| Given the need to detect and monitor the concentration of flammable and explosive gases or gases characteristic of fire to prevent fire and explosion accidents and to ensure the safe use of energy,it is essential to develop a device or technology that can sensitively detect these gases in real time.Solid electrolyte-based potentiometric gas sensors have the advantages of simple structure,low cost and high sensitivity,and have promising applications in the detection of low concentration gases.Although a large number of sensitive electrode materials have been developed,the optimal response performance has not yet been obtained.On the other hand,the high operating temperature of this type of sensor may pose a certain threat to the detection of flammable and explosive gases such as H2.To address these issues,this paper investigates solid electrolyte-based potential gas sensors from two aspects:Firstly,a surface modification pathway with different acidity oxides is proposed to improve the potential response performance of mixed oxide ion-electron conductor electrodes.In this paper,Pr0.1Ce0.9O2-δ(PCO)is selected as the target for modification,and a sensor(PCO-SnO2|YSZ|Pt)with excellent performance is applied to H2 and fire thermolysis gas detection.The results show that the sensor has the ability to detect low concentration of H2 and early warning of PVC cable fires.Acidic oxide,especially SnO2 modification,improves the PCO response performance,while basic oxide modification such as Li2O decreases the PCO response performance.The electrochemical analysis results show that the response behavior of the PCO-SnO2 sensor is consistent with the mixed potential mechanism,and the enhanced H2 response behavior of SnO2 is attributed to an increase in the electrochemical activity ratio,i.e.,the ratio of hydrogen oxidation to oxygen reduction reaction activity,which can be used as an indicator of the response of different materials to various gases,and the enhanced electrochemical kinetics brought about by the presence of H2 in air is mainly related to the electrode surface processes accelerated.PCO-SnO2 sensor has the advantages of high response to PVC cable thermolysis gas,low critical superheat temperature of the response,and will give stronger warning signal to PVC cable pyrolysis gas in complex gas environment.Secondly,the H2 response performance of the sensor(PCO-SnO2)at low temperature(80-200℃)was investigated by combining the surface modified SE with NASICON solid electrolyte.The results show that the fabricated sensors can achieve low-temperature detection of H2,and the response magnitude increases with the increase of temperature.Among them,PCO-SnO2 showed excellent response performance to H2 at low temperature,such as the response value and response recovery time reached-96.52 mV,18 s and 26 s for 300 ppm H2 at 150℃,respectively.The sensitivity to H2 in the range of 100-1000 ppm reached-127.5 mV/decade,and the selectivity and moisture resistance to H2 were relatively good,but the performance could not be measured at RT yet.These results indicate that the sensor fabricated by combining surface-modified SE with NASICON solid electrolyte has great potential for H2 detection at low temperatures. |
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