled microsensor is 0.1466μA/[%O₂].