Co Electrochemical Gas Sensors Based On Water-based Electrodes

Electrochemical gas sensors used as a quantitative analysis instruments are one of the advanced gas sensors. The market of electrochemical gas sensors is monopolized by British, USA etc. developed countries. With actualization of the National Project of Industrialization of New Electronic Instruments and Electronic Components:"Industrialization of Electrochemical Gas-sensing components and Gas sensors", one-million gas sensors product line was built up and put into product in Henan Hanwei Electronics Co., Ltd. The performance of our electrochemical gas sensors gradually approach and reach that of import sensors. However, the imported noble metal catalysts are expensive. At the same time, the electrodes of electrochemical sensors were printed on oil-based ink, the process results in environmental pollution, difficult post processing of the electrodes and high cost of separation and reuse of the solvent. In this thesis, the preparation of platinum black and the water-based electrodes printed by screen-printing technology were studied.The thesis includes two parts. The first section described the preparation and characterization of the platinum black. The platinum black was synthesized by freeze-reduction method. The noble metal electrochemical catalyst was characterized by SEM, TEM, ICP, XRD and BET specific surface area. The preparation of water-based electrodes and the gas-sensing properties of as-made sensors were investigated in the second section. The influence of binders and printing auxiliaries on the printability and the gas-sensing properties of the sensors were discussed. An optimal water-based ink for screen-printing was obtained successfully.The results show that the platinum is cubic crystal structure. The average size of the spherical platinum articles is about5nm, specific surface area is32.18m2/g, and content of platinum black is98.5%. The properties of platinum black are similar to import platinum black.The optimal ink, which the catalyst, printing main agent (cellulose:Triton X-100(6:4) and PTFE emulsion are10g,15ml and8ml, respectively, has better printability and excellent gas-sensing properties. The sensors made by water-based electrodes have high sensitivity which is more than or equal to65nA/ppm to CO gas, low temperature coefficient, short response and recovery time and satisfactory long-term stability. The water-based sensors have the same properties to the oil-based sensors.The water-based electrochemical CO gas sensor not only has all the advantages of oil-based electrode sensor, but also has those of low cost, non-polluting, energy conservation, the safety of the technology development requirements, with good economic and environmental benefits.