Affecting Factors And Mechanism Of Response Of Solid Electrolyte-Based Potentiometric Gas Sensor

Solid electrolyte based potentiometric gas sensors have been widely used in the detection of various gases due to their advantages of high temperature resistance,good selectivity,low cost and simple structure.However,although the performance of potentiometric gas sensor has made progress,the research on its response mechanism is still not systematic,and analysis of factors affecting response is still lacking.In addition,current research simplifies the sensor electrode reaction,but lacks the verification of experimental test results.These problems hinder the further understanding of the response mechanism of potentiometric sensors and the further development of sensors.This paper studies the response mechanism of potentiometric sensor from the following two aspects.Based on the basic assumption of mixed potential and related electrochemical theory,the expressions of response values of mixed potential gas sensors under two different conditions(charge transfer-limiting and mass transport rate-limiting)are derived.Taking the most common case as an example,the mechanism of potentiometric gas sensor is analyzed,and the influence of various factors on the response value of the sensor are discussed.The response value is mainly affected by the standard equilibrium potential difference between the two competing reactions and the ratio of the exchange current density between the two reactions.These are affected by the reaction mechanism,including the electrochemical activity of electrode materials,gas concentration,temperature and other factors.All kinds of influencing factors affect the response value at the same time,and there is mutual influence among the influencing factors.The key factors affecting the induction response are revealed,and the guidance is provided for the material design of potentiometric gas sensor.In addition,based on electrochemical impedance spectroscopy and relaxation time distribution analysis,sensors based on simple semiconductor oxide materials SnO2,ZnO and NiO were tested and analyzed.By analyzing of impedance results in different O2 concentration atmosphere,it is confirmed that the O2 reaction on electrode is controlled by several main reaction processes,and the reaction process of O2 reaction on different materials electrode is speculated.The electrode impedance of mixed conducted perovskite materials PrBSCF and BSCF was studied.It is found that the dominate reaction process of semiconductor electrode materials is the dissociation process of absorbing O2,and the dominate reaction process of mixed conducted perovskite materials is the charge transfer process.In N2 and Air atmosphere,the impedance of SnO2 and PrBSCF electrode varies with different kinds of measured gases.It is found that the reaction of measured gas on the electrode also has multiple reaction processes.O2 reaction compets with the measured gas reaction on SnO2 electrode,while O2 reaction may be dominant on PrBSCF electrode,which may lead to abnormal response behavior of PrBSCF.