Measurement of Hydrogen Sulfide Concentration by use of Carbon Nanotubes and 1-allyl-3-Methylimidazolium Bromide

Objective: In this research, carboxylated multi-walled carbon nanotubes were used to construct working and counter electrodes of the electrochemical gas sensor. The 1-allyl-3- methylimidazolium bromides which is a hydrophilic room temperature ionic liquid was used as the electrolyte. Finally, the sensor was used to measure hydrogen sulfide and carbon monoxide in the air. Methods: The electrochemical method was used to measure the hydrogen sulfide concentration. To record sensor response, chronoamperometry was performed. Also, impedance spectroscopy of screen printed electrodes modified with MWCNTs-COOH was done. The working electrode was characterized by field emission scanning electron microscopy (FESEM), Energy-Dispersive X-Ray Spectroscopy (EDX) and Fourier-Transform Infrared (FTIR) spectroscopy. Results: In the range of 0.6 ppm to 10 ppm, the sensor had a linear behavior and its sensitivity was 0.3716 μA / ppm. The results of the FESEM, EDX and FTIR analysis confirm the desired structure of the working electrode. Impedance spectroscopy shows that by using ionic liquid electrolyte the impedance is less than the case of the sulfuric acid electrolyte. Conclusion: The use of ionic liquid as an electrolyte can increase the sensor sensitivity about 141% with respect to sulfuric acid as the electrolyte, in 0.6 ppm to 10 ppm concentration range of H2S gas. Also, the sensor response to hydrogen sulfide is more than one thousand times greater than its response to carbon monoxide per 1 ppm of gas.