Development Of Electrochemical Hydrogen Gas Sensors Based On PVDF Polymer Electrolyte

Electrochemical gas sensors have a widely application in the field of environmental and safety production due to its small volume, low price and high accuracy. It can detect large variety of gases with bride-range directly in-situ. But this kind of sensor has a short life in practical use. To solve this problem and at the same time, to satisfy the require of smaller sensor's volume in some special fields, they are provided by science researchers; and it may be helpful to lengthen sensor's life and make it smaller. Recently, there is an increasing interest in the study of electrochemical gas sensors using SPE.In this thesis, polymer proton exchange membrane is prepared by using casting method, based on poly (vinylidene fluoride) which has excellent physical and chemical properties. To avoid particles reunion by directly doping inorganic, PVDF SPE is doped liquid SiCl₄ and H₃PO₄ to improve water retention and conductivity. By studying the amount of doping, the membrane drying temperature and holding time, the results show that best preparation conditions are drying temperature 70oC and holding time 2h. PVDF proton exchange membrane are characterized by using XRD,IR and SEM; the results show that the proton conduction channels are formed throughout the whole PVDF membrane. Retention and conductivity of the polymer membrane are higher than Nafion117, and good mechanical properties are characterized. Considering the costs, the conductivity, the mechanical properties, retention of the membrane, and other properties, prepared PVDF SPE may be a good substitute for Nafion membrane. Polymer membrane with high conductivity(the mixing amount of SiCl₄ is 20%, the mixing amount of H₃PO₄ is 30%) and good comprehensive properties is selected as electrolyte of sensor in order to assembly room temperature full solid electrochemical H₂ sensor. After the experiments conditions are determined, the sensor is charactered. By using carbon papers as diffusion layer, platinum as catalyzer layer, controling the flow rate 238 ml/min, respectively, the results reveal that a linear relationship is abtained at the hydrogen concentration of 14⁵08 ppm between the responsing electrical current and H₂ concentration; the response time and comeback time of senor is 42s and 65s, respectively. Experimental results show that the senor has good stable performance, high sensitivity and good reproducibility. It develops a practical way for the development of electrochemical gas sensors oriented to solid, small volume and long life.