The development of new microelectrode gas sensors: an odyssey. Part 2. O2 and CO2 reduction at membrane-covered gold microdisc electrodes

Abstract

Abstract In a previous paper we described the reduction of O 2 and CO 2 , in the presence of each other, at unshielded microdisc electrodes in an aprotic solvent with minimal cross-interference between the competing O 2 and CO 2 reduction reactions. In this new work, we describe a practical Clark-type membrane-covered sensor for the simultaneous measurement of O 2 and CO 2 . The sensor comprises a gold disc microelectrode, housed in a PTFE holder and covered with a PTFE membrane, with dimethylsulphoxide (DMSO) as the solvent and with a silver quasi-reference electrode. The polarizing voltage is swept from 0 to −2.4 V vs. Ag at a typical sweep rate of 0.25 or 0.5 V s −1 and the O 2 and CO 2 concentrations are determined from the limiting currents of the well separated O 2 and CO 2 reduction waves. We demonstrate that the addition of up to 10% v/v H 2 O to the solvent does not appear to compromise the ability of the sensor to analyse O 2 and CO 2 simultaneously.