Effects of electrode material and frequency on carbon monoxide formation in carbon dioxide dielectric barrier discharge

The transformation of carbon dioxide (CO2) to carbon monoxide (CO) employing atmospheric pressure dielectric barrier discharge (DBD) cold plasma is reported. This work is carried out with an objective to re-utilize CO2 in the form of CO, which is extremely useful in various industries. Under the study, neat CO2 gas stream is used to investigate effective conditions for achieving high yields of CO using coaxial cylindrical tube type double and single dielectric DBD reactors. The different central electrodes for example Pyrex and bare metal such as Aluminium (Al), Copper (Cu) and Stainless steel (SS) along with common outer Pyrex tube combinations respectively in double dielectric (DD) and single dielectric (SD) surface reactors are used separately. DBD outlet products such as CO and leftover CO2 are analyzed and estimated with online gas chromatograph-flame ionization detector after separating them with a suitable GC column followed by their conversion to methane using Ni-catalyzed methaniser. Furthermore, the investigation of CO production is made with gas residence time (CO2 flow), applied electric field and working frequency variations. Optical emission spectroscopy (OES) for mechanistic details and power measurement for quantitative analysis are carried out. The production of CO from 200 to 70,000 ppmv is observed with DD reactor respectively at 50 Hz and 19 kHz frequencies. In case of SD reactors, the CO yields obtained are higher with the utmost CO concentration similar to 130,000 ppmv using Cu central electrode following as a minimum 13 % of CO2 transformation.