CO2 Gas Sensing at Microelectrodes in Nonaqueous Solvents

The reduction of CO2 has been examined at gold and platinum microelectrodes in solutions of 0.1 M tetraethylammonium perchlorate (TEAP) in dimethyl sulfoxide (DMSO), acetonitrile (MeCN) and mixed solvent systems. The gold microelectrode in 90 % MeCN/10 % DMSO produced currents 4 times larger than in pure DMSO while still showing a large potential window over which reduction currents can be measured. Films of polyaniline were insoluble in MeCN and acted as a diffusional barrier for CO2 reduction. Polyaniline was soluble in DMSO solutions, but the adsorbates which remained following polyaniline dissolution helped to lower the CO2 reduction overpotential, producing a broad current plateau of 500 mV for the measurement of CO2 concentrations.