Spectroscopic study of CO2 and CO2-N2 mixture plasma using dielectric barrier discharge

Nowadays, increasing concentration of CO2 in the atmosphere is a major threat for the environment and is a main reason for global warming. Variation in gas temperature and dissociation of CO2 into its by-products (CO and O) in a home-made dielectric barrier discharge (DBD) reactor have been reported as a function of discharge parameters, i.e., applied voltage and gas flow rate. To estimate the dissociation fraction of CO2 in the DBD reactor, the optical emission actinometry technique is employed in which 5% N-2 is used as an actinometer. Emission lines of the Angstrom band of CO at 451.09 nm (B1 Sigma+=0) and the 2nd positive system of N-2 at 337.01 nm (C3 pi u '=0-B3 pi g,''=0) are used for actinometry measurements. To estimate the rate coefficients used in actinometry measurements, gas temperature is measured using the Boltzmann plot technique, from the rotational spectra of the Q-branch of the Angstrom band CO (0-1). To avoid discrepancy in gas temperature measurements, rotational temperature of the 2nd positive system, the N-2 (0-1) band, is also measured. For this, synthetic spectra have been fitted over the experimentally recorded spectrum of the N-2 (0-1) band. A slight difference in gas temperature has been noted for the Angstrom band of CO and the 2nd positive system of nitrogen. Conversely, an increasing trend in the dissociation fraction of CO2 with an increase in the applied voltage is noted. About 34% dissociation fraction is achieved for 10 kV applied voltage at a flow rate of 25 SCCM. With an increase in the gas flow rate (25-200 SCCM), a decrease in the dissociation fraction of CO2 from 34% to 11% is noted.