Electrochemical Sensing of H۲S Gas in Air by Carboxylated Multi-walled Carbon Nanotubes

The electrochemical sensor for detecting hydrogen sulfide was fabricated. H۲S gas molecules pass through polytetrafluoroethylene membrane with ۰.۲۲ mm pore size. Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) were used to fabricate working and counter electrodes. It can be seen from Field Emission Scanning Electron Microscopy (FESEM) images of the working electrode that MWCNTs-COOH is distributed fairly uniform on the hydrophobic membrane. Quantitative results of Energy Dispersive X-ray (EDX) analysis show the presence of carbon (۸۵.۹۵ wt %) and oxygen (۱۲.۹۵ wt %) on the working electrode. The cyclic voltammetry results show the MWCNTs-COOH responds to H۲S. The sensor response up to ۵۶ ppm of H۲S gas was measured by chronoamperometry. The sensor showed linear behavior up to ۱۶ ppm. The detection limit of the sensor is ۳۱۰ ppb and its sensitivity ۴۸ hours after assembling is ۰.۱۴۳۶ µA/ ppm. The averages of response and recovery times for ۱۰ ppm of H۲S were obtained ۶.۰۶ and ۴.۱۳ minutes respectively. The sensor with functionalized carbon nanotubes has many advantages than the sensor with raw carbon nanotubes; include more uniformity of fabricated electrodes, greater response, and less noise. Using functionalized carbon nanotubes concerning raw nanotubes increases the response of the sensor by ۱۴.۸ times at ۱۰ ppm of H۲S. Also, the response of the sensor to ۲۵۰ ppm concentration of carbon monoxide gas was ۴.۳۵ nA which is very low concerning sensor response for hydrogen sulfide (۱.۶۴ µA for ۱۰ ppm of H۲S).

کلیدواژه ها:

Hydrogen Sulfide ، Electrochemical sensor ، MWCNTs- COOH ، Hydrophobic Polytetrafluoroethylene Membrane ، Sulfuric Acid