Design And Performance Study Of Planar Electrochemical Gas Sensor

Electrochemical gas sensors have advantages such as low power consumption,high sensitivity and selectivity,good linearity,etc.So they are high-end varieties that can be used for online detection and monitoring in many fields such as petrochemical,aerospace,environmental protection,food safety and so on.However,current electrochemical gas sensors use an aqueous solution as an electrolyte,which is bulky,difficult to miniaturize and array,and limits its use and development.In this paper,a ceramic electrochemical cell was used as the substrate,and a planar electrochemical gas sensor was designed with ionic liquid as the electrolyte.The gas sensing performance of the sensor was tested and the gas sensing mechanism was analyzed.The three-electrode lead was first printed on the designed ceramic substrate by screen printing technology,then the electrode material was printed on the electrode lead by screen printing,and finally the liquid electrolyte was injected for packaging test.The planar electrochemical sensor is small in volume and the aqueous solution is not suitable for its electrolyte.The ionic liquid has the advantages of low melting point,low vapor pressure,wide electrochemical window,high electrical conductivity,high ion mobility,good thermal stability and chemical stability at room temperature.In this paper,the ionic liquid was selected to realize the planarization of the sensor and the rapid response recovery of the gas sensitivity,and the gas sensing mechanism was analyzed.The main work of this paper was as follows:(1)The electrochemical sensor was designed by using a ceramic piece as a substrate to realize detection of gas;the lead wire of the sensor and the coating of the electrode material were prepared by screen printing technology,and the ionic liquid electrolyte was preferred.By analyzing the physicochemical properties of ionic liquids,a variety of ionic liquids were initially selected as electrolytes;tin wire was replaced by soldering to avoid the phenomenon that the leads were easily broken,and the gold electrodes were directly contacted with the electrodes to make full use of the good conductivity of gold.(2)The selected ionic liquid was characterized.Through the infrared spectrum analysis,nuclear magnetic analysis,and measurement of the conductivity temperature relationship of the ionic liquid,some characteristics of the ionic liquid were grasped from the physical properties and chemical structure analysis of the ionic liquid itself.The study of the physicochemical properties of ionic liquids provided a basis for the study of ionic liquid structures and the design of new functional ionic liquids,which facilitated the selection of a suitable environment for use and the best ionic liquid electrolyte.(3)The electrode material was selected and analyzed.The shape and particle diameter of the electrode material were determined by SEM and XRD.The particle size of the electrode material in the SEM characterization was about 13 nm.The XRD and SEM characterization results showed that the prepared electrode material was a nano-scale materials.The XRD characterization of the ruthenium alloy catalyst sample showed a face-centered cubic(fcc)crystal form of ruthenium,and some ruthenium was oxidized during the preparation of the catalyst.(4)In the conventional structure sensor,when the ionic liquid was used as the electrolyte,the response signal value was large and the response recovery is slow.When the ionic liquid was used as the electrolyte at room temperature,the sensitivity of [EMIm]TFO,[EMIm]SCN,[EMIm]BF4 static gas test was high,and the values were 136 nA/ppm,257.6 nA/ppm,164 nA/ppm,respectively.Among them,[EMIm]SCN had the highest sensitivity;LiCl aqueous solution as electrolyte had sensitivity of about 150 nA/ppm,and the response value was low.The gas sensing mechanism of different types of electrolytes was different.(5)The gas-sensitivity signal response of the planar structure sensor recovered quickly.The sensitivity values of [EMIm][BF4] and [EMIm]SCN in the ionic liquid as the electrolyte at room temperature were 32.8 nA/ppm and 37.6 nA/ppm,respectively;When the LiCl aqueous solution was used as the electrolyte,the response signal value was relatively low,and the sensitivity was about 27 nA/ppm.