To investigate catalytic activities of perovskite-type electrodes in a sealed-offCO2laser cavity, we studied the dissociation and reformation reactions ofCO2during electric discharge by monitoring the concentration change ofCO2as a function of time. A photoacoustic spectroscopy detection was introduced to measure the amount ofCO2in a closed discharge system. The catalytic activities in the dissociation ofCO2were demonstrated and compared for both Cu andLa0.7Sr0.3CoO3cathodes. The discharge with the gas mixture ofCO2:N2:He=1:1:8was performed under nine combinations of different conditions at pressures of 10, 20, and 30 Torr and discharge currents of 3, 4, and 5 mA. Within 1 min after the discharge, the concentration ofCO2reduced drastically by as much as 60&percent; for both cathodes. In the case of the Cu cathode, the amounts ofCO2in the tube had not recovered even after 30 min, while with the perovskite cathode theCO2contents recovered slowly up to 90&percent;–95&percent; within 5 min and then remained almost unchanged. The dissociation ofCO2with the Cu cathode increased as the total pressure decreased and the discharge current increased. TheLa0.7Sr0.3CoO3cathode, however, demonstrated strong suppression in the dissociation ofCO2according to the reformation reaction ofCO+(1/2)O2→CO2by its catalytic activity. ©1998 American Institute of Physics.