A New Carbon Dioxide Sensing Method Suitable for Use in Microelectrode Sensors.

摘要

Present electrochemical CO2-sensors are basically modified pH-electrodes; the operating principle of which is based on the measurement of a potential that is effectively a linear function of the logarithm of H+ ion concentration. The relationship between pH and PCO2 is delta pH = 0.97 delta log 10PCO2. Since one unit of pH at room temperature corresponds to less than 60 mV potential change, it is obvious that the PCO2 measurement is intrinsically inaccurate. In addition, this method is not conductive to miniaturization and it is susceptible to the same basic problems associated with the pH-electrode, i.e. low sensitivity, slow response and considerable drift. The feasibility of developing a new electrochemical carbon dioxide sensing method based on the reductive adsorption of CO2 onto a noble metal electrode and the subsequent anodic oxidation of the 'Reduced-CO2' species has been investigated experimentally. It was established that under proper conditions the presence of oxygen does not interfere with the measurement of CO2 concentration.