Research On Fuel Cell Type CO Gas Sensor Based On Nafion

As one kind of the new generation gas sensors, full cell type CO sensorsbased on Nafion proton membrane have many advantages, such as working atroom temperature, intrinsically safe, high accuracy and good stability, etc. Theprotection for the practice of this type of Nafion-based sensor is the rationaldesign of the structure. To improve the sensitivity of the sensor is the basis onsensor applications. In this paper, in order to improve the working stability ofthe CO sensor, a new water supply system was designed; Gas sensingproperties of the sensing electrode materials was improved by exploring thenano-technology of the sensing electrode (noble metal materials). The maincontents include three aspects:Firstly, the shape and appearance of the internal structure of the sensor weredesigned according to the sensing mechanism and the physical and chemicalproperties of Nafion proton exchange membrane. The sensor is composed ofactive carbon filtrated cap, Pt sensing electrode, Nafion membrane, counterelectrode, the isolation and reservoir. The design not only provides thehumidity environment that Nafion membrane needed for the normal work, butalso effectively eliminates the influence of the impurity methanol on thenormal work of the sensor.Secondly, with the H2PtC16and NaBH4as reactants, the Pt/Nafion sensingelectrode was prepared by the chemical deposition method. The keytechnology of depositing Pt electrode on the Nafion is explored and the best technological conditions of chemical deposition method are established: theconcentration of H2PtCl6and NaBH4is5mM and30mM respectively, and thepH value of NaBH4solution is13. The Pt/Nafion sensing electrode wascharacterized by the scanning electron microscope (SEM), and the relationshipbetween the morphology of the Pt/Nafion sensing electrode and the sensor gasperformance was explored. The Pt/Nafion sensing electrode by the optimumconditions showed good gas sensing characteristics when it was exposed to thegas of CO. The response current is107nA, and the response and recovery timeare39s and49s, respectively, when the concentration of CO is400ppm.Finally, with the H2PtC16and NaBH4as reactants, the Pt/Nafion sensingelectrode was prepared by the impregnation reduction method. The SEMimages showed that the diameter of Pt particles is about30nm. The Pt/Nafionsensing electrode prepared by the impregnation reduction method showedgood gas sensing characteristics when it was exposed to the gas of CO. Theresponse current is400nA, and the response and recovery time are30s and26s,respectively, when the concentration of CO is400ppm. The gas sensingcharacteristics of the Pt/Nafion sensing electrode prepared by the impregnationreduction method is better than that prepared by the chemical depositionmethod.In this paper, a new structure of CO gas sensor based on Nafion protonexchange membrane which can work at room temperature was designed andproduced. The Pt/Nafion sensing electrode was prepared by the chemical deposition method and impregnation reduction method. The growth law of thePt/Nafion sensing electrode particle under different conditions was studied, thegas sensing characteristics of the Pt/Nafion sensing electrode was tested, andthe influence on the gas sensing characteristics by the surface morphology wasanalyzed. In order to make sure which the better way to prepare the sensingelectrode is, the chemical deposition method and impregnation reductionmethod were compared.