Sulfonated poly (ether ether ketone) based carbon dioxide gas sensor: Impact of sulfonation degree on sensing behavior at different humid condition

This work presents polymer composite based chemiresistive type carbon dioxide (CO2) gas sensors using different degree of sulfonated poly (ether ether ketone) (SPEEK) incorporated with diethanolamine (DEA)-functionalized multi-wall carbon nanotubes (d-MWCNTs) where incorporation of secondary amide functionalized MWCNTs improves the sensing capability by enhancing the electrical conductivity of the prepared composites. The sensors were fabricated using drop casting method on glass strips. The interaction mechanism mainly depends on the charge transportation between CO2 gas molecules and amide functionalized MWCNTs (d-MWCNTs). In addition, formation of bicarbonate ions (HCO3-) during interaction enhances the sensor sensitivity in different relative humidity. In sensing properties, SPEEK-5/d-MWCNTs (degree of sulfonation, i.e., DS = 71.03%) based sensor shows highest sensitivities (4.09 x 10(-3)-7.58 x 10(-3) % ppm(-1)) for the entire gas sensing measurement (500-5000 ppm) under different relative humidity (30-70% RH) at room temperature. The obtained results indicate that fabricated sensors are capable to detect CO2 gas in different humid conditions.