SO₂ Gas Sensors Based On Composite Solid Electrolyte Membranes

Solid polymer electrolyte (SPE) has many good properties, such as light weight, good membrane-forming, good stability and so on, when it is used in gas sensors, the problems, like the leakage of liquid, short circuit, short lifetime of liquid electrolyte sensor can be resolved. These good performances make SPE has comprehensive application in sensors, lithium ion batteries and electrons.In this paper, the preparation technique and performances of a kind of novel composite solid electrolyte were researched, what's more, the properties of sulfur dioxide sensors based on composite solid electrolyte membranes were studied at room temperature.The organic/inorganic composite solid electrolyte membrane based on Poly(vinyl alcohol (PVA), silicon dioxide and silicotungstic acid (STA,SiO₂·12WO₃·26H₂O) was prepared using sol-gel method and tape casting. The properties of solid electrolyte membranes were analyzed with EIS, XRD, FTIR, TGA, SEM, cyclic voltammetry andσ-εdraw-extend experiments, the results showed that PVA, SiO₂, and STA were incorporated well in the solid electrolyte membranes, meanwhile, electrolyte membranes had good proton conductivity, hot stability, mechanical property, and electrochemistry stability. Therefore, the STA/SiO₂/PVA composite electrolyte membrane was fit to be used in SO₂ gas sensors.The performance testing of amperometric sulfur dioxide (SO₂) electrochemical sensor with STA/SiO₂/PVA composite electrolyte membrane was finished. The SO₂ sensor structure which could be disassembled conveniently was designed out. The electrolyte was STA/SiO₂/PVA membrane, and three electrodes were Pt/C gas diffusing electrodes which are always used in proton exchange membrane fuel cells (PEMFC). By testing working electrode polarization curves of SO₂ sensor, it was concluded that the working voltage was 0.3V (referring to reference electrode), and then current responses of the SO₂ sensor to static state SO₂ /air system were tested using electrochemical system, the results exhibited that at working voltage 0.3V, the relationship between current response signals and SO₂ concentration for SO₂ sensors was linear, and the sensitivity was 23.7μA/(10^-6mol·L^-1), also, the stability of SO₂ sensors was tested.