부산대학교 도서관

A planar solid-state electrochemical carbon monoxide (CO) sensor has been designed, with screen electrodes (platinum as the working and counter electrodes, gold as the reference electrode) and a recast film of a sulfonated styrene/ethylene-butylene/styrene triblock copolymer as the proton conducting solid polymer electrolyte. AC impedance spectroscopy has been found to be a highly sensitive technique for the quantitative characterization of sensor response. A standard equivalent circuit that included the polymer electrolyte and interfacial impedances was employed to fit the ac impedance spectroscopy data in both clean air and in the presence of CO. Chemisorption of CO onto the catalytic platinum electrode surface resulted in a decrease in charge-transfer resistance with an increase in gas concentration. This change in interfacial impedance was due to a limited amount of CO oxidation occurring due to the polarizing effect of the 10 mV ac amplitude utilized during the ac impedance spectroscopy scan. The sensors did not respond to an atmosphere containing methane, while hydrogen, which readily adsorbs onto the surface of a platinum catalyst, did perturb the ac impedance from the plot obtained in clean air.